Experimental and analytical studies on the response of freestanding laboratory equipment to earthquake shaking

This paper presents results of a comprehensive experimental program on the seismic response of full‐scale freestanding laboratory equipment. First, quasi‐static experiments are conducted to examine the mechanical behavior of the contact interface between the laboratory equipment and floors. Based on the experimental results, the response analysis that follows adopts two idealized contact friction models: the elastoplastic model and the classical Coulomb friction model. Subsequently, the paper presents shake table test results of full‐scale freestanding equipment subjected to ground and floor motions of hazard levels with corresponding displacements that can be accommodated by the shake table at the UC Berkeley Earthquake Engineering Research Center. For the equipment tested, although some rocking is observed, sliding is the predominant mode of response, with sliding displacements reaching up to 60 cm. Numerical simulations with the proposed models are performed. Finally, the paper identifies a physically motivated intensity measure and the associated engineering demand parameter with the help of dimensional analysis and presents ready‐to‐use fragility curves. Copyright © 2008 John Wiley & Sons, Ltd.     

Experimental studies on liquefaction and reliquefaction potential of saturated ground subjected to repeated incremental acceleration loading with varying shaking duration

Past research has focused on the factors that influence liquefaction under normal shaking conditions. However, studies on parameters that influence the reliquefaction potential of saturated deposits during repeated shaking events are limited. In this study, an attempt has been made to examine the influence of acceleration amplitude and shaking duration on liquefaction and reliquefaction potential under repeated shaking conditions is conducted. 1-g uni-axial shaking table experiments were perform...     

Experimental and analytical studies on earthquake resisting behaviour of confined concrete block masonry structures

To improve the seismic performance of masonry structures, confined masonry that improves the seismic resistance of masonry structures by the confining effect of surrounding bond beams and tie columns is constructed. This study investigated the earthquake resisting behaviour of confined masonry structures that are being studied and constructed in China. The structural system consists of unreinforced block masonry walls with surrounding reinforced concrete bond beams and tie columns. The characteristics of the structure include: (1) damage to blocks is reduced and brittle failure is avoided by the comparatively lower strength of the joint mortar than that of the blocks, (2) the masonry walls and surrounding reinforced concrete bond beams and tie columns are securely jointed by the shear keys of the tie columns. In this study, wall specimens made of concrete blocks were tested under a cyclic lateral load and simulated by a rigid body spring model that models non‐linear behaviour by rigid bodies and boundary springs. The results of studies outline the resisting mechanism, indicating that a rigid body spring model is considered appropriate for analysing this type of structure. Copyright © 2006 John Wiley & Sons, Ltd.     

考虑桥墩强震损伤的连续梁桥半主动控制策略

在连续梁桥的智能控制研究中,大多以控制梁的加速度和墩顶与梁间的相对位移为目的,而忽略了对桥墩损伤的控制。本文提出一种改进的半主动控制策略,通过在限界Hrovat最优半主动控制算法中引入桥墩的损伤指数,使桥梁的地震反应和桥墩的损伤同时得到控制。本文以一设置了磁流变(MR)阻尼器的两跨连续梁桥为研究对象,采用MATLAB进行数值模拟分析,对所提出的半主动控制策略进行了多种工况下的验证。计算结果表明,采用考虑损伤的半主动控制策略,能够在较好控制桥梁地震反应的同时,有效降低桥墩在强震过程中的损伤指数。     

Experimental and analytical studies on multiple tuned mass dampers for seismic protection of porcelain electrical equipment

Porcelain electrical equipment (PEE), such as current transformers, is critical to power supply systems, but its seismic performance during past earthquakes has not been satisfactory. This paper studies the seismic performance of two typical types of PEE and proposes a damping method for PEE based on multiple tuned mass dampers (MTMD). An MTMD damping device involving three mass units, named a triple tuned mass damper (TTMD), is designed and manufactured. Through shake table tests and finite element analysis, the dynamic characteristics of the PEE are studied and the effectiveness of the MTMD damping method is verified. The adverse influence of MTMD redundant mass to damping efficiency is studied and relevant equations are derived. MTMD robustness is verified through adjusting TTMD control frequencies. The damping effectiveness of TTMD, when the peak ground acceleration far exceeds the design value, is studied. Both shake table tests and finite element analysis indicate that MTMD is effective and robust in attenuating PEE seismic responses. TTMD remains effective when the PGA far exceeds the design value and when control deviations are considered.     

