Concrete panel thickness demand for the design of composite steel plate shear wall

Composite steel plate shear walls (C‐SPWs) are composed of an infill steel plate and reinforced concrete encasements. With an adequate thickness, the concrete encasement can effectively prevent the premature buckling of the infill steel plate. Researchers have provided nonconservative concrete thickness demands through analyses of approximate elastic buckling, for which the analytical model is too simplistic to simulate C‐SPW buckling. In this paper, the buckling of C‐SPW is addressed using a nonlinear finite element method. To assist this method, a formula for the buckling strength of C‐SPW is theoretically developed. Utilizing the results of nonlinear finite element analysis on C‐SPW, the effects of concrete panel thickness, concrete elastic modulus, infill steel plate thickness, panel aspect ratio, and stud spacing on the infill steel plate buckling are analyzed, and the critical drift ratio corresponding to the buckling of the infill steel plate is obtained. According to the criterion that the C‐SPW will not buckle until its drift ratio achieves the drift limit (0.4%), the minimum concrete panel thicknesses demands are captured from finite element analysis. Fitting these predicted minimum concrete thicknesses, an available formula is proposed for the concrete thickness demand in the design of C‐SPW.     

Influence of corrosion on the ultimate compressive strength of steel plates and stiffened panels

This study concentrates on a comparison between steel plate and stiffened panels subject to localised corrosion. A finite element analysis is used to investigate the effect of random corrosion on the compressive strength capacity of marine structural units. Variables include the extent of corrosion; slenderness ratio and aspect ratio. A corrosion prediction model is incorporated to determine the thickness reduction with time. Corrosion-induced volume loss results in a greater reduction of ultimate strength for slender plates compared to stiffened panels, up to 45%, showing the structural element selection can strongly influence the accuracy of the estimated corrosion damage effect.     

Ultimate shear strength of intact and cracked stiffened panels

The present paper focuses on the ultimate shear strength analysis of intact and cracked stiffened panels. Several potential parameters influencing the ultimate shear strength of intact panels are discussed, including the patterns and amplitudes of initial deflection, the slenderness and aspect ratios of the plates, and the boundary conditions defined by the torsional stiffness of support members. An empirical formula for the ultimate shear strength of intact stiffened panels is proposed based on parametric nonlinear finite element analyses in ANSYS. Furthermore, the ultimate shear strength characteristics of cracked stiffened panels are investigated in LS-DYNA with the implicit method. Three types of cracks are considered, namely vertical crack, horizontal crack and angular crack. A simplified method is put forward to calculate the equivalent crack length. And the formula for the ultimate shear strength of cracked stiffened panels is derived on the basis of the formula for intact stiffened panels.     

开洞加劲钢板剪力墙的抗侧承载力分析

为研究墙板开洞对加劲钢板剪力墙抗侧承载力的影响,首先建立了梁 壳混合弹塑性有限元单层墙板模型,研究了极限状态下影响开洞加劲墙板受剪承载力的关键因素。在此基础上,通过大量有限元计算和参数分析,提出了用于计算开洞加劲墙板受剪承载力折减率的简化计算式,并与有限元计算结果进行对比,精度满足要求。以3个加劲钢板剪力墙试件的低周往复荷载试验研究为基础,建立了精细有限元分析模型,有限元分析结果与试验结果吻合良好,证明了模型的合理性和准确性。提出了加劲钢板剪力墙结构抗侧承载力的理论模型和计算公式,理论计算结果与有限元分析结果吻合良好。     

Large deflection orthotropic plate approach to develop ultimate strength formulations for stiffened panels under combined biaxial compression/tension and lateral pressure

