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Seismic behavior of steel-sheathed cold-formed steel shear walls with reinforced end columns
Abstract
In this study, we investigated six full-scale, steel-sheathed, cold-formed steel shear walls (CFS-SWs), three of which were CFS-SWs with reinforced end columns (CFS-SW-Rs), under reversed-cyclic loading and analyzed their damage modes and mechanical properties. Tests were conducted to compare the seismic performance between the CFS-SWs and CFS-SW-Rs and investigate the effects of the horizontal steel bands and aspect ratio on the seismic behavior of the CFS-SWs, and the effects of the thickness of the steel plates, and the aspect ratio on the seismic behavior of CFS-SW-R. According to the results, CFS-SW-Rs exhibited better seismic performance than CFS-SWs. Specifically, the CFS-SW-R benefited from the high strength and stiffness of the square steel tube end columns that could effectively restrain the thin steel plate, such that the tension band formed by the thin steel plate could be fully expanded. In addition, the shear capacity of CFS-SWs was improved by increasing the number of horizontal steel bands and the aspect ratio, the shear capacity of CFS-SW-Rs was also improved by increasing the aspect ratio and thickness of the sheathing plate.
... Associated with the increasing adoption of LSF-built houses, it was not surprising to observe a growth of research studies in this specific area, as several experimental [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and numerical [14,19,21,22] studies were developed to investigate the mechanical behavior of LSF structures. Recently, Hasanali et al. [23] published a critical review of the developments and challenges related to the behavior of LSF seismic-resistant systems. ...
... Xiang et al. [10] and Yu et al. [11] also focused their investigations on the influence of bracing systems on the seismic behavior of LSF walls by studying, respectively, the use of X-and K-strap bracing systems and of a special energy dissipation bracing to improve the ductility of the corrugated sheet sheathed shear walls. Alternatively, to improve the mechanical behavior of LSF walls by means of the end studs instead of by means of bracing, sheathing, or cladding, recently, the use of reinforced end studs [15], the consideration of different crosssections for studs [16], and the adoption of concrete filled steel tubes [17] have also been addressed by some authors. ...
The mechanical behavior of light steel framing (LSF) walls under horizontal (shear) loadings is reported and assessed in this paper. In total, an experimental program with twelve LSF walls (six under monotonic and six under cyclic loading) was conducted, and the main parameters investigated were (i) the thickness and (ii) the material used as the cladding (OSB, a plasterboard, and a steel sheet), (iii) the spacing between fasteners (150 or 75 mm), and (iv) the influence of using steel bracing elements. It is concluded that doubling the number of fasteners and increasing the thickness of OSB by 80% lead to increases in ultimate loads, respectively, of 33 and 13%. The ductility index of the walls with steel sheets was 50 to 75% lower than those of the remaining walls. The wall with the steel strap x-bracing system presented (i) the lowest initial rigidity (a diaphragm effect could not be triggered with these elements) and (ii) the highest damage extent at the end of testing (a damage parameter of 0.85, due to damage of the steel strap-to-steel structure connection). It is confirmed that the results obtained with testing of the walls under a monotonic load can be good predictors of their behavior under cyclic loading as, for instance, the ultimate loads of walls under both loading cases present an average difference of 4%.
This research is concentrated on the structural strength and behavior of cold-formed steel wall frame sheathed with calcium silicate board under shear load. Test specimens with two different thicknesses of sheathing were assembled, 9 mm and 12 mm, with one-side or two-side of attachment. Monotonic shear and cyclic loading tests are conducted on wall specimens utilizing two C sections connected back-to-back to be as chord studs and calcium silicate board sheathing on the exterior. Based on the test results, detailed discussions on the strength, stiffness, energy absorption, ductility ratio, and failure mode of cold-formed steel wall specimens are given. It is noted that the failure mostly occurred at the bottom track of wall specimens due to the large deformation or tearing failure of track. The wall strength is not affected by the change of sheathing's thickness significantly, but wall frames attached with two-side calcium silicate board sheathing provide higher resisting strength and stiffness than those attached with one-side sheathing. In this study, test results are also used to compare with the previous study that single chord stud was used in the assembly of wall frame. In addition, the suggested response modification factor of the wall sheathed with calcium silicate board is proposed for design purpose.