Comparative experimental studies of models of self-controlled and ordinary frames on the shaking table

This paper presents a comparative test of models of self-controlled and ordinary frames on the shaking table. Two tested 1/8-scale models of 4-storey and single-bay RC frames made of cement mortar and reinforced with wires were poured on the same base beam. The dynamic characteristics and earthquake responses in the elastic, cracked and failed stages and the failure modes of these two kinds of frame are studied. It is proved that the seismic behaviour of the self-controlled frame is better than that of the ordinary frame.     

Experimental analysis of the seismic response of one base-isolation building according to different levels of shaking: example of the Martinique earthquake (2007/11/29) Mw 7.3

In recent years, many studies have been focused on the use and effectiveness of passive islotaing devices for reducing the effect of seismic ground motion on buildings. Among the available methods, one consists in isolating the structure using rubber bearings, the solution certainly the most accomplished and having the most feedback. In this study, we focused on the case of Martinique earthquake (Mw=7.4) of 29 November 2007, recorded by accelerometric stations installed at the Centre de Découverte des Sciences de la Terre (Martinique), a base-isolation building with rubber bearings. Several earthquakes are used in this paper, from moderate to strong ground motion. Ambient vibration modal analysis is first described in order to understand the elastic response of the building. The earthquake data are then interpreted, in particular to understand the mechanism of vibration of the structure and its comparison with the experimental modes previously estimated using ambient vibrations.     

强震作用下砌体结构倒塌过程仿真分析

四川汶川地震中大量砌体房屋倒塌,造成巨大人员伤亡。为研究和预防砌体结构震害,本文概述了多层砌体房屋的主要震害特点,研究了砌体结构地震倒塌分析方法、失效单元与结构倒塌等关键技术问题。利用动力有限元程序LS-DYNA模拟了砌体结构的倒塌过程。仿真计算的结果与真实倒塌过程吻合较好,说明通过合理选取计算参数和计算模型,可以对这种特殊的复杂破坏过程进行模拟分析和仿真。通过再现倒塌过程,发现了结构在强震作用下的薄弱环节,为提高砌体结构抗震性能研究、建立结构防倒塌机制提供了有力的技术支撑。     

A note on the wave-passage effects in out-of-plane response of long structures to strong earthquake pulses

Elementary consequences of the wave-passage effects are described for out-of-plane response of long structures, excited by SH wave earthquake ground motion pulses propagating along their longitudinal axis. For the passage times in the range of 0.005–0.10 s, the maximum column drifts can increase several folds due to the combined action of out-of-plane and torsional response. Because most of the seismic wave energy do not arrive at a site vertically, the common engineering assumption that it does, leads to nonconservative response estimates.     

Experimental and analytical studies on the performance of hybrid isolation systems

This paper presents experimental and analytical results on the seismic response of a rigid structure supported on isolation systems that consist of either lead rubber or sliding bearings. Shake table tests are conducted with various levels of isolation damping that is provided from the bearings and supplemental viscous fluid dampers. The table motions originated from recorded strong ground motions that have been compressed to the extent that the mass of the model structure corresponds to the mass of a typical freeway overcrossing. Experimental data are used to validate mechanical idealizations and numerical procedures. The study concludes that supplemental damping is most effective in suppressing displacements of rigid structures with moderately long isolation periods (T_I≤3 sec) without affecting base shears. Friction damping is most effective in suppressing displacement amplifications triggered by long duration pulses—in particular, pulses that have duration close to the isolation period. Copyright © 2001 John Wiley & Sons, Ltd.     