This paper uses the large deflection orthotropic plate approach to develop the ultimate strength formulations for steel stiffened panels under combined biaxial compression/tension and lateral pressure loads, considering the overall (grillage) buckling collapse mode. The object panel has a number of one-sided small stiffeners in either one or both orthogonal directions. The stiffened panel is then modeled as an equivalent orthotropic plate, for which the various elastic constants characterizing structural orthotropy are determined in a consistent systematic manner using classical theory of elasticity. The panel edges are considered to be simply supported. The influence of initial deflections is taken into account. The membrane stress distribution inside the panel under combined uniaxial loading (in either longitudinal or transverse direction) and lateral pressure is analyzed by solving the nonlinear governing differential equations of large deflection orthotropic plate theory. It is presumed that the panel collapses when the most highly stressed boundary location yields, resulting in closed-form expressions for the ultimate strength of the stiffened panel. Based on the insights previously developed through numerical studies, the panel ultimate strength interaction formulation between biaxial loads, with lateral pressure regarded as a secondary load component is then proposed as a relevant combination of the two sets of panel ultimate strength formulations, i.e. one for combined longitudinal axial load and lateral pressure and the other for combined transverse axial load and lateral pressure. The validity of the proposed ultimate strength formulations is verified by a comparison with nonlinear finite element and other numerical solutions.     

Study on the influence of the initial deflection and load combination on the collapse behaviour of continuous stiffened panels

Using the finite element analysis, a series stiffened panels under combined normal loads and biaxial compressions are conducted to investigate the effect of several influential factors on the ultimate limit states. Two spans/bays FE model with periodical boundary condition is adopted to consider the interaction between adjacent structural members. The initial deflections assumed as Fourier components including symmetric and asymmetric modes are used to identify the half-wave number of collapse of the local plate, which is compared with half-wave number of buckling calculated by formula. Based on the numerical results, the influences of half-wave number assumed in the equivalent initial imperfection and loads combination on the collapse behaviours of stiffened panels are discussed. It is found that lateral pressure might increase the ultimate strength of stiffened panels for the stiffener-induced failure modes. The one half-wave region of local plate influences significantly the load carrying capacity of stiffened panels.     

Nonlinear finite element method models for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions—Part II: Stiffened panels

The present paper (Part II) is a sequel to the previous paper (Part I) [Paik JK, Seo JK. Nonlinear finite element method models for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions—Part I: Plate elements. Thin-Walled Struct 2008, this issue, doi:10.1016/j.tws.2008.08.005.] on the application of nonlinear finite element methods for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions. In contrast to Part I dealing with plate elements, the present paper (Part II) treats stiffened panels surrounded by strong support members such as longitudinal girders and transverse frames. In similar to Part I, some important factors of influence such as structural dimensions, initial imperfections, loading types and computational techniques in association with ultimate limit states are studied. Some useful insights in terms of nonlinear finite element method modeling are developed using ANSYS code together with the ALPS/ULSAP semi-analytical method, the latter being for the purpose of a comparison.     

Equivalent thickness of cold-formed thin-walled channel sections with perforated webs under compression

Cold-formed thin-walled channel sections with perforated webs (thermal studs) are widely used in external wall panels in cold regions to reduce the cold bridging effect. However, no design method appears to be available for this type of structure. A possible method is to convert the perforated web of a thermal stud into a solid one with a reduced thickness (which is referred to as the equivalent thickness) and then adopt an existing design method for solid sections (e.g. EN 1993-1-3). This paper presents the development of a method to calculate the equivalent web thickness. The equivalent thickness calculation equation is based on regression analysis of a large number of finite element simulation results of elastic local buckling strength of perforated plates under compression, considering the effects of a number of different design variables such as plate depth, thickness, perforation patterns and dimensions of the plate. The FE simulations were carried out using a general FE software. This study suggests that the equivalent thickness is mainly related to the plate width to thickness ratio, the total width of perforation at the critical section and the width of the perforation zone (total plate width between the first and last perforation). A regression equation has been proposed to relate the equivalent thickness to these parameters. To demonstrate the validity of the proposed equivalent thickness method, the compression strengths of a large range of perforated columns have been simulated by using either the original perforated sections or the equivalent solid section; and a comparison of the simulation results shows good agreement between the two sets of results.     

