基于时域显式随机模拟的隔震结构易损性分析研究

工程结构的地震易损性分析结果是结构抗震性能评价和地震灾害评估的重要依据，考虑地震激励的非平稳随机过程本质，采用随机振动方法来进行易损性分析更具合理性。针对带隔震基础的多层结构，提出基于时域显式随机模拟的隔震结构易损性分析方法。首先建立求解局部非线性运动方程的显式降维迭代列式，继而与随机模拟相结合，求解层间位移和隔震层位移的首超概率，最终考虑不同地震动强度得到隔震结构易损性曲线。算例结果表明，相比于传统蒙特卡罗方法，基于时域显式随机模拟的方法具有一致的计算精度和明显更高的计算效率，有利于隔震结构易损性分析的工程应用。     

考虑翘曲变形的复合材料叠合梁几何非线性的有限元分析

提出了一个用于复合材料叠合梁结构分析的有限元模型,梁结构具有几何非线性性能,包括扭转翘曲变形。采用一个考虑了改进拉格朗日法和广义位移控制法的公式对结构的变形进行计算。采用二次等参有限单元对梁横截面进行离散化,以确定梁的弯扭特性。利用两结点的Hermitean三维有限梁元对结构进行离散化,其中每结点具有7个自由度。运用数个实例,分析了层的取向对结构性能的影响。     

大跨度桥梁极限承载力的几何与材料非线性耦合分析

介绍用几何非线性及材料非线性耦合的方法分析大跨度桥梁的极限承载力问题.几何非线性采用UL列式法,材料非线性采用分层有限单元法,两者结合达到了既保证计算精度又节省内存及机时的目的.通过算例验证,该法已被成功地应用于一座铁路悬索桥方案的极限承载力分析.     

Consistent virtual work approach for the nonlinear and postbuckling analysis of steel frames under thermal and mechanical loadings

The aim of this paper is to provide a consistent virtual work formulation for the nonlinear and postbuckling analysis of steel frames at high temperatures. Central to this study is the derivation of the virtual work terms for the thermal stage, in addition to those for the loading stage, based on the updated Lagrangian formulation. The incremental stiffness equation derived for the beam element, considering both the geometrical and thermal effects, is qualified by the rigid body test. The generalized displacement control (GDC) method is adopted as the path-tracing scheme for postbuckling response. Eurocode-3 reduction factors and transformed section method are both adopted for steel I-sections. Two loading cases are studied. For structures loaded gradually under constant temperature, the critical or ultimate loading strength is obtained from the load-deflection curve. For structures heated gradually under constant loading, the critical or maximum temperature that can be sustained by the structure is computed. Conclusions are drawn for the examples studied in this paper.     

岩石三维弹塑性损伤本构模型研究

基于应变等效假设和真实应力概念的弹塑性损伤理论,在真实应力空间内,结合非线性统一强度模型,以广义塑性剪应变为硬化参数,并同时考虑应力水平对硬化速率的影响,建立了无损状态下岩石材料的弹塑性表达式;在名义应力空间内建立考虑围压对损伤速率影响的损伤演化方程,从而建立了岩石材料的三维弹塑性损伤本构模型。本构模型中各物理参数意义明确,与材料试验结果的对比表明,所建立的三维弹塑性损伤本构模型可较好地描述岩石材料在多轴受力情况下的变形与强度特性,为岩体工程的复杂非线性受力分析提供理论依据。     

基于统计分析的侧墙混凝土最大开裂风险回归模型

地下现浇侧墙结构混凝土开裂渗漏问题是工程界普遍公认的一大顽疾。针对多个工程实体侧墙结构,在采用水化-温度-湿度-约束耦合模型对侧墙混凝土在材料、结构、环境、施工等多种因素耦合作用下的早龄期收缩开裂风险进行量化评估的基础上,进行了四百余种工况的统计分析,通过方差分析进行各参数影响程度分析,并得到适用于厚0.3~1.2 m、强度等级C30-C60的侧墙结构混凝土中心温度和最大开裂风险多元回归模型,结果吻合较好,为快速便捷地预测侧墙结构混凝土的中心温升与最大开裂风险提供了较为有效的方法,为初步制定现浇地下侧墙结构混凝土抗裂方案提供依据。     

斜拉网壳结构的非线性静力分析

斜拉网壳结构是一种新颖的杂交结构体系,是“刚性”和柔性基本结构结合的典型,可跨越更大的跨度。本文基于Taylor展开公式和变分原理,推导了具有二阶精度的空间杆单元新型几何非线性刚度矩阵。研究了斜拉索的非线性问题和塔柱简化计算问题。针对弹性和刚性支座,以及是否考虑塔柱共同工作等影响因素,借助孤长法,数值计算了斜拉柱面和斜拉穹顶网壳结构极限承载力问题;同时,分别与相应的网壳结构计算结果进行了比较,最后,得出了有应用价值的结论和建议。     