矩形钢管混凝土构件抗弯力学性能的试验研究

通过对8个矩形钢管混凝土纯弯构件的试验研究，考察矩形钢管混凝土受弯构件的力学性能。试验结果表明，矩形钢管混凝土受弯构件具有较高的抗弯承载力和抗弯刚度，构件曲率延性良好。最后，比较了设计规程EC4、LRFD、AIJ和GJB在计算矩形钢管混凝土抗弯承载力和抗弯刚度时的差异，所得结论可供有关钢管混凝土工程设计时参考。     

Application of arma models to estimate earthquake ground motion and structural response

This paper deals with the use of ARMA models in earthquake engineering. Tools and methods applied to strong ground motion are discussed emphasizing simulation of probabilistic earthquake response spectra. The ARMA models are applied to Icelandic earthquake data and a tentative model for Icelandic earthquakes is presented. This model, which is derived using 54 accelerograms, is based on a low-order, time-invariant ARMA process excited by Gaussian white noise and amplitude modulated using a simple envelope function to account for the non-stationary characteristics. This simple model gives a reasonable fit to the observed ground motion. Further, this model produces accurate earthquake response spectra, which, combined with accompanying attenuation and duration formulae, might be useful in earthquake hazard and risk assessment.     

强震与微震观测系统的研究

本系统采用动圈型换能器(属于速度型换能器)加电子反馈形成在0.05Hz~50Hz的加速度仪特性,大大减小了甚低频率的影响,而其线性及动态范围也能满足实际使用的要求,避免了位移型换能器在低频段的较大误差,在地震观测中取得较好的效果。     

地震力对高架桥梁轨道车辆影响之动态模型

将轨道车辆系统仿真成由车厢、转向架及轮轴所组成。车厢与转向架间有次悬吊系统,转向架与轮轴间则有主悬吊系统。数学模型之推导将考虑车辆横向、垂向、翻滚(roll)及摇摆(yaw)方向之运动,将车辆仿真成三维具16个自由度之系统。本研究将探讨行驶高架桥梁之轨道车辆受地震激振时,建立轨道车辆与高架桥相互耦合之动态数学模型。     

Experimental and analytical investigation of the response of a mud layer to solitary waves

Ocean Dynamics - Although the different aspects of wave-mud interaction have been studied by many researchers, few studies have been conducted on the effect of solitary wave on the particle...     

汶川地震近断层地震动作用下结构地震响应特征分析

研究了具有不同自振特性的建筑结构在近断层速度脉冲型及非速度脉冲型地震动作用下的结构层间变形分布,揭示了近断层速度脉冲对工程结构地震响应的特殊影响.从汶川M8.0地震近断层强震记录中选取两组典型速度脉冲型记录和非脉冲型记录,根据确定的目标地震动强度水平,利用时域叠加小波函数法对选择的强震记录进行调整,使之与目标地震动水平对应的加速度反应谱保持一致,以此作为结构地震反应分析的地震动输入.选取具有不同自振特征的3层、11层和20层典型钢筋混凝土框架结构,建立有限元分析模型,分别计算在速度脉冲型与非速度脉冲型记录作用下这些结构层间变形分布.研究表明,速度脉冲型记录与非速度脉冲型记录作用下结构层间变形有明显差异,且与结构自振特征有关.就低层结构的层间变形而言,非速度脉冲型记录的影响较速度脉冲型记录的影响大.随着结构自振周期的增加,高阶振型的影响更加明显.与非速度脉冲型记录相比,速度脉冲型记录的结构层间位移反应中值及离散程度较大.速度脉冲型记录更容易激发高层结构的高阶振型,产生较大的层间位移反应.非速度脉冲型记录对中低层结构层间变形影响较大.因此,在开展近断层结构地震影响评价时,应考虑近断层速度脉冲的影响.     

