corso forex trading 6/12 roof trusses

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Corso forex trading 6/12 roof trusses investec wealth and investment fees trust

Corso forex trading 6/12 roof trusses

Make sure that good lumber is used on your trusses to insure a faster, smoother building time along with a long, stable life for the truss. There are 6 main factors that define a truss along with the cost. These factors all vary depending on the project. Span: The distance of the bottom cord from outside of bearing wall to outside of bearing wall.

The span is the length at the bottom. Some spans have a lower rate per foot than others. Trusses are built for the customer to fit any project so anything can be done but it is best to keep the span around an even number, if possible, or just under an even measurement if you are concerned about cost. Roof Pitch or Slope: The vertical rise of the top cord in inches per 12 horizontal inches.

In short, the steeper the roof, the more it will cost unless the roof pitch needs to be raised a little to incorporate some attic storage. But that is another topic. The steeper the roof gets, the longer the boards get and the more the roof area increases. Other costs will begin to climb as well. Overhang: The horizontal distance from the end of the bottom cord or wall to the end of the top cord. The top cord can have either a plump cut or a square cut.

This length can easily be changed to fit the need of the truss. Truss Spacing: The distance between trusses. This makes the roof ready for decking or sheetrock. Almost all residential trusses use this spacing. There is a little misconception about truss spacing and strength. While it is sometimes true that this can raise the strength of the roof, this is not always accurate unless in some high stress situations.

And more trusses usually equal more cost! So keep that in mind. For post frame, the fewer the trusses the cheaper it is even though the price per truss is more since it is holding more weight and designed heavier duty. There are limits to this though and also it depends on the building practice. The connections are harder to make strong as you go farther apart but there is hardware designed for this. Amount of Trusses: This is fairly important. In short, the more trusses needed, the cheaper it gets per truss.

It is just as easy to build 10 trusses the same as it is 1. If only 1 truss is ordered, it must still go through all the same stages of getting it designed, built, and delivered as 10 of them together. Design Loads: The amount of weight per square foot the truss will need to support. This includes all the material for the roof and ceiling along with loading for construction purposes, wind and snow. It is essential that the truss gets the proper load applied. A clay tile roof will weigh much more than a metal roof will.

Remember, the design of your trusses directly affects the price. A Standard Gable truss sits on the end wall of a gable style roof. This is not a structural truss and needs the support of the wall. These trusses cost more than a common truss since there are more parts to cut and more lumber in the truss. This Gable Truss is very handy if you plan having an overhang on the gable.

The whole overhang and connection with this style is very strong and should resist any kind of sag over time. This style of gable truss makes it much easier and faster to put overhang on then an original style. Scissor trusses give a nice cathedral ceiling to a room. It typically makes a room feel larger due to the openness overhead. The workshop provided a platform for aerospace engineers and mathematicians from universities, research centers and industry to discuss the advanced problems requiring an extensive application of mathematics.

The presentations were dedicated to the most advanced subjects in engineering and, in particular to computational fluid dynamics methods, introduction of new materials, optimization in aerodynamics, structural optimization, space missions, flight mechanics, control theory and optimization, variational methods and applications, and so on.

Skip to main content Skip to table of contents. Advertisement Hide. This service is more advanced with JavaScript available. Conference proceedings. Papers Table of contents 19 papers About About these proceedings Table of contents Search within book.

FOREX TRADING MALAYSIA TAXABLE

If accurate data about wood density are available, and coupling problems between wood and transducer's steel are carefully overcome, stress waves techniques can provide useful indications. Both conditions are often quite difficult to meet on site. Pilodyn: a hardened steel pin is driven into the wood by a spring-loaded device. Depth of pin penetration after one or more blows, according to the instrument model is used as a measure of degree of surface degradation.

Results are affected by test location within the member, wood anisotropy, wood density, percentage of spring- and latewood, operator's skill. Drilling resistance: specially built electronic controlled drilling machines rely upon the relationship existing between wood density and the rate of penetration of the bit. These machines can bore up to mm depth, automatically plotting on a chart a pattern from which density variations can be easily detected. Useful for internal decay assessment and for ring width assessment, these instruments give information related to the restricted area under test, not immediately extensible to large zones.

Displacement transducers and strain gauges: these devices are in some cases used during loading tests in order to evaluate local strains, slip in joints, etc. Hardness: hardness tests on the faces of wood members can provide some information on local surface conditions of the material. Strength values for the whole member can be derived, through repeated tests on different points of the same member, only by very rough approximation. Screw withdrawal: the force needed for extracting a screw shows good relationship with wood strength at that point; hence this technique can provide useful information on surface or deep deterioration of members.

Conclusions Timber structures assessment is a complex task. Automatic devices capable of deriving from one or two measurements a complete set of strength and stiffness properties are not available, hence the visual assessment should be the first and the last step of the inspection work. Systematic approach, clear ideas about wood microscopical structure and timber macroscopical behaviour and last but not least a good deal of patience and scientific humility will help in reaching valuable results with inexpensive means.

References Bonamini, G. DAE: defects acoustic emission. Un metodo non distruttivo per la localizzazione di sezioni altamente difettose su travi lignee in opera. Technical Report December Borgin, K. The effects of aging on the ultrastructure of wood.

Wood Sci. Cristelli, F. Caratteristiche fisico-meccaniche di legni antichi variamente degradati ed influenza dell'impregnazione con una resina sintetica. Dissertation No. Ehlbeck, J, and Gorlacher, R. Erste Ergebnisse von Festigkeitsuntersuchungen an altem Konstruktionsholz.

Jessome, A. Strength tests on specimens from wood trussess in service for 97 years. Report of the Forest Products Laboratory, Dept. Kuipers, J. Rug, W. Strength of old timber. Building Research and Information, 19 1 Uzielli Universith degli Studi di Firenze. Objective To provide an outline of the follow-up procedures to inspection work, including a critical analysis of some commonly used techniques for in situ repairs andtor strengthening of timber structures, members and joints.

Summary This lecture describes the wood technologist's approach to the identification of the aims of the work to be undertaken, and of external constraints, in the repair and strengthening of existing timber structures, after an in situ inspection has been performed. It also discusses, briefly, some techniques that are often recommended. This lecture does not include structural design, which is covered by other lectures.

Introduction Following the inspection of the existing timber structure see STEP lecture D3 , decisions have to be made concerning any follow-up work that is necessary. Several aspects have to be considered, in close cooperation with experts, such as structural engineers, architects, wood technologists, restorers, historians, owner or administrators in charge of the building, and other concerned parties such as building authorities or officers in charge of conservation of the cultural heritage.

Consideration of the following three aspects is recommended:. Identification of objectives, requirements and constraints Restoration works on existing timber structures, which are often old or ancient and of some cultural importance, will relate to many different needs, which may often be conflicting. A clear identification of objectives and needs to be satisfied by the restoration work must be made before the technical aspects are considered, so that the experts may work on the basis of clearly stated priorities and constraints.

Amongst others, the following alternative or complementary objectives of a repairtstrengthening intervention may be listed:. For clarity and simplicity only a few of the preceding considerations are detailed. However, it should be appreciated that all the issues are likely to be interactive, and any action taken to solve one of them may significantly affect several others.

Conservation of the original materials and structural concept Because of artistic, historical or cultural reasons, the conservation of old timber structures is becoming more and more important and desirable, and often emphasis is placed more on conservation than on economic aspects.

On the other hand e. Philosophy of restoration and rehabilitation is not an objective of this lecture, but should be considered when establishing the rationale of decisions to be taken Tampone, ; Bertolini, Specific roles of the wood technologist Some aspects of restoration work are peculiar to timber structures, and usually require the specific expertise of a wood technologist. His specific contribution may include the following subjects:. The better knowledge provided by the wood scientist makes it possible nowadays to conserve structural members that until a few years ago would have simply been removed and substituted.

Also, when the original structure does no longer meet the minimum safety requirements, a good knowledge of structural timber often makes it possible to take action so that old members may still contribute to the global loadbearing capacity. Further aspects that the wood expert should especially take care of are:. Conservation of the appearance of the structure The preservation of the appearance of the structure is related to the amount of degradation of timber members.

Insects, fungi and fire normally affect the external wood layers, and repair works would often require their removal. When this is not possible or desirable, hardness and conservation of deteriorated wood may be improved through impregnation with appropriate resins.

Restoration of the original loadbearing capacity Timber members affected by heavy decay or damage can be strengthened through repair works. It should, however, be noted that many old timber structures are oversized, considering the structural requirements. After a detailed inspection and careful assessment it is therefore possible that in spite of past damage suffered by the members residual cross sections are still sufficient to provide a loadbearing capacity complying with present and anticipated service conditions.

In such cases there should be no obstacle to report: "no repair work needed", allowing work to concentrate on the prevention of further decay. Strengthening The loadbearing capacity of a timber structure needs in certain cases to be improved through appropriate structural consolidation, in order to comply with increased performance requirements e.

Compliance with safety, fire, seismic or other regulations It is a matter of fact that in some European countries building regulations have been written by experts with insufficient knowledge and experience of timber structures. The lack of specific regulations may need to be countered by reference to research papers pointing out the good seismic and fire behaviour of timber structures.

A substantial improvement is likely to occur after the implementation in these countries of EC5 Part "General rules Structural fire design", and EC 8: "De,sign provisions for earthquake resistance of structures". Working conditions The available time, expertise, materials, workmanship and technologies should be clearly identified before the working plans are completed, in order to assure that the desired quality of the whole work may be obtained.

Even more than for other kinds of repair works, timber structures require that no shortcuts be seeked, specially at the initial stages; also, the time required for collecting and analysing information should be allowed for, in order to avoid mistakes that would make successive remedies much more expensive or even impossible. Whenever glued or rigid connections are made, special care is needed in order to avoid stresses and possible failures caused by differential deformations related to the following:.

Other compatibility problems may arise from chemical factors, such as corrosion of steel fasteners caused by wood extractives under high moisture conditions. Finally, condensation of moisture and consequent decay problems is often a result of poor compatibility situations, such as:.

