Performance of light-gauge cold-formed steel strap-braced stud walls subjected to cyclic loading

doi:10.1016/j.engstruct.2008.07.016

Engineering Structures

Volume 31, Issue 1, January 2009, Pages 69-83

https://doi.org/10.1016/j.engstruct.2008.07.016 Get rights and content

Abstract

The performance of cold-formed steel (CFS) strap-braced walls is evaluated by experimental tests on full-scale 2.4 m×2.4 m specimens, and techniques to improve their behavior are presented. Different strap arrangements have been introduced, and their performance investigated by means of cyclic loading of a total of twenty full-scale walls. Several factors affecting the performance of cold-formed steel frame shear wall have been considered for each arrangement. This paper presents the failure modes of each system and the main factors contributing to the ductile response of the CFS walls to ensure that the diagonal straps yield and respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud failure. Discussion of the advantages and disadvantages of including the non-structural gypsum board on lateral performance of the walls is also presented.

Introduction

There has been a steady growth in the use of cold-formed steel frames in the residential construction market in Australia in the last two decades. The advantages of cold-formed steel, such as being dimensionally stable, non-combustible, termite and borer proof, durable, lightweight and 100% recyclable, are probably important reasons for this increase in use, as is the increased public awareness and the efforts of supporting organizations such as the National Association of Steel-framed Housing Inc. (NASH). In addition to being a medium for providing information about steel framing to the public, NASH has taken significant steps towards developing more elaborate national standards on cold-formed steel framing.

NASH issued ‘Structural Performance Requirements for Domestic Steel Framing’ in 1991. This provided the first documented guidance in Australia on the structural design of a steel-framed house (in both Allowable Working Stress and Limit States Design). This document was converted into the Australian Standard ‘AS 3623-1993 Domestic Metal Framing’. In 2005, NASH prepared a completely new standard known as ‘NASH Standard Residential and Low-rise Steel Framing Part 1: Design Criteria’, which is referenced in the Building Code of Australia (BCA) and has recently released a draft of the NASH Handbook on Low-rise Steel Framing for public review. Despite significant efforts by NASH, Australian guidelines are far from complete, particularly when it comes to bracing requirements in earthquake-prone regions. As Australian companies are trying to enter potential markets outside Australia, it has become even more important that these guidelines be developed, since many of these markets are located in earthquake-prone regions.

The current research is a starting point in that direction, aiming to experimentally evaluate the cyclic load response of steel braces currently used in Australia and to suggest possible alternative improved methods. In what follows, a review of some of the more notable codes is presented, followed by a review of past studies in this area. Then the current testing program and its results are presented together with suggestions for improving the strap-bracing systems.

Section snippets

Code provisions

Although CFS walls are not new and have been used as non-structural partitions for many decades [2], their application as main structural load-bearing components of frames is fairly new. As a result, the standards that cover appropriate detailing of these systems are yet to be perfected. Some of the more important code provisions are reviewed below.

Past studies

Although in recent years there have been many studies on CFS wall studs with diagonal straps, research on the performance of seismically designed walls has been fairly limited. Adham et al. [15] provided 5 cyclic loading tests of a 2.44 m by 2.44 m CFS shear panel with back-to-back double studs at ends which were sheathed with diagonal straps and gypsum board. Two hold-downs, one at each end, were bolted to the testing rig at the base to prevent specimens from horizontal slide or uplift at the

Experimental program

As mentioned, an experimental program was designed to provide information on the failure modes of walls braced with different types of strap braces and to study the effects of various parameters on the vertical and lateral performance of cold-formed steel (CFS) shear panels subjected to cyclic loads. While conventional strap bracing and conventional connections to studs and top track were used, the following effects were studied.

•
the effect of vertical load on the lateral response,
•
the effect of

Test setup

The tests were performed at the Structural Engineering Laboratory of the University of Queensland using an actuator. Experiments were conducted using a displacement control regime, measuring the shear capacity of the wall at every load interval via a load cell. The testing rig was set up to allow the application of concurrent vertical load and lateral cyclic displacement (Fig. 8).

Experimental results

The first test was devoted to evaluating the performance of the wall panel with gypsum board without strap bracing (specimen BA1). Because of the presence of hinged rivet connections, the wall itself acts like a mechanism and can barely resist any lateral load on its own. As a result, the racking resistance of this wall can only be attributed to the gypsum board on one side. The load–deflection hysteretic cycles for this specimen are shown in Fig. 9(a) and the maximum load (envelope) associated

Discussion and comparison

The response of some of the aforementioned wall panels is shown in Fig. 14. This graph shows that the response of strap type I (AC1) is unacceptable. The benefit of non-structural gypsum board cladding on the lateral performance of strap-braced wall panels is evident in the response of walls AB1 and CB1, and can even be seen in strap type I. However, the benefits are mostly on the lateral resistance capacity and ductility, and the stiffness is not influenced significantly.

Strap types II, III

Conclusion and recommendations

The following conclusions can be made from the findings:

1. Specimens BA1 and AA1 showed that reliance on gypsum board cladding alone is not a good idea, especially in the presence of a compressive vertical load. This is despite the fact that gypsum board helps in improving the racking resistance of wall panels to some extent and delays the distortional buckling of studs and chord members, as was seen in the testing of specimens AB1 and CB1. These tests showed that a strap-braced wall panel clad

Acknowledgements

The materials for this research were donated by Quick Frame Technology P/L, Brisbane. This support is gratefully acknowledged. Special thanks for their contributions throughout the project goes to Dr Sh. Hatami (Visiting Fellow), K. Clark, F. Reid, P. Pezzopane, P. McMillan (Lab staff), and many of the Civil Engineering thesis undergraduate and graduate students who worked on this project.

References (18)

L.A. Fulop et al.
Performance of wall-stud cold-formed shear panels under monotonic and cyclic loading. Part I: Experimental research
Thin Walled Structures
(2004)
T.W. Kim et al.
Shake table tests of cold-formed steel shear panel
J Eng Struct
(2006)
M. Al-Kharat et al.
Inelastic performance of cold-formed steel strap braced walls
J Construct Steel Res
(2007)
FEMA 450. NEHRP recommendation provisions for seismic regulations for new buildings and other structures, 2003 edition....
TI 809-07. Technical instructions: Design of cold-formed load bearing steel systems and masonry veneer/steel stud...
SEI/ASCE 7-02. Minimum design loads for buildings and other structures. Reston (VA, USA): American Society of Civil...
FEMA 302. NEHRP recommendation provisions for seismic regulations for new buildings and other structures, 1997 edition....
AISI. North American Specification for the Design of Cold-Formed Steel Structural Members. Washington (DC, USA):...
AISI. Standard for cold-formed steel framing— General provisions. Washington (DC, USA): American Iron and Steel...

There are more references available in the full text version of this article.

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