Cold-formed Steel Shear Walls Research Articles

A novel modular CFS composite frame-wall structure: Experimental investigation and numerical analysis

Due to the advantages with short-time installation and waste reduction, modular structures are promising. In the process of applying cold-formed steel (CFS) structures in multi-rise buildings, the combination of steel frames and CFS walls can improve the lateral performance of the structures. A novel modular CFS composite frame-wall structure was proposed, which was comprised by modular steel frames and modular CFS shear walls. Five full-scale modular CFS frame-wall components derived from the composite structures were tested under cyclic loads. The layout of sheathings, configuration of CFS diagonal bracings and door openings were varied to study their effects on lateral performance of the modular CFS composite structures. The results indicate the modular steel frames and CFS shear walls can do well in working cooperatively. The bearing capacity of the specimens with sheathings is more than twice that of the specimens without sheathings. In contrast, the effect of the diagonal bracings is not so significant due to the failure of the screw in the ends. Besides, the simplified models based on equivalent line elements was put forward and verified by experiments. A 6-story CFS composite frame-wall archetype structure was designed and its 3D numerical model was built on basis of the mentioned above simplified approaches. The nonlinear time-history analyses were carried out to evaluate the seismic response of the structures. Results show that the inter-story drifts of the designed structures under the earthquake waves of collapse levels are less than the drift limits 1/50. The designed structures have good seismic performance.

Seismic performance of cold-formed steel shear walls with a shear plate of low-yield steel

A novel cold-formed steel (CFS) sheathed and bare shear walls with a low-yield steel shear energy-dissipating plate is proposed by taking advantage of the plastic deformation generated by the shear plates to reduce the damage of CFS shear walls under earthquake. In this paper, the seismic performance of six CFS shear walls with shear plates using low-yield steel is experimentally studied through full-scale cyclic tests. Different configurations of energy dissipation segments and the replacement of the energy-dissipating shear plate after the earthquake (through two walls) are investigated. A list of influencing parameters on the performance of the shear walls is studied including the fixed conditions of the specimens, the type of built-up studs, the rigidity and strength of the shear plates, and the connection method between the shear plates and the walls. Overall, within a certain lateral displacement level, the damage of the shear wall is concentrated in the energy dissipation segment. The shear plate reaches the plastic stage before the CFS frame as designed. Meanwhile, the mechanical performance of repaired structures with the shear plate replacement after the earthquake is maintained well.

Seismic performance and risk mitigation of CFS shear walls with CFRP-reinforced screw connections and special-shape L-section end studs

Cracking damage of screw connections and buckling of end studs always resulted in performance degradation of cold-formed steel (CFS) shear walls. To improve the seismic performance and to avoid the brittle failure of CFS shear walls, two methods for strengthening CFS walls are proposed in this paper: carbon fiber reinforced plastic (CFRP) toughened screw connections (CFRP-SC) and special-shape built-up end studs with L-shaped sections (SBC-L). A total of 5 full-scale strengthened CFS walls with CFRP-SC or SBC-L were tested to examine the performance, and simplified numerical models of strengthened CFS walls and 5-story CFS buildings were developed and validated. Nonlinear dynamic analyses are performed to investigate the effects of those two methods on seismic responses and risks of CFS buildings, and the risk mitigation of CFS buildings is then discussed. The results show that the CFS shear walls with CFRP-SC can mitigate the damage to screw connections and wallboards nearby those connections, especially for the connections at the corners of the walls. The connections could continually dissipate the earthquake energy due to large loading and deformation capacities. The SBC-L can effectively delay the buckling failure of end studs, thus enhancing the shear resistance of CFS walls. Due to the two methods, the collapse probability of the CFS building with CFRP-SC in service life is reduced by almost 40.8%, and that of the building with CFRP-SC and SBC-L is reduced by almost 59.7%.

Shear performance of cold-formed steel shear walls reinforced by moment frame

A novel hybrid structural system consisting of a steel frame and cold-formed steel shear wall has been proposed. The cyclic test was conducted to investigate the impact of the steel frame, sheathing, and opening on the seismic performance of specimens. Furthermore, numerical models were created and validated using experimental data, and the reinforcement of the frame was studied in greater detail. The results indicate that: 1. The steel frame significantly contributes to the preservation of the framing's integrity even after damage to the sheathing. 2. Despite failure, the specimens still retain over 70% of their shear strength when subjected to a large drift ratio of 1/20 rad. 3. The simulated results show good agreement with the experimental results, and the numerical models accurately predict the shear performance of the system.