Structural repairs Broad classification criteria In general, no two identical situations exist in old timber structures: therefore restoration works and repairs need to be chosen, designed and implemented case by case. Also, as already noted, problems and solutions are deeply interconnected and may be not faced separately. Nevertheless it is useful to lay down the following broad classification criteria, in order to help clarify meanings, scopes and limits of the numerous technical solutions which up to now have been, or may in the future be proposed for structural repair work.

Repairs may basically deal with one or more of the following levels of the structure:. A note about strengthening Once the strength properties of timber have been lost because of decay or fracture, the original strength of the wood material can not be recovered even to a partial extent by means of impregnation with any kind of resin or other process.

Repair by gluing new parts Decayed or badly damaged segments often beam ends may be replaced by newly added parts wood, glulam, epoxy, etc. Structural design should mainly rely on adhesion of rods parallel to the grain of wood, since moisture variations and differential shrinkages may impair strength of gluelines perpendicular to the grain Ceccotti, Mannucci and Uzielli, Appearance and authenticity of original materials are lost.

Replacement of inefficient segments of original members with epoxy. Repair by means of traditional joints Decayed or badly damaged segments may be replaced by new parts made of solid wood, connected by means of traditional joining or repairing techniques. However, original strength may seldom be fully recovered. Only traditional methods and materials are used.

Replacement of inefficient segments of original members by means of traditional joints; left, top to bottom : splice joint covered by bolted wooden plates, nailed spliced bevelled joint, bolted end joint, with steel channel; right, top to bottom: splice joint covered by bolted steel plates, shear reinforcement with nails or steel clamps, splice joint with internal steel plate.

Enhancement of cross-section The cross-section of a member may be enhanced by adding gluing, nailing, bolting, etc. Original appearance and aesthetics are usually lost. However nails or bolts may be of great use in providing pressure and keeping members in position while the glue cures. Glued-in plates One or more steel plates almost as deep as the beam may be glued into grooves vertically cut in situ along the whole length of beam see Figure 3. Plates, which are hidden and are protected from fire and corrosion, take up almost all the load.

Special equipment is needed for cutting the grooves Tampone, Geometrical feasibility, buckling, support conditions, etc. Glued-in plates, along the whole length of a white fir beam a from Tampone, , modified , b threaded steel rods, c steel plate, 10 mm thick, d epoxy resin.

Glued-in rods Steel or fibreglass rods may be glued into grooves cut along the tension edge of the beam. Failure is thus no more caused by strength-reducing defects located at tension edge, and occurs at compression edge, whose strength is not increased; failure behaviour also becomes more ductile see Figure 4. Limit-state reliability is therefore increased, rather than strength or stiffness.

Ceccotti and Marradi, Tie-rods Steel cables or rods, equipped with spacers or other devices, may be used in order to contribute to strength and stiffness of individual members or trusses; by means of turnbuckles, the tension may be adjusted either to pre-stress beams or just to control excessive deflections Marradi, Messina and Paolini, Periodic adjustments or insertion of elastic components may be needed to compensate for creep and for shrinkagelswelling caused by moisture variations Ceccotti and Marradi, The structural conception of trusses may turn out significantly modified.

Examples are shown in Figure 5 and 6. Effects of steel or fibreglass rods glued with epoxy resin into grooves cut along the tension edge of the beam on its load-deformation behaviour. Top diagram: beams with large defects, bottom diagram: beams with minor defects.

Modification of support conditions Supports of decayed parts e. Often used for non-visible beams supported by thick walls, where brackets may be effectively fixed see Figure 7. Modification of support conditions: the decayed beam end a has been unloaded by moving the support towards the sound beam part b which rests on a wooden sleeper, which in its turn rests on an I-beam bracket c through a neoprene saddle, intended to prevent moisture condensation caused by temperature differences.

Additional loadbearing members Loads are partially or totally carried by additional members steel or concrete beams, columns, etc. Bertolini, Structural conception is altered. Appearance and authenticity are partly lost. Replacing timber members Some or all of the structural members may be replaced by new timber members, adopting the original techniques as far as possible.

Great care is needed in considering technical compatibility; e. The correctness of replacing original parts in historically significant structures is questionable, since authenticity of materials is lost, whereas aesthetics and authenticity of conception might be conserved. The exceptional case of a six-stories timber-framed house Knochenhaueramtshaus, Hildesheim, Germany , originally constructed in , entirely destroyed in wartime and reconstructed according to historical techniques, reconciling historical claims with the design codes of the present day and vice versa, is reported by Kessel, Speich and Hinkes Authenticity is conserved, with possibly minor aesthetical alterations.

Significant improvements are obtained in static and seismic behaviour, even though the original structural conception might result altered. Great care is needed in designing connections between parts with different anticipated displacements.

Similar means as above may be used to re-establish correct geometry e. Great care and accuracy needed in designing and implementing the work, choosing and manufacturing anchorages, etc. Structural conception might result altered.

Timber-concrete and timber-panel composite structures An effective kind of work, already implemented in a number of cases in different countries, is the timber-concrete composite technique see STEP lecture E13 : a reinforced concrete slab is connected to the beams by means of shear connectors various types exist, such as glued, screwed-in, fitting in grooves, etc.

Bending strength and stiffness greatly increase, and seismic behaviour improves. Beams need to be in good conditions, in order to contribute in the mixed structure. Timber-panel composite technique is similar as above, except that structural wood-based panels, connected by means of nails or similar fasteners, are used in place of the concrete slab.

This system, not yet widely used in rehabilitation of old structures, is much lighter than concrete; on the other hand, it provides a smaller structural improvement. Maintenance and conservation measures Maintenance work should always carried out with a view to the continued conservation of the structure: no work may be considered as "the final one", needing no further care or maintenance. The action of potential deterioration agents both biotic and abiotic should be anticipated and prevented.

Moisture, in its various forms and origins, including the effect of alterations that may have been made on the environment vapour barriers, waterproofing, sources of condensation, increased or decreased ventilation, closed windows or other openings, sealing of beam end supports, etc.

Special care should be taken to ensure the proper execution of recommended repair or prevention works. For instance an inaccurately performed preservative treatment e. References Bertolini, C. Problemi di recupero: metodologie di indagine, tecnologie di intervento. L'Edilizia, 12 , VI, Ceccotti, A,, Mannucci, M. Effetti del riassorbimento di umidith sul comportamento ad estrazione di barre di acciaio ancorate nel legno mediante resina epossidica. In: G. Tampone Ed. Ceccotti, A. Nuove tecnologie negli interventi di recupero delle antiche capriate di legno: materiali e metodi.

Kessel, M. Marradi, P. Recupero di strutture in legno mediante armature parzialmente presollecitate. Tampone, G. Restauro strutturale con lamine metalliche dei solai lignei della sede del Genio Civile di Firenze. Restauro strutturale con legno lamellare di un solaio e di una volta a carena lignei dell'Accademia di Belle Arti a Firenze. Rinforzo di puntoni e consolidamento di una capriata del teatro di Sarteano mediante centine metalliche.

Tecnologia del restauro delle strutture di legno. Vidon Socotec. Objective To describe the main types of connection used, to point out the design problems to note and to present examples of the design of various types of connection. Summary The main types of column to beam connections, hinged or fixed, as well as beam to beam connections are described. The principles of design of these connections to resist shear, axial force and bending moment are described.

The design principles concerning problems specific to wood such as compressive or tensile strength perpendicular to the grain or dimensional changes are also covered. Actual examples are presented. Introduction The design of a connection must allow the function selected to be carried out i.

The connection should be designed to resist all the internal forces and moments about all three principal axes:. The internal forces or moments in the connection are either balanced by mechanical fasteners such as nails, dowels or bolts or by direct wood to wood contact.

Glued connections are not dealt with in this lecture. In general the main internal forces and moments are those which occur in the plane of the frame made up of a column and a beam. The other internal forces and moments essentially arise from the additional forces applied out of the plane of the frame, especially the bracing forces.

In any case, in a column to beam connection, the torsional moment must be counterbalanced by some means to prevent the rotation of the beam around the x-axis. Figure 2 shows the main types of connection. Connection type 4 in Figure 2 is either free to rotate about the y- and z-axis or continuously fixed in three axes. In connection type 5 the secondary beam is usually simply supported by the main beam.

Because of the eccentricity of the secondary beam support the main beam is often subject to a torsional moment see Figure 3. Main types of connection. I Corner connection, column to beam or frame corner, 2 connection between continuous beam and column, 3 column to beam connection in a multi-storey structure, 4 beam to beam connection: two beams in line, 5 beam to beam connection between a secondary beam and a main beam. Joint with steel bars with bolts or screws and with or without connectors.

The bearing plate e. Generally these connections allow free rotation about the y-axis. The support reaction of the beam is transmitted either by direct contact or by mechanical fasteners. If the column is wide, neoprene sheets may be provided in order to keep the load centred on the column.

Both the beam and the column must be torsionally restrained. Joint with nailed gusset plates of steel or plywood. The joint can take up some moment and thereby contribute to the lateral stability of the structure. Joint with a vertical bolt screwed into a round steel bar with a threaded hole. The hole in the column is plugged after assembly. The bolt should be retightened, especially for deep beams. Column to beam connection type 2 This type of connection is often used in column to beam structures at right angles between continuous columns and continuous beams supporting floors.

The connection in Figure 10 needs a large connection area to allow the necessary number of fasteners to be placed. Double beam connected to indented columns using steel angles to increase bearing surface. Central beam resting on spacing blocks of double column. In Figure 11 and 12, the bolts are placed in oval holes to allow for dimensional changes in the timber and are only used to position the beams.

To avoid large compressive stresses on top of the beams in Figure 12, a clearance is provided between the upper face of the beam and the spacing block of the double column. Column to beam connection type 3 This type of joint essentially concerns the connection of a cross member to a continuous column. Except for traditional jointing by means of mortise and tenon, these connections are made using metal fittings. Nailed plywood or steel gusset plates. The joint is effective and easy to make.

It may be necessary to protect the gusset plate against fire. Gusset plates in slots with nails plywood gussets or dowels plywood or steel gussets. The fire properties are very good. Traditional connection by mortise and tenon with hardwood dowel. The support reaction is transmitted by direct contact; the hardwood dowel only keeps the beam in place. This connection is attractive but needs to be carried out by specialised craftsmen and is only suitable for low loads.

