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。     

国际期刊导读

采用有限元方法,对冷弯不锈钢方管、矩形管支撑和弦杆中的T型、X型及预应力X型节点进行数值分析。考虑几何非线性和材料非线性,获得节点承载力、破坏模式及荷载-位移曲线。利用试验结果,对T型、X型矩形管、方管节点的非线性有限元模型进行修正,直到有限元结果和试验结果足够吻合。采用修正后的有限元模型对172个T型、X型节点进行参数分析,研究冷弯不锈钢管节点强度和性能的影响。将数值分析和试验中获得的节点承载力与按规范计算的设计承载力进行对比。对不锈钢管结构,采用澳大利亚规范、新西兰规范计算;对碳素钢管结构,采用国际管结构发展与研究委员会设计规范和欧洲设计规范计算。通过可靠性分析,分别评价本文提出的设计方法和现有规范的可靠度。结果表明：采用本文方法计算的设计承载力更准确、更可靠。     

Simplified nonlinear finite element analysis of buildings with CFS shear wall panels

The use of panelized cold-formed steel framing as the primary structural system has become increasingly popular for low- and mid-rise residential and commercial construction. The primary load-resistant elements in such framing are the structural panels built with uniformly spaced cold-formed steel studs and covered with structural sheathing. By taking advantage of in-line-framing, the framing members can be designed manually by using load tables published by manufacturers or spreadsheets developed in-house. In the case where the overall behaviour of the structure is needed, a finite element analysis has to be carried out. Conducting a finite element analysis for such types of buildings can be time consuming due to the large number of elements involved in modeling the framing member and structural sheathing. In this paper we present a simplified approach for analyzing cold-formed steel buildings by using finite element methods. In the proposed method, a typical 1.2 m wide wall panel which is built with cold-formed steel studs and structural sheathing is modeled by a 16-node shell element having equivalent material properties. In addition, the nonlinear behaviour of shear wall panels is simulated by a stiffness degradation factor. Compared to the conventional finite element method, a lesser number of elements will be used in the proposed method for modeling a building structure. The accuracy and efficiency of the proposed method are demonstrated through the comparison of results of the proposed and the conventional method on single shear wall panels. In addition, an example of nonlinear analysis for a three-storey building is presented.     

Design of cold-formed stainless steel tubular T- and X-joints

This paper describes the numerical investigation of cold-formed stainless steel tubular T-joints, X-joints and X-joints with chord preload using finite element analysis. The stainless steel joints were fabricated from square hollow section (SHS) and rectangular hollow section (RHS) brace and chord members. The geometric and material nonlinearities of stainless steel tubular joints were carefully incorporated in the finite element models. The joint strengths, failure modes as well as load-deformation curves of stainless steel tubular joints were obtained from the numerical analysis. The nonlinear finite element models were calibrated against experimental results of cold-formed stainless steel SHS and RHS tubular T- and X-joints. Good agreement between the experimental and finite element analysis results was achieved. Therefore, an extensive parametric study of 172 T- and X-joints was then carried out using the verified finite element models to evaluate the effects of the strength and behaviour of cold-formed stainless steel tubular joints. The joint strengths obtained from the parametric study and tests were compared with the current design strengths calculated using the Australian/New Zealand Standard for stainless steel structures, CIDECT and Eurocode design rules for carbon steel tubular structures. Furthermore, design formulae of cold-formed stainless steel tubular T- and X-joints are proposed. A reliability analysis was performed to assess the reliability of the current and proposed design rules. It is shown that the design strengths calculated using the proposed equations are generally more accurate and reliable than those calculated using the current design rules.     

冷弯型钢剪力墙结构的非线性有限元简化分析

预制冷弯型钢框架在中、低层住宅及商业建筑中应用越来越广泛,主要通过由等间距螺栓连接且由面层包裹的结构板承载。利用框架特点,可通过厂家提供的负载表或试验数据设计构件。如果要获得结构的弹塑性性能,则需要进行有限元分析。由于需要大量单元来模拟构件和结构面层,此类结构的有限元分析耗时很长。介绍了一种通过有限元分析冷弯型钢结构的简化方法。以某1·2m宽、通过冷弯型钢螺栓连接和面层包裹的典型墙面为例,采用16结点壳单元进行模拟,并以刚度退化因子模拟剪力墙的非线性性能。与传统有限元法相比,新方法所需单元数更少。以某单面剪力墙为例进行分析,结果表明:新方法的精确度及效率更高。最后,采用新方法对某3层结构进行非线性分析。     

The design of bolted joints in cold-formed steel sections

This paper gives background information on the behaviour of bolted joints and the parameters that affect strength and flexibility. Design expressions for the bearing strength of bolted joints and for the joint movement under load are also given.