Parametric study on seismic response modification factor of strap-braced cold-formed steel systems

While cold-formed steel structures have been extensively studied for seismic-resistant construction, existing regulations, and implementation guidelines do not comprehensively address the impact of key design parameters on the seismic behavior of CFS strap-braced shear wall systems. This study investigates the lateral resistance and seismic behavior factor of strap-braced shear walls and compares them with code values, and tries to fully understand the effect of different design parameters on the seismic R-factor of these systems. The effect of parameters such as the strap cross-sectional area, aspect ratio, and distance between the studs is studied using ANSYS finite element software to create datasets for various configurations. The pushover analysis results obtained from this analysis are utilized to perform incremental dynamic analysis, under a set of 22 ground motion records, to evaluate the seismic response modification factor for different residential buildings. For this purpose, one to four-story residential buildings are designed based on four seismic hazard zones: low, moderate, high, and very high and then, they are analyzed. Results of pushover analysis show that increasing the strap cross-sectional area and aspect ratio increases capacity, but changing the distance between studs does not have a significant effect, and the R factor presented by codes is conservative. Incremental dynamic analysis results also indicate that the behavior of studied buildings varies depending on the structure and selected record and the suggested R factor by codes for diagonal straps braced cold-formed steel structures is acceptable for buildings up to three stories in low, medium, and high seismic zones, and for buildings up to two stories in very high seismic zones. Overall, this study shows that strap-braced cold-formed steel shear walls have the potential to achieve higher seismic R-values in comparison to design codes.

Physical damage‐hysteretic response correlation for steel sheet sheathed cold‐formed steel‐framed wall‐lines

AbstractUse of cold‐formed steel (CFS) framing as load‐bearing system for gravity and lateral loads in buildings is becoming increasingly common in the North American construction industry, notably in high seismic regions where light‐weight construction is an attractive option. Buildings framed with closely spaced and repetitively placed CFS members can be detailed to develop lateral resistance using a variety of sheathing options. A relatively new option involves the use of steel sheet as sheathing. Steel sheet sheathed CFS shear walls offer high lateral strength and stiffness, and provide ductility courtesy of tension field action within the steel sheet. Despite their acceptance, gaps in the understanding of their behavior do exist, notably, behavior under dynamic loading, the contribution of nonstructural architectural finishes, and the behavior of wall‐lines: shear walls placed inline with gravity walls. To this end, a two‐phased experimental effort was undertaken to advance understanding of the lateral response of CFS‐framed wall‐line systems. Specifically, a suite of wall‐lines, detailed for mid‐rise buildings, were evaluated through simulated seismic loading imposed via shake table and quasi‐static cyclic tests. Damage to the wall‐lines was largely manifested in the form of damage to fastener connections used for attaching the sheathing and gypsum panels, and separation of exterior finish layer. This paper documents and quantifies the progressively incurred physical damage observed in the tested wall‐line assemblies, and correlates it with the evolution of dynamic characteristics and hysteretic energy dissipated across a spectrum of performance levels.

Simplified numerical model development for advanced design of lightweight-concrete encased cold-formed steel shear wall panels

Since cold-formed steel (CFS) elements are susceptible to complex buckling phenomena that decrease their structural capability, many strengthening trends have been developed so far. One of these methods is the use of polystyrene aggregate concrete (PAC) as bracings in order to restrain the global and distortional buckling modes of CFS members, where a new structural system comprising CFS elements encased in PAC has been proposed. In this research, PAC-encased CFS shear panels have been investigated numerically, where a simplified finite element model was developed to predict the structural behavior and capacity of such members. This goal was achieved using ANSYS software, where a geometrically and materially nonlinear analysis with imperfections (GMNI) was used to solve the problem of PAC-encased CFS shear panels. The full detailed volume-contact element-based concrete model was replaced by spring elements perpendicular to the plate’s plane with equivalent properties, and beam elements that could represent the concrete block more accurately regarding the global lateral stiffness and shear resistance. Consequently, for this case, the combination of local and global stiffness of PAC could produce the actual shear behavior of PAC-filled wall panels. The developed model was validated against previous experimental tests from the literature. Parametric studies were conducted in terms of the imperfection amplitudes, the stiffness of springs and the properties of PAC. Finally, the structural performance of PAC-encased panels under combined axial and shear loading was examined, where the effect of different axial load levels on the lateral strength was determined, and an interaction equation was proposed.

