共查询到20条相似文献，搜索用时 31 毫秒
1.
The dynamics of an elastic column subjected to vertical as well as horizontal ground acceleration during an earthquake strong motion is considered. The Liapunov method of stability analysis is employed and several bounds on the maximum lateral displacement and bending stress are obtained and discussed. 相似文献
2.
地震是诱发边坡破坏的重要因素之一,而抗滑桩是一种重要的边坡防治工程措施,因此开展地震作用下抗滑桩机理对于边坡防护具有重要的工程意义。本文以广东省梅州市茶阳车站为工程实例,运用ABAQUS软件建立三维模型,对地震作用下的桩土作用机理进行数值模拟分析。研究表明:(1)在地震作用下,边坡中上部水平位移较大,最大值为87.05mm,凹陷处水平位移远小于凸起处;(2)地震作用下抗滑桩会由于地震荷载产生远大于地震前的应力:静力作用下桩身最大值是147.24kPa,地震波输入14s时桩身最大值达到了326.36kPa;(3)地震作用下抗滑桩的应变亦远大于静力作用下的应变:静力作用下抗滑桩应变最大值是4.63×10~(-5),在地震波输入的第14s时桩身应变最大值是34.10×10~(-5)。因此在工程实践中对于地震作用下的抗滑桩边坡加固需要考虑桩的强度与刚度。研究结论对于边坡防治以及工程实践具有一定的指导意义。 相似文献
3.
A structure may exhibit a severe strain-softening behaviour when subjected to strong earthquake excitation. Pseudodynamic testing of such structures using an implicit time-integration algorithm may be conceived of as a problem, since the Newton-type iterations, which are often required when structural non-linearity develops, may not converge under these circumstances. An unconditionally stable implicit time-integration algorithm implemented with Newton-type iterations is analysed to provide an insight into this problem. A simple convergence condition is derived to detect possible divergence. The condition is shown to be a sufficient criterion for convergence for general multiple-degree-of-freedom structures, and it is used later on to develop an adaptive time-stepping strategy to avoid divergence under severe strain-softening conditions. The implementation of this technique for pseudodynamic testing is presented. As demonstrated by numerical examples, the algorithm proves to be effective and reliable. 相似文献
4.
文中以OPENSEES有限元软件为工具,利用基于柔度法的钢筋混凝土柱纤维单元,考虑钢筋与混凝土材料的应变率效应,对钢筋混凝土柱进行了动态响应分析,并用试验结果验证了文中方法的正确性.通过数值模拟,研究了钢筋混凝土柱在不同轴压比、不同混凝土强度、不同纵筋率条件下的动态力学特性.结果表明,随着轴压比的提高,钢筋混凝土柱的应... 相似文献
5.
In many regions of the world, a bridge will experience multiple extreme hazards during its expected service life. The current American Association of State Highway and Transportation Officials (AASHTO) load and resistance factor design (LRFD) specifications are formulated based on failure probabilities, which are fully calibrated for dead load and non-extreme live loads. Design against earthquake load effect is established separately. Design against scour effect is also formulated separately by using the concept of capacity reduction (or increased scour depth). Furthermore, scour effect cannot be linked directly to an LRFD limit state equation because the latter is formulated using force-based analysis. This paper (in two parts) presents a probability-based procedure to estimate the combined hazard effects on bridges due to truck, earthquake and scour, by treating the effect of scour as an equivalent load effect so that it can be included in reliability-based failure calculations. In Part I of this series, the general principle for treating the scour depth as an equivalent load effect is presented. In Part II, the corresponding bridge failure probability, the occurrence of scour as well as simultaneously having both truck load and equivalent scour load effect are quantitatively discussed. The key formulae of the conditional partial failure probabilities and the necessary conditions are established. In order to illustrate the methodology, an example of dead, truck, earthquake and scour effects on a simple bridge pile foundation is represented. 相似文献
6.
