Influence of central cracks on buckling and post-buckling behaviour of shear panels

It is generally accepted that cracks degrade the load bearing capacity of thin plates. The aim of the present paper is to investigate the influence of central cracks on the residual strength and stiffness degradation of shear panels using numerical finite element analysis. Various geometrical and mechanical characteristics of cracked panels such as the crack length, crack angle of inclination, panel aspect ratio, slenderness of panel, boundary conditions, Poisson's ratio, and Young's modulus are considered in the analyses. It is shown that the length and the angle of cracks may change the buckling behaviour of shear panels, and their combinational effects can result in substantial degradation.     

Shear resistance of longitudinally stiffened panels — Part 2: Numerical parametric study

This paper presents the FE analysis of the influence of different parameters on the shear resistance of panels with different arrangements of longitudinal stiffeners. The studied parameters were the stiffener bending stiffness, the panel aspect ratio, the stiffener position, the web slenderness and the flange rigidity. Longitudinal stiffeners of trapezoidal shape were compared to open T-stiffeners. The former proved to be more efficient, since a larger panel resistance is achieved, for which in addition a smaller stiffness of trapezoidal stiffeners is needed. Different features of the new Eurocode rules were verified against the FEA results as well. Three different procedures for the determination of panel slenderness were tested and the reduction of stiffener bending stiffness, prescribed due to a better correlation with tests on open stiffeners, was verified for both closed and open stiffeners. The influence of bending moment was also considered and the verification of shear and bending interaction was discussed. Finally, the flange contribution to shear resistance was critically analysed.     

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.     

Shear buckling in foam-filled web core sandwich panels using a Pasternak foundation model

Web core panels, foam-filled sandwich panels with interior webs, are a structurally efficient option for transverse load bearing applications. In web core panels, the interaction between the webs and core material can have a substantial impact on web shear buckling strength and is a key element of lightweight structural design. The present work is an investigation of web buckling behavior in web core panels under a distributed load. To solve this problem, web shear buckling was analyzed for the case of pure shear loading with foam support, and this analytic model was extended to the case of panels with a transverse distributed load. The webs are modeled as simply supported plates resting on a Pasternak elastic foundation. To that end, a buckling model for plates on a Pasternak foundation is presented, along with closed-form approximations of the solution for square and infinitely long plates. An accurate model for the foundation constants is developed using energy methods. Applicability of the plate buckling model to web core panels with transverse loads is presented via a finite element study. In panels, the slenderness and spacing of the webs have a slight effect on the boundary conditions between the webs and face sheets. The effect is relatively small, however, and the model presented in this work underpredicts buckling strength by less than 25%. The model in this work is thus a reasonable approach to the practical design of web core panels.     

十字加劲钢板剪力墙的抗剪极限承载力

我国《高层民用建筑钢结构技术规程》规定了钢板墙剪切弹性屈曲不先于剪切屈服,其明显的不足是没有利用板的屈曲后强度,同时弹性屈曲也不能作为结构在弹塑性阶段的设计指标。本文应用板的大挠度弹塑性有限元方法对十字加劲方形钢板剪力墙的屈曲后性能和极限承载力进行了系统的研究,并在大量数值分析的基础上,提出了以板的平均剪切应变相应的剪应力作为钢板剪力墙承载能力的极限状态,以达到利用薄板屈曲后强度的目的,进而提出了钢板剪力墙承载力的设计简化计算公式及钢板墙侧柱刚度阈值的计算公式,供设计参考。数值计算结果表明,影响钢板墙抗剪性能主要有三个参数:板高厚比、肋板刚度比和边柱刚度。     

钢筋混凝土剪力墙板的剪切滞回性能试验研究

为提高低矮钢筋混凝土剪力墙板的数值模拟精度,完善混凝土在循环荷载作用下的剪切本构理论,进行6个钢筋混凝土剪力墙板的循环剪切试验,研究配筋率及钢筋角度对钢筋混凝土剪力墙板在循环剪切应力作用下滞回性能及累积耗能能力的影响,得到试件的滞回曲线、骨架曲线、延性、刚度退化、累积耗能能力等。试验结果表明：所有试件均发生剪切破坏模式。配筋率对钢筋混凝土剪力墙板的抗剪承载力有一定影响,对其变形能力影响不明显。钢筋角度对钢筋混凝土剪力墙板的滞回曲线有显著影响,分布钢筋与剪力墙剪切斜裂缝夹角越小,其滞回曲线越饱满,累积塑性剪切角、累积延性比、等效黏滞阻尼比及累积塑性耗能系数越大,但其初始剪切刚度反而越低。该文的试验结果可为完善混凝土的本构理论提供参考。     

Steel–concrete composite shear walls using precast high performance fiber reinforced concrete panels