Beam to beam connection type 4 Purlins are often designed with cantilever connections or with continuity over the supports. Both solutions are advantageous compared with simple beams on two supports. The necessary timber volume is decreased and the stiffness of the structure increased. Cantilever connections Figure 18 to 21 are very economic in labour and time.

The simplest joint: the short beam is hanging in the cantilever. Where the forces are not too large, the beam can be supported directly on the cantilever. Joint with a special steel shoe. In the version shown, only shear forces can be transferred. Joint with doweled steel plate in slots.

The dowels are placed close to the unloaded edges to prevent splitting. Beam to beam connection type 5 This type of joint essentially concerns the connection of a cross member to a continuous main beam.

Beam from one side only supported on a steel bracket. In this case it is necessary to design the main beam for the torsional moment. Common problems to be avoided Due to slipping and rotation of the connection, the forces which must be counterbalanced by the fasteners act in the tangential direction of the rotation circles through the bolt lines and may not be parallel to the grain see Figure The fastener force components perpendicular to the grain, which are resisted by the stiff metal side plates or channels, cause tensile and compressive stresses parallel to the grain.

The side plates or channels are very rigid and tend to split the wood. In order to avoid this problem, the stiffness of the metal fittings should be decreased at the joint. The net area indicated in Figure 26c has to be large enough to resist the force F in order to avoid a local tensile failure parallel to the grain. For very deep glulam beams the dimensional changes in the wood due to moisture content changes may cause splitting of the timber, if free shrinkage is prevented see Figure The column in Figure 27, less thick than the beam and better ventilated, dries out more quickly and its shrinkage is hindered by the circle of bolts which attach it to the beam.

Since the beam hardly shrinks in grain direction, a split occurs in the centre area of the circle of bolts. Splitting failure due to differential shrinkage and different moisture variation in beam and column. For secondary beam to main beam connections it is necessary to place the steel connector of the secondary beam as high as possible to limit the tensile stresses perpendicular to the grain. However, it will be necessary to check that the fitting does not prevent dimensional changes of the main beam which would cause cracks due to resisting the shrinkage effects.

Objective To describe different ways of connecting and supporting timber elements in arches and frames by using steel plates. Summary The lecture describes the different principles to be followed when designing hinges and supports based on steel plates. The design of the details is discussed, and examples of actual hinges in existing timber structures are presented.

Introduction As pointed out in STEP lecture C1, the serviceability and the durability of a timber structure depend mainly on the design of the joints between the elements. This statement includes the hinges and supports, which in large structures are often connections between two glulam parts. Basic considerations The selection and design of connections are controlled not only by the loadcarrying and durability conditions, but include other considerations such as aesthetics, the cost-efficiency, the fabrication and the erection.

A basic requirement is that all steel details shall be well adjusted to the glulam parts, to avoid time-consuming and costly work at the building site. It is very important to design the connections in such a way that shrinkage and swelling of the timber parts are possible without creating problems. The moisture content in the glulam during production is normally very well controlled, but the equilibrium moisture content in timber will vary during the year.

If free movement due to shrinkage is not allowed, the result may be splitting of the timber caused by tension perpendicular to the grain. The design should avoid the possibility of water being trapped in the joint area, and if necessary drainage holes or slots should be introduced.

It is essential to protect end grain from water, because the water absorption parallel to the grain is much larger than the absorption perpendicular to the grain. In many cases a moisture barrier is recommended or gaps may be introduced. If exposed to the weather, or other severe conditions, corrosion of the steel parts may be resisted by rust proofing or by using corrosive-resistant metals.

The designer should also consider the compatibility of the metal with the timber treatment. For example, as pointed out in STEP lecture C1, caution should be taken with the installation of steel components into timber treated with preservatives containing copper. Hinges for frames and arches For hinges in the apex of frames and arches the details shown in Figure 1 may be used. The hinge in Figure l a may be used for frames and arches with slopes of 40 degrees or more.

A bolt with a diameter of at least 20 mm should be used with nails as indicated in the figure. In the detail shown in Figure l b the bolts may be reinforced with single-sided toothed-plate connectors, if heavy lateral tension forces occur. The hinge shown in Figure 2 is a true hinge, which may be used in Service Class 3. Column supports based on steel plates, a for vertical and horizontal forces, 0 for vertical and horizontal forces and moment about the strong axis of the glulanz member. In Figure 3a the compression force is transferred directly through contact pressure and not via the bolt.

The connectors indicated are "single-sided toothedplate connectors" as described in STEP lecture C10, for example "Bulldog" connectors. Supports for columns, frames and arches For supporting light frames and arches, or for pin-ended columns, the details shown in Figure 4 may be used. The horizontal and vertical forces are transferred through contact pressure between timber and steel. Horizontal forces acting outwards and lifting forces are transferred through the bolt.

The bolt may be reinforced with single-sided toothed-plate connectors. The need for constructional tolerances when casting concrete bases is essential. A moisture barrier is necessary to avoid moisture transfer into end grain.

Supports for frames and arches For simply supported frames and arches the details shown in Figure 5 may used. Compression forces are not transferred through the bolts, and single-sided toothed-plate connectors may be added. The support in Figure 5b is a true hinge anchorage, which may be used for outdoor exposure Service Class 3. Design of hinges and supports All the steel plate based hinges and supports described in this lecture must be designed separately according to EC5.

Welding should be checked to accord with EC3. The resistance to corrosion should meet the protection specifications in EC5 Table 2. The detail in Figure 6 is used in a warehouse building in Norway. The slotted-in "connector" is made of steel plates with thickness 8 mm.

The outer steel plates 8 mm x mm x mm are connected to the glulam members with four 20 mm bolts on each side of the hinge. The support shown in principle in Figure 5b is used in many structures in Europe and other parts of the world. Figure 7a shows an example from a Norwegian structure. Slotted in steel plates are welded to the upper part of the steel support, and the glulam parts are connected to the steel plates using steel dowels.

Strength class GL32 according to prEN The steel parts should be checked according to EC3. The serviceability and the durability of a timber structure depend mainly on the design of joints and supports. Design the joints and supports in such a way that shrinkage and swelling of the glulam parts are possible without creating problems.

Objectives To illustrate the modes of transport for timber construction elements and the most frequent methods of erection for various timber structures. Summary Transport and erection influence the design and the fabrication of timber structures. The lecture describes the means of transport for various types of structural elements and the erection modes for the different structural configurations. Some suggestions are provided for designers of timber structures so as to optimise costs, quality and safety on-site.

Introduction The final phases in the provision of a timber structure are transport and erection. These may appear insignificant in the realisation of a project but they require the same attention as the preceding phases, in that together they can influence not only the design but also the budgeting and the management of the project. Transportation Timber constructions can be built using solid wood, glued laminated timber, plywood or other wood based panels.

Solid wood and panel elements will normally have dimensions that can be easily transported. Conversely, glulam structural elements can be manufactured in very large sizes and in a variety of shapes. As a consequence transport solutions are correspondingly diverse. In these cases the ability to transport the structure must be verified at an early design stage both in terms of equipment and route. This is important in estimating costs and in making a rational choice between different types of structural system.

In general glulam beams are long, with a deep, narrow cross section. They can be manufactured up to approximately 45 m long. The length and the overall height determine the best transport solution. The width of the beam, including also the room for any pre-fixed steel hardware shoes , determlnes the number of units that can be loaded without exceeding the width of the truck 2,5 m.

When the overall height of the element is relevant, it is important to gay attention to the limits imposed on the free passage of the vehicle to the site due to the dimensions of viaducts and bridges clear height of 4,O to 4,8 m. Elements with an overall height exceeding 4,O m are not transportable by road or rail.

In these cases structures have to be designed so that the beams can be manufactured in two pieces. They can then be end jointed at the site with steel or timber bolted connections. Loading The operation is usually carried out using a gantry-crane for the structural elements and a fork-lift for the accessories.

The loading operations must be carried out in accordance with safety regulations and the goods must be well secured on the truck in order to avoid problems during transportation. For domestic deliveries transport is mostly done by road haulage with a few exceptions. Rail transport, for example, is mostly used in a situation where large quantities of standard beams need to be delivered to stock warehouses maximum length allowed in one wagon, 18 m.

Exceptional transportation When the beams' dimensions exceed the dimensions of the truck body the load is considered exceptional and a special transport solution is required. When this solution is not possible, special trucks have to be used. Transportation of very long or high beams requires special vehicles that can be classified in four groups:.

Tractors with low-bed telescopic semi-trailer Figure 4a : these are suitable for short and very cambered beams. Tractors with telescopic semi-trailer Figure 4b : these are suitable for beams up to 3,O m high and up to 24 m long. The semi-trailer telescopic lattice can be extended up to 20 m. Tractors with low-bed trailer Figure 4c : these are suitable for beams with an overall height up to 4,O m. The trailer is in two parts connected by a non-loadbearing lattice. The beam's large overall height can be slung very low in the trailer which permits the beams to travel only mm from the road level.

It must be pointed out that in these cases the road's path has to be carefully checked. Tractors with cradle trailer Figure 4d : these are suitable for any sort of beams with a height up to 3,5 m. The beams are supported by the front centre plate on the tractor and by the back centre plate on the trailer. Centre plates permit articulation between load and conveyance. Limitations Road regulations prescribe some limitations to exceptional transportation. When the length to be conveyed exceeds 25 m or the width exceeds 3 m, a police escort is required.

Regulations can be different in the individual countries. In Germany, when the overall height exceeds 4,O m, transportation has to be done during the night. In Italy, the number of units of loads exceeding the legal limit of 43 to 44 tonnes must not exceed three pieces per convoy. In general a special pass must be obtained from the transport authorities whenever timber elements exceed legal dimensions. On site Unloading The lifting system available on the site is normally used for unloading.

Because transport methods do not include a lift except for a few trucks it is necessary to use the site jib crane or a truck crane. Beams are slung with special bands to avoid damage. The bands are slung and tightened around the beams in order to avoid slippage while moving. Handling should always be carried out with the utmost care to avoid possible damage to timber. In the case of trusses, wherever possible the points of lifting should be at the eaves joints, with the truss in the vertical plane, apex uppermost.

