蒙皮支撑的钢构件静力工作性能研究

提出了蒙皮支撑钢构件静力工作性能的非线性有限元分析方法，用该方法分析了蒙皮支撑梁和蒙皮支撑柱的基本受力性能，并考虑了多种因素对蒙皮支撑构件性能的影响。分析结果表明，蒙皮对构件的侧向支撑及扭转约束作用可以大大改善构件的静力性能并提高构件的承载力。     

门式刚架蒙皮抗剪支撑作用的研究

通过分析受力蒙皮单元抗剪支撑作用,利用刚度等效原理把受力蒙皮单元等效成支撑,从而建立考虑蒙皮效应的门式刚架轻钢结构计算模型,提出蒙皮抗剪支撑作用的实用计算方法。     

钢管混凝土框架结构力学性能非线性有限元分析

在考虑材料非线性和几何非线性的基础上进行了钢管混凝土柱-钢梁平面框架结构力学性能的非线性有限元分析,核心混凝土采用考虑钢管约束效应的应力-应变关系,钢材采用二次塑流模型或线性强化模型,通过在有限元公式中引入几何刚度矩阵,并在荷载步中更新坐标描述二阶效应来反映框架结构的几何非线性效应。基于近似修正的拉格朗日表述来反映框架结构变形前后位形之间的关系,利用虚功原理建立相应的增量平衡方程,并采用位移增量法求解非线性有限元方程,理论计算结果得到试验结果的验证。分析表明,基于非线性纤维梁-柱单元理论的分析方法可以反映钢管混凝土框架在受力过程中构件屈服和塑性分别沿截面和杆长两个方向扩展的分布塑性特征,并考虑初始缺陷、残余应力等,因此可较好地反映钢管混凝土框架的力学性能。在此基础上对影响钢管混凝土框架力学性能的主要因素进行了参数分析,分析的具体结果可供有关研究或工程应用参考。     

金属蒙皮支撑C形檩条的计算理论

归纳了开口冷弯薄壁截面的几何特征和薄壁杆件的受力性能、特征,对蒙皮支撑C形檩条的抗剪刚度和抗扭刚度进行了分析,研究蒙皮支撑C形檩条在风吸力作用下的基本性能,旨在更深入了解金属蒙皮支撑檩条在整体蒙皮结构中所起的作用。     

圆钢管混凝土结构非线性有限元分析

基于合理的钢管混凝土拉、压材料数值本构模型,采用U.L.列式单元增量平衡方程,引入分层梁单元材料非线性分析理论,通过调整截面形心应变和曲率,使梁端内外力平衡,完善了分层单元法,编制了相应的非线性有限元程序,并对已有钢管混凝土结构面内受力,如钢管混凝土偏压柱、不等端弯矩钢管混凝土偏压柱、钢管混凝土压弯构件和钢管混凝土模型拱肋等试验资料进行双重非线性有限元分析。结果表明:几组钢管混凝土模型拱和钢管混凝土压弯构件的荷载-变形曲线和极限承载力与试验结果最接近,验证了本文方法与程序的可靠性,通过与其他学者计算结果相比,表明本文方法具有较高的计算精度。     

无粘结预应力混凝土平板-T形中柱节点抗震性能试验研究

在6个1:1.5缩尺无粘结预应力混凝土平板-T形中柱节点试件的试验基础上,本文对各试件在低周反复荷载作用下的受力过程和破坏特性进行描述,分析了无粘结预应力钢筋应力增量变化特点、板暗梁面筋和节点区附近板暗梁箍筋的应力变化特点,对比了T形柱不同截面参数和不平衡弯矩不同加载方向对该节点抗震性能和不平衡弯矩分配的影响,对该节点的抗震性能进行了评价。试验结果表明,节点的不平衡弯矩主要靠板的弯曲作用来传递,T形柱腹板长度c1对节点的抗震性能和不平衡弯矩分配系数等方面具有决定作用。文中采用隔离体方法对板柱节点进行受力分析,推导了节点剪力传递弯矩系数的计算公式,提出了节点理论抗弯承载力的计算方法。试验结果对工程设计有一定的参考价值。     