Fire is a frequent disaster, which has lasting effects on mechanical properties of high-strength steel (HSS). For HSS structures after fire, it is important to assess if the structure can continue to service, should be repaired or demolished. The experimental and numerical investigations are performed to investigate the effects of exposure temperature on residual resistance of Q690 HSS plate girder considering the post-buckling capacity. In this study, the post-fire mechanical properties of Q690 HSS are investigated experimentally. The appearance characteristics of Q690 HSS with different exposure temperatures are obtained. The effects of exposure temperature on mechanical properties of Q690 HSS were discussed. To investigate the residual resistance of Q690 HSS plate girder after fire, the post-fire mechanical properties of Q690 HSS are introduced in the plate girder model, which has been strictly validated. Based on numerical results, the effect of exposure temperature on the initial stiffness of HSS plate girder can be ignored. The nonlinear properties of the Q690 HSS have the certain effect on the nonlinear characteristics of resistant curve of Q690 HSS plate girder considering the post-buckling capacity, which are influenced by the exposure temperature. The effect of exposure temperature on the buckling resistance of Q690 HSS plate girder is relatively small. With the raise of exposure temperature, the postbuckling capacity of Q690 HSS plate girder decreases. Effects of exposure temperature on the resistant properties of Q690 HSS plate girder were investigated, which were quantified by a suggested equation. The increase of exposure temperature has an adverse effect on the proportion of safety reserve of the Q690 HSS plate girder with post-buckling capacity.
Titanium-clad bimetallic steel (TCBS) consisting of titanium (cladding) and carbon steel (substrate) has been proposed to reduce the effects of corrosion on the durability of steel structures. Fire is a frequent disaster in steel structures. The elevated temperature caused by a fire and the cooling method to prevent it have a long-term influence on the mechanical properties of structural steels. In this study, the post-fire mechanical properties of a TCBS were investigated experimentally to accurately predict the residual service capacity of steel structures after a fire. The post-fire appearances of TCBS specimens were examined. The bonding interface of all TCBS specimens remained intact after exposure to elevated temperatures. The deformations of the cladding and substrate metals were coordinated before necking. Based on the fractured order, three different typical failure modes were determined in the TCBS. The differences in the cooling method and the exposure temperature resulted in differences in the nonlinear properties of the stress-strain curves. The effects of the exposure temperature and the cooling method on the yield strength, ultimate strength, elastic modulus, and percentage elongation after fracture were investigated and quantified using predictive equations. To comprehensively reveal the post-fire performance of TCBS comprehensively, the residual mechanical properties of different structural steels were compared.
Fire is a frequent disaster, which performs the irreversible effects on mechanical properties of structural steels. When the structure experiences a fire and does not collapse, it is important to clarify the remaining resistance accurately. The stainless-clad bimetallic steel bar (SCBSB) consisting of the S30408 stainless-steel cladding layer and the HRB400 carbon steel substrate has the wide application in reinforced concrete structures serving in corrosive conditions. To evaluate residual resistance of SCBSB-concrete structures exposed to fire, post-fire mechanical properties of SCBSB are investigated experimentally. After the heating and cooling procedures, no cracking is observed in the cladding layer. Microstructures of SCBSB specimens are discussed. The stress–strain properties of SCBSB specimens exposed to elevated temperature and cooled with various methods are studied through the tensile coupon test. The dimensionless coefficients are selected to clarify effects of exposure temperature and cooling method on mechanical performances. These effects (at exposure temperatures lower than 600 °C) are relatively small. Predictive equations are suggested to determine mechanical performances of SCBSB specimens exposed to elevated temperature. The stress–strain models are proposed based on experimental results. Various energy indexes are selected to comprehensively investigate the ductile properties of the SCBSB specimens.