Moment connections are considered and design expressions for moment capacity and moment/rotation relationships for various bolt groups under practical conditions are given.

Computer analysis of cold-formed steel assemblies is outlined and two worked examples of manual analysis, incorporating the above design expressions, are given. It is shown how economical design may be achieved by selecting the correct semi-rigid joint in such assemblies.     

Effect of stressed-skin action on optimal design of cold-formed steel square and rectangular-shaped portal frame buildings

Cold-formed steel (CFS) portal frames can be a viable alternative to conventional hot-rolled steel portal frames. They are commonly used for low-rise commercial, light industrial and agricultural buildings. In this paper, the effect of stressed-skin action on the optimum design of CFS portal frames is investigated by conducting a minimum cost design optimisation on a building of span of 6 m, height-to-eaves of 3 m and frame spacing of 3 m; the effect of different number of bays are considered. For the purpose of this study, it is assumed that gables are rigid.The effect of stressed-skin action is larger for“square-shaped” buildings (i.e. when the span and length are the same on plan) and decreases as more bays are added(i.e. as the building becomes more “rectangular-shaped” on plan). The results of the minimum cost optimisation indicate that if stressed-skin action is taken into account, the cost of the internal frame can be reduced by around half for “square-shaped” buildings. It should be noted that this is a minimum cost optimisation, which is not the same as a minimum weight optimisation. It is also shown that a safe design of internal frames could be obtained by ignoring wind loads (i.e. designing the frame only for gravity loads),but this is limited to buildings having a “square-shape”.     

Einfluß der Nachgiebigkeit standardisierter Stirnplattenverbindungen auf die Bemessung verschieblicher Hallenrahmen

Effects of flexibility of standardized bolted end plate connections on the design of portal frames. This paper deals with standardized end plate connections of the German DSTV/DASt Catalogue [1]. In practice such joints are assumed rigid in the global analysis. Eurocode 3, part 1.8 [2] contains a calculation procedure for moment capacity and rotational stiffness of the joints, based on the component method. Studies [3], [4] showed that for most of the joints the flexibility has to be taken into account in the global analysis. The main question in practice is whether the design results of portal frames are changed if the flexibility of the joints is considered. Then in addition simple rules can be given and the common easier rigid analysis can be applied for simple structures. The presented results are limited to single sway frames with pinned and fixed end columns. The results are also applicable to non‐sway frames. In the paper the effects of the joint flexibility on the load carrying behaviour, the ultimate limit states and the serviceability limit states for the individual members and also on the design of the frames are shown. For the studied frames simple rules are given to execute a simple global analysis with rigid joints.     

基于滑移连接的防屈曲支撑钢框架节点抗震性能研究

防屈曲支撑（BRB）是一种拉压均可全截面屈服耗能而不屈曲的金属阻尼器,在建筑结构的抗震减震设计中得到广泛应用。然而,由于大变形下支撑框架节点存在显著开合效应,在罕遇地震作用下易出现节点板和相邻梁柱构件的提早断裂现象,限制了BRB抗震性能的充分发挥。为此,在总结BRB钢框架节点的现行设计方法及节点失效模式基础上,提出了可释放节点开合效应的滑移连接节点板,采用低摩擦材料减小接触面摩擦力。建立有限元模型,通过与传统焊接节点板对比,分析两种不同连接对节点板、梁柱和BRB受力性能的影响。以此为基础,设计该类节点足尺试验模型,对其进行拟静力试验,分析其在往复荷载下的抗震性能。研究结果表明：所提出的滑移连接可有效释放节点板与梁柱之间的切向约束和开合效应,显著降低了节点板的塑性损伤,实现了罕遇地震作用下节点板弹性的性能目标;梁塑性铰由节点板端部移至梁柱交界面处,降低了梁柱构件的剪力水平和塑性损伤;在层间位移角4%下各关键构件仍具有饱满稳定的滞回性能,显著提高了BRB钢框架的抗震性能。     

