Eob

Where Nd is the design axial load and A is the cross-sectional area of the member. Cj0jd is the design compressive strength parallel to the grain and where kmod is the modification factor for load duration and service classes as given in Table 2.4 ksys is a strength factor for load-sharing systems. When dealing with single column members this factor is not relevant and is taken to be unity ym is the partial coefficient for material properties, given in Table 2.6 c> 0jk is the characteristic...

Jph

Different types of rotational stiffness, k, in a timber connection. structures but to a lesser degree in timber structures, is to represent the rotational stiffness of each connection by a spring. Where the rotational stiffness varies, an iteration procedure has to be incorporated into the analysis to take account of the non-linear behaviour. However, where the rotational stiffness can be considered to be linear this procedure is not required. As stated in 10.10 and 11.8, in EC5 the...

Bending Stiffness Of Builtup Columns

In Chapter 5 it is shown that when dealing with solid section columns, for normal design situations the design strength will generally be determined by the buckling strength of the member. This is also the case for columns made from built-up sections. With built-up sections, however, the determination of the buckling strength is a more involved exercise, because of the following reasons Materials having different properties can be combined. There will be slip within the section when mechanical...

Combined Axial Loading And Moment

Whether a built-up column is formed by gluing or by mechanical fixings, the design procedure is only applicable where the column is subjected to axial loading acting through the centre of gravity of the built-up section and to the cases where there are only small moments (e.g. due to self-weight) in addition to the axial loading. Under such conditions, the design requirements for built-up columns are the same as those for solid sections detailed in 5.4.1(b). Because of the small moment...

Def

ser.fin (EC5, equation (2.12)) (2.40) where the functions are as previously defined and f 2 is the factor for the quasipermanent value of the action causing the largest stress in relation to the strength. If this is a permanent action, a value of 1 should be used. If the determination of f 2 is assessed to be a complicated or difficult exercise, a safe result will be obtained by adopting a value of 1 for the factor (see Table 2.2 for the value of f 2). (c) When undertaking a second-order...

Design Of Glued Composite Sections

Because these sections are designed to function as solid units, the strain is taken to vary linearly over their depth. However, as the value of the modulus of elasticity, E, of each material in the section will normally be different, the theory of bending cannot be directly applied. To analyse these sections the equivalent section approach (sometimes referred to as the modular ratio approach) can be is adopted and has been incorporated into the design procedure used in this chapter. In this...

Design Of Members Subjected To Axial Actions

5.3.1 Members subjected to axial compression These are members that are subjected to a compressive action acting parallel to the grain and along the centroidal x-x axis of the member, as shown in Figure 5.2. Such members function as columns, posts, stud members in walls or struts in pin jointed trusses. When a member is subjected to axial compression its failure strength is dependent on several factors strength stiffness - compressive strength and modulus of elasticity of the timber geometry of...

Design Of Stud Walls

In timber frame construction, the main functions of walls are to provide vertical support for floor and roof structures and strength and stability against the effects of lateral loading, generally caused by wind actions. The design of walls subjected to vertical loading and out of plane lateral actions, and where the sheathing is not designed to function compositely with the wall studs, is addressed in this chapter. The strength of stud walling in which the sheathing and the studs are designed...

Design Value Of The Effect Of Actions

To verify the ultimate and serviceability limit states, each design effect has to be checked and for each effect the largest value caused by the relevant combination of actions must be used. In the case of the ultimate limit states, the largest values will be derived from the application of the fundamental combination of actions referred to in 2.2.24 and given in Table 2.8. Where accidental situations have to be designed for, the combination of actions given in Table 2.9 must also be used. For...

Bwz

(b) At the condition associated with the final mean value of stiffness (i) where the permanent action produces the design condition Aef,fin Af + (Epa- ) ( ) Aw (7.5) Emeanw ( 1 + kdef,f Ief,fin If + - M - Iw (7.6) (ii) where a variable action condition Qi produces the design condition Aef,fin Af + ( ) ( 1 ++ ldef,f ) Aw (7.7) ( -Emean X ( 1 + f 2,ikdef,f . (78) ef,fin if + - 77 --- I lw ( .8) V Emean,f 1 + f 2,i& def,v Here the symbols are as previously defined and Af is the total flange...