受力蒙皮体的有限元计算分析

以蒙皮组合体为研究对象,采用非线性有限元方法,将受力蒙皮体离散成不同单元,对其进行了计算分析,得出了蒙皮组合体在平面内剪切荷载作用下的工作性能以及各种因素对其抗剪性能的影响。最后将有限元计算结果与欧洲建议(EUR)的简化计算结果进行了比较,结果表明二者吻合较好。     

钢筋混凝土柱低周反复试验数值分析的参数研究

为较好研究钢筋混凝土柱抗震性能的数值模拟方法,本文通过合理选取材料本构关系,采用有限元软件OpenSees中由纤维截面建立的基于力的梁柱单元对课题组2根及清华大学4根钢筋混凝土柱低周反复加载试验试件进行数值模拟,并与试验结果进行对比。结果表明,采用基于力的纤维截面梁柱单元能够较好地模拟低周反复荷载作用下柱的滞回反应以及耗能特性;基于修正的Kent-Park方法计算的受约束混凝土本构关系参数能较好地体现柱的受力特征。     

双向偏压异形柱构件非线性分析方法的研究

基于双向偏压作用下钢筋混凝土异形柱的材料非线性和几何非线性,通过修正x、y方向的曲率间的关系,以x方向的曲率和截面形心应变为基本未知量,采用数值积分方法对钢筋混凝土异形柱构件进行非线性全过程分析,得到了截面的M-曲线。通过与实验结果得到的M-全曲线进行对比,两者计算结果吻合较好。此法概念清晰,理论严密,适用于截面单元划分成大单元的计算。     

巨型钢框架预应力复合支撑体系中复合支撑内力调平方法研究

为了消除巨型柱与支撑连接处的剪力突变,提高巨型柱的受力性能,提出了在竖向均布荷载和水平荷载作用下的复合支撑内力调平方法。以巨型钢框架预应力复合支撑体系为例,通过改变支撑预应力初始取值、支撑截面等参数来实现复合支撑水平方向内力的平衡,连接处巨型柱没有发生剪力突变,验证了调平方法的正确性。研究表明:在竖向均布对称荷载作用下,通过调节拉索初拉力可实现复合支撑内力调平;在反对称水平均布荷载和集中荷载作用下,通过改变拉索截面面积可实现复合支撑内力平衡。     

重组竹压弯构件承载力非弹性分析方法

重组竹是一种类似于木材的定向复合材料,其顺纹受压应力-应变非线性特征显著,故重组竹受弯构件和压弯构件在承载能力极限状态下亦呈明显的非线性特征。而现行相关设计规范仍采用线弹性计算方法,不能准确预估压弯构件的承载力。为此,将重组竹受弯构件和偏心受压构件统一为压弯构件,基于Euler梁理论,考虑材料的非线性应力-应变关系,建立了压弯构件在非弹性工作状态下的承载力计算方法。通过重组竹梁受弯试验和重组竹柱偏心受压试验,验证了所提方法的准确性。     

Multi-level enhancement of structural behavior of bracing systems with coupling beams at floor level

Despite good rigidity, braced frames have weak nonlinear behavior and inadequate distribution of ductility in stories, which cause significant structural damage. In this research, a seismic resistant system called coupled concentrically braced frame (CCBF) is developed to enhance the performance of braced frames by coupling them with a beam. In this case, the coupling beams are the primary source for ductility of the system, and after their yielding in more severe earthquakes, the structure continues to benefit from the ductility of the braces as the secondary source; therefore, the system has two-level behavior caused by different probable seismic excitations. In this case, in addition to maintaining the stiffness of the two concentrically braced frames, the coupling beams resist against the movement of the braced frames, and as a result, the stiffness of the system is increased. Therefore, lighter elements can be used to resist lateral loads. Linear and nonlinear analyses of CCBF, and its comparison with other braced frames, indicate that participation of the coupling beams provides an adequate stiffness and ductility. These frames have more stable nonlinear behavior than conventional ones and continue their nonlinear behavior even after fracture of coupling beams in severe earthquakes.     