H. Wada 《地震工程与结构动力学》1983,11(1):21-31
An analysis is presented of the transient flexural vibrations of an elastic column supported by an elastic half-space under the condition that an arbitrarily shaped free-field lateral acceleration and displacement are given as inputs. Applying Laplace transformations with respect to time and numerical inverse Laplace transformations, the time histories of the column acceleration at the interface and free end, and the column and half-space displacement distributions are obtained. After the input free-field acceleration terminates, slightly damped and almost harmonically variable acceleration is observed. The acceleration frequency after the disappearance of the input acceleration nearly coincides with the resonant frequency of the system. The slight damping with the first resonant frequency, even if the half-space is soft compared with the column, is characteristic of the transient flexural vibrations of a column supported by a half-space. Such a phenomenon is not typical of the transient longitudinal vibration problem. Therefore, it may be concluded: when buildings and structures are subjected to an earthquake or an explosive force, their flexural vibrations will continue with their first resonant frequencies, even if their foundations are soft. 相似文献
7.
H. Kit Miyamoto Amir S. J. Gilani Akira Wada Christopher Ariyaratana 《地震工程与结构动力学》2010,39(11):1279-1297
Fluid viscous dampers are used to control story drifts and member forces in structures during earthquake events. These elements provide satisfactory performance at the design‐level or maximum considered earthquake. However, buildings using fluid viscous dampers have not been subjected to very large earthquakes with intensities greater than the design and maximum considered events. Furthermore, an extensive database of viscous damper performance during large seismic events does not exist. To address these issues, a comprehensive analytical and experimental investigation was conducted to determine the performance of damped structures subjected to large earthquakes. A critical component of this research was the development and verification of a detailed viscous damper mathematical model that incorporates limit states. The development of this model and the laboratory and simulation results conclude good correlation with the new model and the damper limit states and provide superior results compared with the typical damper model when considering near collapse evaluation of structures. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
8.
The goal of this study is to provide a better understanding on the behavior of pinching and softening effects for bridge column under earthquake loading. In the first part, a nonlinear cyclic loading test on a well-designed ductile RC bridge column was carried out experimentally. The hysteretic behavior of the bridge column was generated. In the second part, finite element analyses were used to predict the response under earthquake excitation. The hysteretic behavior obtained by experiment will be used as an input in material modeling for finite element programs. Discussions were made by using different computer codes to simulate the effects of pinching and softening of bridge column subjected to earthquake loading. Due to the inadequate functions of the element modeling, the theoretical system may underestimate the structural response under strong earthquake loading particularly on the prediction of softening and pinching effects. 相似文献
9.
Previous studies have suggested that rocking vibration accompanied by uplift motion might reduce the seismic damage to buildings subjected to severe earthquake motions. This paper reports on the use of shaking table tests and numerical analyses to evaluate and compare the seismic response of base‐plate‐yielding rocking systems with columns allowed to uplift with that of fixed‐base systems. The study is performed using half‐scale three‐storey, 1 × 2 bay braced steel frames with a total height of 5.3 m. Base plates that yield due to column tension were installed at the base of each column. Two types of base plates with different thicknesses are investigated. The earthquake ground motion used for the tests and analyses is the record of the 1940 El Centro NS component with the time scale shortened by a factor of 1/√2. The maximum input acceleration is scaled to examine the structural response at various earthquake intensities. The column base shears in the rocking frames with column uplift are reduced by up to 52% as compared to the fixed‐base frames. Conversely, the maximum roof displacements of the fixed and rocking frames are about the same. It is also noted that the effect of the vertical impact on the column associated with touchdown of the base plate is small because the difference in tensile and compressive forces is primarily due to the self‐limiting tensile force in the column caused by yielding of the base plate. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
10.
11.
避难建筑通常采用置换混凝土方法抗震,建筑对高强度地震的抗震性能差。因此提出高强度地震下带钢避难建筑抗震设计方法,采用复杂网络带钢避难建筑加固模型对加固前建筑的混泥土强度与荷载能力进行计算,增大框架柱截面,提升带钢避难建筑荷载。采用复合墙体受力加固模型提升建筑墙体抗震性。对加固后建筑模型的坍塌风险评估时,采用带钢避难建筑坍塌的全概率衡量加固后建筑在设计使用年限内的抗坍塌安全性。设计使用年限内加固后的带钢避难建筑的强震CRC超出概率是P(IMCRC),确保其在高强度地震下具有较高的抗震性能。实验结果说明,所提方法下的带钢避难建筑在遇到强震情况时具有较高的抗震性能。 相似文献
12.