Eurocodes General Structure

Eurocodes form a set of documents that will enable building and civil engineering structures to be designed to common standards across the European Union using different structural materials. The documents are structured on a hierarchical basis, led by EN 1990, Eurocode - Basis of structural design, defining the basis of structural design, followed by EN 1991, Eurocode 1 Actions on structures, which comprises ten parts, defining the actions that have to be withstood. These documents are...

Examples

To be able to validate that the critical design effect of actions is being used, the design effects arising from all possible load combinations have to be investigated as part of the design process. Example 4.8.1 is given to show the load cases that have to be investigated in the case of a simply supported beam subjected to a permanent and a variable action. In the remaining examples, unless otherwise stated, only the load combination(s) giving the greatest design effects have been considered,...

Wxk

(a) Typical nailed screwed connection (b) Typical bolted connection Fmax is the maximum load taken by the connection ulnst is the instantaneous slip at the SLS. Fig. 10.22. Typical instantaneous load-slip behaviour of a metal dowel fastener connections. type being used, and typical load-slip curves for a nailed or screwed connection and for a bolted connection are shown in Figure 10.22. With bolts, because of the tolerance required to enable the bolt to be fitted and the bedding in process of...

Fh rfTNmm

Smooth round nails (EC5, equation (8.14)) Square nails (EC5, equation (8.14)) Smooth shank screws with a smooth shank diameter d < 6 mm Smooth shank screws with smooth shank diameter d > 6 mm d is the diameter of the nail, bolt, staple or dowel (in mm). For staples with rectangular sections, d is the square root of the product of the leg dimensions and for screws d is the effective diameter referred to in Table 10.3. fu is the tensile strength of the nail wire (or screw material) (in N...

Fig Ea

Thickness of each plywood gusset plate, tp Cross-sectional area of member 1, A1 Cross-sectional area of member 2, A2 A1 h1 tt A2 h2 tt d 3.0mm dh 2.25 d Minimum penetration of nail in inner member, ipoint.pen (10.3.5.1(1) (EC5, 8.3.1.2(1))) Minimum nail penetration criteria met Table 1.3, strength class C18 (BS EN 338 2003(E), Table 1) Characteristic density of the timber, pk pk 320 kg m3 Table 1.9, 12-mm-thick Finnish birch plywood Characteristic tensile strength at 90 to the face grain...

Fig Eb

Example 10.13.3 The five-member single-bolt (12 mm diameter) joint of a truss functioning in service class 2 conditions and supporting medium-term variable loading is shown in Figure E10.13.3. All members are 150 mm wide C18 timber to BS EN 338 2003 and the member thicknesses are as detailed below. The design forces in the members are a combination of permanent and medium-term variable actions. Check that the joint complies with the design requirements of EC5. (There is no requirement to check...

Frame Analysis Incorporating The Effect Of Lateral Movement In Metal Dowel Fastener Connections

In 10.10 the stiffness of connections at the SLS and the ULS are defined and a method for determining the displacement at the connection when it is subjected to a lateral load is also given. The displacement effect caused by slip in connections in a structure must be taken into account in any displacement analysis of the structure. Unless the structure is statically determinate, the slip at the connections will also affect the stress distribution around the structure and this must also be taken...

Info

Note For strength-related calculations, take Gg,05 E0,g,05 16. Mean density is taken to be the average of the mean density of the inner and outer laminates, based on BS EN 338. * Based on the properties given in BS EN 1194 1999. Note For strength-related calculations, take Gg,05 E0,g,05 16. Mean density is taken to be the average of the mean density of the inner and outer laminates, based on BS EN 338. * Based on the properties given in BS EN 1194 1999. In BS EN 1194 examples are given of beam...