Nonlinear analysis model and seismic resilience assessment of LEM-filled CFS residence

Lightweight EPS materials (LEM)-filled cold-formed steel (CFS) shear wall structure is a new type of green, low-carbon and prefabricated rural residence, which has drawn in expanding consideration due to the promotion of the rural revitalization strategy. However, most of the existing research on this type of residence has focused on its behaviours of components, with little attention was paid to its overall response to resist earthquake disasters. During the past two decades, significant advancements have been made in effectively mitigating building collapses and reducing casualties resulting from earthquakes. Thus, the concept of seismic resilience is proposed, and the seismic performance requirements of structural design have been elevated from “safety” to “resilience”. To analyze the seismic resilience of LEM-filled CFS residence, this paper proposed a strut and tie- equivalent spring model to establish the simplified analysis model of a single composite wall, and the precision of the model was confirmed by test results, in which the nonlinear characteristic and the supporting effect of fillers was considered. Subsequently, three LEM-filled CFS residences are designed using the direct displacement-based design method. Then the three-D models are established for nonlinear analysis, and the inter-drift ratio (IDR) and residual inter-drift ratio (RIDR) are adopted to estimate the seismic response of the three archetypes. The seismic resilience of the three archetypes are assessed based on FEMA P58. This paper would provide a guidance for the nonlinear analysis and seismic resilience assessment of this type of residences, and promote the application and popularization of this kind of residence.

Numerical evaluation of shear strength of CFS shear wall panel with OSB sheathing

Outside of the American Iron and Steel Institute AISI S400-15 limitations of Shear Wall Panel (SWP) height-to-width (h/w) aspect ratio, the present paper puts forward a sufficiently detailed Finite Element Modeling (FEM) using “Abaqus” software, capable to evaluate with a reasonable precision the shear strength of Cold Formed Steel (CFS) SWP with Oriented Strand Board (OSB), under lateral load. In terms of nonlinear response, shear strength and failure modes, the numerical results of the SWP with and without an opening are validated against available experimental data, accounting for nonlinear mechanical and geometrics characteristics, as well as the nonlinear behavior of connection. Subsequently, the conducted comprehensive parametric studies have revealed that the variation of the screw spacing, from 50.8 mm up to 152.4 mm, provides a nonlinear variation of shear strength that cannot be extrapolated for different screw spacings. In addition, the shear strength of a two-sided OSB-sheathed SWP is less than twice one-sided OSB-sheathed SWP. Furthermore, the door’s and window’s openings’ position between the center and the edge of the SWP provide the best performance in terms of shear strength up to 33 % and 24 % than the center and edge openings’ positions respectively.

Numerical Study on the Seismic Performance of Cold-Formed Steel Shear Walls with Steel Sheathing and Gypsum Board.

The cold-formed steel shear wall with steel sheathing has gained increasing popularity due to its excellent shear capacity. To extend the applicability of this system to multi-story residences, aside from experimental investigations on the shear walls, it is essential to conduct a comprehensive study on the seismic performance of buildings. In this paper, numerical simulations were conducted on specimens subjected to monotonic and cyclic loading. Subsequently, seismic analysis of mid-rise building models was also carried out to investigate the influence of the proposed shear wall on building seismic performance. The research findings indicate that this study's modeling method can effectively simulate the shear performance of the proposed shear wall under monotonic and cyclic loading. In addition, the proposed shear wall significantly enhances the structural stiffness and improves the seismic performance of the structure under seismic action.

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.

Effect of wall sheathings on seismic behaviour of phosphogypsum-filled CFS shear walls

To improve the seismic behaviour of cold-formed steel (CFS) walls, a novel infilled CFS wall covered with different wall sheathings (gypsum wallboard, oriented strand board and fibre cement board) was assessed. Four full-scale specimens were tested under cyclic lateral loads to investigate the impacts of the wall sheathings on the seismic performance of the CFS wall. The failure process, failure mode, load–displacement curve, strength degradation, stiffness degradation, energy dissipation, deformation and strain variation of the walls were investigated. The failure modes of the walls were found to be failure of the connections between the CFS frame and the sheathing as well as crushing of the infill material. Compared with a specimen without sheathing, the peak load and lateral stiffness of the walls with sheathing were increased by 1.25–1.72 times, indicating that the sheathings played an important role in the lateral resistance of the wall. An analysis model and formulas for predicting wall lateral stiffness were developed. Comparisons between the calculations and experimental data showed that the proposed theoretical method was able to predict the lateral stiffness of the infilled CFS walls accurately.

