DETERMINATION OF THE LATERAL STRENGTH OF SHEAR WALL PANELS. WITH COLD-FORMED STEEL FRAMES
Joel Martinez1 and Lei Xu
Department of Civil Engineering, University of Waterloo
Waterloo, Ont., Canada N2L 3G1
In current construction practice, lateral strengths of shear wall panels with cold formed steel framing are primarily determined by tests owing to the lack of analytical methods. Meanwhile, the use of numerical methods such as the finite element method has been limited to researchers investigating the behaviour of SWP. Moreover, the finite element method has rarely been employed in design practice to determine the lateral strength of shear wall panels because the modelling is cumbersome. Presented in this paper is an analytical method to determine the ultimate lateral strength of shear wall panels. The method accounts for the factors that affect the behaviour and the strength of shear wall panels, such as material properties and thickness of sheathing, sizes of the C-shape steel studs, spacing of fasteners, and so on. Lateral strengths obtained from the proposed method for sheathing wall panels were compared with those of recent experimental investigations. The results of the comparison demonstrate that the predicted lateral strengths are in good agreement with those of the tests. Therefore, the proposed method is recommended for engineering practice.
Keywords: lateral strength, shear wall panels, cold formed steel framing.
In the search for new constructive methods and materials for low – and mid-rise residential buildings, where the quality of living, ease of construction, and cost-efficiency could be improved, cold formed steel (CFS) has been an attractive alternative to traditional materials such as timber. In cold formed steel framing construction, the shear wall panel (SWP) is one of the primary lateral load resisting systems, which has been extensively used in seismic applications in North America.
Typically, SWP in cold formed steel wall framing are constructed with vertically spaced and aligned C-shape cold formed steel studs. The ends of the studs are connected to bottom and top tracks of the wall. Sheathing may be present on either one or both sides of the wall with screw fasteners. In practice, studs are generally designed to support vertical loads, while sheathing is considered to resist lateral loads. However, the lateral strength of SWP cannot be determined alone by the strength of the sheathing, as the interaction among the sheathing, the studs, and the fasteners affect both the behaviour and lateral strength of SWP considerably. Generally, a SWP may experience both in-plane gravity and lateral loads as well as out-of-plane wind loads in the case of exterior walls. This study is focused on the evaluation of the lateral strength of SWP, which is the primary function of SWP. The strengths of SWP to resist in-plane gravity and out-ofplane loading are not considered.
To determine the behaviour and lateral strength of SWP, Serrette et al (1997, 2002) and Rogers et
al (2004a) have carried out extensive experimental investigations. Gad et al (1999) conducted the
1 Corresponding Author: j3martin@engmail. uwaterloo. ca
M. Pandey et al. (eds), Advances in Engineering Structures, Mechanics & Construction, 401-409. © 2006 Springer. Printed in the Netherlands.
finite element analysis on SWP, in which the studs and tracks were modelled by beam elements while sheathing was modelled with shell elements and sheathing-to-framing connections were modelled by nonlinear springs. Fulop and Dubina (2004b) conducted a series of tests and proposed a simplified model for determining the lateral strength of SWP based on replacing the sheathing with a pair of equivalent cross-bracing. A tri-linear force displacement relationship calibrated with test results was proposed for using the finite element method of analyzing SWP.
In practice, the lateral strengths of different SWP are available in the AISI design guideline (Brockenbrough, 1998) and standard (AISI, 2004). The values of the nominal lateral strengths of SWP presented in a tabulated form in the Lateral Design Standard of AISI (2004) are convenient to use and primarily determined on the basis of experimental tests, which provide an acceptable degree of confidence to the practitioners. However, as limited by the number of the tests being carried out, the freedom of selecting different sheathing materials, stud sizes and configurations of SWP is restricted as the tabulated values may not be applied or extended to SWP with different materials, configurations and construction details. Therefore, a reliable analytical method for determining the lateral strength of SWP is of importance to promoting cold formed steel framing technology.
Presented in this paper is an analytical method to determine the ultimate lateral strength of shear wall panels. This method accounts for the aspects that affect the behaviour and strengths of SWP associated with dimensions of the panel, material and cross-section properties of both sheathing and steel studs, and as well as the construction details such as the spacing of screw fasteners. The ultimate lateral strengths of different SWP are evaluated with the proposed method and the comparisons are made between the analytical results and the results obtained from recent experimental investigations (Serrette et al, 2002; Rogers et al 2004a; Fulop and Dubina 2004a).