Info Tse

Equation (5.23) is valid for the condition where lateral torsional buckling will not occur, i.e. A.rel,m < 0.75, at which crit 1. For this situation the boundary condition for equation (5.23), based on the use of solid timber, LVL (or glulam) rectangular sections, will be as defined by the solid line in Figure 5.13. Where the relative slenderness ratio for bending exceeds 0.75, the EC5 strength criteria will be as given in 5.4.2. 5.4.2 Lateral torsional instability under the effect of bending...

K

Bnet bw d dc de h,i,k ax,k c,0,d c,w,d c,f,d m,k m.y.d m,z,d in, a,d p,osb,c Design racking capacity of a wall diaphragm Design value of a material strength property Characteristic value of a material strength property Spacing, parallel to the grain, of fasteners within one row Spacing, perpendicular to the grain, between rows of Distance between fasteners at an unloaded end Distance between fasteners at a loaded end Distance between fasteners at an unloaded edge Distance between fasteners at a...

L

Compressive strength of a member loaded at an angle a to the grain. 5.3.3 Members subjected to axial tension These are members that are subjected to a tensile action acting parallel to the grain and through the centroidal x-x axis of the member as shown in Figure 5.8. Such members function as ties in pin jointed trusses and provide tensile resistance to overturning forces in stud walls. Although the tensile strength, t,0,k, of clear wood samples is greater than the compression...

Loaded at an angle to the grain

When connectors are laterally loaded at an angle to the grain, the force components parallel and perpendicular to the grain have to be derived, and (i) the component of the design force acting parallel to the grain must not exceed the load-carrying capacity of the connection determined as defined in 11.8.1, and (ii) the component of the design force acting perpendicular to the grain must not exceed the lesser of load-carrying capacity of the connection determined as defined of the load-carrying...

Loaded parallel to the grain

The design strength of a laterally loaded single connector, Fv Rd, is obtained from the characteristic load-carrying capacity of the laterally loaded connector as follows kmod is the modification factor referred to in 2.2.20, and where the connection comprises two timber elements, kmod,1 and kmod,2, the value used in the equation will be kmod k mod, 1 kmod ,2, as required by EC5, equation (2.6). km is the partial factor for connections given in Table 2.6. Except when determining the plate...

Moment Behaviour In Timber Connections Rigid Model Behaviour

Validation of the strength of a connection required to transfer a moment in a structure is undertaken in two stages. There is the analysis of the structure to determine the stress resultants the connection will be subjected to and this is followed by the design procedure to demonstrate that the connection is strong enough to resist these forces. Unless a structure is statically determinate, depending on whether connections behave in a rigid or a semi-rigid manner, the force distribution in a...

Multiple Shear Plane Connections

Where a connection involves multiple shear planes and the connected members are at varying angles to each other, it is not possible to directly apply the joint strength equations given in Tables 10.2 and 10.3. For such situations, the guidance in EC5, 8.1.3(1), is that the resistance of each shear plane is derived on the assumption that the shear plane in the connection forms part of a series of three-member connections and the connection strength is derived by combining the strength values of...

N N

Stiffness of each elastic supports C span a t m, where m is the number of supported elements along the member length span a t m, where m is the number of supported elements along the member length Fig. 9.3. Plan view on the lateral buckling modes of an elastically supported member. Fig. 9.3. Plan view on the lateral buckling modes of an elastically supported member. 9.3.2 Bracing of single members (subjected to direct compression) by local support The method detailed in 9.2.5.2 of EC5 is...

Pa p p

The characteristic lateral resistance per shear plane per nail will be Fv.Rk min(Fv.Rk.a, Fv.Rk.b, Fv.Rk.c, Fv.Rk.d, Fv.Rk.e, Fv.Rk.f, Fv.Rk.dd) Fv.Rk 764 N The design resistance per nail per Fv Rd shear plane, Fv Rd Number of nails for member 1 connection per shear plane Number of nails required per Mnaiis side, Mnails For a symmetrical nailing pattern N1nails ceil(N1nails) adopt 2 nails per side Number of nails for member 2 connection per shear plane Number of nails required per side, N2naUs...