Assessment of the ultimate strength of narrow stiffened panel test specimens

The ultimate strength of five narrow stiffened panels tested with two stiffeners under axial compression until collapse and beyond is determined by finite element analysis, and is compared with experimental results. Models with two half bays plus one full bays in the longitudinal direction are used in the finite element analysis. The material properties used in the finite element analysis have been evaluated by tensile tests. The initial geometrical imperfections also affect significantly the collapse behavior of the stiffened panels. Hence, the initial imperfections of the stiffened plates were measured before the experiment. The results of the FE analysis with measured and with equivalent initial imperfections are compared and conclusions are derived about the possible bias of the results when the initial imperfections are not measured.     

支管偏心对插板连接管节点承载力的影响分析

通过有限元数值分析方法,开展了不同支管偏心距及主管径厚比对插板连接管节点极限承载力的影响研究。负偏心越大,节点承载能力随之增强,节点板材料也越经济;同时需留意,负偏心并不一定总是有利的。总之,偏心距及主管径厚比的影响应在工程设计中加以合理、有效的利用。     

U形肋加劲板局部稳定性试验研究

U形肋加劲板是构成钢箱梁顶板、底板的主要板件,U形肋腹板与被加劲板局部失稳是其两种主要失稳破坏模式。为研究U形肋加劲板的局部稳定性能,分别设计并制作了U形肋腹板与被加劲板壁板两组局部稳定试件,并考虑U形肋腹板宽厚比、被加劲板宽厚比以及U形肋翼缘与腹板间弯曲半径变化。通过轴压试验得到了U形肋加劲板的局部失稳破坏模式、稳定承载力、应力-位移曲线以及局部稳定折减系数。试验研究表明：随着局部板件宽厚比的增大,试件由强度破坏转变为失稳破坏,且失稳破坏特征表现得越明显。当板件宽厚比不小于22.5时,宽厚比较大的板件先于其他板件失稳。U形肋腹板与翼缘之间弯曲半径增大时,U形肋腹板宽度及宽厚比变大,导致U形肋腹板稳定承载力降低。将试验结果与公路钢桥规范中的稳定系数曲线对比发现,对于钢桥规范中的稳定曲线,采用钢材屈服强度计算得到的板件稳定承载力明显小于试验值,而采用抗拉强度计算得到的板件稳定承载力接近试验值,说明采用钢桥规范计算U形肋加劲板稳定承载力,其安全系数和钢材的抗拉强度与屈服强度比值相当。     

混合钢U肋加劲板受压整体稳定承载力数值模拟与计算方法

建立受压混合钢U肋加劲板梁单元有限元模型并进行整体稳定分析,通过在梁单元模型中施加等效应力模拟U肋和被加劲板的不同强度,以5种不同强度组合的U肋加劲板试验试件的破坏模式和荷载-位移曲线对数值模拟方法进行验证。采用经试验验证的有限元模型,变化U肋高度、U肋与被加劲板强度与厚度、构件长度,得到混合钢U肋加劲板整体稳定系数,并与各国规范的柱曲线进行比较。结果表明:在压力荷载作用下,由于非等强钢U肋加劲板中钢材强度较低部分较早达到屈服,这将使得构件整体偏心受压,从而导致构件整体稳定系数均小于1; 等强钢M345-U345柱子曲线位于JTG D64—2015中的a,b类柱子曲线之间,并随着相对长细比的增大逐渐向b类柱子曲线靠近; 非等强钢柱子曲线在相对长细比较小时均低于等强钢M345-U345柱子曲线,而在相对长细比较大时的走势基本一致,其中M345-U420和M420-U345两条柱子曲线与JTG D64—2015中的b类柱子曲线接近; M345-U390和M390-U345两种柱子曲线随着相对长细比的增大逐步与等强钢M345-U345柱子曲线重合接近。     