13.
将土体视为固-液两相介质,基于饱和土体有效应力原理,建立饱和土体-地下综合管廊结构体系相互作用动力模型:在地应力平衡的静力状态下采用Duncan-Chang非线性弹性本构模型,在地震波作用的动力状态下采用Davidenkov非线性黏弹性本构模型;考虑饱和土体黏弹性动力人工边界条件,将地震动作用转化为作用在人工边界节点上的动力荷载。模型考察不同地震波时程、地震波加速度峰值、入射角度、孔隙率以及地应力场的影响,得出如下结论:(1)地震波的卓越周期与场地卓越周期相近时引起结构上的变形最大;随着地震波加速度峰值的增大结构变形增大;随着地震波入射角度的增加结构变形增大,地震波斜入射情况下产生的行波效应使得结构变形最大。(2)土体材料的孔隙水压力是影响地震中结构变形的主要因素之一。(3)将土体材料考虑为单相介质时结构上的变形要比考虑为固-液两相介质时大得多,直接将饱和土体场地中得到的地震波等效荷载施加到单相土介质-结构动力相互作用模型上,能够得到与完全基于有效应力法一致的结果。 相似文献
14.
为讨论近断层地震动下摇摆-自复位(Rocking Self-Centering, RSC)桥墩连续梁的地震反应及其抗震优缺点。基于OpenSees有限元分析平台讨论了RSC桥墩三维建模方法,通过对6个试验构件的模拟,比较模拟与试验桥墩滞回曲线、预应力筋最大应力等指标,验证了模型准确性。建立设置RSC桥墩和普通钢筋混凝土(Reinforced Concrete, RC)桥墩的上部结构相同的两座连续梁桥,输入3组含有强速度脉冲的近断层地震波进行非线性动力时程分析,对比其抗震性能。结果表明：在0.4 g近断层地震动下,RSC桥墩与普通RC桥墩相比,RSC桥墩的最大位移角为普通RC桥墩的78.1%～97.6%,墩底曲率延性系数仅为普通RC桥墩的24.0%～34.0%,减小了桥墩的最大变形,也减轻了桥墩地震损伤,不利的一点是使用RSC桥墩会导致支座位移增大。RSC桥墩震后的残余位移较小,且预应力筋处于弹性受力阶段,为实现震后桥梁功能的快速恢复提供了条件。 相似文献
15.
油气储运系统钢结构设备地震火灾效应研究 总被引：3，自引：0，他引：3
预防和减轻油气储运系统地震火灾危险性是防震减灾中的重要课题。本文论述了油气储运系统的地震火灾特征及防火要求，对钢结构的防火涂料在遭到破坏和平时情况下的抗火性能进行了对比分析，并应用有限元法对油气储运系统中典型钢结构设备在地震火灾荷载作用下的抗火性能进行了数值模拟。研究结果表明，防火涂料遭到强地震荷载破坏后，钢结构的抗火性能大大降低。 相似文献
16.
An accurate estimation of the applied load pattern is an essential component in each pushover procedure. Recently, a number of adaptive pushover methods have been proposed in which the effects of the higher modes as well as the progressive changes in the dynamic characteristics of structures are taken into account to compute the applied load pattern. The basic shortcoming of these advanced pushover methods is related to employing the quadratic modal combination rule, whereby the sign reversals of the modal load vectors are suppressed. In this study, an improved displacement-based adaptive pushover method is developed in which the applied load pattern is computed using the factor modal combination rule(FMC). In the proposed procedure, multiple load patterns, depending on the number of the modes considered, are determined in order to take into account the sign reversals of different modal load vectors. The accuracy of the proposed method is verifi ed for seven moment resisting frame buildings of 3, 9 and 20 stories with regularity or vertically geometric and mass irregularities subjected to 60 earthquake ground motion records. The results showed that the proposed methodology is capable of reproducing the peak dynamic responses with very good accuracy. 相似文献
17.