Plywood

Plywood is a flat panel made by bonding together, and under pressure, a number of thin layers of veneer, often referred to as plies (or laminates). Plywood was the first type of EWP to be invented. Logs are debarked and steamed or heated in hot water for about 24 hours. They are then rotary-peeled into veneers of 2-4 mm in thickness and clipped into sheets of some 2 m wide. After kiln-drying and gluing, the veneers are laid up with the grain perpendicular to one another and bonded under...

Preservative Treatment For Timber

Under ideal conditions timber should not deteriorate, but when timber is used in exposed (outdoor) conditions, it becomes susceptible to degradation due to a variety of natural causes. It will suffer rot and insect attack unless it is naturally durable or is protected by a preservative. In general, timber with a moisture content of over 20 is susceptible to fungal decay timber of any species kept in dry conditions will remain sound however, dry timber may be subjected to insect attack. Timber...

References

Structural Wood Design. West Publishing Company, St Paul, MN, 1990. 2 Illston, J.M. Construction Materials - Their Nature and Behaviour. E& FN Spon, London, 1994. 3 BS 5359. Nomenclature of Commercial Timbers Including Sources of Supply. British Standards Institution, London, 1991. 4 Johansson, C.J. Grading of timber with respect to mechanical properties. In Thelandersson, S., Larsen, H.J. (eds), Timber Engineering. Wiley, London, 2003. 5 Hoffmeyer, P. Wood as a Building...

Stiffness Behaviour Of Toothedplate Ring And Shearplate Connectors

The lateral stiffness of toothed-plate, split-ring and shear-plate connectors is determined in the same way as discussed in 10.10 for metal dowel type fasteners. The content of 10.10 is applicable to connections formed using these types of connector and although some matters of detail have been repeated in the following paragraphs for clarity, generally the content relates to areas where differences arise. The slip modulus Kser per shear plane per connector at the serviceability limit state is...

Suspended Timber Flooring

A suspended flooring system generally comprises a series of joists closely spaced, being either simply supported at their ends or continuous over load-bearing partition walls. The floor boarding or decking is applied on the top of the joists and underneath ceiling linings are fixed. A typical suspended floor arrangement is shown in Figure 1.18a. The distance between the centres of the joists is normally governed by the size of the decking and ceiling boards, which are normally available in...

The Analysis Of Structures With Semirigid Connections

If the connections in a statically indeterminate structure exhibit semi-rigid rather than fully fixed rotational behaviour, there will be a reduction in the stiffness of the structure leading to smaller moments at connections, an increase in member span moments and an increase in those displacements that are affected by the moment distribution in the structure. By taking the effect of semi-rigidity into account, in the analysis process a more realistic assessment of the moment distribution and...

The Effective Number Of Fasteners In A Row In A Moment Connection

When a connection is subjected to a moment the direction of the force in each fastener in the connection will vary and where the fastener configuration is such that (a) no row exists where a force component from two or more fasteners in the row is parallel to the grain in any of the connected members, (b) or there are rows where the above situation will arise but the spacing between the fasteners parallel to the member grain complies with the criteria given in Table 12.2, the full number of...

The Structure Of Timber

Structural timber is sawn (milled) from the trunk of the tree, which provides rigidity, mechanical strength and height to maintain the crown. Trunk resists loads due to gravity and wind acting on the tree and also provides for the transport of water and minerals from the tree roots to the crown. Roots, by spreading through the soil and acting as a foundation, absorb moisture-containing minerals from the soil and transfer them via the trunk to the crown. Crown, comprising branches and twigs to...

What Is Mathcad

Mathcad (developed by MathSoft Engineering and Education Inc.) 1 is an electronic notepad (live worksheet) that allows mathematical calculations to be performed on a computer screen in a format similar to the way it would be carried out for hand calculations. While Mathcad employs the usual mathematical symbols (i.e. +, -, , ), for algebraic operations it also uses the conventional symbols of calculus for differentiation and integration to perform these operations. It preserves the conventional...