残余应力和应变率对地震作用下钢柱的循环屈曲影响

对4个足尺W型柱试件进行受压屈曲试验,研究强震下多层支撑钢框架中柱的屈曲性能。工况包括单调、循环的轴心和偏心加载。在其中一个试验中施加动力循环荷载,在另一个循环试验中施加端弯矩。柱截面尺寸为W310×129(类型1),材质为ASTMA992钢。研究柱的长细比为48时绕弱轴屈曲的性能。基于杆件横截面的纤维离散化,采用数值方法模拟试件的响应。在数值模型中,描述并考虑了柱残余应力和应变率对材料属性的影响。研究表明:在地震作用下,钢柱能持续几个非线性屈曲循环,并承受重力荷载。仅在首次屈曲时,残余应力对柱的性能有影响,并在屈曲和降低受压承载力之前逐渐降低柱的切向刚度。强震下的高应变率提高了柱的屈曲强度和后屈曲强度。当采用非线性梁柱单元时,能充分预测钢柱的循环屈曲性能。在本模型中,通过横截面纤维离散化考虑了残余应力和应变率的影响。     

低周反复荷载下约束混凝土模型的比较研究

从众多约束混凝土应力-应变规律模型中优选出其中四种,部分改造并添加了滞回关系,将其分别加到基于纤维模型梁柱单元的三维空间框架非线性动力反应分析程序中,最后以R.Park等人的低周反复荷载下压弯柱的试验为校准基础,主要从构件层次进行了模拟、比较,分析了各种混凝土应力-应变关系模型中不同的骨线线取法和滞回规律取法对钢筋混凝土柱性能模拟效果的影响。     

A comparison of dynamic nonlinear behavior of ordinary and buckling restrained braced frames subjected to strong ground motion

In this paper nonlinear dynamic analyses of 4‐ to 12‐story frames with two types of bracing behavior are performed. In the first series of analyses, the bracing post‐buckling behavior is modeled using a Jain‐phenomenological model. In this model bracing buckled against compressive loading and yielded when subjected to tensile loading. In the second series, buckling restrained brace frames subjected to strong ground motion have been analyzed using elements with a bilinear behavior. The results in terms of story drifts, story shears, story shear versus drift hysteresis behavior and plastic hinge locations were compared. By comparing the response of the frame with the buckling restrained brace and the ordinary brace, better performance was observed for the buckling restrained braced frames. Copyright © 2007 John Wiley & Sons, Ltd.     

Special braced stairs versus typical braced frames. New architectural-structural-seismic approach to stair design

This paper presents a new approach to the project of steel buildings, mainly focused on the architectural, structural, and seismic design of stairs. The objective is to design a structural stair system capable of controlling seismic damage and contributing to the bracing system of the building. The article begins with a review of the seismic standard (ATC, FEMA, and EC8) on which the current design criteria for new buildings with stairs are based. The research is based on two spatial building models (A–B) with the same bracing elements but placed differently. Reference Model A follows classical design approaches. It means, stairs are considered nonstructural elements that do not influence the seismic behavior of the building. This structure corresponds to typical braced frames (IV-CBF and EBF) according to EC8. Model B includes a stair system designed to help control the effects of inter-story drifts and inertia forces. In this case, the same bracing elements of Model A were integrated into the stair structure of Model B. A comparative seismic behavior analysis of typically braced frames (A) versus specially braced stairs (B) is presented. The research was based on the static nonlinear (pushover) analysis and the capacity spectrum method (ATC-40) according to the seismic performance levels (FEMA) and damage limitation (EC8). Finally, the braced stairs was verified via nonlinear time-history analysis in order to better capture the structural safety of the evacuation routes and their influence on the behavior of the building. This deterministic analysis of the braced stairs verified satisfactory results compared to reference bracing systems.     