汶川地震近断层地震动作用下 结构地震响应特征分析

研究了具有不同自振特性的建筑结构在近断层速度脉冲型及非速度脉冲型地震动作用下的结构层间变形分布,揭示了近断层速度脉冲对工程结构地震响应的特殊影响. 从汶川M_S8.0地震近断层强震记录中选取两组典型速度脉冲型记录和非脉冲型记录, 根据确定的目标地震动强度水平,利用时域叠加小波函数法对选择的强震记录进行调整, 使之与目标地震动水平对应的加速度反应谱保持一致, 以此作为结构地震反应分析的地震动输入. 选取具有不同自振特征的3层、11层和20层典型钢筋混凝土框架结构, 建立有限元分析模型, 分别计算在速度脉冲型与非速度脉冲型记录作用下这些结构层间变形分布. 研究表明,速度脉冲型记录与非速度脉冲型记录作用下结构层间变形有明显差异, 且与结构自振特征有关.就低层结构的层间变形而言, 非速度脉冲型记录的影响较速度脉冲型记录的影响大. 随着结构自振周期的增加, 高阶振型的影响更加明显. 与非速度脉冲型记录相比,速度脉冲型记录的结构层间位移反应中值及离散程度较大. 速度脉冲型记录更容易激发高层结构的高阶振型, 产生较大的层间位移反应. 非速度脉冲型记录对中低层结构层间变形影响较大.因此, 在开展近断层结构地震影响评价时, 应考虑近断层速度脉冲的影响.     

Experimental and analytical studies on the vibration serviceability of long-span prestressed concrete floor

An extensive experimental and theoretical research study was undertaken to study the vibration serviceability of a long-span prestressed concrete floor system to be used in the lounge of a major airport.Specifically,jumping impact tests were carried out to obtain the floor’s modal parameters,followed by an analysis of the distribution of peak accelerations.Running tests were also performed to capture the acceleration responses.The prestressed concrete floor was found to have a low fundamental natural frequency(≈8.86 Hz)corresponding to the average modal damping ratio of≈2.17%.A coefficients plate with simply-supported edges.The calculated analytical results(natural frequencies and root-mean-square acceleration)agree well with the experimental ones.The analytical approach is thus validated.     

在地震力作用下高架桥梁上轨道车辆的动态分析与安全性研究

本文将轨道车辆系统仿真成由车厢、转向架及轮轴所组成。车厢与转向架间有次悬吊系统,转向架与轮轴间则有主悬吊系统。数学模型的推导将考虑车辆横向、垂向、翻滚及摇摆方向的运动,将车辆仿真成三维具16个自由度的系统。本研究将探讨行驶高架桥梁的轨道车辆受地震激振时的响应和安全性,结果显示,移轨力及脱轨系数会随着地表加速度的增加而增加,而轨道不平整度及速度参数对脱轨系数及移轨力的影响不大。     

2022年6月1日四川芦山MS6.1强震构造精细特征

2022年6月1日, 四川芦山发生M_S6.1(M_W5.9)强震, 龙门山断裂带南段的地震危险性再次引起广泛的关注和讨论.本次研究根据震源机制、余震重定位和深地震反射剖面, 详细分析了发震断层, 并刻画了芦山震区同震断层的三维结构和模型.此次地震为典型的逆冲型地震, 震源机制两组节面参数(走向/倾角/滑动角)分别为节面Ⅰ: 221.5°/44.4°/103.3°; 节面Ⅱ: 23.2°/47.1°/77.3°, 矩心深度为15.5 km.结合余震展布特征, 认为发震断层为一条倾向SE的反冲断层, 初始破裂深度约19 km, 倾角约50°.研究重新解译了芦山震区上地壳的地质构造, 认为龙门山断裂带南段存在两套重要的滑脱层, 具有分层滑脱变形(解耦)的特征: 浅部滑脱层之上为叠瓦构造, 深浅滑脱层之间为双重构造.2013年M_S7.0地震与2022年M_S6.1地震的发震断层, 均为发育在基底约20 km深度的滑脱层上的盲冲断层, 为早期先存构造并重新活化的产物.芦山M_S6.1地震的余震丛集相对独立, 与之前2013年芦山M_S7.0地震的发震断层并非相同的断层, 因此认为是一次相对独立的破裂事件.2008年汶川M_S8.0地震与2013年芦山M_S7.0地震之间的地震空区, 先存断裂众多, 就空区的断层规模而言可以产生7级左右强震.而深部基底盲断层和浅部盖层隐伏断层的广泛存在, 增加了该地区地震灾害风险评估的难度和不确定性.