In this research, seismic performance of composite steel plate shear walls (CSPSWs) using high performance fiber reinforced concrete (HPFRC) panels is experimentally and numerically investigated. Three one‐story one‐bay CSPSW specimens using precast HPFRC panels were designed and fabricated for cyclic quasi‐static experiments. The HPFRC panels of composite shear wall specimens did not have any steel rebars. The main purpose of the study was to understand the effects of rigid and semirigid HPFRC panels on the seismic behavior of the system. Shear capacity, ultimate shear strength, lateral stiffness, energy dissipation, and ductility ratios of the specimens are evaluated. The experimental results demonstrate that specimens were able to resist lateral load up to at least interstory drift of 6%. Using HPFRC panels, CSPSW specimens becomes stiffer in the elastic region, and the yield displacement of the shear wall is decreased; therefore, the ductility ratio of the system is increased. It should be noted that ultimate shear strength, initial elastic stiffness, and energy absorption of specimens with an HPFRC panel on one side or both sides of the infill steel plate were approximately the same. However, using two HPFRC panels is not economical in comparison with CSPSW with an HPFRC panel on one side. Additionally, the second panel increases the seismic mass of the structure.     

Consideration of the problem of shearing and torsion of thin-walled beams with arbitrary cross-section

In structural analysis it is often necessary to determine the geometrical properties of cross-sectional areas. The location of the shear center is of greater importance for a thin-walled cross-section. The purpose of this paper is the computation of the shear center of arbitrary thin-walled cross-sections using the finite element method. The coupling problem of shearing and torsional deformation of thin-walled beams based on Saint Venant's theory is considered. This problem of coupled shearing and torsional deformation was analyzed using the finite element method in which the matrix of shear rigidity and torsional rigidity were determined. The shear center can be obtained by determining the coordinate axes so as to eliminate the nondiagonal terms. Then, applying the stiffness matrix of shear rigidity and torsional rigidity obtained in the above, the stiffness matrix of the space framework elements in which the shear deformation is taken into consideration is developed.     

用墙板单元研究确定剪力墙的合理位置

根据框架剪力墙结构的工作特点，采用一种墙板单元分析研究了剪力墙的合理布局等问题，简明地推导了墙板单元刚度矩阵，编制了电算程序。算例表明，该单元模型计算量小、精度高、又能直接给出剪力墙各分肢内力，可将剪力墙组合到框架中的任意位置。最后，提出一种经济实用、整体工作性能良好的新型隔层错跨剪力墙结构体系。     

含线连接夹心保温外挂墙板装配式混凝土剪力墙结构抗震性能研究

预制混凝土夹心保温外挂墙板与主体结构间常采用线支承的连接方式。为研究采用这一连接方式的外挂墙板对主体结构的刚度与抗震性能的影响,设计制作了2个分别含不开洞和开洞外挂墙板的剪力墙试件和1个作为对比的纯剪力墙试件,并进行了拟静力试验。结果表明：剪力墙试件的破坏模式差别不大,均是梁端先出现塑性铰,然后墙肢端部纵筋屈服,最终均是梁端、墙肢端部塑性铰区混凝土被压碎而破坏;采用上部线连接且避开塑性铰区,底部限位连接的方式能够实现与纯剪力墙试件相同的梁铰屈服机制;含外挂墙板可使结构初始刚度、承载力和耗能能力略有提高。在试验研究的基础上,采用ANSYS有限元软件对试件受力过程进行了数值模拟研究,与试验结果对比表明,所建立的有限元分析模型可以较好地模拟试件受力过程和破坏形态,可为下一步研究提供参考。     

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.     

Shear resistance of longitudinally stiffened panels—Part 1: Tests and numerical analysis of imperfections

This paper deals with the results of four full-scale tests, numerical simulation of tests and initial geometric imperfection analysis for longitudinally stiffened panels in shear. The tests examine the influence of varying position and bending stiffness of one trapezoidal longitudinal stiffener on the panel shear resistance and its buckling behaviour. The stiffeners were designed such as to obtain both global and local buckling shapes. Numerical simulations (FEA), based on the test girder geometry, the measured initial geometric imperfections and elastic-plastic material characteristic from the tensile tests, demonstrate a very good agreement with the tests. The initial geometric imperfection study on different verified numerical models shows a limited sensitivity of the panel shear capacity to any kind of imperfection shape variation with amplitude at the allowable fabrication tolerances. Finally, the paper offers some ideas for modelling geometric imperfections with regard to the design or research demands.     

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.     