After unloading at the site, the timber and its accessories must be stored until assembly takes place. During this period the members and the other materials must not be damaged and they must not represent a hazard to people. Stored members have to be protected from moisture coming from the soil and from rain and snow.

For these reasons the elements must be stored to avoid contact with the ground and should be protected by a waterproof cover. This avoids the wood getting stained and mouldy especially when it has not had a preservative treatment. Where large size structural elements have to be stored in the upright position, it is necessary to stabilise them to prevent buckling.

Machining Timber elements beams, columns, purlins, etc. It is preferable to avoid any activity on site that could have been carried out in the factory at a lower costs and with higher quality. Accurate shop drawings must specify for each timber element how they have to be machined; in the factory rather than on the site.

They should also be drilled, slotted and grooved to accommodate connecting hardware. To carry out all this pre-assembly work, it is necessary to develop very accurate shop drawings showing all the details and connections. When possible, a sensible reduction in the erection costs can be achieved by pre-assembling steel connecting parts on the beams. Unless otherwise specified an anti-fungi and antiinsect coating, available in different shades, is brushed on.

Nothing should be improvised on the site. Only when site conditions do not permit pre-fabrication of the structural elements, should they be trimmed and machined on-site. The work in this case must be carried out in accordance with highest standards. The construction will be, as a consequence, more expensive. Site inspection Before erection it is appropriate to check if the site is ready to receive the timber and if foundations and supporting elements are installed properly according to the drawings.

It is advisable to check if all materials are on site before assembly begins. Erection Erection represents, in the construction of a timber structure, the moment in which all the previous stages are verified.

A well executed assembly is a primary condition to achieve a good building but it is not a sufficient condition. It is necessary that all the previous phases design, engineering, fabrication, machining and transportation are correctly executed, to be followed by skilled erection of the structure. Workmen have to be skilled, with experience in timber construction and with complete and efficient tools and machines.

The site must be ready for receiving the timber structural elements in order to allow workmen to operate easily and with safety. Erection of a timber structure is usually carried out by placing first the main beams and then the secondary elements. Due to the fact that these frequently have a role in bracing the structure, provisional bracing must be provided. As soon as possible bracing wood rafters and counter braces have to be connected to the main beams.

Assembly procedure depends on the type of structural system. It is useful to consider some typical situations:. Domestic roofs There are two fundamental types of timber roof for housing and similar types of buildings. The first type is characterised by steep pitches and consist of solid wood trussed rafters positioned at close centres.

In most cases the structure is hidden by the ceiling. Normally the greatest stresses which truss joints will undergo are those caused by handling. It is important to carefully plan the handling of trusses, taking into account weight, size, access, lift height and whether manual or mechanical handling is required.

Temporary raking braces are used during the erection until the last trussed rafter is erected. After that permanent diagonal braces are fixed on both sides of the roof, longitudinal members are fixed making sure that the ceiling ties are accurately spaced at the correct centres. The second type consists of main beams and purlins. These structures have modest dimensions but, due to the high level of finish required, they need to be assembled accurately.

Frequently it is preferabIe to hide the steel hardware. This involves more sophisticated connections systems in which the beams have to be machined to insert the steel parts, or indented on the sides to support purlins. As a consequence, machining and assembly are more expensive, but the results are excellent.

Scaffolding and jig cranes are normally required on-site. Beams They are used normally for simple and linear structures. Purlins are frequently supported by standard steel shoes nailed onto the beams. They can be preassembled in the factory or nailed on-site. If the ground under the structure permits it, it can be convenient to use a mobile rise tower. This system is used very frequently because it permits coverage of large areas with a simple and economic structure.

Each half portal can be made of a single curved piece or of some straight pieces jointed together. In the case of curved beam portals, it can be highly convenient for economy and for workers' safety to pre-assemble on the ground pairs of arches complete with purlins and bracing.

They can then be lifted from the centre of the construction allowing them to rotate through the base hinges. The two semi-portals must be lifted beyond their final position so that they czn be dropped down to meet at the top hinge with no interference. A workman operating from a rise tower or from a platform crane fixes the top hinge. This erection system requires the use of two cranes, but it is fast and does not require a central scaffolding to support the semi-portals until they become load bearing.

With highly skilled workmen it is possible to pre-assemble four or five semiportals on the ground and to lift them up simultaneously. Two auxiliary beams are necessary to hang the portals from the crane see Figure 7. By assembling size limited structural elements, it is possible to build long span trusses up to m that solve transportation or production problems.

As a result assembly becomes rather heavy because the various members must be jointed and connected on site. Fastening is often carried out using dowelled and bolted connections. Dowels must be hammered and for this reason the truss has to be laid down on one side. The use of bolts requires the truss to be supported clear of the ground.

Normally the assembly area available on-site is limited and movement of the trusses by crane is expensive. So, often it is convenient to place rails running along the two trusses support lines. In this way the trusses can be placed in the position nearest to the assembly area and then they can be shifted using trolleys to their final positions. Radial and geodetic domes There are two types of domes: radial and geodetic.

When their diameter is under 80 meters they can be erected as a series of radial arches connected at the top. When they are of larger dimensions a geodetic design system is normally used. Their general behaviour is that of a "shell" structure configuration.

Assembling a radial dome involves building a scaffolding tower at its centre as support for the steel compression ring to which the top part of each arch must be connected. In geodetic domes a large number of provisional supports is required.

Safety Erection of timber structures requires in the majority of cases that great attention is paid to the prevention of accidents at work. From the first project stage it is necessary to consider how the various elements will be assembled. The structure must be designed taking into account systems and connections that reduce risks for workmen.

Erection drawings and instructions must be prepared for important constructions. They have to describe unloading, storage and erection of the timber elements. Instructions must be given clearly and it is preferable when they are illustrated by sketches. When possible, preference has to be given to erection systems which permit pre-assembly on the ground.

When it is necessary to operate at height, necessary safety measures must be imposed. To protect workmen from the danger of falling from the erected structure holding nets or pre-anchored wire lines should be available. Wire lines can be fixed through special posts pre-anchored to main girders before lifting.

Workmen who have to walk on the erected beams, must tie their safety belt to the wire lines. Other facilities that can be used to reach the roof level are fixed or mobile scaffolding and crane-platforms. In addition to safety belts, workers must wear personal protection aids as hard-hats, gloves and shoes with steel toe and anti-punching sole.

These safety means together with good training of the workmen and with a correct erection design, permit competitive assembly without neglecting safety requirements. Transportation and erection of timber structures, particularly long span or large structural elements, should be considered at an early stage as they can affect the design and cost of the project. Transportation of exceptional loads should conform to the requirements of the relevant highways authorities.

Machining and all pre-assembly preparation should be carried out in the factory where possible. Erection of timber structures will have to reflect site conditions and available lifting equipment. Objectives To describe the types of frame corners commonly used depending on the structural form and the jointing technique. To present design optirnisation of the momentresisting knee joints allowed by EC5. The applications of these frame corner systems are described and some details are given to ensure the structural performance of the frames.

In the second part, a design example of a frame corner presents the possible choices for optimising the dowelled moment-resisting joints commonly used in Europe. Introduction Industrial and recreational buildings are often built using a frame with tapered members, or curved frames, as the main structural system. They are simple systems which permit large areas to be covered with spans ranging from 15 to 50 rn and with spacings of 5 to 10 m.

Frames with tapered members a and curved frames b : I knee joints, 2 secondary structural roofing elements. The most critical action effects forces and moments are found in the frame comer which has to be designed first. This preliminary design defines the largest crosssection for curved frames, or the knee-joint and the largest cross-section for the tapered members.

Though curved frames are mechanically more efficient, their use requires:. Because of these disadvantages, the choice of a frame with tapered members is generally preferred. In this case, the designer is faced with the transfer of the moment and forces between the rafter and the column.

Frame corner systems Mechanical fastening techniques The most common frames are built, for spans up to 50 m, using tapered members: a single rafter and paired columns Figure 2a. They are three-hinged to avoid overload due to globally imposed deformations. At the frame corner the internal forces are transferred by using mechanical fasteners placed in a circular or rectangular pattern.

To accommodate the fasteners, the mean depth of the members in the area of the joints varies between Ll20 and Ll30, where L is the span of the frame. The main disadvantage of this moment-resisting joint is the possibility of splitting induced by moisture content variations or time effects on the joint behaviour. In case of toothed-plate connectors, the extent of the splits is limited by staggered location of the connectors in the inner pattern relatively to the outer pattern Figure 2b.

The steeper the roof gets, the longer the boards get and the more the roof area increases. Other costs will begin to climb as well. Overhang: The horizontal distance from the end of the bottom cord or wall to the end of the top cord. The top cord can have either a plump cut or a square cut. This length can easily be changed to fit the need of the truss.

Truss Spacing: The distance between trusses. This makes the roof ready for decking or sheetrock. Almost all residential trusses use this spacing. There is a little misconception about truss spacing and strength. While it is sometimes true that this can raise the strength of the roof, this is not always accurate unless in some high stress situations. And more trusses usually equal more cost! So keep that in mind. For post frame, the fewer the trusses the cheaper it is even though the price per truss is more since it is holding more weight and designed heavier duty.

There are limits to this though and also it depends on the building practice. The connections are harder to make strong as you go farther apart but there is hardware designed for this. Amount of Trusses: This is fairly important. In short, the more trusses needed, the cheaper it gets per truss. It is just as easy to build 10 trusses the same as it is 1.

If only 1 truss is ordered, it must still go through all the same stages of getting it designed, built, and delivered as 10 of them together. Design Loads: The amount of weight per square foot the truss will need to support. This includes all the material for the roof and ceiling along with loading for construction purposes, wind and snow.

It is essential that the truss gets the proper load applied. A clay tile roof will weigh much more than a metal roof will. Remember, the design of your trusses directly affects the price. A Standard Gable truss sits on the end wall of a gable style roof. This is not a structural truss and needs the support of the wall. These trusses cost more than a common truss since there are more parts to cut and more lumber in the truss.

