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。     

Strength and stiffness determination of shear wall panels in cold-formed steel framing

Shear wall panels, as the one of the primary lateral load resisting elements, have been extensively used in lightweight framing of low- and mid-rise residential construction, particularly in seismic applications. In current practice, lateral strengths of shear wall panels with cold-formed steel framing are primarily determined by tests, owing to the lack of applicable analytical methods. Meanwhile, the use of numerical methods such as the finite element method has rarely been employed in the design practice to determine the lateral strength of shear wall panels due to the extensive amount of computational effort associated with the modelling. Presented in this paper is an analytical method to determine the ultimate lateral strength of the shear wall panel and its associated displacement. The method takes into account the factors that primarily affect the behaviour and the strength of the shear wall panel, such as material properties, geometrical dimensions and construction details. Lateral strengths obtained from the proposed method for shear wall panels with different sheathing materials and steel stud thicknesses, sizes and spacing of sheathing-to-stud fasteners were compared with those of recent experimental investigations. The comparison demonstrates that the predicted results are in good agreement with those of the tests. Therefore, it is recommended that the proposed method be used in engineering practice.     

钢网格剪力墙力学性能试验研究及有限元分析

为解决现有加劲钢板剪力墙现场安装难度高、焊接工作量大等问题,提出了装配式钢网格剪力墙结构。为考察该抗侧力体系的静力性能和抗震性能,对2个缩尺模型进行了单调水平加载和低周往复加载试验。基于ABAQUS建立有限元分析模型,验证钢网格剪力墙有限元模型的准确性。研究结果表明：在单调荷载或低周往复荷载作用下,试验与有限元分析结果较为一致,试件均表现出良好的抗侧刚度、延性和耗能能力;其破坏过程为中间位置的T形钢构件首先出现全截面屈服,随着位移荷载的增大,靠近梁柱节点位置的较短T形钢构件开始局部屈服,最终所有T形钢构件均达到了全截面屈服,试件破坏形式为中部T形钢构件拉断,失效模式较为合理;试件破坏时的层间位移角均达到了3.6%以上,延性系数达到5.35以上,试件在每级荷载循环后的强度退化系数均在0.92以上,受力性能稳定。     

Buckling and post-buckling strength of shear panels degraded by near border cracks

There have been many reports on fatigue cracks induced on slender webs breathing under repeated loading. Cracks may also initiate due to welding, corrosion, or mishandling. Edge cracks are generally formed adjacent to the flange, stiffeners or any kind of boundary members. It is also generally accepted that cracks degrade the load bearing capacity of thin panels. The aim of this paper is to investigate the buckling and the post-buckling behaviour of shear panels that have edge cracks. Cracks are presumed to be either parallel or normal to the boundaries. The influence of various geometrical and mechanical characteristics of cracks and panels, (such as the length and the position of cracks, boundary conditions, the aspect ratio and slenderness of panels, and Poisson’s ratio and Young’s modulus of materials) is determined by means of linear and nonlinear finite element analysis. It is shown that a substantial degradation can be anticipated if a crack forms in the area at which tension field occurs.     

钢筋混凝土剪力墙非线性有限元分析

对钢筋混凝土剪力墙非线性有限元分析的几个问题做了一些探讨，进一步完善了剪力墙非线性有限元分析方法，为人们认识及分析钢筋混凝土剪力墙提供了工具。     

高层建筑结构计算软件中的剪力墙模型简化

在高层结构分析中 ,对剪力墙的模型化是其关键问题 ,它直接决定了高层结构分析模型的科学性 ,同时也决定了分析软件的精度。本文主要介绍现在高层结构分析计算软件中剪力墙的三种简化模型。最后就高层建筑结构计算分析软件在分析剪力墙的精确性方面作一点展望     

Ultimate shear strength of long web panels

Both the Basler model and the Rockey model developed during the early 1960s and 1970s predict reasonably well the postbuckling strength of plate girder web panels subjected to pure shear for panels having an aspect ratio (stiffener spacing/web depth) less than or equal to 1.5. The accuracy of these models deviates significantly when applied to panels with an aspect ratio equal to or greater than 3.0. The majority of all steel structures in the world have been designed and built based on these two major theories or their derivatives that recognize the reserve strength afforded by tension field action in the postbuckling stage. However, no single theory has ever emerged that explains the seemingly elusive stress distributions present in web panels during postbuckling until Yoo and Lee shed light on the true mechanics of web panel postbuckling behavior in shear.This paper revisits the validity of an arbitrary limit imposed by Basler on the maximum aspect ratio of a transversely stiffened web panel and develops a new method of predicting the ultimate shear strength of web panels with high aspect ratios.     

