Cold-formed Steel Framed Shear Walls Research Articles

Lateral performance of cold-formed steel framed shear walls using slitted sheathing with stiffeners

Cold-formed steel (CFS) framed shear walls with steel sheathing are promising lateral-force-resisting members of mid-rise buildings in seismic regions. Previous studies have demonstrated that steel sheathed CFS framed shear walls have high shear capacity but some shortcomings, such as the low ductility caused by the premature damage of the frame and the shear buckling of the sheathing. This paper presents an experimental study on a novel type of CFS framed shear wall with slitted steel sheathing (CFS-SSWs), which uses longitudinal slits to change the failure mode of the sheathing so that the ductility of the wall can be improved; Meanwhile, stiffeners are utilized to enhance the out-of-plane stability of the slitted sheathing and the integrity of the wall. Six full-scale CFS-SSW specimens were tested under monotonic and cyclic lateral loading. Three types of stiffening approaches (Type I, Type II and Type III) were adopted for the walls. Test results were analysed to investigate lateral performances of walls under different stiffener arrangements, including failure modes, load-displacement hysteresis curves, backbone curves, stiffness and strength degradation, and energy dissipation capacity. The measured strengths of the walls in the tests were assessed using theoretical indexes. It is found that peak loads and energy dissipation capacity of stiffened walls are noticeably higher than those of the unstiffened wall. Type II and Type III are effective stiffening approaches that could mitigate the buckling of the slitted sheathing and enable the links between the slits to reach the full plastic strength. By connecting the stiffeners and studs through stiffener connectors, Type III has the most significant enhancement on the stiffness, strength and ductility of the wall.

Cold-formed steel framed shear wall test database

Many monotonic and cyclic tests have been conducted on cold-formed steel framed shear walls in the last 20 years. Cold-formed steel framed shear wall provisions in AISI S240, AISI S400, and ASCE 41 are supported by the data obtained through these tests. The main objective of this article is to introduce a recently compiled cold-formed steel framed shear wall test database, to reveal the database structure, and to explain how to access and present the data. Most recently, the database has been standardized and expanded to include additional tests, complete cyclic information from tests, limit states, and code prediction information. The database structure incorporates a central Excel spreadsheet that includes descriptive information; ordered plain text files for each individual test; and custom MATLAB codes, which can read, process, and plot designated database subsets. The provided database can advance the understanding and modeling of cold-formed steel framed shear walls.

Shear behavior of gypsum boards sheathed CFS framed shear walls with enlarged edge members

This study investigates the influence of nonshear components on the shear performance of cold-formed steel (CFS) framed shear walls. Regarding the connection fields between nonshear components and shear walls as reinforced edge members (REMs), full-scale model tests of six gypsum board sheathed CFS framed shear walls were conducted with a focus on investigating the shear behavior of CFS framed shear walls with enlarged edge members. A numerical simulation method for predicting the shear performance of CFS framed shear walls with enlarged edge members was established and verified. The results show that, (1) After the “diaphragm effect” was weakened or even eliminated, the REMs still had the ability to resist the bending moment and shear force, preventing CFS structures from collapse. (2) The REMs (containing wing walls) changed the mechanical feature of CFS framed shear walls that depended only on the “diaphragm effect” to resist the shear force and transformed the wall’s plastic development mechanism, improving the energy dissipation capacity of the walls over four times. Such a “wing wall effect” should be considered when estimating the influence of nonshear components. (3) The recommended response modification factor should be increased by at least 1.3 times due to the REMs. (4) The relative errors between the simulated and test results were within 8%.

Behaviour of cold-formed steel framed shear walls with slitted sheathing under lateral loading

Cold-formed steel (CFS) framed shear walls (CFS-SWs) with steel sheathing have emerged as promising lateral-force-resisting members in mid-rise buildings of seismic regions. This paper presents a combined experimental and numerical study on a new type of steel sheathed CFS-SWs, whose novel feature is the use of central CFS sheathing with vertical slits. Five full-scale wall specimens were tested under monotonic and cyclic lateral loading to examine the performance of the shear walls. Then a finite element (FE) modelling of CFS-SWs with slitted steel sheathing was established and verified by the experimental data. Further analyses on the parametric effects and the load-carrying mechanism of CFS-SWs with slitted sheathing were conducted. It is found that the slitted sheathing alleviates the premature damage of boundary studs and mitigates the tremors as well as noises during the loading. The wall with slitted sheathing shows good ductility with a 22.84% higher ductility factor than the wall with non-slitted sheathing. The width-to-thickness ratio and the height-to-width ratio of the flexural links between the slits have considerable effects on the stiffness as well as the peak load of the wall. Lastly, the ultimate lateral resistance of CFS-SWs with slitted sheathing was estimated using a simplified method.