This Gable Truss is very handy if you plan having an overhang on the gable. The whole overhang and connection with this style is very strong and should resist any kind of sag over time. This style of gable truss makes it much easier and faster to put overhang on then an original style. Scissor trusses give a nice cathedral ceiling to a room. It typically makes a room feel larger due to the openness overhead.

A standard rule of thumb is the cathedral roof pitch can be up to one half of the roof pitch. This will give quite an amazing look and an open and airy feeling to a room. Now here is a little about how much a scissor truss costs: There are so many variables with these trusses with everything from span to roof pitch and so on that there can only be an average estimate given.

The trusses on the ends of the house will be Drop Top Gable Trusses. Here is a layout view of the house:. The measurements on truss layouts are all feet-inch-sixteenths. So if you look at the chained measurements in the middle on the left side, you will see the trusses are spaced 2 feet on center. The gable trusses on each end are labeled T01GE, the common trusses are labeled T01 and the scissor trusses in the middle are S Here are pictures of each of them.

And there is enough of each truss style to help bring the price down per piece.

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Often used for non-visible beams supported by thick walls, where brackets may be effectively fixed see Figure 7. Modification of support conditions: the decayed beam end a has been unloaded by moving the support towards the sound beam part b which rests on a wooden sleeper, which in its turn rests on an I-beam bracket c through a neoprene saddle, intended to prevent moisture condensation caused by temperature differences. Additional loadbearing members Loads are partially or totally carried by additional members steel or concrete beams, columns, etc.

Bertolini, Structural conception is altered. Appearance and authenticity are partly lost. Replacing timber members Some or all of the structural members may be replaced by new timber members, adopting the original techniques as far as possible. Great care is needed in considering technical compatibility; e. The correctness of replacing original parts in historically significant structures is questionable, since authenticity of materials is lost, whereas aesthetics and authenticity of conception might be conserved.

The exceptional case of a six-stories timber-framed house Knochenhaueramtshaus, Hildesheim, Germany , originally constructed in , entirely destroyed in wartime and reconstructed according to historical techniques, reconciling historical claims with the design codes of the present day and vice versa, is reported by Kessel, Speich and Hinkes Authenticity is conserved, with possibly minor aesthetical alterations. Significant improvements are obtained in static and seismic behaviour, even though the original structural conception might result altered.

Great care is needed in designing connections between parts with different anticipated displacements. Similar means as above may be used to re-establish correct geometry e. Great care and accuracy needed in designing and implementing the work, choosing and manufacturing anchorages, etc. Structural conception might result altered.

Timber-concrete and timber-panel composite structures An effective kind of work, already implemented in a number of cases in different countries, is the timber-concrete composite technique see STEP lecture E13 : a reinforced concrete slab is connected to the beams by means of shear connectors various types exist, such as glued, screwed-in, fitting in grooves, etc.

Bending strength and stiffness greatly increase, and seismic behaviour improves. Beams need to be in good conditions, in order to contribute in the mixed structure. Timber-panel composite technique is similar as above, except that structural wood-based panels, connected by means of nails or similar fasteners, are used in place of the concrete slab. This system, not yet widely used in rehabilitation of old structures, is much lighter than concrete; on the other hand, it provides a smaller structural improvement.

Maintenance and conservation measures Maintenance work should always carried out with a view to the continued conservation of the structure: no work may be considered as "the final one", needing no further care or maintenance. The action of potential deterioration agents both biotic and abiotic should be anticipated and prevented. Moisture, in its various forms and origins, including the effect of alterations that may have been made on the environment vapour barriers, waterproofing, sources of condensation, increased or decreased ventilation, closed windows or other openings, sealing of beam end supports, etc.

Special care should be taken to ensure the proper execution of recommended repair or prevention works. For instance an inaccurately performed preservative treatment e. References Bertolini, C. Problemi di recupero: metodologie di indagine, tecnologie di intervento.

L'Edilizia, 12 , VI, Ceccotti, A,, Mannucci, M. Effetti del riassorbimento di umidith sul comportamento ad estrazione di barre di acciaio ancorate nel legno mediante resina epossidica. In: G. Tampone Ed. Ceccotti, A. Nuove tecnologie negli interventi di recupero delle antiche capriate di legno: materiali e metodi. Kessel, M. Marradi, P. Recupero di strutture in legno mediante armature parzialmente presollecitate.

Tampone, G. Restauro strutturale con lamine metalliche dei solai lignei della sede del Genio Civile di Firenze. Restauro strutturale con legno lamellare di un solaio e di una volta a carena lignei dell'Accademia di Belle Arti a Firenze.

Rinforzo di puntoni e consolidamento di una capriata del teatro di Sarteano mediante centine metalliche. Tecnologia del restauro delle strutture di legno. Vidon Socotec. Objective To describe the main types of connection used, to point out the design problems to note and to present examples of the design of various types of connection. Summary The main types of column to beam connections, hinged or fixed, as well as beam to beam connections are described. The principles of design of these connections to resist shear, axial force and bending moment are described.

The design principles concerning problems specific to wood such as compressive or tensile strength perpendicular to the grain or dimensional changes are also covered. Actual examples are presented. Introduction The design of a connection must allow the function selected to be carried out i. The connection should be designed to resist all the internal forces and moments about all three principal axes:.

The internal forces or moments in the connection are either balanced by mechanical fasteners such as nails, dowels or bolts or by direct wood to wood contact. Glued connections are not dealt with in this lecture. In general the main internal forces and moments are those which occur in the plane of the frame made up of a column and a beam. The other internal forces and moments essentially arise from the additional forces applied out of the plane of the frame, especially the bracing forces.

In any case, in a column to beam connection, the torsional moment must be counterbalanced by some means to prevent the rotation of the beam around the x-axis. Figure 2 shows the main types of connection. Connection type 4 in Figure 2 is either free to rotate about the y- and z-axis or continuously fixed in three axes. In connection type 5 the secondary beam is usually simply supported by the main beam. Because of the eccentricity of the secondary beam support the main beam is often subject to a torsional moment see Figure 3.

Main types of connection. I Corner connection, column to beam or frame corner, 2 connection between continuous beam and column, 3 column to beam connection in a multi-storey structure, 4 beam to beam connection: two beams in line, 5 beam to beam connection between a secondary beam and a main beam. Joint with steel bars with bolts or screws and with or without connectors.

The bearing plate e. Generally these connections allow free rotation about the y-axis. The support reaction of the beam is transmitted either by direct contact or by mechanical fasteners. If the column is wide, neoprene sheets may be provided in order to keep the load centred on the column.

Both the beam and the column must be torsionally restrained. Joint with nailed gusset plates of steel or plywood. The joint can take up some moment and thereby contribute to the lateral stability of the structure. Joint with a vertical bolt screwed into a round steel bar with a threaded hole. The hole in the column is plugged after assembly. The bolt should be retightened, especially for deep beams. Column to beam connection type 2 This type of connection is often used in column to beam structures at right angles between continuous columns and continuous beams supporting floors.

The connection in Figure 10 needs a large connection area to allow the necessary number of fasteners to be placed. Double beam connected to indented columns using steel angles to increase bearing surface. Central beam resting on spacing blocks of double column. In Figure 11 and 12, the bolts are placed in oval holes to allow for dimensional changes in the timber and are only used to position the beams.

To avoid large compressive stresses on top of the beams in Figure 12, a clearance is provided between the upper face of the beam and the spacing block of the double column. Column to beam connection type 3 This type of joint essentially concerns the connection of a cross member to a continuous column.

Except for traditional jointing by means of mortise and tenon, these connections are made using metal fittings. Nailed plywood or steel gusset plates. The joint is effective and easy to make. It may be necessary to protect the gusset plate against fire. Gusset plates in slots with nails plywood gussets or dowels plywood or steel gussets. The fire properties are very good. Traditional connection by mortise and tenon with hardwood dowel.

The support reaction is transmitted by direct contact; the hardwood dowel only keeps the beam in place. This connection is attractive but needs to be carried out by specialised craftsmen and is only suitable for low loads. Beam to beam connection type 4 Purlins are often designed with cantilever connections or with continuity over the supports.

Both solutions are advantageous compared with simple beams on two supports. The necessary timber volume is decreased and the stiffness of the structure increased. Cantilever connections Figure 18 to 21 are very economic in labour and time. The simplest joint: the short beam is hanging in the cantilever. Where the forces are not too large, the beam can be supported directly on the cantilever. Joint with a special steel shoe. In the version shown, only shear forces can be transferred.

Joint with doweled steel plate in slots. The dowels are placed close to the unloaded edges to prevent splitting. Beam to beam connection type 5 This type of joint essentially concerns the connection of a cross member to a continuous main beam. Beam from one side only supported on a steel bracket. In this case it is necessary to design the main beam for the torsional moment. Common problems to be avoided Due to slipping and rotation of the connection, the forces which must be counterbalanced by the fasteners act in the tangential direction of the rotation circles through the bolt lines and may not be parallel to the grain see Figure The fastener force components perpendicular to the grain, which are resisted by the stiff metal side plates or channels, cause tensile and compressive stresses parallel to the grain.

The side plates or channels are very rigid and tend to split the wood. In order to avoid this problem, the stiffness of the metal fittings should be decreased at the joint. The net area indicated in Figure 26c has to be large enough to resist the force F in order to avoid a local tensile failure parallel to the grain. For very deep glulam beams the dimensional changes in the wood due to moisture content changes may cause splitting of the timber, if free shrinkage is prevented see Figure The column in Figure 27, less thick than the beam and better ventilated, dries out more quickly and its shrinkage is hindered by the circle of bolts which attach it to the beam.

Since the beam hardly shrinks in grain direction, a split occurs in the centre area of the circle of bolts. Splitting failure due to differential shrinkage and different moisture variation in beam and column. For secondary beam to main beam connections it is necessary to place the steel connector of the secondary beam as high as possible to limit the tensile stresses perpendicular to the grain. However, it will be necessary to check that the fitting does not prevent dimensional changes of the main beam which would cause cracks due to resisting the shrinkage effects.

Objective To describe different ways of connecting and supporting timber elements in arches and frames by using steel plates. Summary The lecture describes the different principles to be followed when designing hinges and supports based on steel plates. The design of the details is discussed, and examples of actual hinges in existing timber structures are presented.

