An experimental investigation on the lateral behavior of knee-braced cold-formed steel shear walls

Experimental investigations were conducted to evaluate the lateral seismic characteristics of light-weight knee-braced cold-formed steel structures. In all, four full-scale 2.4×2.4 m² specimens with different configurations were tested under a standard cyclic loading regime. This paper focuses on the specimens' maximum lateral load capacity and deformation behavior and provides a rational estimate of the seismic response modification factor, R, of knee-braced walls. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of CFS walls. That is in order to suggest improvements so that the shear steel walls respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling. A discussion on the calculated response factors in comparison to those suggested in the relevant codes of practice is also presented.     

Seismic characteristics of K-braced cold-formed steel shear walls

Detailed investigation of the lateral performance of K-braced cold-formed steel structures and their response modification coefficients, R factor, are presented in this paper. A total of 12 full-scale 2.4 × 2.4 m specimens of different configurations are considered, and the responses investigated under a standard cyclic loading regime. Of particular interest are the specimens' maximum lateral load capacity and deformation behavior as well as a rational estimation of the seismic response modification factor. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of the CFS walls in order to suggest improvements so that the shear steel walls respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling. A discussion on the calculated response factors in comparison to those suggested in the relevant codes of practice is also presented.     

Comparison of nonlinear behavior of steel moment frames accompanied with RC shear walls or steel bracings

In this paper, the seismic behavior of dual structural systems in forms of steel moment‐resisting frames accompanied with reinforced concrete shear walls and steel moment‐resisting frames accompanied with concentrically braced frames, have been studied. The nonlinear behavior of the mentioned structural systems has been evaluated as, in earthquakes, structures usually enter into an inelastic behavior stage and, hence, the applied energy to the structures will be dissipated. As a result, some parameters such as ductility factor of structure (μ), over‐strength factor (R_s) and response modification factor (R) for the mentioned structures have been under assessment. To achieve these objectives, 30‐story buildings containing such structural systems were used to perform the pushover analyses having different load patterns. Analytical results show that the steel moment‐resisting frames accompanied with reinforced concrete shear walls system has higher ductility and response modification factor than the other one, and so, it is observed to achieve suitable seismic performance; using the first system can have more advantages than the second one. Copyright © 2011 John Wiley & Sons, Ltd.     

Seismic behavior analysis for composite structures of steel frame‐reinforced concrete infill wall

The composite structure of steel frame–reinforced concrete infill wall (CSRC) combines the advantages of steel frames and reinforced concrete shear walls. Reinforced concrete infill walls increase the lateral stiffness of steel frames and reduce seismic demands on steel frames thus providing opportunities to use partially restrained connections. In order to study seismic behavior and load transfer mechanism of CSRC, a two‐story one‐bay specimen was tested under cyclic loads. With that, the main characters such as, strength, stiffness, ductility, energy dissipation, load distribution, performance of steel frames, partially restrained connections and studs, are analyzed and evaluated. The experimental results show that the structure has adequate strength redundancy and sufficient lateral stiffness. The CSRC system has good ductility and energy dissipation capability. Partially restrained connections could enhance ductility and avoid abrupt decreases in strength and stiffness after the failure of infill walls. The composite interaction is ensured by headed studs, which have failed because of low‐cycle fatigue. Steel frames bear 80%–100% of overturning moments, and the remainder is undertaken by infill walls; steel frames and infill walls resisted 10%–20% and 80%–90% of lateral loads, respectively. Furthermore, relevant design recommendations are presented. Copyright © 2011 John Wiley & Sons, Ltd.     

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

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.     

轻质脱硫石膏改性材料填充冷弯型钢组合墙体抗震性能试验研究

为研究轻质脱硫石膏改性材料填充冷弯型钢组合墙体的抗震性能,对5片轻质脱硫石膏改性材料填充冷弯型钢组合墙体的足尺试件进行低周反复加载试验。研究该类墙体的破坏机理、承载力及抗侧刚度、滞回性能、延性及变形、耗能性能等。试验结果表明：填充墙体内填石膏分块形成斜向受压带,发挥其抗侧力功能,最终以各块填充物与墙架立柱之间的黏结滑移破坏以及轻质石膏块角部的受压破坏为主要破坏特征;较空腔墙体,填充墙体的受剪承载力和抗侧刚度均有大幅度提高,受剪承载力提高了55%~88%,抗侧刚度提高了142%~217%;随着填充材料强度的提高,墙体的抗侧刚度和受剪承载力逐步提高,但其提高幅度低于材料强度的提高幅度。     