Improved equivalent bracing model considering the mechanical properties of hold-downs

Hold-downs have a dominant role in the force transmission of a cold-formed steel (CFS) structure, and their mechanical properties have a significant impact on the lateral resistance of the structure. Therefore, a total of 24 specimens of four types of hold-downs were designed and tested, focusing on the impacts of the number of anchor bolts and loading modes on the mechanical behaviour of hold-downs. The test results show that (1) the bending capacity of steel plates, the strength of weld joints, the arrangement of anchor bolts, and the load conditions are the key factors that determine the failure modes and damage degree of hold-downs. Moreover, the load–displacement relationship of hold-downs has obvious nonlinear characteristics. (2) The load and resistance factor design (LRFD) load capacities of the hold-downs significantly decrease with an increase in repeated deformation times. When assessing the load-bearing capacity of a CFS structure during the whole service period, the definition of LRFD load capacities of the hold-downs recommended in AISI S913-13 is conservative. Furthermore, an improved mechanical analysis model of a CFS shear wall that reflects the real mechanical characteristics of hold-downs was established by modifying the commonly utilized equivalent bracing model, and the effectiveness of the model was verified according to previous experimental results. The results confirm that the improved model adequately reflects the anchorage degradation of hold-downs and its influence on the shear properties of a wall, providing a more reliable modelling method for the collapse capacity assessment of CFS structures.

Simulation of Cold-Formed Steel Shear Wall Sheathed with Steel Plate: Non-Linear Finite Element Modelling and Analysis

The usage of cold-formed steel (CFS) is gaining popularity all around the world these days. Buildings made of such elements as an independent structural system are applied in the construction of small commercial complexes, low-raised buildings, industrial units, and single-story sports halls. CFS shear walls sheathed with steel sheets are the most popular lateral-load resisting system in low to mid-raised structures. In this paper, a full-scale steel seated CFS shear wall has been simulated by a non-linear finite element method. Furthermore, parametric studies have been carried out to analyze the effects of the blocking members, fastener spacing at steel plate to boundary frame connections, and steel sheet thickness on the behavior of CFS shear wall sheathed with steel plate. It was concluded that the blocking members prevent the studs from twisting and decrease the local bucking of the studs. Meanwhile, the results indicate that the thickness of the steel plate affects the shear strength of the CFS shear wall system to an extent. Besides, increasing the spacing of the fasteners at the connection of the steel plate to the frame system affects the buckling mode of the steel plate, and by increasing the spacing of the fasteners from 100 mm to 150 mm and 200 mm the nominal shear strength of the wall system decreased by 6.5% and 14.1% respectively, while decreasing the fastener spacing causes web distortion of the boundary column elements.

Development of hysteretic model for LEM-filled CFS shear walls under cyclic loading

Lightweight EPS materials (LEM)-filled cold-formed steel (CFS) shear wall, as a novel-type CFS shear wall, is extensively used in low- and multi-storey rural residences. The previous experiments have revealed that this type of wall appeared significant load-bearing properties and elastic stiffness, and the hysteresis loop appeared obvious stiffness degeneration, slipping and pinching effect. This paper developed a hysteretic model for seismic analysis of these shear walls. Four feature points including elastic, yield, peak and ultimate point are put forward to determine the skeleton curve. Besides, the feature points are determined by considering the stress type of bending and shearing respectively. Through analyzing the typical hysteresis loop, four characteristic points were obtained to express the characteristic of the hysteretic loop. Through the combination of the skeleton curve and hysteretic rule, a multi-linear hysteretic model was established to represent the hysteretic curves. The representative characteristic points of the hysteretic loop were obtained based on test data and the existing literature. The generated skeleton and hysteretic curves were compared with test results and the comparison results showed great agreements in terms of feature points and hysteretic loops. The method would provide a meaningful theoretical basis to assessing the seismic response of the LEM-filled CFS shear wall.

Experimental Study on Seismic Behavior of Lightweight Concrete-Filled Cold-Formed Steel Shear Walls Strengthened Using Horizontal Reinforcement

ABSTRACT To improve the seismic behavior and thermal property of traditional cold-formed steel (CFS) walls for satisfying the requirements multistory structures, a new type of fiber-reinforced lightweight concrete (FLC)-filled CFS shear wall strengthened using horizontal reinforcement is proposed in this study. Four full-scale specimens were tested under reversed cyclic loading to investigate the seismic behavior, including failure mode, hysteresis curve, shear capacity, deformability, stiffness degradation, and energy-dissipating capacity. Test results indicated that the restrictive effect of FLC on the studs and its diagonal-bracing effect improved the wall’s hysteretic behavior, making the wall exhibit the ductile shear failure. Increasing the wall thickness increased the shear strength, lateral stiffness, and energy-dissipating capacity, whereas installing the coupling-section interior studs enhanced the ductility. Finally, a simplified strut-and-tie model was proposed to evaluate the shear capability of FLC-filled walls, and the calculated values exhibited good agreement with the test results, but the further verification is required.

