Rigid‐plastic seismic design of reinforced concrete structures     

J. L. Domingues Costa  R. Bento  Vsevolod Levtchitch  M. P. Nielsen 《地震工程与结构动力学》2007,36(1):55-76

In this paper a new seismic design procedure for Reinforced Concrete (R/C) structures is proposed—the Rigid‐Plastic Seismic Design (RPSD) method. This is a design procedure based on Non‐Linear Time‐ History Analysis (NLTHA) for systems expected to perform in the non‐linear range during a lifetime earthquake event. The theoretical background is the Theory of Plasticity (Rigid‐Plastic Structures). Firstly, a collapse mechanism is chosen and the corresponding stress field is made safe outside the regions where plastic behaviour takes place. It is shown that this allows the determination of the required structural strength with respect to a pre‐defined performance parameter using a rigid‐plastic response spectrum, which is characteristic of the ground motion alone. The maximum strength demand at any point is solely dependent on the intensity of the ground motion, which facilitates the task of distributing required strength throughout the structure. Any artificial considerations intended to adjust results according to empirical observations are avoided, which, from a conceptual point of view, is considered to be an advantage over other simplified design procedures for seismic design. The procedure is formulated using a step‐by‐step format followed by a design example of a 4‐storey‐R/C‐plane‐frame. Results are compared with refined NLTHA and found to be extremely encouraging. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Multiobjective heuristic approaches to seismic design of steel frames with standard sections     

M. Ohsaki  T. Kinoshita  P. Pan 《地震工程与结构动力学》2007,36(11):1481-1495

Seismic design problem of a steel moment‐resisting frame is formulated as a multiobjective programming problem. The total structural (material) volume and the plastic dissipated energy at the collapse state against severe seismic motions are considered as performance measures. Geometrically nonlinear inelastic time‐history analysis is carried out against recorded ground motions that are incrementally scaled to reach the predefined collapse state. The frame members are chosen from the lists of the available standard sections. Simulated annealing (SA) and tabu search (TS), which are categorized as single‐point‐search heuristics, are applied to the multiobjective optimization problem. It is shown in the numerical examples that the frames that collapse with uniform interstorey drift ratios against various levels of ground motions can be obtained as a set of Pareto optimal solutions. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Seismic Behaviour of Slightly Reinforced Concrete Walls: Experiments and Theoretical Conclusions     

Philippe Bisch  André Coin 《Bulletin of Earthquake Engineering》2007,5(1):45-65

In order to develop new standards related to structures in seismic regions, a series of research programmes has been conducted on slightly reinforced structural walls commonly used in France. Based on these researches, a method of design of such walls submitted to a seismic action has been set up. This method used in the PS92 code differs from that used for ductile walls, where a plastic hinge can develop at the base of the wall. The analysis is similar to the push over analysis presently given in Eurocode 8. These various researches have confirmed the validity of the design concept developed for the PS92 code, on one hand, and highlighted a number of phenomena linked to the non linear behaviour of reinforced concrete walls, on the other hand. The present article aims at presenting a synthesis of the results obtained during these research programmes.  相似文献   

吐鲁番市地膜春小麦气候适应性及其高效栽培技术的研究     

普宗朝  董海虎  宋水华  房应征 《沙漠与绿洲气象(新疆气象)》2000,(3)

根据田间试验资料 ,讨论了不同地膜覆盖方式对麦田土壤温度、土壤有效水分含量以及小麦生长发育产量形成的综合影响。结果表明 :地膜覆盖具有显著的增温效应 ,可使春小麦生育期提前 ,产量提高 ,并可提高土壤有效水分的利用率。吐鲁番市地膜春麦最佳栽培方案应采用“膜下条播、3月初播种、525万株/hm2基本苗”。  相似文献   

广义塑性力学的加卸载准则与土的本构模型——广义塑性力学讲座(3)   总被引：6，自引：2，他引：4  

郑颖人  陈瑜瑶  段建立 《岩土力学》2000,21(4):426-429

首先介绍了广义塑性力学的加卸载准则,该准则能准确判断各应变分量的加卸载状态,可以方便地应用于数值分析。然后提出了基于广义塑性力学的土本构模型。通过试验,给出了硬化压缩土和硬化剪胀土的屈服条件与计算参数,并由算例说明了其合理性。  相似文献   