Quasi-static loading procedure of CFS framed shear walls considering ground motion duration

Cold-formed steel (CFS) structures framed with CFS framed shear walls exhibit clear characteristics of strength and stiffness degradation during seismic events, thus the influence of ground motion duration on their seismic responses should not be ignored. The purpose of this study is to construct a quasi-static loading procedure for CFS framed shear walls considering the effect of ground motion duration, which can help to acquire accurate shear performance of the walls and lay a foundation for evaluating the actual seismic performance of the structures. The main research contents and results are as follows: (1) sixty ground motions were selected and adjusted to be spectrally equivalent records, which ensured that the effect of the ground motion duration could be decoupled; (2) nonlinear time-history analysis of eight CFS framed shear wall models were performed, whereafter, considering the influences of both structural responses and the input energy of ground motions, a determination method for the number of loading cycles of the quasi-static loading procedure was proposed, and a prediction model for the number of loading cycles was established; (3) the influence of the amplitude distribution of the quasi-static loading procedure was analysed, and a value range of the amplitude distribution parameter was suggested. Finally, a method to construct the quasi-static loading procedure for CFS framed shear walls was formed and verified.

Evaluation of Seismic Deflection Amplification Factor for Buildings Utilizing Cold-Formed Steel–Framed Shear Walls

The seismic deflection amplification factor for a series of archetype buildings utilizing cold-formed steel–framed shear walls was investigated. A total of 118 archetype buildings were considered, of which 83 employed cold-formed steel–framed shear walls with steel sheet sheathing, and 35 employed wood structural panel sheathing. Using nonlinear equivalent single-degree-of-freedom (SDOF) models, nonlinear time-history analyses for the 118 archetype buildings subjected to the 44 FEMA P-695 earthquakes were conducted. In these SDOF models, the actual response of shear walls obtained from experimental studies was used to define the nonlinear material parameters. The AISI S400 deflection expression was evaluated using experimental data, and numerically predicted deflection amplification factors were calculated and compared against that recommended in current practice. The results show that current practice may overestimate expected deflections. To address this issue, and to simplify design, a linearization of the AISI S400 deflection expression is recommended. With appropriate choice of the force level, the linearized AISI S400 deflection expression leads to acceptable drift predictions with the currently employed deflection amplification factor.

Seismic performance cold-Formed steel framed shear walls using in-Frame corrugated steel sheathing

To meet the increasing demand for high strength and non-combustible shear wall systems in mid-rise cold-formed steel (CFS) constructions, this paper investigates the seismic performance and design method of an innovative CFS shear wall system with in-frame corrugated steel sheathing based on previous studies. Shear wall and bearing wall specimens with in-frame corrugated steel sheathing are tested under combined lateral and gravity loading. Simplified numerical models of whole archetype buildings are established. The seismic performance evaluation is performed using methodology recommended in FEMA P695 and the seismic performance factors are examined. The test results show that the shear strength of the innovative shear wall is much higher than currently code certified wood-based shear walls in AISI S400. Also, the shear strength of bearing walls is approximately one-third of the shear strength of shear walls, which proves that bearing walls also contribute significant shear resistance in a structure. The seismic performance evaluation results verified that the existing seismic performance factors (R = Cd = 6.5 and [Formula: see text] = 3.0) for CFS shear walls with flat steel sheathings can also be used for the innovative shear wall system. The innovative CFS shear wall system with in-frame corrugated steel sheathing could be employed for mid-rise buildings in areas that are prone to high seismic and wind loads.

Nonlinear Seismic Analysis of Perforated cold-formed steel shear wall with Upright Section

During the last few decades, cold-formed steel (CFS) is extensively used in mid- and low-rise housing due to the increasing demand of rapid constructions along with its various advantages in comparison with other structural material. Cold-formed steel framed shear walls (CFSFSW) are most common and primary lateral load resisting system. However, adopting it in the seismic zone is difficult, especially because many design components remain open. In this research an effort has been made to design the shear wall system with both unperforated and perforated upright sections using nonlinear static analysis method. In ABAQUS, a general-purpose finite element analysis software, three-dimensional models using shell elements are used to simulate a shear wall system. A comparative study regarding the lateral load capacities with respect to maximum allowable lateral deflection including different parameters like column sections, thickness and perforation arrangements are presented here. It was found that increasing thickness and including Chanel stiffeners improves the lateral strength of original upright section. The developed modelling protocol helps to estimate its lateral performance under earthquake with reasonable accuracy.