Design of cold-formed stainless steel tubular columns undergoing local-overall flexural interactive buckling is investigated in this paper. A numerical study has been carried out to study the interactive buckling behavior of square hollow section (SHS) and rectangular hollow section (RHS) columns of various stainless steel grades that are employed in structural applications. A finite element model was developed and verified against available experimental cold-formed stainless steel SHS/RHS column data. Extensive parametric studies, with cross-section aspect ratio, plate slenderness, overall slenderness and stainless steel grade selected as key variable parameters, were carried out thereafter to generate further numerical data featuring the tubular columns undergoing local-flexural interactive buckling. The obtained interactive buckling strengths were used to assess the design provisions in current European, American, Australian/New Zealand and Chinese design standards for stainless steel structures as well as available Direct Strength Method (DSM) design rules in the literature. It is shown that better predictions can be achieved when material nonlinearities of different material grades are accounted for. A modified DSM, which relies on simple hand calculations, is developed in this paper. It is demonstrated that the modified DSM is a suitable and efficient design alternative for cold-formed stainless steel SHS/RHS columns subjected to local-flexural interactive buckling.
The S600E high-strength stainless steel (HSSS) is a new type of sorbite stainless steel. Compared with the traditional stainless steel, the S600E HSSS performs the higher yield strength and faster strain hardening property. The numerical analysis for S600E and S30408 stainless steel plate girders was performed, which includes the material and geometrical nonlinearity. The results indicated that differences in the material property would influence the resistant property of plate girders developing postbuckling capacity (PC). After the verification, the design formulae in EN 1993-1-4 + A1 are too conservative to be directly used to predict the ultimate shear resistance of the S600E HSSS plate girder. Hence, the objective of this study is to quantify the ultimate shear resistance and propose the modified formulae for S600E HSSS plate girders with PC. The effects of a/hw, hw/tw and tf on the ultimate shear resistance were investigated through a parametrical study. The results stated that the a/hw has an adverse effect on the ratio c/a, which is not included in the traditional design formula. Based on the numerical outcomes, the factor ρ was introduced. To consider the strain-hardening effect, a strengthen factor δ = 1.2 is recommended in the formula for the contribution from flange. The contribution from the web was investigated by Vbw.Rd = Vb.Rd - Vbf.Rd. Then, the new formula was proposed for the contribution from the web based on the resistant property of S600E HSSS plate girders with PC.
Through an experimental investigation of the lateral resistance of seven full-scale cold-formed steel (CFS) framed sheathed walls under monotonic loading and reversed-cyclic loading, the mechanical properties, failure modes, and seismic performance of the walls are elucidated. The influence of loading mode, vertical load and sheathing material on the shear bearing capacity and hysteresis performance dissipation of the walls are analyzed. The results show that the shear bearing capacity of the single-sided 12-mm-thick gypsum panel CFS wall is about 34%—37% that of the single-sided 9-mm-thick oriented strand board panel CFS wall, and the shear bearing capacity of the double panel CFS wall is nearly equal to the sum of the two kinds of single-sided panel CFS wall. The mode of loading has a significant influence. The shear resistance of the CFS wall under monotonic loading is 5%–20% higher than that of the CFS wall under the reversed-cyclic load. The application of the vertical load improves the stiffness and the shear bearing capacity of the CFS wall, but the ductility coefficient is slightly decreased.