超薄加劲钢板剪力墙受剪性能试验研究及数值分析

对于超薄加劲钢板剪力墙,由于钢板超薄,采用传统焊接工艺将导致严重的焊接变形,故需要采用改进焊接工艺,即将钢板墙在加劲肋处断开,进行弯折组合后焊接并形成加劲肋。为研究采用改进焊接工艺完成的超薄加劲钢板剪力墙的受剪性能,进行了足尺试件的受剪性能试验,研究了钢板墙的受剪破坏形态、滞回特性、承载能力及耗能能力等,验证了在竖向加劲肋位置采用的改进连接构造及焊缝工艺满足受剪承载力要求,并对不同钢柱截面、不同墙宽高比对钢板墙受剪性能的影响进行了对比分析。结果表明:采用改进工艺的钢板剪力墙满足受剪承载力要求且具有稳定的耗能能力,随着钢柱截面积增大,钢板墙的侧移刚度、峰值荷载均有所增加,相应的极限位移、耗能能力有所下降;随着墙宽高比减小,钢板墙的侧移刚度、屈服荷载、峰值荷载均相应降低,相应的极限位移、耗能能力有所提高。采用通用有限元分析软件ANSYS对超薄加劲钢板剪力墙的受剪性能试验进行了数值模拟,有限元结果与试验结果总体吻合良好,有限元分析可以很好地模拟超薄加劲钢板剪力墙的全受力过程和破坏模式。     

A simplified method for elastic large deflection analysis of plates and stiffened panels due to local buckling

A computational model for analysis of local buckling and postbuckling of stiffened panels is derived. The model provides a tool that is more accurate than existing design codes, and more efficient than nonlinear finite element methods. Any combination of biaxial in-plane compression or tension, shear, and lateral pressure may be analysed. Deflections are assumed in the form of trigonometric function series. The deformations are coupled such that continuity of rotation between the plate and the stiffener web is ensured, as well as longitudinal continuity of displacement. The response history is traced using energy principles and perturbation theory. The procedure is semi-analytical in the sense that all energy formulations are derived analytically, while a numerical method is used for solving the resulting set of equations, and for incrementation of the solution. The stress in certain critical points are checked using the von Mises yield criterion, and the onset of yielding is taken as an estimate of ultimate strength for design purposes.     

微孔混凝土预制叠合板力学性能试验研究

为得到微孔混凝土叠合板预制底板的力学性能,采用结构试验和有限元分析相结合的方法进行分析。首先对预制底板进行加载试验,得到预制底板的极限承载力,然后利用有限元分析软件ABAQUS模拟,所得数据与加载试验数据吻合,最后对比两种不同容重下微孔混凝土对叠合板底板极限承载力的影响。结果表明,微孔混凝土抗压强度越大,预制叠合板底板的极限承载力越大,与有限元模拟的极限承载力趋于一致。     

不同面外约束下带缝钢板剪力墙的抗剪性能研究

采用有限元软件ABAQUS,考虑几何非线性和面外初始缺陷的影响,对比分析钢筋混凝土板约束、刚性板约束以及无面外约束的带缝钢板剪力墙在水平荷载作用下的刚度、抗剪承载力、延性和耗能能力,并研究面外约束对带缝钢板的应力分布和面外屈曲的影响。结果表明:钢筋混凝土板可以抑制带缝钢板的弹性屈曲,降低带缝钢板的拉力带效应,提高带缝钢板剪力墙的延性、抗剪承载力和耗能能力。为了使钢筋混凝土板能更好地约束带缝钢板的面外屈曲,建议在剪力墙的小变形阶段,混凝土板不参与抗剪。     

Web openings in horizontally curved composite plate girders

The paper is concerned with the effects of circular or square web openings on the ultimate strength of horizontally curved composite plate girders. Finite element analysis using the computer package LUSAS has been employed to investigate the behavior and ultimate strength capacity of the girders with web openings of different proportions. The opening sizes and their locations within the web panels have been studied in detail, and the results are presented in the form of load–deflection and load–opening size plots. An approximate method to determine the ultimate strength capacity of horizontally curved composite plate girders accounting for the presence of web openings and composite action between the steel girder and concrete slab is presented. The accuracy of the method is established by comparing the predicted strength with the corresponding values predicted by the finite element method.     