Seismically induced cyclic buckling of steel columns including residual-stress and strain-rate effects

Compression buckling tests were performed on four full-scale W-shaped column specimens to investigate the buckling response of columns in multi-storey braced steel frame structures subjected to seismic strong ground motions. The test protocols included monotonically and cyclically applied concentric and eccentric axial loading. One test was conducted under dynamic cyclic loading. End moments were applied on one cyclic test. The columns were W310×129 compact (class 1) sections made with ASTM A992 steel. Weak axis buckling was studied and the column had an effective slenderness ratio of 48. The response of the test columns was also examined using numerical simulations based on fibre discretization of the member cross-section. Column residual stresses and strain rate effects on the material properties were both characterized and accounted for in the numerical models. The study showed that steel columns can sustain several cycles of inelastic buckling under seismic induced loading while maintaining sufficient compressive resistance to support the applied gravity loads. Residual stresses affected the column response only at the first buckling occurrence with a gradual reduction of the columns’ tangent stiffness prior to buckling as well as a reduction of the column’s compressive resistance. High strain rates anticipated during strong earthquakes increased the column buckling and post-buckling strengths. The cyclic buckling response of steel columns can be predicted adequately when using nonlinear beam-column elements and cross-section fibre discretization provided that residual stresses and strain rate effects are included in the modelling.     

Seismic performance of Y‐type eccentrically braced frames combined with high‐strength steel based on performance‐based seismic design

In the Y‐type eccentrically braced frame structures, the links as fuses are generally located outside the beams; the links can be easily repairable or replaceable after earthquake without obvious damage in the slab and beam. The non‐dissipative member (beams, braces, and columns) in the Y‐type eccentrically braced frames are overestimated designed to ensure adequate plastic deformation of links with dissipating sufficient energy. However, the traditionally code design not only wastes steel but also limits the application of eccentrically braced frames. In this paper, Y‐type eccentrically braced steel frames with high‐strength steel is proposed; links and braces are fabricated with Q345 steel (the nominal yield stress is 345 MPa); the beams and columns are fabricated with high‐strength steel. The usage of high‐strength steel effectively decreases the cross sections of structural members as well as reduces the construction cost. The performance‐based seismic design of eccentrically braced frames was proposed to achieve the ideal failure mode and the same objective. Based on this method, four groups Y‐type eccentrically braced frames of 5‐story, 10‐story, 15‐story, and 20‐story models with ideal failure modes were designed, and each group includes Y‐type eccentrically braced frames with ordinary steel and Y‐type eccentrically braced frames with high‐strength steel. Nonlinear pushover and nonlinear dynamic analyses were performed on all prototypes, and the near‐fault and far‐fault ground motions are considered. The bearing capacity, lateral stiffness, story drift, link rotations, and failure modes were compared. The results indicated that Y‐type eccentrically braced frames with high‐strength steel have a similar bearing capacity to ordinary steel; however, the lateral stiffness of Y‐type eccentrically braced frames with high‐strength steel is smaller. Similar failure modes and story drift distribution of the prototype structures designed using the performance‐based seismic design method are performed under rare earthquake conditions.     

偏心支撑钢框架有限元分析

偏心支撑钢框架是近二十多年来发展起来的一种支撑结构形式，具有很好的抗震性能。为了更好地了解偏心支撑框架抗侧力性能和耗能梁段的受力特性，本文对偏心支撑钢框架进行非线性有限元分析。分析结果表明，偏心支撑中的耗能梁段在加载后期发生剪切屈服型破坏，保证了框架其他杆件不屈服，提高了结构的耗能能力和变形能力，显著地改善了钢框架的抗震性能。