弹塑性有限元模拟分析影响基坑位移的因素   总被引：1，自引：0，他引：1  

姚爱国  Smith I M 《煤田地质与勘探》2000,28(6):43-45

分析影响基坑支护破坏因素对于防止基坑事故的发生,优化基坑支护设计有重要意义。本文用弹塑性有限元方法模拟基坑破坏过程,分析了影响基坑支护破坏的因素。分析结果表明,土体和桩墙的弹性模量都对基坑的位移有一定影响,但土体弹性模量的影响比桩墙弹性模量的影响更大。根据这些结果,推论出传统基坑设计方法与弹性地基梁法的不足之处。另外,分析结果还表明,基坑坑顶水平位移与土体弹性模量的关系无固定规律,而坑底最大位移与弹性模量呈非线性的关系。由此推论出基坑坑顶水平位移监测方法的不可靠性。   相似文献   

采用有厚度接触单元对桩基沉降的研究   总被引：9，自引：2，他引：7  

陈开旭  安关峰  鲁亮 《岩土力学》2000,21(1):92-96

选用描述桩土接触面特性的有厚度接触面本构模型与土塑性特点的弹塑性本构模型, 利用研制的二维有限元程序, 研究了在荷载作用下桩的几何特征、物理特性与土及接触面的物理特性对桩基沉降的影响, 得出了几点规律性的结论。  相似文献   

广义塑性力学中的屈服面与应力-应变关系   总被引：7，自引：2，他引：5  

郑颖人  段建立  陈瑜瑶 《岩土力学》2000,21(3):305-308

详细讨论了广义塑性力学中屈服面和塑性势面的对应关系以及岩土材料的三类屈服面(即体积屈服面与 q 方向上及方向上的剪切屈服面)的基本特征, 尤其是提出了能考虑剪胀与剪缩的体积屈服面和应力 Lode 角θσ方向的剪切屈服面。指出在广义塑性力学中不必采用硬化定律, 就能得出塑性应变增量与应力增量的关系, 给出了求弹塑性矩阵的方法。  相似文献   

岩土材料塑性损伤模型及拱坝的变形局部化分析     

陈新  杨强  周维垣 《岩土力学》2007,28(5):865-870

常规的弹塑性模型难以模拟材料破坏时由于内部损伤累积引起的变形局部化带形成过程。将岩土材料抽象为含有孔洞的球形体胞单元的集合体,采用一个标量--孔洞体积百分比来刻划单元的损伤程度,基于细观损伤力学提出了一个适用于岩土材料的塑性损伤模型。将该模型通过用户子程序嵌入到大型有限元商业软件MRAC中,研究岩土材料的局部化剪切带形成过程。采用该模型,成功地对平面应力条件下岩土材料单轴受压和单轴受拉试件的局部化破坏分别进行了数值模拟。采用该模型,对拱坝在超水载作用下的变形局部化进行了研究,数值计算结果表明,上游坝踵处最先发生变形局部化现象。  相似文献   

离子土固化剂加固滑坡滑带土的试验研究   总被引：3，自引：0，他引：3  

项伟  崔德山  刘莉 《地球科学》2007,32(3):397-402

研究开发快速经济和行之有效的滑坡治理方法与理论, 一直是各国滑坡防治研究工作的重点.本试验研究使用一种经济适用的离子土固化剂(Ionic Soil Stabilizer, 简称ISS) 对提高滑带土的抗剪强度进行了探索.滑带土首先通过ISS不同配比水溶液的处理, 然后进行阿太堡试验、剪切试验、固结试验和自由膨胀率试验.试验结果表明: 滑坡滑带土在加入离子土固化剂后, 土的塑性指数降低, 粘聚力提高, 孔隙比和自由膨胀率减小.其机理为: 在以粘性土为主的滑带土中加入离子土固化剂, 通过物理化学原理, 它能取代吸附在粘土表面的可交换性阳离子, 改变粘土颗粒表面的双电层结构, 减小结合水膜厚度, 将滑带土的亲水性改为憎水性, 从而提高滑带土的抗剪强度.   相似文献