索网结构两种找形方法的比较与分析

由于现在的计算机硬件和程序的开发平台相对于过去有了很大的改进并放松了许多的限制 ,因此对于承受均布荷载的索网结构有必要采用更精确的有限单元模型对过去的简化两节点模型进行改进。采用五节点曲线单元模型建立索网结构的有限元模式 ,自编程序 ,对索网结构考虑其自重作用下的找形分析 ,并和原来的两节点不考虑自重作用的找形分析的结果作了比较和分析 ,结果证明自重对找形有一定的影响 ,表明五节点模式精度很高     

Stochastic dependency in life-cycle cost analysis of multi-component structures

It is crucial to assure that civil engineering structures can operate properly and safely, as damages during the service life may lead to catastrophic loss of property, fatalities and long-term consequences. The approaches for structural management through a life-cycle cost analysis need to address explicitly the dependencies between elements. The evaluation of the life-cycle maintenance cost of structures in this article considers stochastic, degradation and economic dependencies. A new approach to include stochastic and degradation dependencies, structural redundancy and load redistribution in structural management is developed herein. The proposed model uses the fault tree analysis and the conditional probabilities to take into account stochastic dependencies between the structural elements. The degradation consequences are evaluated and a method is proposed to account for load redistribution. Also, a practical formulation to approximate the reliability of systems formed by interrelated components is proposed, by the mean of a redundancy factor that can be computed by structural analysis. The proposed approach provides effective optimal maintenance decisions for civil engineering structures by considering the interaction between elements.     

Practical nonlinear analysis of steel–concrete composite frames using fiber–hinge method

A fiber–hinge beam–column element considering geometric and material nonlinearities is proposed for modeling steel–concrete composite structures. The second-order effects are taken into account in deriving the formulation of the element by the use of the stability functions. To simulate the inelastic behavior based on the concentrated plasticity approximation, the proposed element is divided into two end fiber–hinge segments and an interior elastic segment. The static condensation method is applied so that the element comprising of three segments is treated as one general element with twelve degrees of freedom. The mid-length cross-section of the end fiber segment is divided into many fibers of which the uniaxial material stress–strain relationship is monitored during analysis process. The proposed procedure is verified for accuracy and efficiency through comparisons to the results obtained by the ABAQUS structural analysis program and established results available from the literature and tests through a variety of numerical examples. The proposed procedure proves to be a reliable and efficient tool for daily use in engineering design of steel and steel–concrete composite structures.     

边坡稳定安全系数求解格式的分类统一

根据极限平衡条分法所满足的平衡条件，将现行13种极限平衡条分法分为4大类：M类(仅考虑对选定求矩中心的力矩平衡)、VM类(考虑垂直方向力的平衡和对选定求矩中心的力矩平衡)、HV类(考虑水平方向力的平衡和垂直方向力的平衡)和HVM类(考虑所有平衡条件)。其中，M类(瑞典法)有显式解，VM类(简化Bishop法)有隐式的安全系数表达式，迭代并不困难。将现有极限平衡条分法对条问力的假定表示成统一形式，根据力和力矩的平衡，推导出十分简明的条间力递推方程和条问力矩递推方程。根据条问力递推方程，建立了传统意义上(保持原有方法所满足的平衡条件、对条间力的假定和未知量小变)基于力平衡(HV类)的安全系数统一求解格式。根据条间力递推方程和条问力矩递推方程，通过Newton-Raphson法建立了传统意义上基于严格半衡(HVM类)的安全系数统一求解格式。不但便于程序的编写，而且有利于不同方法优缺点的比较和理解。     

A probabilistic approach for earthquake loss estimation

Emergency responses following an earthquake and recovery of damaged structures have major impact on the government budget, thus setting back economic development. In earthquake countries, taking effective measures to reduce earthquake loss becomes important issue. This paper presents a probabilistic model for earthquake loss estimation of a town under earthquake risk. The model enables the decision-makers to make more reliable decisions, before and after an earthquake that strikes the town, by considering probability distribution and variability instead of deterministic approach. Life cycle cost concept is taken into account in the formulation of earthquake loss. Therefore, the model simulates all the benefits and costs, which are prone to variation within Monte Carlo framework. Adapazari, which is extensively damaged city in 1999 earthquake of Turkey, is chosen for the application of Monte Carlo Simulation Model. The model can be used to assess the effects of recovery periods.     