冷弯不锈钢管T型及X型节点设计

采用有限元方法,对冷弯不锈钢方管、矩形管支撑和弦杆中的T型、X型及预应力X型节点进行数值分析。考虑几何非线性和材料非线性,获得节点承载力、破坏模式及荷载-位移曲线。利用试验结果,对T型、X型矩形管、方管节点的非线性有限元模型进行修正,直到有限元结果和试验结果足够吻合。采用修正后的有限元模型对172个T型、X型节点进行参数分析,研究冷弯不锈钢管节点强度和性能的影响。将数值分析和试验中获得的节点承载力与按规范计算的设计承载力进行对比。对不锈钢管结构,采用澳大利亚规范、新西兰规范计算;对碳素钢管结构,采用国际管结构发展与研究委员会设计规范和欧洲设计规范计算。通过可靠性分析,分别评价本文提出的设计方法和现有规范的可靠度。结果表明:采用本文方法计算的设计承载力更准确、更可靠。     

Stiffness of joints in bolted connected cold-formed steel trusses

Web members in cold-formed steel trusses are usually assumed to have pinned connections at the ends, but the latest AISI Cold-Formed Steel Truss Design Standard allows for the joint stiffness to be considered in design. The paper summarizes experimental research performed for several years at the University of Timisoara, Romania, aimed at evaluating the real behaviour of bolted joints in cold-formed steel trusses. By means of tests on single lap joints and on truss sub-assemblies, a theoretical model for joint stiffness was proposed. The formula for the joint stiffness, from which the buckling length of web members was further determined, was also validated through a test on a full-scale truss.     

Analysis of bolted moment connections in cold-formed steel beam-column sub-frames

An extensive experimental investigation on bolted moment connections between cold-formed steel sections was carried out, and a total of 16 internal and external beam-column sub-frames with various connection configurations were tested under lateral loads. It is found that for those six beam-column sub-frames with large bolt pitches and thick gusset plates in the connections, flexural failure of connected sections is always critical. The moment resistances of the connections attain at least 85% of the moment capacities of the connected sections.This paper presents a theoretical investigation for predicting the structural behaviour of bolted moment connections between cold-formed steel sections. An analysis and design method for internal force distribution of the connections is presented, and hence a set of design rules for section failure of connected sections under combined bending and shear is proposed. Moreover, a non-linear finite element model of the beam-column sub-frames incorporating the effect of semi-rigid joints is also presented. On the basis of the measured moment joint rotation curves of the bolted moment connections, the overall lateral load-deflection curves of the sub-frames are predicted, and they are found to follow closely the curves obtained from tests. Furthermore, a semi-empirical formula for flexibility prediction of the bolted moment connections is also proposed after careful calibration against test data.It is demonstrated that the proposed rules are highly effective for predicting the structural performance of cold-formed steel frames with bolted moment connections. Hence, structural engineers are encouraged to design and build cold-formed steel structures with bolted moment connections to achieve practical and efficient construction.     

Tests of cold-formed high strength stainless steel compression members

The paper describes a test program on cold-formed high strength stainless steel compression members. The duplex stainless steel having the yield stress and tensile strength up to 750 and 850 MPa, respectively, was investigated. The material properties of the test specimens were obtained from tensile coupon and stub column tests. The test specimens were cold-rolled into square and rectangular hollow sections. The specimens were compressed between fixed ends at different column lengths. The initial overall geometric imperfections of the column specimens were measured. The strength and behaviour of cold-formed high strength stainless steel columns were investigated. The test strengths were compared with the design strengths predicted using the American, Australian/New Zealand and European specifications for cold-formed stainless steel structures. Generally, it is shown that the design strengths predicted by the three specifications are conservative for the cold-formed high strength stainless steel columns. In addition, reliability analysis was performed to evaluate the current design rules.     

Column tests of cold-formed steel non-symmetric lipped angle sections

The geometry of angle sections is simple, but the behaviour and design calculations of angle sections can be quite complicated. Furthermore, lipped angle sections with unequal flange widths form a non-symmetric section and the behaviour of the section is even more complicated than a singly-symmetric angle section with equal flange widths. A test program on cold-formed steel non-symmetric lipped angle columns is presented. The non-symmetric angle sections were brake-pressed from high strength structural steel sheets having nominal yield stresses of 450 and 550 MPa with plate thicknesses of 1.0, 1.5 and 1.9 mm. The material properties of the column specimens were obtained by tensile coupon tests. The behaviour and strengths of cold-formed steel non-symmetric lipped angle columns were investigated. The test strengths are compared with the design strengths calculated using the North American Specification for the design of cold-formed steel structural members. In addition, the current design rules in the North American Specification for cold-formed steel non-symmetric lipped angle columns are assessed using reliability analysis. It is shown that the design strengths are generally quite conservative.     

