Estimation of relations among hysteretic response measures and design parameters for RC rectangular shear walls

Seismic design of RC structures requires estimation of structural member behavioral measures as functions of design parameters. In this study, the relations among cyclic behavioral measures and design parameters have been investigated for rectangular RC shear walls using numerical simulations calibrated based on the published laboratory tests. The OpenSEES numerical simulations modeling of plastic hinge hysteretic behavior of RC shear walls and estimation of empirical relations among wall hysteretic indices and design parameters are presented. The principal design parameters considered were wall dimensions, axial force, reinforcement ratios, and end-element design parameters. The estimated hysteretic response measures are wall effective stiffness, yield and ultimate curvatures, plastic moment capacity, yield and ultimate displacements, flexural shear capacity, and dissipated energy. Using results of numerous analyses, the empirical relations among wall cyclic behavioral measures and design parameters are developed and their accuracy is investigated.     

Application of line sampling simulation method to reliability benchmark problems

A procedure denoted as Line Sampling (LS) has been developed for estimating the reliability of static and dynamical systems. The efficiency and accuracy of the method is shown by application to the subset of the entire spectrum of the posed benchmark problems [Schuëller GI, Pradlwarter HJ, Koutsourelakis PS. Benchmark study on reliability estimation in higher dimensions of structural systems. In URL: http://www.uibk.ac.at/mechanik/Publications/benchmark.html. Institute of Engineering Mechanics, Leopold-Franzens University, Innsbruck, Austria, 2004], i.e. in particular linear systems with random properties. The notion of design point excitation for non-linear systems is discussed and its use extended for reliability estimations of conservative non-linear MDOF systems considering critical conditional excitation.For solving the hysteretic MDOF system with uncertain structural parameters subjected to general Gaussian excitation, however, the general applicable subset procedure [Au SK, Beck JL. Estimation of small failure probabilities in high dimensions by subset simulation. Probab Eng Mech 2001;16:263–277] has been used combined with Importance Sampling.     

Building life-cycle cost analysis due to mainshock and aftershock occurrences

The objective of this paper is to develop formal stochastic expected financial loss estimation models over the lifetime of the building due to mainshocks and their subsequent aftershock sequences. Mainshocks are typically modeled as a homogeneous Poisson process with constant mean rate of occurrence, while the resulting aftershocks are modeled as a nonhomogeneous Poisson process with random magnitudes which has parameters (mainshock magnitude, m_m, and location) that are conditional on the random mainshock. The initial model to compute expected losses is the simplified homogeneous Poisson mainshock process and nonhomogeneous Poisson aftershock process with “immediate” repair of the building to the initial building state. We then develop a more general Markov and semi-Markov framework where we consider both Poisson and renewal processes for modeling mainshock occurrences with various building damage progression scenarios. Finally, we will incorporate the random aftershock losses into pre-mainshock financial loss estimation. The ability to compute the expected building life-cycle cost due to both mainshocks and aftershocks will be useful as an input to seismic decision making (both post- and pre-mainshock).     

砌体结构TMD减震体系非线性地震反应研究

根据随机振动理论推导了多层剪切型结构TMD减震系统的随机地震响应,分析了参数的变化对TMD减振系统减震效果的影响,从而优化了取得最佳减震效果所需要的关键参数.以砖砌体结构为研究对象,建立了用于非线性地震反应的三线型骨架曲线及其滞回规律,编制了非线性地震反应分析程序,计算了一幢六层砌体结构减震前和采用TMD减震后的地震反应,分析结果表明,在7度多遇烈度和7度基本烈度地震动作用下减震效果良好,在7度罕遇烈度地震动作用下,TMD系统应通过加强构造措施保证抗震性能.     

Cyclic bond behaviour of plain bars. Part II: Analytical investigation

The development of monotonic and cyclic non-linear analysis models for reinforced concrete (RC) structures has become a key issue both in order to define seismic design “displacement-based” procedures for new constructions and for the seismic evaluation of older ones. These models have to properly account for interaction mechanisms between reinforcing bars and surrounding concrete. The existing literature regarding the bond performances of deformed reinforcing bars offers many experimental data and constitutive relationships, monotonic and hysteretic, taking into account the main parameters that influence bond capacities. With respect to plain bars, whose study is very important in seismic analysis of existing RC structures, it is noted that bond–slip relationships are substantially absent, particularly in cyclic field. Low bond capacities and cyclic degradation phenomena, however, have a great influence on different deformation sources, especially on fixed end rotation, which makes a significant contribution to the total deformation capacity of the element. In this paper, basing on experimental results from monotonic and cyclic pull-out tests reported in the companion paper, an analytical investigation of bond–slip hysteretic behaviour for plain reinforcing bars is presented and discussed.     