冷弯薄壁型钢墙体恢复力模型及房屋地震反应简化分析方法研究

基于10片1∶1冷弯薄壁型钢墙体抗剪滞回性能试验结果,采用SAP2000中多线段塑性Pivot连接单元的滞回规则,进行墙体的恢复力模型及冷弯薄壁型钢房屋的动力非线性简化分析方法研究。研究表明:墙体的骨架曲线可采用退化四线型模型模拟;双柱墙体Pivot模型参数可取α=10、β=0.1,单柱墙体可取α=10、β=0.15;非线性简化分析与试验分析得到的滞回曲线的外包络线基本一致,耗能能力相当,简化方法能较好地模拟墙体的强度、刚度退化和捏缩效应;三层房屋结构简化计算模型的第1、第2阶振型与试验观测一致,频率分别相差11%和2%;模型结构与试验的地震反应分析结果吻合较好,表明简化计算方法可用于冷弯薄壁型钢房屋的弹性和弹塑性地震反应分析。     

Monotonic shear tests of cold-formed steel wall frames with sheathing

This research is focused on the experimental study of the structural strength of cold-formed steel wall frames with sheathing under monotonic shear loading. Two aspect ratios, 1.0 and 2.0 were utilized in the design of wall specimens. Three different kinds of sheathing material, gypsum board, calcium silicate board, and oriented-strand board, with two different thicknesses (9 and 12 mm) were adopted in the test specimens. The ultimate strength, stiffness, energy absorption, and ductility ratio were studied for each test specimen. In final, the ductility ratios of the cold-formed steel wall frames similar to the wall configuration conducted in this study are proposed.     

带竖缝钢板剪力墙滞回性能有限元分析

阐述了带竖缝钢板剪力墙是一种新型的抗侧力构件,具有良好的结构性能,通过ANSYS对其进行有限元模拟分析,分析了其滞回性能,并与试验结果进行比较,分析其产生误差的原因,指出设计时应注意的问题。     

Tests and finite element analysis of pin-ended channel columns with inclined simple edge stiffeners

This paper presents an experimental investigation and a finite element analysis on cold-formed channels with inclined simple edge stiffeners compressed between pinned ends. Compression tests of pin-ended channel columns with inclined simple edge stiffeners have not been performed till now. A total of 36 channel specimens including three different cross sections with different edge stiffener inclined angles and column lengths were tested. Detailed measurements of initial geometric imperfections and material properties of the specimens were also conducted before the above tests. Failure modes include local buckling, distortional buckling, flexural buckling and interaction among these buckling modes were observed in tests. The results indicate that inclined angle and loading position significantly affect the ultimate load-carrying capacity and failure mode of specimens. Moreover, a non-linear finite element model was developed and verified against tests. Geometric and material non-linearities were included in the model. Results from the finite element analysis agree well with experimentally ultimate loads and failure modes. However, it should be improved on prediction for certain displacement.     

浅谈建筑结构中剪力墙有限元分析模型

介绍了薄壁柱、墙组元、壳墙元、板—梁墙元以及通用有限元的力学模型,阐述了各种模型的假定,分析了各种墙单元模型的特点以及各自在工程中的应用情况,通过对剪力墙单元力学模型的分析,有助于深入认识不同结构分析软件的特点。     

Fire performance of cold-formed steel wall panels and prediction of their fire resistance rating

Recent research at the Queensland University of Technology has investigated the structural and thermal behaviour of load bearing Light gauge Steel Frame (LSF) wall systems made of 1.15 mm G500 steel studs and varying plasterboard and insulation configurations (cavity and external insulation) using full scale fire tests. Suitable finite element models of LSF walls were then developed and validated by comparing with test results. In this study, the validated finite element models of LSF wall panels subject to standard fire conditions were used in a detailed parametric study to investigate the effects of important parameters such as steel grade and thickness, plasterboard screw spacing, plasterboard lateral restraint, insulation materials and load ratio on their performance under standard fire conditions. Suitable equations were proposed to predict the time–temperature profiles of LSF wall studs with eight different plasterboard-insulation configurations, and used in the finite element analyses. Finite element parametric studies produced extensive fire performance data for the LSF wall panels in the form of load ratio versus time and critical hot flange (failure) temperature curves for eight wall configurations. This data demonstrated the superior fire performance of externally insulated LSF wall panels made of different steel grades and thicknesses. It also led to the development of a set of equations to predict the important relationship between the load ratio and the critical hot flange temperature of LSF wall studs. Finally this paper proposes a simplified method to predict the fire resistance rating of LSF walls based on the two proposed set of equations for the load ratio–hot flange temperature and the time–temperature relationships.     