Y I

Forces in a row of fasteners in a connection subjected to combined moment and lateral loading. Fig. 12.10. Forces in a row of fasteners in a connection subjected to combined moment and lateral loading. The capacity of each fastener in the row, Fv d, will be nef k mod Fv,Rk nais Fv,d - ' --(IZ.JI) where the symbols are as previously defined and Fv Rk is the characteristic load-carrying capacity of the fastener, derived as described in Chapters 10 and 11 for metal dowel type fasteners...

Strength behaviour

Ring and shear-plate connectors are circular in shape and manufactured from aluminium alloy, hot rolled or temper rolled steel strip, hot rolled steel alloy strip, grey cast iron or cast metal, in accordance with the requirements of BS EN 912. They fit into preformed grooves in the timber members that accurately profile the connector and are capable of taking much greater loads than are achievable with toothed-plate connectors. The strength equations for these types of connectors are given in...

Structural Timber Design Examples

As stated in 4.3, Chapter 4, in order to verify the ultimate and serviceability limit states, each design effect has to be checked and for each effect the largest value caused by the relevant combination of actions must be used. However, to ensure attention is primarily focussed on the EC5 design rules for the timber or wood product being used, only the design load case producing the largest design effect has generally been given or evaluated in the following examples. Example 6.7.1 A series of...

Axial Loading Of Metal Dowel Connection Systems

Perpendicular Grain

The strength equations given in the following sub-sections assume that the tensile strength of fasteners will always exceed their withdrawal capacity from the connection. If, however, there is a need to evaluate the tensile strength of the fastener, it should be carried out in accordance with the requirements of EN 1993-1-1. The withdrawal capacity of nails loaded axially is dependent on the type of nail being used. Smooth round wire nails give the poorest result and with threaded nails the...

Fhk

In deriving these equations, friction forces between the members of the connection are ignored as well as the withdrawal resistance of the fasteners. In EC5 the Johansen yield equations form the basis of the strength equations, however for those failure modes that involve yielding of the fastener, the equations have been modified to include for friction and withdrawal effects. There are two types of friction effects that can arise in a connection. One will develop if the members are in contact...

N I

Medium duration variable loading acting downwards on the beam, Qk.1 Instantaneous duration variable loading acting upwards on the beam, Qk.2 Table 2.2, f values UKNA to EN 1990 2002 TableNA.Al.1 Factor for the combination value of medium duration f01 0.7 Factor for the combination value of wind action Qk 2, f0 2 f0 2 0.5 a Partial factors for equilibrium ULS Table 2.8, equation EQU a UKNA to EN 1990 2002 TableNA.A1.2 A For permanent favourable actions, yG.e yG.e 0.9 For variable unfavourable...

Timber Tension Member Design

As stated in 4.3, in order to verify the ultimate and serviceability limit states, each design effect has to be checked and for each effect the largest value caused by the relevant combination of actions must be used. However, to ensure attention is primarily focussed on the EC5 design rules for the timber or wood product being used, only the design load case producing the largest design effect has generally been given or evaluated in the following examples. Example 10.13.1 A timber-to-timber...

Table 8.6 In Ec5

In the draft proposal, the content of Table 8.6 in EC5 is to be altered and the minimum end and edge distances are to be based on the distance to the centre of gravity of the threaded part of the screw in the relevant member. Providing the timber thickness is gt 12 d, where d is the screw diameter, for joints formed as indicated in Figure C2, the minimum spacings, edge and end distances are to be as follows Minimum screw spacing in a plane parallel to the grain, a1 5d. Minimum screw spacing...

The Inplane Racking Resistance Of Timber Walls Under Horizontal And Vertical Loading

The stud walls associated with timber-framed buildings are usually sheathed on one or both faces with the sheathing securely fixed to the studs, enabling the wall to act as a rigid diaphragm. The fixings e.g. nails provide the bulk of the racking resistance through timber bearing and nail deformation when the lateral external force is applied as shown in Figure 9.8b. Horizontal sliding of the wall is resisted by anchorages such as nails or bolts along the sole plate sufficient to resist the...