型钢自密实混凝土叠合剪力墙恢复力模型

为了研究型钢自密实混凝土叠合剪力墙的抗震性能以及恢复力特性,对1个全现浇型钢普通混凝土剪力墙试件和5个型钢自密实混凝土叠合剪力墙试件进行了低周反复加载试验。通过分析试验所得的剪力墙的水平荷载-位移骨架曲线,建议将其简化为以屈服点、峰值荷载点、极限点为特征点的三折线模型,并根据试验现象以及理论分析结果给出骨架曲线中各特征点参数的计算方法。对试验所得滞回曲线进行回归分析,得到了墙体的抗侧刚度退化规律,据此得出适用于型钢自密实混凝土叠合剪力墙的恢复力模型,并用试验得到的骨架曲线与滞回曲线进行验证。结果表明,由此恢复力模型求得的计算曲线与试验曲线吻合程度较好,该模型可以较好地反映型钢自密实混凝土叠合剪力墙的恢复力特性,可用于计算地震作用下以受弯破坏为主的型钢自密实混凝土叠合剪力墙的荷载-位移滞回曲线。     

焊接环式箍筋约束高强混凝土柱恢复力模型试验研究

对6个1/2比例焊接环式箍筋约束高强混凝土柱进行了低周反复加载试验,研究了轴压比和配箍率对柱变形性能和滞回特征的影响。通过试验结果的回归分析,以位移比、轴压比和配箍率等为主要参数,建立了卸载刚度和反复加载下的承载力退化率的计算式。在试验研究基础上,对滞回曲线特征进行了分析,并根据试验 P-Δ滞回曲线的特征,得到了柱恢复力模型。研究结果表明：采用由弹性、强化和承载力退化三阶段所组成的三折线型骨架曲线,可以反映焊接环式箍筋约束高强混凝土柱的恢复力特性,该骨架曲线按试验实测数据统计回归分析法以及截面条带分析法确定,其强化段和承载力退化段均考虑了轴压比和配箍率的影响。在试验研究基础上,建立了焊接环式箍筋约束高强混凝土柱剪力-侧移恢复力模型。分析和试验结果表明：所建立的恢复力模型能较好地反映不同轴压比与配箍率对柱的滞回规律特性的影响,可用于该类柱的抗震性能分析。     

Biaxial and torsional response of inelastic structures under random excitation

Structures under strong motion earthquake excitation often go into the inelastic range, and the restoring force becomes nonlinear and hysteretic. Since only very rarely the excitation direction perfectly aligns with the structural orientation, the response is generally biaxial and torsional motion often becomes important for structures which have geometric of a random vibration method to predict the inelastic response including the biaxial interaction and torsional motion. A previously developed differential equation model for the restoring force and the equivalent linearization solution procedure are generalized for this purpose. The methods are tested using a single-story space-frame and a three-story space-frame with setbacks. Comparisons with Monte Carlo simulations are made and methods for improvement of the accuracy are suggested.     

Development of a new direct test method for estimating cutter life, based on the Sievers’ J miniature drill test

The Sievers’ J-miniature drill test (SJ) has been used extensively at NTNU/SINTEF since the 1960s in connection with drillability testing of rock samples. Nearly 3000 samples have been tested, and the method is at present internationally recognised as a reliable method for determination of surface hardness of rock samples. A new test method for estimation of cutter life has evolved as a result of a recent update of the SJ test. This update was made possible by the development of instrumentation of the test apparatus. The new test method analyses the penetration depth and speed during the testing. The point in time where an interception occurs between the tangent lines for what could be defined as the “effective drilling” part and the “worn out” part of the penetration curve is defined as the Sievers’ J interception point or SJIP. Testing of 212 rock samples, representing different rock types, and correlations of the results to some of the most widely used methods for estimation of cutter life, show that it is possible to obtain a direct cutter life estimate by use of the SJIP value. The demand for representative parameters for rock properties in connection with underground excavations is increasing, as this constitutes the fundamental input for obtaining the most reliable cost estimates. The new test method provides information that was previously unavailable. This will improve the understanding on how different rock types and properties affect the drilling process and the wear on cutter tools. This test method is not meant to act as a substitute for well established and currently used test methods, but rather constitute an additional tool that can contribute to “bridge the gap” between laboratory testing, modelling and the actual excavation process estimates.     