基于OpenSees-OpenFresco-MTS混合试验系统,选取关键构件底层中柱,进行大空间地下结构地震响应混合试验研究。在混合试验过程中,取结构底层中柱为试验子结构,取结构剩余部分与土体为数值子结构。为了满足试验要求,开发了一种专用于混合试验的可变刚度钢构件。通过更换柱脚螺杆改变试验装置侧向刚度。在混合试验前,根据数值模型中对应单元侧向刚度确定钢构件侧向刚度;根据幅值比和相位差等频域指标评价混合试验结果。试验结果显示:在上海人工波工况、El Centro波工况和Kobe波工况中,理论结果与试验结果匹配良好。在以大空间地下结构地震响应为研究对象时,基于OpenSees-OpenFresco-MTS的混合试验系统具有良好的稳定性与精确性。 相似文献
18.
A base-isolated building is liable to have a small horizontal eccentricity between the centre of mass of the superstructure and the centre of rigidity of the supporting bearings. In seismic analysis, the structure is modelled as a rigid block with tributary masses supported on massless elastomeric rubber bearings placed at a constant elevation below the centre of mass. This simplified system has three degrees of freedom: two translations and one rotation in the vertical plane. The investigation of the dynamic behaviour of a base-isolated building is carried out for both the detuned and the perfectly tuned cases. In the detuned case, the natural frequencies of the system are assumed to be well separated. In the perfectly tuned case, the uncoupled rocking frequency is assumed to be identical to the vertical translational frequency, which may result from an unusual mass distribution and/or an extreme aspect ratio of the superstructure. Perturbation methods are implemented in finding the dynamic characteristics for both cases. However, the dynamic response of the perfectly tuned case is the major concern in this investigation. The Green's functions for the displacement response of the three-degree-of-freedom system are derived for both the undamped and damped conditions. The response spectrum modal superposition method is used in estimating the maximum acceleration response. A simple method, accounting for the effect of closely spaced modes, is proposed for combining modal maxima and results in an approximate solution corresponding to a single-degree-of-freedom system. This approximate solution may be used for the preliminary design of a base-isolated structure. Numerical results for a base-isolated building subjected to the vertical component of the El Centro earthquake of 1940 were carried out for comparison with these analytical results. The proposed modal combination method showed superiority over the conventional Square Root of the Sum of the Squares method in estimating maximum responses. The results also indicated that the approximate single-degree-of-freedom system yields accurate estimations. It is shown that the effect of rocking coupling on the vertical response of base-isolated structures subjected to transient loadings, such as earthquake motions, can generally be neglected as a result of the combined effects of the time lag between the maximum translational and rotational responses and the influence of damping in the isolation system, which for elastomeric bearings can be as high as 8 to 10 per cent of critical. 相似文献
19.
In many regions of the world, a bridge will experience multiple extreme hazards during its expected service life. The current American Association of State Highway and Transportation Officials (AASHTO) load and resistance factor design (LRFD) specifications are formulated based on failure probabilities, which are fully calibrated for dead load and nonextreme live loads. Design against earthquake loads is established separately. Design against scour effect is also formulated separately by using the concept of capacity reduction (or increased scour depth). Furthermore, scour effect cannot be linked directly to an LRFD limit state equation, because the latter is formulated using force-based analysis. This paper (in two parts) presents a probability-based procedure to estimate the combined hazard effects on bridges due to truck, earthquake and scour, by treating the effect of scour as an equivalent load effect so that it can be included in reliability-based bridge failure calculations. In Part I of this series, the general principle of treating the scour depth as an equivalent load effect is presented. The individual and combined partial failure probabilities due to truck, earthquake and scour effects are described. To explain the method of including non-force-based natural hazards effects, two types of common scour failures are considered. In Part II, the corresponding bridge failure probability, the occurrence of scour as well as simultaneously having both truck load and equivalent scour load are quantitatively discussed. 相似文献
20.
The effect of higher modes on the maximum response of buildings subjected to one horizontal component of earthquake ground motion is discussed with the objective of developing better design formulas for use in building design. Ideal buildings of different numbers of storeys and structural systems are defined; their dynamic properties that define higher mode contribution are identified and are shown to be representative of real buildings. Design formulas that give the required number of modes to be used in a dynamic analysis are developed from parametric studies as a function of the admissible error, the number of storeys and the relation between the fundamental period and the corner spectrum period. The recommendations are simple to use and more rational and accurate than the ones actually in use in most seismic design codes. 相似文献