考虑混凝土徐变后轴心受压柱的最大配筋率

从理论与应用两方面,分析了混凝土徐变对钢筋混凝土轴心受压柱最大配筋率的影响;在反复荷载作用条件下,导出了防止混凝土卸载开裂的混凝土轴心受压柱最大配筋率的计算公式;分析了影响钢筋混凝土轴心受压柱最大配筋率的几种因素,并用实例演示了考虑混凝土徐变后,该公式在结构设计中的应用.成果可以为港口、仓储与码头等建筑物的结构设计提供参考.     

Modeling and analysis of uncertainties for risk-informed decisions in infrastructures engineering

Engineers deal with uncertainties in all their activities, and must often make decisions under conditions of uncertainty and risk. Infrastructures engineering is no exception—design codes are developed to ensure a desired level of safety and performance, or to ensure a specified operational life with a prescribed level of reliability; the required decisions must often be formulated without complete information and thus contain uncertainties. In considering uncertainties, it is important to recognize two broad types; namely, the aleatory type which is associated with natural randomness and the epistemic type which is associated with imperfect knowledge. Proposed here is a framework for the proper modeling and treatment of each type of uncertainty in the formulation of risk-informed engineering decisions. The concepts are illustrated with applications to bridges and offshore marine structures.     

Reliability of maintained ship hull girders subjected to corrosion and fatigue

A formulation is presented to account for the effect of corrosion and fatigue on the reliability of ship hulls. A time variant formulation is presented in which the effect of these degradation phenomena on the hull section modulus is quantified. The effect of maintenance actions is accounted for by considering that the repaired elements are restored to a state as new. Different repair policies can be studied and the approach can be used as a tool to plan the maintenance actions based on reliability results.     

Fundamental periods of steel eccentrically braced frames

This paper describes formulation of a hand method that can be used to estimate the computed fundamental periods of vibration of building structures in general and steel eccentrically braced frames (EBFs) in particular. The developed method uses the Rayleigh's method as a basis and utilizes the roof drift ratio (RD_R) under seismic forces as a parameter. To obtain RD_R, more than 4000 EBFs were designed by considering the seismic hazard, number of stories, braced bay width and link length to bay width ratio as prime variables. A model was developed to estimate RD_R, which depends on the rigid plastic deformation mechanism for a typical EBF. The method was verified using design data produced as a part of this work as well as data published in literature. The verifications indicate that the proposed formulation is capable of providing acceptable estimates of the computed period. When compared with existing empirical period–height relationships, the proposed formulation offers closer estimates with reduced scatter. The method was further refined to derive new period–height relationships for two different seismicity regions. The accuracy of the relationship for high seismic regions was verified using measured periods of EBF buildings. Copyright © 2014 John Wiley & Sons, Ltd.     

Risk Management of Large RC Structures within Spatial Information System

Abstract: The present article addresses the development of a spatial information system (SIS), which aims to facilitate risk management of large‐scale concrete structures. The formulation of the SIS is based on ideas developed in the context of indicator‐based risk modeling for concrete structures subject to corrosion and geographical information system based risk modeling concerning large‐scale risk management. The term “risk management” here refers in particular to the process of condition assessment and optimization of the inspection and repair activities. The SIS facilitates the storage and handling of all relevant information to the risk management. The probabilistic modeling utilized in the condition assessment takes basis in a Bayesian hierarchical modeling philosophy. It facilitates the updating of risks as well as optimizing inspection plans whenever new information about the condition of the structure becomes available. In the SIS, the various data of relevance for the risk management can be visualized in three dimensions. This feature and the other functionalities of the SIS are illustrated in an example considering the Danish Farø bridges.     

滑移隔震结构考虑土-结构动力相互作用的动力分析

介绍了考虑土 结构动力相互作用的滑移隔震结构的动力分析方法。应用正交多项式系逼近连续型基底摩擦力函数 ,实现了基底摩擦力的傅立叶变换 ;然后利用地基土动力刚度矩阵 ,在频域内采用子结构法 ,建立了考虑土 结构动力相互作用的滑移隔震结构的运动方程 ;通过数值仿真两个具有埋置刚性基础的剪切型滑移隔震结构的地震反应 ,分析了土 结构动力相互作用对滑移隔震结构地震反应的影响 ,以及上部结构刚度的不同引起相互作用影响程度的差异 ,从而得出结论 :考虑土 结构动力相互作用 ,会降低滑移隔震结构的隔震效果 ,其降低程度与上部结构的刚度成正比 ;能显著地减小隔震层的侧移 ,有利于地震时穿越隔震层的电路和管线等设备的保护。     

H型截面杆件考虑其局部屈曲的空间计算

本文采用单位宽有限条带法构造了 H型截面杆件考虑其局部屈曲的空间位移模式。用U.L.列式法对 H型截面杆件进行了空间计算