Global optimum design of cold-formed steel hat-shape beams

Using the computational neural network model developed recently by the authors, a comprehensive parametric study is performed for global optimization of cold-formed steel hat-shape beams based on the AISI Specifications. Design curves are presented for global optimum values of the thickness, the web-depth-to-thickness ratio, and the flange width-to-thickness ratio for unbraced beams having steel yield strengths of 250 and 345 N/mm². The computational neural network model guarantees a local optimum solution. The global optimum is found by an exhaustive search that is guided by a heuristic approach to reduce the search effort. An extensive parametric study yielded insights into the behavior of cold-formed steel beams that are then used as rules to reduce the search space and guide the exhaustive search. The procedure for finding the global optimum design of cold-formed steel beams is presented in a few recursive steps. The optimum design curves presented in this article can be of great value to structural design engineers.     

Experimental investigation for seismic performance of framed structures having longitudinally profiled plates

This paper presents an application of hot-rolled-thickness tapered steel plates, longitudinally profiled (LP) plates, for improving seismic resistance performance of portal-framed bridge pier bents. The scale of the model was 2.0 m beam length, 2.0 m column height using centerline framing dimensions and the rectangular stiffened cross section of LP plate for flange and constant thickness plate for web. One portal model which has different tapering ratios at both the end panels of the column flanges was tested, and another model with the constant cross section of 330×250×6 mm was also tested for comparison.

The main conclusion of this study is that the optimum tapering ratio of the LP plates can lead to larger spread of yield zones with less strain concentration compared to the uniform thickness plate. Seismic design guidelines are also proposed for portal frames having LP plates.     

Ultimate strength of bolted moment-connections between cold-formed steel members

The behaviour and design of bolted moment-connections between cold-formed steel members, formed by using brackets bolted to the webs of the section, is considered. The particular problem of the moment-capacity of such joints being lower than that of the cold-formed steel sections being connected because of web buckling, caused by the concentration of load transfer from the bolts, is addressed. In this paper, a combination of laboratory tests and finite element analyses is used to investigate this mode of failure. It is demonstrated that there is good agreement between the measured ultimate moment-capacity and that predicted by using the finite element method. A parametric study conducted using the finite element model shows that the moment-capacity of a practical size joint can be up to 20% lower than that of the cold-formed steel sections being connected. Web buckling so-caused must therefore be considered in the design of such connections.     

门式刚架的参数优化及设计建议

根据设计经验和规范的建议,本文选取了门式刚架的常用建筑尺寸和梁柱形状,在满足规范对门式刚架强度、刚度和稳定的前提下,以单位面积用钢量最小为优化目标,对影响刚架用钢量的主要离散参数（如结构形式、荷载、柱距、跨度、高度、坡度和梁柱构件等）进行了优化分析和设计.根据分析结果,提出了结构的最优布置及诸参数的建议取值,以供设计参考.     

门式轻钢建筑结构材料选用的经济性

基于大量门式轻型建筑结构试设计用钢量的统计数据和结构材料的市场价格、加工运输费用等成本消耗 ,建立了相关的数学模型 ,进而分析了在门式轻型建筑的结构设计中 ,不同强度等级的主次结构材料的相对经济性表现。分析表明 :在不同的条件下 ,不同等级材料的经济性能表现会发生优与劣的转换。分析主要考虑实际工程的应用 ,对具体的结构设计具有指导意义。     

屈服强度550MPa高强冷弯薄壁型钢轴压构件承载力设计

高强冷弯薄壁型钢结构在国外低层住宅和门式刚架体系中应用较广,国内已开始采用,但尚无相应设计规范可依。针对屈服强度550MPa高强钢材冷弯薄壁型钢结构常用的轴压构件的承载力设计方法进行了研究,包括其承载力计算模式及设计可靠度分析,并据此提出了相应的设计方法。最后,通过国内外现有相关试验数据的分析,验证了所提出的强度设计指标及承载力设计方法的合理性与可靠性。