Investigation of the effect of modular construction details on the lateral behaviour of cold-formed steel framed shear walls

This paper investigates the effect of modular construction details on laterally-loaded cold-formed steel (CFS) framed shear walls sheathed with wood- and cement-based panels by means of finite-element (FE) analyses. Shell FE-based models have been developed in ABAQUS with the aim of accurately capturing the behaviour, strength and stiffness as well as the corresponding failure modes of CFS framed shear walls subjected to monotonic lateral load (i.e., wind). User-defined element subroutines were adopted for precise modelling of sheathing-to-CFS screws shear behaviour. The proposed modelling protocol is validated using experimental test results, where an acceptable concordance (4% difference) has been achieved. Subsequently, the effect of modular construction details, which go beyond the scope of the current lateral design provisions (AISI S400), on the lateral behaviour of CFS framed shear walls is assessed. In particular, this paper investigates the impact of: (i) floor and ceiling ledger beams on the interior face of the shear wall, (ii) sheathing boards having different sizes from the overall shear wall and thus the presence of both vertical and horizontal seams, (iii) cement particle boards at the bottom stripe of the shear wall and (iv) different screw spacing in the top and bottom stripes from the middle part of the shear wall. The key parameters, which have most affected the lateral behaviour, were identified, and based on that, rules have been established for optimizing the screws pattern and sheathings layout efficacy in the above-described lateral load resisting system. The obtained results shed light on the capability of the developed modelling protocol to be used as a virtual test bench, particularly in offsite mass production and manufacture (DfMA), for the development of a new CFS framed wall system for lateral stability of lightweight modular houses.

Numerical investigation into the performance of cold-formed steel framed shear walls with openings under in-plane lateral loads

Recently, there has been a resurgence in the adoption of lightweight cold-formed steel (CFS) profiles as structural elements in low- to mid-rise modular construction. Typically, openings for doors and windows are ever-present in the front and rear elevations where shear walls find their optimal position to ensure lateral stability in CFS modular structures. These architectural design features translate into reduced areas for lateral load resistance throughout the structure. This paper discusses the performance of CFS framed shear walls with openings under lateral loads through experimental tests and numerical simulations. Overall, three shear wall typologies were designed for force transfer around opening (FTAO) and tested under monotonic lateral loads (nine tests in total). An advanced finite element analysis (FEA) modelling protocol was elaborated to simulate the lateral behaviour of the tested walls as well as to interpret the physical tests. Evaluation of the numerical and experimental test results validated the FEA modelling protocol that demonstrated to be reliable in predicting the strength and stiffness as well as failure modes of CFS framed shear walls with openings subjected to lateral loads. The effects of sheathing-to-CFS screw spacing, the size and number of openings as well as the geometry of sheathing panels on the lateral behaviour of CFS framed shear walls were scrutinized. Subsequently, load-path mappings from the developed modelling protocol enabled the analysis of the flow of the in-plane lateral loads from the sheathing-to-CFS screw level into the wall system level where insight into a more efficient lateral design of CFS framed shear walls with openings have been highlighted. The obtained results shed light on the conservative nature of the AISI S400-15 design provisions for Type II shear walls and that of the perforated design methods available in the literature.

Cold-Formed Steel Framed Shear Walls with In-Frame Corrugated Steel Sheathing

AbstractThis paper presents the experimental results of an innovative configuration for cold-formed steel (CFS) framed shear walls using corrugated steel sheets as sheathing material. The shear wal...

Updated seismic fragility functions for cold-formed steel framed shear walls per FEMA P-58 methodology

Performance-based earthquake engineering (PBEE) provides a robust alternative to traditional earthquake design. PBEE enables engineers to estimate expected damage, repair costs, and economic losses due to downtime for a candidate design, potentially leading to novel new designs or retrofit solutions. With the increasing application of light-frame structural systems, such as cold-formed steel (CFS) panels, in residential and commercial construction, it is necessary to develop and employ fragility functions for these systems to enable PBEE. In this regard, a set of fragility functions was previously developed by researchers based on a series of monotonic and cyclic tests for CFS framed shear walls with wood structural panel sheathing, flat strap X-bracing, and steel sheet sheathing. Recently, the senior author has led in the development of a large database of CFS framed shear wall tests, including 617 monotonic and cyclic tests conducted in the last 20 years from 25 primary sources. Based on the wider database, the fragility functions for CFS framed shear walls are re-evaluated. The developed fragility functions provide updated knowledge for application of PBEE per the FEMA P-58 methodology and are recommended for future use.