In this paper, the seismic performance of cold-formed thin-walled steel walls with diagonal braces is studied by means of experiments and finite element analysis. In total, horizontal hysteretic loading tests were carried out on six full-scale cold-formed thin-walled steel walls. The influence of diagonal bracing, the screw spacing, wall panels and vertical loads on the seismic performance of the walls was investigated from the aspects of hysteretic curves, skeleton curves, the lateral stiffness degradation and the energy dissipation capacity. It was found that diagonal bracing could significantly improve the load-bearing capacity, stiffness, and energy dissipation capacity of the walls. However, the lateral resistance increased slightly because of premature buckling of the transverse braces at the connection between the diagonal and transverse braces. In addition, finite element models of the wall specimens were established by ABAQUS software and validated against the experimental data. A preliminary parametric study was also conducted to further examine the influence of essential parameters on the behavior of cold-formed steel walls with diagonal braces.
This paper describes an investigation of web crippling behaviour of aluminium alloy plain and lipped channels with flanges restrained. A total of 340 data is presented that include 52 test results and 288 numerical results. A series of tests was conducted on plain and lipped channels fabricated by extrusion using 6063-T5 and 6061-T6 heat-treated aluminium alloys under end-two-flange (ETF) and interior-two-flange (ITF) loading conditions. The concentrate loads were applied by means of bearing plates. The flanges of the channels were either bolted (fastened) to one or two bearing plates. A finite element model was developed and verified against the experimental results. Geometric and material non-linearities were included in the finite element model. It was shown that the finite element model closely predicted the web crippling strengths and failure modes of the tested specimens with flanges restrained. Hence, the finite element model was used for an extensive parametric study of cross-section geometries, and the web slenderness value ranged from 24.0 to 207.3. The test results and the web crippling strengths predicted from the finite element analyses were compared with the design strengths obtained using the American, Australian/New Zealand and European specifications for aluminium structures. A unified web crippling equation with new coefficients for aluminium alloy channels with flanges restrained under ETF and ITF loading conditions is proposed in this study. Since two failure modes of web buckling and web yielding were also observed in the aluminium plain and lipped channels with flanges restrained, design rules of web crippling strengths are also proposed by considering the lesser of the web buckling strength and web yield strength.
Cold-formed steel (CFS) framed buildings have shown potential towards innovative and efficient building design in high seismic regions. The objective of this study is to expand the knowledge and breadth of design options of CFS construction into higher capacity lateral force resisting systems; as such, the lateral performance of CFS shear walls sheathed with fiber cement board (FCB) and composite steel-gypsum (SG) panels are the focus of this work. Three-dimensional finite element shell modeling is used by focusing on the impact of sheathing type, screw type and fastener pattern. The computational method includes fastener-based modeling which necessitates the use of experimentally-derived connection behavior. An experimental program of monotonic and cyclic fastener testing was conducted to provide shear response of CFS-to-sheathing connections with various sheathings (FCB, SG), screws, and screw spacing. Monotonic connection means are derived from the experiments and introduced in the finite element model. The numerical results demonstrate significant capacity benefits and different failure modes from traditional wood-sheathed shear walls. This work not only aims to provide an innovative and accurate computational tool for FCB- and SG-sheathed shear walls to the research community, but also to expand CFS practice through higher capacity design options. To enable adoption by practitioners, prescriptive design recommendations are provided. As the developed finite element model is computationally expensive, Pinching4 parameters from the cyclic testing are also provided to aid in the development of reduced-order models.
Highlights
• The bracing effect of the particle cement board for the CFS wall panels is explored.
•The suitability of the current sheathing braced design method of AISI is examined.
•The reasons for the inaccurate design predictions are highlighted.
•The modifications required for accurate design predictions are suggested.
Recent research showed that shear walls with corrugated steel sheathing demonstrated high strength, high initial stiffness but low ductility under cyclic loading and thus were not favorable for seismic applications. A possible solution by creating openings in the field of the corrugated sheets in order to improve the ductility was newly proposed by the authors. This paper presents an experimental study on the seismic behavior of the cold-formed steel shear walls using corrugated steel sheathings with different slits configurations. A total of 14 full scale shear wall specimens, including seven different slit configurations and one unperforated wall configuration, were tested under lateral cyclic loading. The test results indicate that with proper slit configurations on the sheathing, the corrugated steel sheathed shear wall shows an improved high ductility without significant reduction in shear strength and stiffness. Details of the test program and general results are presented in this paper.