Residual ultimate strength of cracked steel unstiffened and stiffened plates under longitudinal compression

This paper numerically deals with the influence of cracks (in terms of length and location) on the ultimate compressive strength characteristics of unstiffened and stiffened plate elements used in thin-walled structures. The cracks were presumed to be through-thickness, having no contact between their faces and no propagation was allowed. A series of nonlinear finite element analyses was conducted using ANSYS commercial finite element code in which the Newton–Raphson method has been employed to solve the nonlinear governing equations.This study indicates that the length of cracks and especially its location can significantly affect the ultimate strength characteristics of unstiffened and stiffened plate elements subjected to axial compressive action.     

板肋加劲板整体稳定数值模拟与受力机理研究

分别采用梁单元与板壳单元建立同时考虑初始几何缺陷和焊接残余应力的受压板肋加劲板整体稳定分析有限元模型,并以相应试验结果进行验证,得到梁与板壳单元模拟受压板肋加劲板整体稳定的异同。采用经验证的数值模拟方法,对不同弯曲失稳方向板肋加劲板的受力机理进行了研究。结果表明:采用板壳单元可以较好还原板肋加劲板整体稳定受力性能,板壳有限元模型与试验试件的承载力最大相对误差为4.2%,平均相对误差为1.48%; 梁单元模型与长(中长)柱试验试件的承载力最大相对误差为5.4%,平均相对误差为1.92%,与短柱试件的承载力相对误差虽仅为0.7%,但由于不能考虑板件发生的塑性失稳,其应力-位移曲线拟合情况相对较差; 不同弯曲失稳方向板肋加劲板整体稳定构件的破坏特征不同,其中对于板肋侧弯曲的板肋加劲板整体稳定构件,被加劲板边缘部分受压达到材料屈服强度且板肋边缘受拉达到屈服强度时,构件整体达到其承载极限; 对于被加劲板侧弯曲的板肋加劲板整体稳定构件,当板肋边缘部分受压达到材料屈服强度时,构件整体达到其承载极限; 对于实际工程中组成钢箱梁顶板的板肋加劲板,制作时应避免朝向板肋侧的变形。     

Ultimate strength of stiffened aluminium panels with predominantly torsional failure modes

The aim of this paper is to investigate the ultimate strength of aluminium plates with flatbar stiffeners with a torsional buckling or tripping failure mode. The formulations for torsional buckling of stiffeners in steel plating are still debated. Compared with steel structures, the ultimate strength of aluminium structures is sensitive not only to residual stresses and initial deformations, but also to the deterioration of mechanical strength in heat-affected zones (HAZ). In the present paper, the ultimate strength of stiffened aluminium panels with predominantly torsional failure modes is investigated by experimental and theoretical analysis. Stiffened panels made of the aluminium alloy AA5083-H116 and AA6082-T6 are considered. Various height of flatbar and various thickness of plate and stiffener were studied. The test results are compared with numerical predictions by using the finite element code ABAQUS (ABAQUS Version 5.7 (1997)), considering the influence of initial deflections, welding residual stresses and HAZ. The influence of HAZ and residual stresses on the ultimate strength of stiffened aluminium panels with the actual failure mode is discussed in detail. The numerical predictions are also compared with strength of material formulations used in DNV Rules for Classification of High Speed and Light Craft (Rules for classification of high speed and light craft, Hull structural design (1996)), NORSOK (Design of steel structures (1998)) all for steel, using the relevant values of the modulus elasticity and yield strength of aluminium, as well as EUROCODE 9 (Eurocode 9, Part 1-1: General rules (1998)).