剪力墙结构有限元分析

简述了剪力墙结构研究的现状,针对目前数值分析中单元选取的不便之处,通过理论研究,构造出一种适合短肢剪力墙有限元分析的新的单元,通过数值分析模拟和理论分析计算,发现该单元具有较高的计算精度和速度,应用价值较高。     

双肢剪力墙有限元计算模型的研究

在使用有限元分析软件进行分析计算时,连梁有两种建模方式:按框架梁输入和按墙开洞输入。不同的建模方式对应不同的计算模型,不同的计算模型会导致结构性质和构件内力产生较大差异,所以进行双肢剪力墙结构计算时,必须结合实际情况,综合考虑各种因素选择合适的建模方式。本文拟通过SAP2000分析不同跨高比下两种模型的楼层位移、梁端弯矩,进而找出双肢剪力墙如何建立有限元模型的方法。     

Detailing recommendations for 1.83 m wide cold-formed steel shear walls with steel sheathing

The paper presents an experimental investigation on 1.83 m wide, 2.44 m high cold-formed steel (CFS) stud framed shear walls using steel sheet sheathing. Four wall configurations were studied through monotonic and cyclic tests. The test results indicated that besides the sheet buckling and screw pull out, the buckling of interior studs might occur for the 1.83 m CFS walls. To prevent the failure in the studs, special detailing was developed in this research. It was discovered that the special detailing could increase both the shear strength and the ductility of the shear walls. The research also found that the codified nominal shear strengths can be conservatively used for walls with an aspect ratio of 3:2. Based on the test results, the nominal seismic shear strength for 1.83 m wide CFS shear walls was established for design purposes.     

Experimental study of screw connections in CFS-calcium silicate board wall panels

Cold-formed steel (CFS) wall panels with different board materials are used extensively in residential and commercial buildings to resist lateral loads by in-plane shear, in addition to helping the studs resist gravity loads. Generally the screw connection between the board and CFS skeleton frame, which experience shear, dictates the behaviour and strength of such panels. In this paper, details of an experimental study on behaviour and strength of the screw connections between the cold-formed steel profiles and calcium silicate boards, under monotonic and cyclic shear loading, are presented. The objectives of the experimental study are: (a) to develop a new test procedure that realistically represents the behaviour and failure of screw connections in CFS wall panels; (b) to investigate the effect of edge distance of the screws and thickness of the boards on behaviour and strength; (c) to study behaviour under monotonic and cyclic loading; (d) to develop the values of the important parameters that determine the load–deformation behaviour of the screw connection in such wall panels under in-plane shear; and (e) to develop design equation to evaluate the ultimate shear strength and its resistance factor required in load resistance factor design (LRFD).     

Strain based finite element for the vibration of cylindrical panels with openings

This paper investigates the effect of cut-outs on the dynamic behaviour of cylindrical panels, using a newly developed strain based finite element. The developed element is based on assumed strains and has only five necessary degrees of freedom at each corner node. The displacement fields of the element satisfy the exact requirement of rigid body displacements. The efficiency of the element is tested by applying it to the calculation of natural frequencies of shells. Investigations are first carried out to test the convergence of the element and to establish the mesh size to be used. The element is further applied to analyse cylindrical panels with cut-outs. Simply supported as well as clamped panels on their edges were considered and the effects of the size and location of the openings on the natural frequencies are investigated. The subspace iteration technique which is shown to have an economising effect, is used to obtain the natural frequencies and the associated modes of vibration.     

Modal analysis of cold-formed pallet rack structures with semi-rigid connections

The three dimensional (3D) model of conventional pallet racking systems were prepared using the finite element program ANSYS and free vibration modal analysis carried out on conventional pallet racks with the 18 types of column sections developed along with semi-rigid connection. The stiffness of the connector was tested using the conventional cantilever method and also using a double cantilever method. Non-linear finite element analysis of both the tests was carried out. From the experimental study on connection and finite element modal analysis, a simple analytical model that captures the seismic behavior of storage racks in their down aisle direction is proposed. The model is aimed at developing simplified equation for the fundamental period of storage racks in their down aisle direction. A parametric study was carried out to find out fundamental mode shape and time period. Finite element method is used for the accuracy and appropriateness of cold-formed steel frame.     

Numerical modelling for buckling analysis of cracked shear panels

Utilizing shear panels is a common practice in civil, naval and aerospace engineering structures and the performance of the one with thin steel plate shear walls is an interesting issue of ongoing related researches. It is a well-recognized phenomenon that the behaviour, and consequently the design procedure, of shear panels are mostly dominated by pre-yield buckling occurrence. However the existence of crack defects due to corrosion, fatigue, welding or mishandling may shed more complexities to such panels in terms of bearing capacity degradation.

In this paper, a procedure for modelling and analysis of shear panels containing central or edge cracks, using the finite element method, is presented. Results can be incorporated to recognize the required mesh refinements around the crack tips and edges. In addition, the effect of relative crack length on buckling capacity of shear panels is investigated.