Introduction As pointed out in STEP lecture C1, the serviceability and the durability of a timber structure depend mainly on the design of the joints between the elements. This statement includes the hinges and supports, which in large structures are often connections between two glulam parts. Basic considerations The selection and design of connections are controlled not only by the loadcarrying and durability conditions, but include other considerations such as aesthetics, the cost-efficiency, the fabrication and the erection.

A basic requirement is that all steel details shall be well adjusted to the glulam parts, to avoid time-consuming and costly work at the building site. It is very important to design the connections in such a way that shrinkage and swelling of the timber parts are possible without creating problems.

The moisture content in the glulam during production is normally very well controlled, but the equilibrium moisture content in timber will vary during the year. If free movement due to shrinkage is not allowed, the result may be splitting of the timber caused by tension perpendicular to the grain. The design should avoid the possibility of water being trapped in the joint area, and if necessary drainage holes or slots should be introduced. It is essential to protect end grain from water, because the water absorption parallel to the grain is much larger than the absorption perpendicular to the grain.

In many cases a moisture barrier is recommended or gaps may be introduced. If exposed to the weather, or other severe conditions, corrosion of the steel parts may be resisted by rust proofing or by using corrosive-resistant metals. The designer should also consider the compatibility of the metal with the timber treatment. For example, as pointed out in STEP lecture C1, caution should be taken with the installation of steel components into timber treated with preservatives containing copper. Hinges for frames and arches For hinges in the apex of frames and arches the details shown in Figure 1 may be used.

The hinge in Figure l a may be used for frames and arches with slopes of 40 degrees or more. A bolt with a diameter of at least 20 mm should be used with nails as indicated in the figure. In the detail shown in Figure l b the bolts may be reinforced with single-sided toothed-plate connectors, if heavy lateral tension forces occur. The hinge shown in Figure 2 is a true hinge, which may be used in Service Class 3.

Column supports based on steel plates, a for vertical and horizontal forces, 0 for vertical and horizontal forces and moment about the strong axis of the glulanz member. In Figure 3a the compression force is transferred directly through contact pressure and not via the bolt.

The connectors indicated are "single-sided toothedplate connectors" as described in STEP lecture C10, for example "Bulldog" connectors. Supports for columns, frames and arches For supporting light frames and arches, or for pin-ended columns, the details shown in Figure 4 may be used.

The horizontal and vertical forces are transferred through contact pressure between timber and steel. Horizontal forces acting outwards and lifting forces are transferred through the bolt. The bolt may be reinforced with single-sided toothed-plate connectors. The need for constructional tolerances when casting concrete bases is essential.

A moisture barrier is necessary to avoid moisture transfer into end grain. Supports for frames and arches For simply supported frames and arches the details shown in Figure 5 may used. Compression forces are not transferred through the bolts, and single-sided toothed-plate connectors may be added.

The support in Figure 5b is a true hinge anchorage, which may be used for outdoor exposure Service Class 3. Design of hinges and supports All the steel plate based hinges and supports described in this lecture must be designed separately according to EC5. Welding should be checked to accord with EC3.

The resistance to corrosion should meet the protection specifications in EC5 Table 2. The detail in Figure 6 is used in a warehouse building in Norway. The slotted-in "connector" is made of steel plates with thickness 8 mm. The outer steel plates 8 mm x mm x mm are connected to the glulam members with four 20 mm bolts on each side of the hinge.

The support shown in principle in Figure 5b is used in many structures in Europe and other parts of the world. Figure 7a shows an example from a Norwegian structure. Slotted in steel plates are welded to the upper part of the steel support, and the glulam parts are connected to the steel plates using steel dowels. Strength class GL32 according to prEN The steel parts should be checked according to EC3. The serviceability and the durability of a timber structure depend mainly on the design of joints and supports.

Design the joints and supports in such a way that shrinkage and swelling of the glulam parts are possible without creating problems. Objectives To illustrate the modes of transport for timber construction elements and the most frequent methods of erection for various timber structures.

Summary Transport and erection influence the design and the fabrication of timber structures. The lecture describes the means of transport for various types of structural elements and the erection modes for the different structural configurations. Some suggestions are provided for designers of timber structures so as to optimise costs, quality and safety on-site. Introduction The final phases in the provision of a timber structure are transport and erection. These may appear insignificant in the realisation of a project but they require the same attention as the preceding phases, in that together they can influence not only the design but also the budgeting and the management of the project.

Transportation Timber constructions can be built using solid wood, glued laminated timber, plywood or other wood based panels. Solid wood and panel elements will normally have dimensions that can be easily transported. Conversely, glulam structural elements can be manufactured in very large sizes and in a variety of shapes. As a consequence transport solutions are correspondingly diverse. In these cases the ability to transport the structure must be verified at an early design stage both in terms of equipment and route.

This is important in estimating costs and in making a rational choice between different types of structural system. In general glulam beams are long, with a deep, narrow cross section. They can be manufactured up to approximately 45 m long. The length and the overall height determine the best transport solution. The width of the beam, including also the room for any pre-fixed steel hardware shoes , determlnes the number of units that can be loaded without exceeding the width of the truck 2,5 m.

When the overall height of the element is relevant, it is important to gay attention to the limits imposed on the free passage of the vehicle to the site due to the dimensions of viaducts and bridges clear height of 4,O to 4,8 m. Elements with an overall height exceeding 4,O m are not transportable by road or rail. In these cases structures have to be designed so that the beams can be manufactured in two pieces. They can then be end jointed at the site with steel or timber bolted connections.

Loading The operation is usually carried out using a gantry-crane for the structural elements and a fork-lift for the accessories. The loading operations must be carried out in accordance with safety regulations and the goods must be well secured on the truck in order to avoid problems during transportation.

For domestic deliveries transport is mostly done by road haulage with a few exceptions. Rail transport, for example, is mostly used in a situation where large quantities of standard beams need to be delivered to stock warehouses maximum length allowed in one wagon, 18 m. Exceptional transportation When the beams' dimensions exceed the dimensions of the truck body the load is considered exceptional and a special transport solution is required.

When this solution is not possible, special trucks have to be used. Transportation of very long or high beams requires special vehicles that can be classified in four groups:. Tractors with low-bed telescopic semi-trailer Figure 4a : these are suitable for short and very cambered beams.

Tractors with telescopic semi-trailer Figure 4b : these are suitable for beams up to 3,O m high and up to 24 m long. The semi-trailer telescopic lattice can be extended up to 20 m. Tractors with low-bed trailer Figure 4c : these are suitable for beams with an overall height up to 4,O m. The trailer is in two parts connected by a non-loadbearing lattice. The beam's large overall height can be slung very low in the trailer which permits the beams to travel only mm from the road level.

It must be pointed out that in these cases the road's path has to be carefully checked. Tractors with cradle trailer Figure 4d : these are suitable for any sort of beams with a height up to 3,5 m. The beams are supported by the front centre plate on the tractor and by the back centre plate on the trailer.

Centre plates permit articulation between load and conveyance. Limitations Road regulations prescribe some limitations to exceptional transportation. When the length to be conveyed exceeds 25 m or the width exceeds 3 m, a police escort is required. Regulations can be different in the individual countries. In Germany, when the overall height exceeds 4,O m, transportation has to be done during the night. In Italy, the number of units of loads exceeding the legal limit of 43 to 44 tonnes must not exceed three pieces per convoy.

In general a special pass must be obtained from the transport authorities whenever timber elements exceed legal dimensions. On site Unloading The lifting system available on the site is normally used for unloading. Because transport methods do not include a lift except for a few trucks it is necessary to use the site jib crane or a truck crane.

Beams are slung with special bands to avoid damage. The bands are slung and tightened around the beams in order to avoid slippage while moving. Handling should always be carried out with the utmost care to avoid possible damage to timber. In the case of trusses, wherever possible the points of lifting should be at the eaves joints, with the truss in the vertical plane, apex uppermost.

After unloading at the site, the timber and its accessories must be stored until assembly takes place. During this period the members and the other materials must not be damaged and they must not represent a hazard to people. Stored members have to be protected from moisture coming from the soil and from rain and snow.

For these reasons the elements must be stored to avoid contact with the ground and should be protected by a waterproof cover. This avoids the wood getting stained and mouldy especially when it has not had a preservative treatment. Where large size structural elements have to be stored in the upright position, it is necessary to stabilise them to prevent buckling. Machining Timber elements beams, columns, purlins, etc. It is preferable to avoid any activity on site that could have been carried out in the factory at a lower costs and with higher quality.

Accurate shop drawings must specify for each timber element how they have to be machined; in the factory rather than on the site. They should also be drilled, slotted and grooved to accommodate connecting hardware. To carry out all this pre-assembly work, it is necessary to develop very accurate shop drawings showing all the details and connections. When possible, a sensible reduction in the erection costs can be achieved by pre-assembling steel connecting parts on the beams.

Unless otherwise specified an anti-fungi and antiinsect coating, available in different shades, is brushed on. Nothing should be improvised on the site. Only when site conditions do not permit pre-fabrication of the structural elements, should they be trimmed and machined on-site. The work in this case must be carried out in accordance with highest standards. The construction will be, as a consequence, more expensive.

Site inspection Before erection it is appropriate to check if the site is ready to receive the timber and if foundations and supporting elements are installed properly according to the drawings. It is advisable to check if all materials are on site before assembly begins.

Erection Erection represents, in the construction of a timber structure, the moment in which all the previous stages are verified. A well executed assembly is a primary condition to achieve a good building but it is not a sufficient condition. It is necessary that all the previous phases design, engineering, fabrication, machining and transportation are correctly executed, to be followed by skilled erection of the structure.

Workmen have to be skilled, with experience in timber construction and with complete and efficient tools and machines. The site must be ready for receiving the timber structural elements in order to allow workmen to operate easily and with safety.

Erection of a timber structure is usually carried out by placing first the main beams and then the secondary elements. Due to the fact that these frequently have a role in bracing the structure, provisional bracing must be provided. As soon as possible bracing wood rafters and counter braces have to be connected to the main beams. Assembly procedure depends on the type of structural system. It is useful to consider some typical situations:.