Study of a new type of self‐centering beam‐column joint in steel frame structures

A new type of self‐centering beam‐column joint with installed steel arc plates is proposed in this study. First, mechanical behavior of the self‐centering joint using prestressed steel strands to provide the centering force is theoretically analyzed in detail, followed by experimental validation. New joints with different arc plate parameters are designed and tested under cyclic loading. Test results show that the hysteretic curve of the new joint exhibits typical characteristic of self‐centering capacity. By parametric analysis of five design parameters of the arc plate, it is found that vector height has the greatest influence on the joint's moment‐rotation skeleton curve, which is consistent with experimental findings. A simplified model of the joint is built in OpenSees to simulate its hysteretic behavior, which agrees well with the tested results. To demonstrate the effectiveness of the new joint to improve the seismic performance of the overall structure, a series of nonlinear time history analysis on a steel frame structure with the new joint under earthquakes are conducted, which show that the joint is particularly effective in reducing the residual interstory drift response.     

岩土体的非均质性及力学参数的条件模拟赋值

根据工程岩土体通常为非均质体，其力学参数具有空间变异二重性，应看成是空间随机场这一事实，对工程岩土体经过分级分区后，各分区岩土力学参数随机场的空间变异性分析以及岩土工程有限元计算中单元体力学参数的条件模拟赋值作了探讨。应用条件模拟法对单元体力学参数进行赋值不仅能同时考虑到岩土力学参数随机场所具有的空间变异二重性特征，而且比克立格法能更真实地再现岩土力学参数随机场所具有的离散性和波动性。     

铅芯橡胶支座隔震储罐地震响应特性分析

利用双线性恢复力模型模拟铅芯橡胶支座力学特性,探讨了不同类型场地上,隔震储罐在铅芯橡胶支座(LRB)与叠层橡胶支座(RB)两种隔震方式下的地震响应特点.研究表明:铅芯屈服力、场地类型和地震强度是影响LRB减震性能的主要因素.与RB隔震方式相比,LRB具有降低基底剪力、支座位移、晃动波高等优点,但减震效果并不总是好于RB方式,与场地类型和铅芯屈服力的选取有关.特别是Ⅳ类场地上RB支座更适合储罐隔震设计.支座最优屈服力参数选取需要根据储罐自振特点、场地类型和地震强度共同确定.LRB支座更适合在高烈度地区应用,减震效率高而且稳定.     

滑移摩擦支座摩擦力模型研究

采用微分连续模型模拟滑移摩擦支座的单向和双向耦合摩擦力,表明该模型可以较好地描述摩擦力的非线性特征和双向耦合效应.同时,从计算分析也可看出,考虑双向耦合作用与未考虑双向耦合作用的摩擦力滞回曲线有较大差别,因而支座应采用双向耦合摩擦力模型,以考虑双向耦合作用对结构地震反应和支座性能的影响.     

Dual criterion equivalent linearization approach for yielding structures under earthquake excitation

In order to estimate both maximum displacement and maximum inertia force of bilinear hysteretic system subjected to earthquake motions, an equivalent linearization approach with new effective parameters is presented. Effective mass and effective damping ratio as pair of effective parameters instead of the effective period and effective damping ratio in existing equivalent linear systems are introduced. Two error measures for displacement and inertia force are defined. Error distributions over a two‐dimensional parameter space of effective parameters are analysed, and the parameters are determined through a statistical approach with a dual optimization criterion for displacement and inertia force errors applicable to structural design. Single‐degree‐of‐freedom systems with bilinear hysteretic model; natural periods from 0.1 to 3.0 s; linear damping ratios from 3 to 50%; ductility ratios from 1.5 to 6; and post‐yield slope ratios 0, 0.05, 0.1 are considered. Analytical expressions for the effective parameters, and the ratio of the maximum inertia force to the maximum restoring force as functions of response ductility, elastic damping ratio and natural period of inelastic system are proposed for different site conditions and post‐yield slope ratios. Evaluation of proposed equations is performed, which reveals that the linear parameters lead to permissible error ranges. Copyright © 2010 John Wiley & Sons, Ltd.     