High-strength cold-formed steel framed shear wall with steel sheet sheathing

The North American specifications for the design of cold-formed steel (CFS) framed shear walls (CFS-SSSW) with steel sheet sheathing provides tabulated values and equations for determining the shear strength when the thickness of frame is between 0.838 mm and 1.370 mm. At present, high-strength CFS framed shear walls with steel sheet sheathing can be needed in mid-rise construction, particularly in the seismic area. A research project was recently completed to improve the shear capacity for CFS framed shear walls with steel sheet sheathing by two methods: (1) thicker studs, tracks and blockings (thickness: 1.727 mm), (2) more sheathing screws (screws spacing: 50.8 mm). This paper presents the findings on the shear strength for high-strength CFS framed shear walls with steel sheet sheathing. Ten full-scale shear wall specimens with aspect ratios of 2:1 were tested, including four different shear wall configurations and two test methods. This paper details the test methods, specimen configurations, the test results, and provides the nominal shear strength values for the high-strength CFS framed shear walls with steel sheet sheathing. Additionally, the applicability of the effective strip method in the high-strength CFS framed shear walls with steel sheet sheathing is analyzed.

STUDY ON THE MECHANICAL PROPERTIES OF COLD-FORMED STEEL FRAMED SHEAR WALL WITH SLITS

In order to study the mechanical behavior of the cold-formed steel framed shear wall with slits (CFS-WS) which is suitable for low-rise and multi-story cold-formed thin-walled steel buildings, pseudo-static tests of 1 ordinary CFS-WS and 3 buckling-restrained CFS-WS were conducted to gain the mechanical properties of CFS-WS, including the failure modes, load-displacement hysteresis curves, skeleton curves and energy dissipation capacities, and the design value of shear capacity was put forward. The test results indicates that the CFS-WS relies on the torsion-recovery-reverse torsion of steel plate between vertical slits and the deformation of the steel frame to resist horizontal loads and dissipate energy. The steel plate tears and the end of the hat column buckles when the CFS-WS is broken. The CFS-WS has good bearing capacity, plasticity, ductility and energy dissipation capacity; however, the rheostriction of its load-displacement hysteresis curve is rather severe. Compared with ordinary CFS-WS, the buckling-restrained CFS-WS has higher shear stiffness, bearing capacity and energy dissipation capacity, and the rheostriction of its load-displacement hysteresis curve is mitigated. Furthermore, the stiffeners and the cold-formed steel beams and columns are connected to form a steel frame through the stiffener connectors, which can effectively enhance the early shear stiffness, bearing capacity and energy dissipation capacity of CFS-WS, and greatly improve the seismic performance of the structure.

Connections used for cold-formed steel frame shear walls sheathed with engineered bamboo panels

This paper presents experimental research on the load-bearing behaviors of self-drilling screw connections in cold-formed steel (CFS) frame shear walls sheathed with engineered bamboo panels. In total, 105 specimens were tested using monotonic and cyclic loading protocols. The performance of the CFS–bamboo connections was studied under various conditions with respect to differently engineered bamboo sheathing panels, screw features, end distances, and loading rates. The failure modes and performance parameters are discussed. The test results obtained in this study indicate that engineered bamboo panels can be used as efficient sheathing panels for CFS structures with good mechanical performances. Based on the connection test information, fast modeling was carried out on the lightweight CFS–bamboo shear walls.

Seismic performance of cold-formed steel framed shear walls with steel sheathing and gypsum board

Cold-formed steel (CFS) framed shear walls with steel sheathing and gypsum board can achieve higher shear resistance compared to conventional CFS framed shear walls. Monotonic and cyclic loading tests on nine full-scale CFS shear walls were conducted to determine the influence of stud and steel sheathed thickness, sheathing material, wall aspect ratio and loading mode. The failure modes, ultimate shear capacity, load-deformation relationships, shear strength, lateral stiffness and ductility of walls were obtained. The structural analysis software OpenSees was used to establish nonlinear simplified models of shear walls under cyclic loading. The hysteresis curve obtained from simplified models showed significant pinch effect and degradation of strength and stiffness. The conclusions and the numerical simulation methods can be applied to the seismic design of CFS framed shear walls with steel sheathing and gypsum board.