Seismic response of Cfs strap-braced stud walls: Theoretical study

The use of cold-formed steel (CFS) profiles in low-rise residential buildings has increased in European construction sector. The reason of this interest is related to potentialities offered by this constructive system, which are the high structural performance, lightness, short construction time, durability and eco-efficiency. Nevertheless, the current structural codes, such as Eurocodes, do not provide enough information about the seismic design of this structural typology. In an effort to investigate the seismic response of CFS structures, a theoretical and experimental research has been carried out at University of Naples Federico II, with the main aim to support the spreading of these systems in seismic areas. This study focuses on an “all-steel design” solution in which strap-braced stud walls are the main lateral resisting system. In the present paper the outcomes of theoretical phase are shown with the aim of defining the criteria for the seismic design of such structures. In particular, a critical analysis of the requirements for CFS systems provided by the American code AISI S213 has been carried out by comparing it with those given by Eurocodes for traditional braced steel frames.     

Load carrying capacity enhancement of cold formed steel walls using shotcreted steel sheets

Recently worldwide cold formed steel buildings are recognized as viable alternatives to reinforced concrete buildings especially in seismic areas. This is because they are lightweight (easy to handle), fast constructed, energy efficient (green houses), economical, dimensionally stable and they do not need skilled worker. Under vertical loading the design principles of these buildings are well established and codified, however, under lateral loadings such as wind and earthquake loads efficiently design is needed. In this paper a new sheathing technique uses shotcreted ribbed steel sheets is proposed to improve the stability and increase the lateral load carrying capacities of the CFS walls in order to withstand earthquake and wind loads safely. The idea is to sheath the outer side of CFS structure external walls with thin ribbed steel sheets, then shotcreted the sheets with cement or gypsum mortars. To test the concept full size wall specimens were prepared in the laboratory and tested under monotonic vertical and lateral loads. Some of the specimens were sheathed with the traditional fiber cement boards or gypsum boards with mat reinforcement, while the others were sheathed with the proposed technique. Test results indicates that the lateral load carrying capacities of the walls sheathed with the proposed technique increases by about two times compared with the walls sheathed with traditional boards. And under ultimate loads they fail in local failure modes rather than overall buckling failure modes which commonly occur in the walls sheathed with traditional boards.     

半刚性连接钢框架-非加劲钢板剪力墙结构性能研究

半刚性连接钢框架-非加劲钢板剪力墙结构弥补了传统抗弯钢框架侧向刚度不足的缺点,为采用更加经济的半刚性节点提供了可能。为研究不同梁柱连接刚度对双体系结构抗震性能的影响,完成了3个单跨两层不同梁柱连接刚度试件的水平低周往复加载试验研究,系统分析了三者的整体性能和破坏模态,拟从承载力、刚度、延性、耗能、整体性能和节点性能六个方面对双体系的节点刚度与墙体的匹配效果进行评价。结果表明:在半刚性框架内设置钢板墙能较大程度提高结构的极限承载力与侧向刚度;结构具有理想的屈服顺序,内填板在加载初期非常有效。屈服区域延伸至整个墙体时,附加荷载将基本上由边缘构件承担,试件破坏主要由内填板的屈服和框架柱的弯扭失稳控制;节点刚度退化小,且内填板的设置缓解了节点区自身的延性要求,梁柱连接形式对试件的抗侧刚度和整体强度的影响不大,降低连接刚度有利于提高试件延性和耗能能力。     

带填充墙钢框架结构抗侧力性能试验及理论研究

介绍了7榀钢框架及带填充墙钢框架结构的水平静力及低周反复加载试验。通过测试有墙和无墙钢框架试验模型在侧向力作用下的变形全过程,得到了墙体对钢框架结构强度和刚度的影响,了解了节点的破坏特征及墙体本身的工作性能,得到了有墙及无墙钢框架结构的滞回性能。试验中发现,填充墙体和钢框架之间的连接性能很好,墙体和框架可以共同工作。通过参数分析,给出了结构抗震弹性层间角位移的建议取值为1/350。在理论分析的基础上,提出了填充墙框架体系抗侧刚度简化公式,得到了试验结果的验证。     

