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 to function as a composite section is covered in Chapter 8 and the in-plane racking strength of a wall is addressed in Chapter 7. Design guidance on how to calculate the lateral deflection of walls under combined out of plane bending and axial load is given in this chapter. Examples of stud walls during construction are shown in Figure 5.15.

5.5.1 Design of load-bearing walls

This covers the design of walls subjected to axial stresses as well as a combination of axial stress and bending stress due to the effect of out of plane actions (e.g. wind loading).

In general, load-bearing walls in timber-framed buildings are constructed using vertical timber members spaced at regular intervals and secured at their ends to continuous timber header and sole plates, as shown in Figure 5.16.

both edges

Fig. 5.16. Details of a typical stud wall (insulation, breather membrane, etc. not shown).

both edges

Fig. 5.16. Details of a typical stud wall (insulation, breather membrane, etc. not shown).

The vertical timbers are generally called studs and the walls are commonly referred to as stud walls. The studs are aligned so that the stronger axis (y-y) is parallel to the face of the wall and are secured in position by the header and sole plates, as shown in Figure 5.17. In-plane restraint is provided by battens that are prevented from moving laterally by diagonal or equivalent bracing members and that function during construction as well as for persistent design situations. If the wall sheathing cannot provide adequate lateral resistance, provided diagonal or equivalent bracing is used, the effective length of the stud about the z-z axis will be based on the greatest length of stud between the plate and the batten support. Where the sheathing material is able to provide adequate lateral restraint, the risk of buckling of the studs about the z-z axis can be ignored. Adequate lateral resistance will be provided by the sheathing material, provided it is secured to the studs and plates in accordance with the manufacturer's fixing recommendations or as required by the design. If sheathing is only fixed to one side of the wall, the studs will not be fully restrained laterally and a reduced effective length should be used.

It is unlikely that stud walls will have any degree of fixity at their ends and, for out of plane buckling about the y-y axis, the studs are considered to be effectively held in position and torsionally restrained by the fixings to the header and sole plates but are free to rotate laterally at these positions. The effective length of the stud about this axis is taken to equal the height of the stud wall.

Header plate

0 0

Post a comment