An innovative configuration for cold-formed steel (CFS) framed and sheathed shear walls developed to address the need for a ductile lateral framing system of high shear resistance appropriate for mid-rise buildings is presented in this paper. This shear wall configuration comprises a sheathing placed at the mid-line of the framing, and hence is known as either a centre-sheathed or mid-ply wall. A laboratory based research program was conducted following an iterative design, analysis and testing process. The testing included fifteen 1218 mm × 2438 mm shear walls subjected to in-plane displacement-based monotonic and cyclic loading. The test specimens were able to reach shear resistances substantially exceeding the capacity of the CFS walls listed in the AISI S400 Standard, while attaining storey drift values superior to 6% in the best case. A preliminary equation-based nominal shear strength prediction method has been developed, reflecting the shear wall's innovative configuration and superior behaviour.
In this paper, the seismic performance of cold formed steel shear walls sheathed by fiber cement boards (FCB) is investigated. Of particular interest is the seismic response modification factor of FCB shear walls. Nonlinear incremental dynamic analyses of multi-story cold formed steel framed structures were carried out following an approach adopted by FEMA-P695 on the description of building seismic behavior. Different scaled earthquake records in three different earthquake prone regions located on low, medium and high seismic risk zones in Iran were taken into account. One, two and three story CFS archetype buildings were analyzed using models created in OpenSees software to predict structural performance of the buildings. Nonlinear dynamic time history analyses were carried out employing OpenSees software utilizing 2D models of a FCB braced wall tower. A stick model was created whose behavior was fitted to the lateral resistance versus deformation of each story that braced elements in the model. The elements were defined via material Pinching4 to construct a uniaxial material exhibiting pinched load-deformation response and demonstrate degradation under cyclic loading. The results show that most relevant codes which suggest the value of seismic response modification factor equal to 2 for cold formed steel shear walls sheathed by FCB are acceptable only for up to three story buildings in low seismic risk zone, up to two story in medium seismic zone and one story in high seismic risk zone.
Cold-formed steel shear wall with corrugated sheet steel sheathing is a newly proposed lateral force resisting system from recent research work. The advantages of noncombustibility, high shear strength and high shear stiffness enable this new wall system to be a feasible solution for low- and midrise construction at high wind and seismic zones. The design provisions for this new type of shear wall have not been developed in current design specifications. The initial phase of this research project involved the displacement-based testing of bearing wall and shear wall specimens under combined lateral and gravity loading. The phase two research, presented here, includes the nonlinear finite element analysis and the performance evaluation of a set of light framed steel buildings using the corrugated sheet sheathed shear walls. Incremental dynamic analyses were performed on six archetype buildings and seismic performance assessment was evaluated. The results verify a set of seismic performance factors (R=Cd=6.5 and ω=3.0) for the corrugated sheet sheathed shear wall systems.
This paper presents the results of an experimental study on the behaviour and strength of the cold-formed steel shear wall panel (CFSSWP) with calcium silicate board as sheathing, when subjected to monotonically increasing and reversed cyclic in-plane shear deformation. These specimens were specifically designed to reach the strength as governed by the strength of the screw connection between the board and the CFS framing and avoid all other modes of failure, ahead of this. The main objectives of the experimental study are (a) to study the influence of board thicknesses and the distance of the screws from the nearest free edge of the board on the wall panel behaviour and strength; (b) to study the behaviour of different wall board configurations normally used in construction practice (c) to develop the values of the important parameters that determine the load-deformation behaviour of the wall panels under in-plane shear and (d) to determine the different limit states in the failure of the screws connecting the board and the CFS framing in such CFSSWP. In addition, a simplified design equation is proposed to evaluate the ultimate shear strength of CFSSWP based on the strength of the screw connection obtained from a sub assemblage shear strength test.