喷涂保温材料冷弯薄壁型钢组合墙体抗震性能试验研究

喷涂保温材料冷弯薄壁型钢组合墙体是在冷弯薄壁型钢骨架区格内设置聚苯乙烯泡沫板,并在骨架外侧喷涂轻质保温材料制成。通过对1个冷弯薄壁型钢骨架试件和2个喷涂保温材料冷弯薄壁型钢组合墙体试件的低周反复加载试验,分析了试件的受力过程和破坏形态,研究了试件的滞回曲线、骨架曲线、承载能力、抗侧刚度以及延性等力学特征,并将试验结果与已有的两侧挂板冷弯薄壁型钢组合墙体的试验数据进行了对比分析。研究结果表明：冷弯薄壁型钢骨架的节点刚度较弱,承载能力较低,不宜单独作为抗侧力构件;与两侧挂板冷弯薄壁型钢组合墙体相比,轻质保温材料的连续喷涂使得组合墙体更具整体性,其承载能力和抗侧刚度显著增加,并具有良好的抗震性能。     

A numerical study on seismic performance of strap-braced cold-formed steel shear walls

This paper presents a non-linear finite element analyses in order to optimize the seismic characteristics of strap-braced cold formed steel shear walls enhanced with brackets in the four interior corners of the wall. The numerical models presented here are verified based on experimental tests considering different structural characteristics including: material nonlinearity, geometrical imperfection, residual stresses and perforations. A comparison between the numerical simulations and the test results shows a good agreement proves that the finite element analysis can be used effectively to predict the ultimate capacity of strap-braced CFS shear panels. A total of 16 models with different variants of bracket length are investigated. Of particular interests were the specimens' maximum lateral load capacity and deformation behavior in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the optimum seismic characteristics of strap-braced CFS shear walls and the corresponding dimensions and configuration.     

设置粘滞阻尼墙钢框架结构耗能性能试验研究

设计了三榀不同类型的钢框架结构模型,通过对模型的快速水平周期加载试验,进行了设置粘滞阻尼墙钢框架结构减振性能的比较和分析。对设置阻尼墙后钢框架结构的破坏形态、滞回特性、骨架曲线、阻尼力、抗剪刚度、耗能性能、等效阻尼比等进行了研究,对阻尼墙不同布置方式对上述各项性能的影响进行了分析,并对上述各项性能与加载频率、位移幅值的变化关系进行了探讨。结果表明,设置阻尼墙后,钢框架结构的耗能能力和阻尼均有显著提高,结构的抗剪刚度增加,结构的地震响应显著减小。设置阻尼墙钢框架结构的滞回特性与频率、位移幅值相关。阻尼墙不同布置方式对结构滞回特性的影响不明显。     

A numerical study on seismic characteristics of knee-braced cold formed steel shear walls

Non-linear finite element analyses were carried out to evaluate and optimize the seismic characteristics of knee-braced cold formed steel shear walls using software ANSYS. Different structural characteristics including: material nonlinearity, geometric imperfection, residual stresses and perforations are taken into account. The numerical models were verified based on experimental tests. Agreement of the numerical simulations and the test results showed that finite element analysis can be used effectively to predict the ultimate capacity of knee-braced CFS shear panels. A total of 12 models with a various ranges of knee-elements' lengths were investigated. Of particular interests were the specimens' maximum lateral load capacity and deformation behavior in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the optimum seismic characteristics of knee-braced CFS shear walls and the corresponding dimensions and configuration.     

A numerical study on seismic characteristics of knee-braced cold formed steel shear walls

Non-linear finite element analyses were carried out to evaluate and optimize the seismic characteristics of knee-braced cold formed steel shear walls using software ANSYS. Different structural characteristics including: material nonlinearity, geometric imperfection, residual stresses and perforations are taken into account. The numerical models were verified based on experimental tests. Agreement of the numerical simulations and the test results showed that finite element analysis can be used effectively to predict the ultimate capacity of knee-braced CFS shear panels. A total of 12 models with a various ranges of knee-elements' lengths were investigated. Of particular interests were the specimens' maximum lateral load capacity and deformation behavior in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the optimum seismic characteristics of knee-braced CFS shear walls and the corresponding dimensions and configuration.     

钢管混凝土柱-钢梁平面框架抗震性能的试验研究

为了探讨钢管混凝土柱-钢梁平面框架的抗震性能,本文进行了12个框架试件在恒定轴力和水平反复荷载作用下的试验研究,主要考察了柱截面形状(圆形、方形)、含钢率(圆形:α=0.06,0.103;方形:α=0.125,0.126)、柱轴压比(圆形:n=0.06~0.60;方形:n=0.04~0.60)、梁柱线刚度比(圆形:i=0.36~0.58;方形:i=0.34~0.62)等参数对其力学性能的影响。试验结果表明:钢管混凝土柱-钢梁框架滞回曲线较为饱满,强度和刚度退化不明显;柱轴压比和含钢率对框架的承载力和抗震性能影响较大,随着轴压比的增大,框架的水平极限承载力下降,位移延性和耗能能力降低,而含钢率影响规律则相反;圆形截面柱框架抗震性能整体上优于方形截面柱框架。按照《钢管混凝土结构技术规程》(DBJ13—51—2003)设计的钢管混凝土框架能够满足结构抗震设计要求。     