Testing and numerical analysis on cold-formed steel shear walls using corrugated steel sheathing

Cold-formed steel framed shear wall sheathed with corrugated steel sheets is a promising shear wall system for low- and mid-rise constructions at high wind and seismic zones due to its advantages of non-combustibility, high shear strength, and high shear stiffness. Monotonic and cyclic tests on full-scale wall assemblies using corrugated steel sheathing was conducted. To investigate the effect of vertical/gravity loading, shear wall specimens were tested under two different loading conditions: lateral loading, and a combined lateral and vertical/gravity loading. The test results are presented and discussed in this paper. Besides, finite element model of the proposed shear wall was created in Abaqus software. The validity of the numerical model was verified based on the test results. A series of parametric analysis were conducted, including the thickness of framing members, the cross section of stud members, yield strength of the frame members, stud spacing, and the influence of gravity loads. The detailed modeling information, relevant parametric analysis and recommendations for practical application of this type of shear resisting system are also presented.

Reliability of cold-formed steel framed shear walls as impacted by variability in fastener response

The objective of this paper is to examine the reliability of cold-formed steel framed shear walls with a particular emphasis on walls sheathed with wood structural panels. A sheathed cold-formed steel framed shear wall is a system consisting of studs, tracks, and sheathing often with bridging and/or blocking, connected with steel-to-steel and sheathing-to-steel fasteners. The shear walls may be integrally connected to foundations, floors, or other shear walls through a variety of means including hold downs, straps, diaphragm chords and collectors. Shear wall lateral resistance in cold-formed steel framed buildings varies because of the randomness in the components and connections that comprise the wall. The interaction between fasteners and sheathing is particularly important because (1) sheathing-to-steel fastener response is the main source of shear wall nonlinearity (2) there is high variability in this fastener response. Although the nominal strengths for different shear wall configurations are stated in current design specifications (e.g., AISI S400), variability of shear walls has not been explicitly considered. Existing resistance factors are extrapolations from steel diaphragm testing. To explore the impact of fastener response variability on shear wall reliability, Monte Carlo simulation of typical cold-formed steel framed wood sheathed shear walls with random fastener input was conducted. Variability in fasteners was determined based on existing physical fastener tests. Statistical properties of shear wall strength, demand capacity ratio of key fasteners, as well as relations between fastener strength and shear wall strength are all explored. Reliability evaluation is provided for four different design methods. The results indicate that shear wall strength benefits from a system effect whereby variability in fastener response is reduced through redistribution resulting in reduced variability in overall shear wall strength. Concomitant with this is a slight decrease, approximately 3%, in the mean system strength that also must be considered.

Seismic behavior of cold-formed steel frame shear walls sheathed with ply-bamboo panels

This paper presents an experimental study on the monotonic and cyclic lateral loading behavior of cold-formed steel (CFS) shear walls sheathed with glued laminated bamboo (glubam ply-bamboo) panels. A total of 16 model shear wall specimens with two types of aspect ratios were tested using ASTM loading protocols. The observed phenomena and the effects of different cyclic loading regimes are discussed. The shear capacity and deformability of ply-bamboo sheathed CFS shear walls are evaluated and compared with wood sheathing panel (WSP) sheathed CFS shear walls through four seismic equivalency parameters recommended by American Iron and Steel Institute (AISI) in 2010 (AISI-RP10-4 2010). The load distribution of the screws along the vertical edges of the panels and the forces in the shear anchors are discussed. The results obtained in this study can further promote the application of bamboo-based material in CFS structures, as potential options for eco-friendly and cost-effective construction.

A pilot study on cold-formed steel framed shear wall assemblies with corrugated sheathing

Flat steel sheet is the common steel sheathing for cold-formed steel (CFS) framed shear walls. Compared to wood sheathing, the practical sheet steel sheathing gives lower shear strength and it tends to fail in the shear buckling which results in large out of plane deformation. On the other hand, sheet steel sheathing is non-combustible material which has great applications in mid-rise residential or commercial buildings. In order to develop a high strength CFS shear wall assemblies with steel sheathing, a pilot research was conducted at University of North Texas to experimentally investigate the behaviour and shear strength of CFS framed wall assemblies with 0.027 in. (22 gauge) corrugated sheet steel sheathing. The parameters considered in the test program included the framing member thickness, the fastener size and spacing, and the boundary stud configurations. Both monotonic and cyclic tests were conducted. The test results indicated that with appropriate framing members and the fastener configurations, the corrugated steel sheet can provide much higher shear strength than the flat steel sheet having the same thickness. This paper presents the test details, test results, and the analysis on the ductility of the shear wall system under monotonic and cyclic loading.