木质变摩擦阻尼器滞回性能的试验研究与理论分析

基于对摩擦阻尼器材料及构造的改进,研制了一种木质变摩擦阻尼器。对9个不同参数的木质变摩擦阻尼器试件进行了低周反复荷载试验,研究了阻尼器的滞回性能,分析了摩擦块的坡度、螺栓预紧力等因素对阻尼器耗能性能的影响。根据木质变摩擦阻尼器的构造特点及工作原理,建立了其力学分析模型,确定了适用于该摩擦阻尼器的滞回规则和相应的滞回模型,并利用试验数据对滞回模型进行了验证。研究结果表明：木质变摩擦阻尼器的输出力在大变形时显著提升,滞回曲线较为饱满,具有分阶段耗能的特点,表现出稳定且良好的耗能性能;木质变摩擦阻尼器的耗能能力与木质摩擦块坡度和螺栓预紧力呈正相关。建立的滞回模型能较准确地反映木质变摩擦阻尼器的工作性能,理论与试验滞回曲线吻合较好。     

A comparison of stochastic process models for definition of design contours

So-called design contour methods are frequently applied for large and complex structures in order to minimize the number of time-consuming structural analyses. These methods are based on first identifying extreme environmental conditions with a given probability of exceedance based on the relevant joint distribution function. These conditions are located along a level surface (i.e. “contour”) in the space of load parameters. As the second step, response analyses are performed for a selection of extreme conditions which are located along this contour. The highest response level which is obtained as a result of these analyses is then applied for design purposes.This approach is based on a representation of the underlying stochastic processes in terms of a sequence of piecewise constant levels. In the present paper, the extreme environmental conditions which are obtained based on such a model are compared to those obtained by instead applying a continuous process model. Furthermore, various alternative and relevant definitions of design contours are compared for the two-component case.In the present analysis, mainly stochastic processes which represent load parameters are considered. However, the approach for identification of level surfaces is of a general nature and can be applied to any types of random vector processes.     

土钉墙三维稳定极限分析的可靠度计算

本文介绍了应用上限理论建立的土钉墙稳定性评估的三维极限分析模型。将该模型中的三个参数,土粘聚力、内摩擦角及土体与土钉表面极限摩阻力作为随机变量,采用可靠度分析方法,计算土钉墙失稳概率。通过在实际工程应用表明,与传统的用安全系数作为评判指标的计算方法相比,该方法具有可真实反映土性变化特征、计算工作量增加不多的优点。     

非比例滞变阻尼线性体系的反应谱CCQC法

基于比例阻尼体系建立的振型分解反应谱法应用广泛,是各国规范常用的结构地震作用效应计算方法,直接将其用于非比例阻尼体系(如设置耗能阻尼器的结构)是不合理的。为拓展规范反应谱法的适用范围,在基于复阻尼模型的滞变阻尼模型复模态叠加法基础上,该文结合虚拟激励法和平稳随机理论,推导基于滞变阻尼模型的反应谱CCQC(complex complete quadratic combination)法表达式,适用于非比例阻尼混合结构的地震作用效应计算。算例分析表明：与基于分块Rayleigh阻尼模型的反应谱CCQC法相比,基于滞变阻尼模型的反应谱CCQC法仅依赖于材料阻尼参数和结构刚度,计算结果唯一,不受振型组合的影响;与基于等效阻尼比的反应谱CQC法相比,基于滞变阻尼模型的反应谱CCQC法可有效考虑结构的非比例特性,适用于非比例特性显著的混合结构。     

Improved stochastic linearization method using mixed distributions

A new procedure for the random vibration analysis of hysteretic structures using stochastic equivalent linearization is reported. Its aim is to improve the prediction of the response obtained by conventional Gaussian linearization technique. To this purpose, mixed discrete-continuous Gaussian distributions are used taking into account the bounded nature of the non-linear restoring force. The simple but important property of the mixed distribution is its linearity, which allows the use of the previous results obtained by the Gaussian hypothesis, avoiding the need of employing non-Gaussian continuous distributions or other time-consuming techniques such as local Monte Carlo simulations. Closed-form expressions of the new linearization coefficients for the Bouc-Wen-Baber model are then provided. The relative weights of the discrete and Gaussian distributions are calculated in dependence of the degree of non-linearity in each time step. The comparison of the results with previously published ones obtained by simulation shows a good agreement, providing a substantial improvement of the method with respect to the conventional Gaussian technique with the same calculation effort.     

考虑泥浆触变性的顶管顶力计算方法

顶管的顶力是顶管工程设计的关键控制参数之一,直接影响到其它参数的确定和工程造价,它的准确计算对顶管工程具有重要意义。在分析了目前顶管顶力计算方法的缺陷之后,基于弹性力学半无限空间柱形圆孔扩展理论和黏性流体力学平板模型理论,采用顶管顶进过程中管土"固—液"接触状态,推导了考虑泥浆触变性的顶管顶力的一种新的计算方法,并进行了实例验证。与既有方法的对比分析表明:该方法的计算结果与实测值更为吻合,而既有方法相对保守。