Cold-formed steel shear wall panel (CFSSWP) is a main lateral load resisting system in the CFS wall panel building system. It consists of CFS framing members attached to sheathing with screw connections. The hysteretic behaviour of a properly designed CFSSWP is dictated essentially by the hysteretic behaviour of the screws connecting the sheathing to the CFS framing. A numerical model of the hysteretic behaviour of such panels is necessary to study the system behaviour under various earthquake loading. In this paper, Bouc–Wen–Baber–Noori (BWBN) model is used to capture the deteriorating behaviour, such as the strength and stiffness degradation with severe pinching, observed in the screw connections between the CFS framing members and sheathing, as well as the full wall panels under cyclic loading. The system identification technique based on Nelder and Mead’s simplex algorithm is used to identify the unknown parameters of the model. The representation of the constitutive relationship, both under static and cyclic loading of the screw connections and the wall panel sub-system, is demonstrated using the BWBN model.
This paper presents the results of two 6 10 mm X 2,438 mm and six 1 219 rum X 2,438 rum reverse cyclically tested cold-formed steel frame shear walls where the sheathing was attached with a structural adhesive and pneumatically driven steel pins. The sheathing materials included 0.69-mm sheet steel and 11.1-mm OSB rated sheathing. Limited in scope, the goal of the study was to explore potential structural and economical benefits that may be available when the primary mechanism of load transfer between the framing and the structural sheathing is a continuous adhesive bond. Mechanical fasteners (steel pins) are expected to provide a means of keeping the sheathing tight against the framing as the adhesive Cures and a minimum level of postpeak load resistance. The results showed that the peak wall resistances significantly exceeded the nominal values in the current building codes and standards for similarly sheathed walls without adhesives. However, compared to shear walls without adhesives, the tested walls exhibited more linear responses with higher stiffness and generally larger degradation in strength after the peak resistance. Based on these limited test results and a relatively simple interpretation of the test data, the use of structural adhesives with mechanical fasteners may be beneficial in sonic applications and warrants a more comprehensive study.
This paper presents detailed results on the shear behavior of 2.44 m by 2.44 m light-gauge steel stud walls for three different shear resisting systems: framed walls with 20 gauge flat strap X-bracing on the face - type A; framed walls with 12.5 mm (1/2 in.) single-ply gypsum wallboard on the back and 12.5 mm (1/2 in.) single-ply gypsum sheathing board on the face - type B; and framed walls with 12.5 mm (1/2 in.) single-ply gypsum wallboard on the back, 12.5 mm (1/2 in.) gypsum sheathing board on the face, and 20 gauge flat strap X-bracing on face - type C. The steel framing used in these tests is typical of framing used in residential construction. The behavior of the type A walls was governed by the yield strength of the straps with practically no resistance provided by flexure in the studs. In the type B and type C tests, the measured maximum load was controlled by the breaking of the wallboard along its edges. The failure mechanism was initiated by a rotation of the screws at the edges. This was followed by the partial pull-through of the screws at the edges of the gypsum board and simultaneous breaking of the board at the edges. Each 1.22 m by 2.44 m (4 ft by 8 ft) gypsum panel was observed to behave independently during loading. A comparison of the results from the type B and type C tests showed that the use of 50.8 mm, 20 gauge tension bracing prevented cracking of the boards at the perimeter, reduced the lateral displacement, and increased the maximum load capacity of the wall by as much as 28%.
The ever-increasing need for housing generated the search for new and innovative building methods to increase speed, efficiency and enhance quality, one direction being the use of light thin steel profiles as load bearing elements and different materials for cladding. The same methodology can be employed to build small steel structures for offices, schools or other purposes. Earthquake behaviour of these structures is influenced, together with other parameters, by the hysteretic characteristics of the shear wall panels. Results of a full-scale shear test programme on wall panels are presented, together with some numerical results concerning expectable earthquake performance of this structural typology.
The development and application of cold-formed steel system
- Yi