On braced trapezoidal corrugated steel shear panels: An experimental and numerical study

In this study, a new system consisting of a combination of braces and steel infill panels called the braced corrugated steel shear panel (BCSSP) is presented. To obtain the hysteretic behavior of the proposed system, the quasi-static cyclic performances of two experimental specimens were first evaluated. The finite element modeling method was then verified based on the obtained experimental results. Additional numerical evaluations were carried out to investigate the effects of different parameters on the system. Subsequently, a relationship was established to estimate the buckling shear strength of the system without considering residual stresses. The results obtained from the parametric study indicate that the corrugated steel shear panel (CSSP) with the specifications of a = 30 mm, t = 2 mm, and θ = 90° had the highest energy dissipation capacity and ultimate strength while the CSSP with the specifications of a = 30 mm, t = 2 mm, and θ = 30° had the highest initial stiffness. It can thus be concluded that the latter CSSP has the best structural performance and that increasing the number of corrugations, corrugation angle, and plate thickness and decreasing the sub-panel width generally enhance the performance of CSSPs in terms of the stability of their hysteretic behaviors.     

Buckling analysis of stiffened circular cylindrical panels using differential quadrature element method

Differential quadrature element method (DQEM) for buckling analysis of stiffened circular cylindrical panels subjected to axial uniform compressive stresses is presented for the first time. The methodology and procedures are worked out in detail. The circular cylindrical panel and the stiffeners are treated separately. Governing differential equations are derived based on the equilibrium of the panel and the stiffener, and on compatibility conditions along the interface of panel elements and stiffeners. Torsional stiffness of the stiffener is ignored. Circular cylindrical panels with a stringer stiffener or a chordwise stiffener are analyzed by the DQEM, and the results are compared with previously published data to verify the established methodology and procedures. Some new results are presented for the circular cylindrical panels with two orthogonal stiffeners.     

Experimental assessment of the seismic performance of a prefabricated concrete structural wall system

In this study the authors investigated experimentally the behaviour of prefabricated reinforced concrete sandwich panels (RCSPs) under simulated seismic loading through a large experimental campaign. Tests were carried out on single full-scale panels with or without openings, simulating the behaviour of lateral resisting cantilever and fixed-end walls. Tests were also carried out on a 2-storey full-scale H-shaped structure constructed by individual panels which were properly joined together. The performance and failure mode of all panels tested revealed strong coupling between flexure and shear due to the squat-type geometry of the panels. However due to their well-detailed reinforcement, all panels exhibited only a relatively gradual strength and stiffness degradation and in no case did any panel suffer from sudden shear failure. The prefabricated walls of the structural system investigated herein seem to meet all the requirements of Eurocode 8 for walls to be designed as “large lightly reinforced walls”; however this assumption should be supported with further experimental and analytical studies.     

加劲钢板剪力墙抗剪性能分析

利用ANSYS有限元软件对交叉加劲钢板剪力墙的抗剪性能进行了研究,重点分析了肋板刚度比和加劲肋宽厚比对剪力墙荷载—位移曲线的影响。研究表明,设置交叉加劲肋能够显著提高钢板剪力墙的承载能力;肋板刚度比对于厚板和薄板抗剪性能的影响不同,对薄板的影响大于厚板;然而无论是厚板还是薄板,加劲肋宽厚比对于墙板荷载—位移曲线的影响都很小。     

形状优化的装配式剪切型金属阻尼器力学性能研究

为了解决剪切型金属阻尼器应力集中和焊接区的热应力影响问题，提高其耗能效率，提出一种采用等应力线优化形状的装配式剪切型金属阻尼器。根据弹塑性力学J2理论寻找在一定外力条件下的等应力线，以等应力线同时进入屈服为条件设定剪切型金属阻尼器耗能片形状，并进一步推导了供设计使用的阻尼器初始刚度与承载力的计算式；建立了阻尼器的精细有限元数值模型，以模拟其低周往复加载的力学性能，分析阻尼器的变形模式与耗能能力，并进行了4个阻尼器的拟静力试验研究。试验与数值分析结果表明：提出的阻尼器初始刚度与承载力计算式的计算值与数值分析和试验结果吻合较好；形状优化阻尼器具有良好的低周疲劳性能与稳定的耗能能力；与未优化阻尼器相比，形状优化剪切型金属阻尼器的塑性变形分布更加均匀，最大累积等效塑性应变明显减小；采用全螺栓连接，易于更换。     

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。     

FRP蜂窝夹芯板在扭矩作用下的有限元分析

本文对FRP蜂窝夹芯板在扭矩作用下的工作性能进行了研究。采用ABAQUS有限元软件,建立了两类模型,即实际尺寸的模型和等效应力的模型。特别是等效应力模型,采用微观、宏观力学确定了面板的材料属性,采用均质化方法和材料力学方法得到了蜂窝芯层的材料属性,这都为有限元建模奠定了基础。经过比较,实际尺寸的模型与理论结果吻合较好。然而,由于这些模型比较复杂,需要大量的要素,采用等效应力模型也是合适的。与理论数据相比较,等效应力模型也能提供满意的结果。