钢结构住宅墙体(板)连接节点应用与研究现状

墙体(板)与钢框架结构的连接节点对提高钢框架的抗震性能有重要影响,节点的承载力、刚度是保证墙体(板)与钢框架共同作用的关键因素。对砌块墙体、钢筋混凝土墙体、轻钢龙骨墙板、蒸压加气混凝土墙板和复合墙板与钢框架的连接节点以及节点的破坏形式和作用机制进行概述,提出节点对钢框架抗震性能的影响程度,并对新型连接节点进行展望,为以后的工程应用提供理论与试验依据。     

波形钢板-混凝土组合剪力墙抗震性能试验研究

为研究波形钢板-混凝土组合剪力墙的抗震性能,完成了竖向波形钢板-混凝土组合剪力墙、水平波形钢板-混凝土组合剪力墙以及平钢板-混凝土组合剪力墙拟静力试验,研究了波形钢板-混凝土组合剪力墙在低周往复荷载作用下的变形能力和破坏模式,分析了荷载-位移滞回曲线、骨架曲线、各阶段特征荷载和位移值等,以及结构的破坏特征、变形和耗能能力、刚度和承载力退化。试验结果表明：波形钢板-混凝土组合剪力墙具有较大的抗侧刚度、较好的延性和耗能能力;与平钢板-混凝土组合剪力墙相比,波形钢板-混凝土组合剪力墙有较好的界面黏结性能,而平钢板-混凝土剪力墙由钢板变形引起的混凝土剥落严重;波形钢板-混凝土组合剪力墙的初始刚度较平钢板-混凝土组合剪力墙的高,竖向波形钢板-混凝土组合剪力墙的承载力和极限位移较水平波形钢板-混凝土组合剪力墙的高,波形钢板-混凝土组合剪力墙的承载力退化和刚度退化比平钢板-混凝土组合剪力墙的慢,表现出较好的受力性能。采用ABAQUS有限元软件可以较好地模拟试验,有限元分析结果表明,波形钢板的应力分布比较均匀,组合作用效应明显,适合在抗震结构中采用。     

钢带加强螺钉孔型冷弯型钢组合墙体抗震性能

为研究钢带加强螺钉孔对冷弯型钢组合墙体抗震性能的影响,对3个冷弯型钢组合墙体足尺试件进行低周反复加载试验,分析该加强形式对冷弯型钢组合墙体的破坏模式、侧向刚度、承载能力、延性以及耗能性能的影响。同时采用有限元软件OpenSEES对墙体进行数值分析。结果表明:钢带加强螺钉孔型冷弯型钢组合墙体的破坏形式仍然为螺钉连接失效和板缝滑移,钢带能够使覆面板的螺钉连接处得到加强,从而提高组合墙体的抗侧刚度和受剪承载力; 与螺钉孔未进行钢带加强的墙体试件(HS-140-A)相比,2个加强式的组合墙体试件(HS-140-B,HS-140-C)受剪承载力分别提高了32.5%,58.1%,抗侧刚度分别提高了31.7%,59.3%; 螺钉孔由钢带加强后,墙体试件的耗能性能显著提升; 3个试件的延性系数均大于8,呈现出良好的变形能力; 有限元模型能反映螺钉连接非线性行为对墙体滞回性能的影响,有限元分析结果与试验结果的相对误差控制在10%以内,模型具有较好的精度。     

Composite steel and concrete structural systems for seismic engineering

Research within the United States on seismic engineering of buildings using composite steel/concrete structural systems has increased dramatically in the past decade. This paper summarizes recent research on a number of these composite lateral resistance systems, including unbraced moment frames consisting of steel girders with concrete-filled steel tube (CFT) or steel reinforced concrete (SRC) columns; braced frames having concrete-filled steel tube columns; and a variety of composite and hybrid wall systems. The benefits of these structural systems relative to more common systems include their performance characteristics when subjected to service or ultimate loads, and their economy with respect both to material and construction. In addition, more in-depth research results will be presented on one of these composite systems, consisting of partially-restrained steel frames with composite reinforced concrete infill walls. The paper concludes with a summary of probable future design provisions for these composite systems.