Domestic roofs There are two fundamental types of timber roof for housing and similar types of buildings. The first type is characterised by steep pitches and consist of solid wood trussed rafters positioned at close centres. In most cases the structure is hidden by the ceiling. Normally the greatest stresses which truss joints will undergo are those caused by handling. It is important to carefully plan the handling of trusses, taking into account weight, size, access, lift height and whether manual or mechanical handling is required.

Temporary raking braces are used during the erection until the last trussed rafter is erected. After that permanent diagonal braces are fixed on both sides of the roof, longitudinal members are fixed making sure that the ceiling ties are accurately spaced at the correct centres. The second type consists of main beams and purlins.

These structures have modest dimensions but, due to the high level of finish required, they need to be assembled accurately. Frequently it is preferabIe to hide the steel hardware. This involves more sophisticated connections systems in which the beams have to be machined to insert the steel parts, or indented on the sides to support purlins. As a consequence, machining and assembly are more expensive, but the results are excellent.

Scaffolding and jig cranes are normally required on-site. Beams They are used normally for simple and linear structures. Purlins are frequently supported by standard steel shoes nailed onto the beams. They can be preassembled in the factory or nailed on-site. If the ground under the structure permits it, it can be convenient to use a mobile rise tower.

This system is used very frequently because it permits coverage of large areas with a simple and economic structure. Each half portal can be made of a single curved piece or of some straight pieces jointed together. In the case of curved beam portals, it can be highly convenient for economy and for workers' safety to pre-assemble on the ground pairs of arches complete with purlins and bracing.

They can then be lifted from the centre of the construction allowing them to rotate through the base hinges. The two semi-portals must be lifted beyond their final position so that they czn be dropped down to meet at the top hinge with no interference. A workman operating from a rise tower or from a platform crane fixes the top hinge.

This erection system requires the use of two cranes, but it is fast and does not require a central scaffolding to support the semi-portals until they become load bearing. With highly skilled workmen it is possible to pre-assemble four or five semiportals on the ground and to lift them up simultaneously. Two auxiliary beams are necessary to hang the portals from the crane see Figure 7. By assembling size limited structural elements, it is possible to build long span trusses up to m that solve transportation or production problems.

As a result assembly becomes rather heavy because the various members must be jointed and connected on site. Fastening is often carried out using dowelled and bolted connections. Dowels must be hammered and for this reason the truss has to be laid down on one side. The use of bolts requires the truss to be supported clear of the ground.

Normally the assembly area available on-site is limited and movement of the trusses by crane is expensive. So, often it is convenient to place rails running along the two trusses support lines. In this way the trusses can be placed in the position nearest to the assembly area and then they can be shifted using trolleys to their final positions. Radial and geodetic domes There are two types of domes: radial and geodetic.

When their diameter is under 80 meters they can be erected as a series of radial arches connected at the top. When they are of larger dimensions a geodetic design system is normally used. Their general behaviour is that of a "shell" structure configuration. Assembling a radial dome involves building a scaffolding tower at its centre as support for the steel compression ring to which the top part of each arch must be connected.

In geodetic domes a large number of provisional supports is required. Safety Erection of timber structures requires in the majority of cases that great attention is paid to the prevention of accidents at work. From the first project stage it is necessary to consider how the various elements will be assembled.

The structure must be designed taking into account systems and connections that reduce risks for workmen. Erection drawings and instructions must be prepared for important constructions. They have to describe unloading, storage and erection of the timber elements. Instructions must be given clearly and it is preferable when they are illustrated by sketches. When possible, preference has to be given to erection systems which permit pre-assembly on the ground.

When it is necessary to operate at height, necessary safety measures must be imposed. To protect workmen from the danger of falling from the erected structure holding nets or pre-anchored wire lines should be available. Wire lines can be fixed through special posts pre-anchored to main girders before lifting.

Workmen who have to walk on the erected beams, must tie their safety belt to the wire lines. Other facilities that can be used to reach the roof level are fixed or mobile scaffolding and crane-platforms. In addition to safety belts, workers must wear personal protection aids as hard-hats, gloves and shoes with steel toe and anti-punching sole.

These safety means together with good training of the workmen and with a correct erection design, permit competitive assembly without neglecting safety requirements. Transportation and erection of timber structures, particularly long span or large structural elements, should be considered at an early stage as they can affect the design and cost of the project.

Transportation of exceptional loads should conform to the requirements of the relevant highways authorities. Machining and all pre-assembly preparation should be carried out in the factory where possible. Erection of timber structures will have to reflect site conditions and available lifting equipment. Objectives To describe the types of frame corners commonly used depending on the structural form and the jointing technique. To present design optirnisation of the momentresisting knee joints allowed by EC5.

The applications of these frame corner systems are described and some details are given to ensure the structural performance of the frames. In the second part, a design example of a frame corner presents the possible choices for optimising the dowelled moment-resisting joints commonly used in Europe. Introduction Industrial and recreational buildings are often built using a frame with tapered members, or curved frames, as the main structural system.

They are simple systems which permit large areas to be covered with spans ranging from 15 to 50 rn and with spacings of 5 to 10 m. Frames with tapered members a and curved frames b : I knee joints, 2 secondary structural roofing elements. The most critical action effects forces and moments are found in the frame comer which has to be designed first. This preliminary design defines the largest crosssection for curved frames, or the knee-joint and the largest cross-section for the tapered members.

Though curved frames are mechanically more efficient, their use requires:. Because of these disadvantages, the choice of a frame with tapered members is generally preferred. In this case, the designer is faced with the transfer of the moment and forces between the rafter and the column. Frame corner systems Mechanical fastening techniques The most common frames are built, for spans up to 50 m, using tapered members: a single rafter and paired columns Figure 2a.

They are three-hinged to avoid overload due to globally imposed deformations. At the frame corner the internal forces are transferred by using mechanical fasteners placed in a circular or rectangular pattern. To accommodate the fasteners, the mean depth of the members in the area of the joints varies between Ll20 and Ll30, where L is the span of the frame.

The main disadvantage of this moment-resisting joint is the possibility of splitting induced by moisture content variations or time effects on the joint behaviour. In case of toothed-plate connectors, the extent of the splits is limited by staggered location of the connectors in the inner pattern relatively to the outer pattern Figure 2b. For both types of fastener, reinforcement glued at the end of the members reduces the risk of splitting Figure 2c.

Frames with mechanically jointed members: a typical frame corner, b toothed-plate connectors, c reinforcement of members: 1 glued-in rod or 2 glued-on plywood, d special arrangement for dowelled joint. To reduce the stresses near the end-grain of the members, the mechanical behaviour could also be controlled by positioning a stiff rod at the rotation centre. The bending moment is transmitted by a partial pattern of fasteners located along the line of thrust in the area of the joint Figure 2d.

Furthermore, the current trend is to develop knee joints with higher strengths and stiffnesses and with ductile behaviour. In European countries, this has led to studies involving side reinforcement of the members in the joint area using glued plywood or densified veneer wood Leijten et al.

These reinforcements prevent overloading of the end corner of the members and ensure plastic behaviour at failure. Another way, used in Japan and Australia, is to design single in-plane members rafter and column and to install internal steel plates with dowel fasteners or external plywood gussets Figure 3. The first arrangement is a good solution for appearance and fire resistance.

In both cases, the equilibrium of forces and moment is achieved in the centre section of the plate and the designer has to pay attention to the internal strength of the plate. Frames with mechanically jointed in-plane members: a joint with internal steel plate, b nailed plywood gusset. V-shaped column Another concept is to change the loading path using a V-shaped column fixed to the rafter Figure 4. Depending on the stability criteria and horizontal action effects, this type of frame could be two-hinged with a continuous pitched and curved beam with spans up to 30 rn.

For greater spans, they should be three-hinged. The depths of the beam vary between W30 and W40 for h,, and W40 to Ll60 for h,. To transfer the bending moment, the tension and compression members should make an angle a within the range 10 to 20". With the internal timber member in compression, either a vertical internal timber member or an external steel rod in tension may be used.

For such a frame, the design must investigate all combined action effects to take into account possible reversal of loading in the column members. Glued jointing techniques This technique is carried out using large finger joints or glued-in bolts Figure 5. Mainly developed in Scandinavian countries, these glued joints lead to high local force transfer and very stiff connections.

The main restriction in use results from the brittle behaviour of these joints. So, their production and installation require extended quality control and must fulfil specific requirements as specified for large finger joints in prEN, "Glued laminated timber - Production requirements for large finger joints".

Members connected by large finger joints is the more common glued joint for frames. The joint profile is cut along the depth of the member. In general the knee joint is produced by installing a comer block and cutting two large finger joints. This enables the angle between the forces and the grain direction to be reduced and hence the joint strength is increased.

As on-site installation is not allowed for large finger joints, the use of such nondemountable joints is also limited by transportation conditions. To overcome this disadvantage and to limit the risk associated with a single component brittle joint, another solution is to used glued-in bolts see STEP Lecture C Figure 6 shows an installation with inclined glued-in bolts to reduce the influence of possible splitting on the joint strength Turkowskij, In this example, forces and moment are transferred by separate compression and tension components and low load reversal is permitted.

Design of frame corners Especially for dowelled moment-resisting joints, EC5 rules and linked standards allow new possibilities for frame optirnisation. Aimed at increasing the use of timber, the first stage is to design the most efficient joints mechanically and economically. This section presents a design example showing the possible choice for designers and the timber industries.

A three-hinged frame Figure 7 is designed with glued-laminated tapered members. The mechanical properties of the fasteners have the following values: embedding strength:. Design with improved steel grade frame B Choosing dowels of smaller diameter and greater tensile strength, EC5 allows the plastic behaviour of the moment-resisting joint to be improved. Table 3 gives the results of the design calculations. For the calculation of the deflection in service, the design has to take into account the joint rigidity:.

Design with improved glued laminated timber and steel grade frame C The other way to optimise the timber structures is to select glued laminated timber of a greater strength class. It should be mentioned that this choice implies greater control requirements during the fabrication process.

In comparison with design A, the best cost-efficiency could be reached with the design B or C2 depending on the cost of each operation during the fabrication and erection processes. References Heimeshoff, B. Berechnung vonRahmenecken rnit Keilzinkenverbindungen.