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.

Research on the Simplified Method of Nonlinear Finite Element Analysis for CFS-SPR Connections

This study reviewed some simplified methods of finite element analysis (FEA) for connections in cold-formed steel (CFS) structure, and summarized eight simplified methods divided into three categories. Shear performance tests were performed for six groups of self-piercing riveted (SPR) connection in CFS. A constitutive model of shear behavior for SPR connections was proposed, which was simplified from the load–displacement curve of shear performance test results. The models of SPR connection were established in ABAQUS by the eight simplified methods, and then the FEA results and the test results were compared. The applicable scope of each simplified model was explored, and a simplified method of FEA that was most suitable for the shear behavior of the CFS-SPR connection was proposed. Moreover, the shear performance test of the CFS shear wall with SPR was conducted by considering the rivet spacing, and failure modes and load–deformation curves were obtained. On this basis, numerical models of the CFS-SPR connection shear wall were established. By comparing the test results and the FEA results for the CFS-SPR connection shear wall, the feasibility of a simplified method of FEA applied to the CFS-SPR connection was verified. The main failure modes of the CFS-SPR connection were that the rivet tail pulled out from the bottom sheet and the rivet head pulled over from the top sheet. The SPR connection of the CFS frame could be simplified with a pin or a fastener element, and the SPR connection between the steel frame and the sheathing could be simulated by a Cartesian connector or a Spring2 element. The FEA results were highly similar to the test results for the CFS-SPR shear wall.

Experimental study on cold-formed steel shear walls with different corrugated steel sheathings

Recent research identified the feasibility of adopting corrugated steel sheets as the sheathing material in the cold-formed steel (CFS) shear wall system. However, different experimental results were reported when using different corrugated cross-sections. To determine the effect of different corrugated steel sheathings on the shear capacities of CFS shear walls, this paper conducted an experimental study on the seismic behavior of corrugated steel sheet sheathed shear walls with different cross-section profiles. The selection of corrugated cross-sectional dimensions was informed by the existing research, including corrugated steel sheets with a rib height of 5 mm, 15 mm, and 38 mm. The experiments involved ten full-scale shear wall specimens evaluated under lateral monotonic loading and cyclic loading. The test results indicate that shear walls with 5 mm-rib-height corrugated steel sheets are most likely to produce shear buckling waves, and therefore have the best ductility and highest utilization of sheathing capacity. Shear walls are more apt to screw connection failure and sheathing local buckling as the rib height increases. There is no obvious difference in the shear capacity between the three types of shear walls due to the premature failure of 15 mm- and 38 mm-rib-height corrugated steel sheets. Sheathing buckling was detected and a substantial increase in the shear capacity was achieved when the reduced screw spacing was adopted in the 15 mm-rib-height corrugated sheet sheathed shear walls. The design of corrugated steel sheet sheathed shear walls needs to consider the influence of both the corrugation and screw arrangement.

Behavior of CFS shear walls infilled with lightweight ceramsite concrete under cyclic loading

To meet the lateral resistance requirement for cold-formed steel (CFS) shear walls in multistory buildings, a novel CFS shear wall filled with lightweight ceramsite concrete is proposed in this paper. Three full-scale specimens were conducted under cyclic loading to evaluate their failure mode, bearing capacity, lateral stiffness, ductility, and energy dissipation. The experimental results showed that the main failures of the walls were bond-slip cracks between the CFS framing and fillers, cracking of sheathings, and compression failure at the corners of the fillers. The bearing capacity and energy dissipation of the infilled walls were superior to that of unfilled wall. Increasing the stud section area could improve the lateral behavior of the wall. Finite element (FE) models were introduced to simulate the shear performance of the test specimens. The numerical simulation results were in good agreement with the experimental results; hence, the FE models for simulating CFS shear walls were validated. Subsequently, a parametric study was performed by varying the parameters, including the ceramsite concrete strength, wall thickness, aspect ratio, steel strength, and sheathing material. Furthermore, a calculation method was proposed to determine the bearing capacity of the CFS shear walls. The calculated results agree well with the experimental results. A comparison between the proposed CFS shear walls and existing CFS shear walls showed that the lateral performance of the proposed walls was higher than that of CFS shear walls.