Leijten, A. Physical and mechanical properties of densified veneer wood DVW for structural applications. Reyer, E. Development and calculation of kinked timber joints elastically prestressed perpendicular to the grain. Turkowskij, S. Prefabricated joints of timber structures on inclined glued-in bars.

The lecture includes H. Briininghoff Gesamthochschule Wuppertal examples of bracing as well as the necessary detailing and joints. Summary The behaviour of bracing is discussed and simplified design rules are provided to assist design engineers. Some advice on structural modelling and detailing of the joints is provided. Introduction It is essential that principal structural members which are liable to buckle are connected to walls, columns, beams or bracing structures which are able to resist the forces involved, in order to ensure local and overall structural stability.

The bracing elements prevent large lateral displacements which will otherwise occur perpendicular to the principal axislplane of the structural element. At the same time, they can be used as structural elements for resisting external forces such as wind loading. If main structural elements are perfectly straight and the external loads are applied only in their principal planes, i.

However, in practice, it is necessary to allow for the lack of straightness due to imperfections in the production process and which can occur during the erection process. Bucking forces will also occur if wind or other external loads occur in the plane of the bracing, resulting in lateral deflections.

Uses of bracing Structural bracing can be used to resist external forces which do not arise from the behaviour of the structure but are applied onto the structure and have to be transmitted to the foundations. Examples are wind loads or horizontal loads e. The second type of forces are internal forces which result from deviations of the main structural element from its intended position.

These forces can be balanced within the structure which is correctly detailed and therefore do not have to be transmitted to the foundations. Examples are. Transfer of external loads through bracing into the foundation. The designer usually considers these actions separately and the design of the main elements and bracing is carried out in two steps. In reality, however, structures are threedimensional systems such as the simple truss, shown in Figure 8, with upper and lower purlins.

In this case two diagonal bracing elements, which together with the purlins acting as chords form a truss system in the plane of the roof, to ensure lateral stability of the simple truss. There are eight support reactions. Thus the system is statically indeterminate to one degree. For design purposes, the design may be simplified by neglecting one of the support reactions in the x-direction see Figure 8 and assigning the horizontal bracing forces to the two supports in the y-direction.

This simplification is only possible if the displacements of the supports assumed as fixed in the y-direction are nearly the same; otherwise the "omitted" support will have to resist forces in the xdirection resulting from the rotation of the structure in plan. This approach is also only valid if the deformations of the chords purlins are small enough to be negligible but would only cause displacements in the y-direction.

Due to the extensions in the internal members of the truss and movements in the joints, shear deformation as shown in Figure 9 will occur. Hence the vertical element at the support will remain vertical without causing any horizontal reaction at the top of the truss.

In sloping roofs, the span of the bracing system is assumed to be equal to the length of the roof plane and is a plane structure. This is a practical calculation model. For roofs with large slopes, it is sensible not to consider the transfer of shear forces along the apex of the roof resulting in two cantilever beams, as shown in Figure If the structural system and the loading are symmetrical and the deformations of the chords are not considered, the horizontal displacement of the apex is the same for both bracings.

Thus there would be no forces along the apex but there would be two horizontal support reactions in the x-direction which have to be considered. These support forces should be transferred to structural strong points, say at the eaves - see Figure In such cases, where the stiffness of the support system is sufficiently high, small deformations of the bracing system would occur, resulting in smaller lateral forces.

In general this is a sensible approach, however, with nailed plate trusses which are usually narrowly spaced, it is impossible to provide such a bracing systems with sufficient depth and hence stiffness. Bracing details Types of bracing Bracing systems are mostly formed by adding diagonal members to the main structural elements e.

Prefabricated trusses which are placed in between the members to be braced can also be used. In this lecture only trusses are considered although beams, shear walls or single members can also be used for bracing purposes. In most cases, the main structural elements also form the chords of the bracing system. In the case of trusses, the compression cord which needs to be braced should also be part of the bracing system.

Where beams have to be braced, the bracing system should be placed in the compression zone. For roof structures with purlins, the purlins can be used as part of the bracing system. This is achieved by adding diagonal members.

The characteristics of the different possible forms are described below. Crossed diagonals resisting only tensile forces usually made of steel e. N-trusses this system is only sensible if the external loading in one direction produces relatively higher forces;. Trussed beam ease of erection e. Connections Connections can be detailed in a number of ways and the examples shown in F w e s 19 to 21 have worked well in practice. Timber diagonals can be connected with steel plates Figure 19 and nails or dowels.

Slotted steel plates should be predrilled together with the timber since the required spacings are smaller and the connections are stiffer and more effective when compared with non-predrilled nailed connections. For small forces, thin steel plates on one side are sufficient. The connection area required for non-predrilled nailed connections is four times larger than that required for predrilled connections with slotted steel plates. The diagonals have also to be designed for the bending moments resulting from the eccentricity of the steel plates.

Timber diagonals connected by slotted steel plate. The diagonals can be connected through specially designed steel connections such as those shown in Figure If we go any larger, it will require more webbing inside the truss, which will directly affect the cost of the truss. The same is true if we make it steeper. Steeper roof pitches require longer webs, which add to the cost. We can figure the rough cost of a truss by the lineal feet of truss ,which in this case is 26 feet.

One thing to keep in mind right away is that four main things affect the common truss price: grade of lumber, amount of trusses, tax, and delivery. The webbing is necessary for the strength of the truss and it is needed in a truss this size. Remember that quality high-grade lumber will cost a little more than a lower and cheaper grade, which can change the price of the truss.

However, cheaper is not always better. Make sure that good lumber is used on your trusses to insure a faster, smoother building time along with a long, stable life for the truss. There are 6 main factors that define a truss along with the cost. These factors all vary depending on the project. Span: The distance of the bottom cord from outside of bearing wall to outside of bearing wall. The span is the length at the bottom. Some spans have a lower rate per foot than others.

Trusses are built for the customer to fit any project so anything can be done but it is best to keep the span around an even number, if possible, or just under an even measurement if you are concerned about cost. Roof Pitch or Slope: The vertical rise of the top cord in inches per 12 horizontal inches. In short, the steeper the roof, the more it will cost unless the roof pitch needs to be raised a little to incorporate some attic storage. But that is another topic. The steeper the roof gets, the longer the boards get and the more the roof area increases.

Other costs will begin to climb as well. Overhang: The horizontal distance from the end of the bottom cord or wall to the end of the top cord. The top cord can have either a plump cut or a square cut. This length can easily be changed to fit the need of the truss. Truss Spacing: The distance between trusses. This makes the roof ready for decking or sheetrock. Almost all residential trusses use this spacing. There is a little misconception about truss spacing and strength. While it is sometimes true that this can raise the strength of the roof, this is not always accurate unless in some high stress situations.

And more trusses usually equal more cost! So keep that in mind. For post frame, the fewer the trusses the cheaper it is even though the price per truss is more since it is holding more weight and designed heavier duty. There are limits to this though and also it depends on the building practice. The connections are harder to make strong as you go farther apart but there is hardware designed for this. Amount of Trusses: This is fairly important. In short, the more trusses needed, the cheaper it gets per truss.

It is just as easy to build 10 trusses the same as it is 1. If only 1 truss is ordered, it must still go through all the same stages of getting it designed, built, and delivered as 10 of them together. Design Loads: The amount of weight per square foot the truss will need to support. This includes all the material for the roof and ceiling along with loading for construction purposes, wind and snow. It is essential that the truss gets the proper load applied. A clay tile roof will weigh much more than a metal roof will.

Remember, the design of your trusses directly affects the price.

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Usually, these steel trusses are smaller than other materials, and they can be quite lightweight too, which means that moving the trusses from one place to another is a lot easier than expected. At the same time, the steel trusses offer quite a lot of durability for any roof. The reality is that the curved steel roof trusses are designed to offer an ultimate performance at all times, and the results are definitely more than well worth it.

This is very important for the trusses that do not have a normal shape, such as the curved ones. When it comes to pricing, the curved timber roof trusses can be a little more expensive than the curved steel roof trusses, it all depends on the materials used for the truss.

These curved wood roof trusses are harder to implement than the steel ones, and depending on the density of the wood used there, they can also be heavier. But this more than makes up for it when it comes to the natural look that the entire truss provides.

Of course, aside from the looks, the curved wood roof trusses are designed with a lot of durability in mind. One has to wonder though, which type of curved truss is better, the ones made out of steel or wood? It all depends on the magnitude of the project, as well as its destination. Most of the time, the curved timber roof trusses are a lot better suited for the residential properties and homes, whereas, the curved steel roof trusses are designed mostly for commercial places, where a lot more space has to be covered.

For the latter, it can be a lot more expensive to use wood trusses, because wood is obviously coming at a higher price than steel. The King Post Truss spans up to 8m, which makes it perfect for multiple types of houses, especially the smaller ones.

This is one of the most popular steel roof truss types and it is quite economical. This particular type of truss offers some interesting features mainly thanks to the fact that the vertical members provide tension, while the diagonal ones are bringing in compression. The Queen Post Truss is designed to be a very reliable, simple and versatile type of roof truss that you can use at any given time. It offers a good span, around 10m, and it has a simple design which makes it perfect for a wide range of establishments.

This type of truss is a combination of steel and wood, which makes it elegant, while also offering a very appealing design. Almost everything is made out of wood, however, the tension members or the vertical members are manufactured out of steel in order to offer extra support and reliability!

One thing that makes the Howe Truss extraordinary is the fact that it has a very wide span, as it can cover anything from m. This makes it versatile and very useful for a wide range of project types. In this particular situation, the trusses form a fink roof truss. On top of that, the main characteristic here is that the top chords are split into smaller lengths, as this allows the build to obtain purlin support.

Also, you get a medium span with this type, around m, which is more than enough for most projects. The North Light Roof Truss is suitable for the larger spans that go over 20m and get up to 30m. This method is one of the oldest, as well as most economical ones that you can find on the market, as it allows you to bring in proper ventilation.

Plus, the roof has more resistance too because of that. If you are looking for types of roof trusses design that bring in durability and versatility, this is a very good one to check out.