砌体结构抗震抗剪强度分析

进行了墙体抗剪强度理论和公式的研究。将主拉强度理论与剪摩强理论相结合,形成了一种新和强度理论,即拉摩强度理论。根据该理论,导出了墙体抗剪强度公式。给出了公式系数的确定方法,并确定了砖墙体的公式系数。将本文建议的砖墙体抗剪强度公式与抗震和砌体规范采用的抗剪强度公式进行了比较,比较结果表明：抗震规范公式值较小;砌体规范公式值较在,本文公式值介于两者中间。     

地震区多层石结构抗震抗剪能力的模糊可靠性分析

本文通过考虑地震烈度的随机性和模糊性,以及石结构强度破坏等级界限的模糊性,研究多层石结构抗震抗剪能力的可靠性问题.将地震地面运动模拟为含有模糊烈度参数的平稳过滤有色噪声的随机过程,引入抗剪强度破坏指数,建立了石结构抗震抗剪能力的模糊安全准则,为研究多层石结构的抗震抗剪能力可靠性提供了一个合理的评定方法。     

石粉灌浆石砌体的抗震抗剪强度及其应用研究

基于灌浆石砌墙体的拟动力试验、工程实践和震害经验，经分析研究，首次提出灌浆石砌体的抗震抗剪强度及抗震加固验算方法。经对工程实例验算，验证了本研究的可靠性和实用性。     

石砌体结构抗震抗剪强度理论的应用

本文基于石砌墙体的拟动力实验、工程实践及震害经验,经分析研究,提出石砌体结构的抗震设计强度验算及抗震设计方法,并结合实际工程计算,验证了本研究的可靠性与实用性。     

温控参数折减有限元法在拟静力土石坝坝坡稳定分析中的应用

土石坝的拟静力计算与温控参数折减有限元法相结合,对土石坝边坡稳定性进行有限元计算与分析。按《水工建筑物抗震设计规范》(SL203-97)的规定,依据坝高动态分布系数施加水平等效地震惯性力,然后用温控参数折减有限元法确定土石坝边坡的临界失稳状态及其所对应的安全系数。结果表明:采用此法进行拟静力土石坝边坡稳定分析与传统的Bishop法相比,计算结果相一致,且可以反映土石坝的应力、应变和整个边坡破坏发展过程。     

对美国桥梁抗震规范中桥墩抗剪强度计算公式的评价

按照能力设计思想，必须防止延性构件内部发生脆性剪切破坏，以确保塑性铰的转动能力。本文对美国ATC－32、Caltrans规范及Priestley建议的抗剪强度计算公式进行了比较，并结合一座在1994年Northridge地震中发生剪切破坏的桥梁，按照这三者公式分别进行了剪切强度评价。可以得出结论，ATC－32和Caltrans规范的抗剪强度计算公式相对保守，但对低延性墩的评价却偏高。Priestley等人建议的公式能较真实地反映剪切破坏机理。     

混凝土多孔砖和组合配筋砖小截面墙体抗震性能的试验研究

针对农村窗间墙过窄的现状,提出一种组合配筋砌体以抵抗地震剪力,并提出混凝土多孔砖组合配筋砌体的参考公式.通过对混凝土多孔砖和组合配筋砖小截面墙体进行反复荷载下的抗震性能试验研究,讨论两种不同类型砌体的破坏特征、滞回特性、骨架曲线和抗剪强度等问题.组合配筋砌体与无筋砌体相比,抗震性能明显提高,延性增强.结果表明组合配筋砌体是一种能够明显改善小截面墙体抗震性能的实用方法,可在农村地区推广.     

反复荷载下钢筋混凝土框架柱杭剪承载力分析

钢筋混凝土框架柱作为高层房屋建筑的主要承重构件,在历次地震中因框架脆性剪切破坏而造成结构严重损坏甚至倒塌的现象十分常见。本文通过分析有关试验资料,提出了钢筋混凝土框架柱塑性铰区剪切强度的计算公式及有关构造措施,以保证框架柱在一定延性条件下具有足够的抗剪强度,实现“强剪弱弯”的抗震设计原则,使抗震设计的框架结构具有足够的强度和良好的延性,以配合混凝土结构设计规范（ＧＢＪ１０－８９）的修订工作。本文的     

按新规范设计的不规则框架非线性抗震性能分析

按2002新规范设计了两栋不规则空间框架，分析了结构在小震、中震及大震作用下结构的反应，重点考察了结构在中震及大震作用的非线性响应，主要包括最大层间位移、层间扭转角以及构件混凝土纤维和钢筋纤维的最大应变等，对新抗震规范要求的设防水准及目标进行了初步评估。     

Seismic stability of earth-rock dams using finite element limit analysis

In this study, a finite element limit analysis method is developed to assess the seismic stability of earth-rock dams. A pseudo-static approach is employed within the limit analysis framework to determine the lower and upper bounds on the critical seismic coefficients of dams. The interlocking force in the soil is considered, and the rockfill material is assumed to follow the Mohr–Coulomb failure criterion and an associated flow rule. Based on the native form of the failure criterion, the lower and upper bound theorems are formulated as second-order cone programming problems. The nonlinear shear strength properties of rockfill materials are also considered. The developed finite element limit analysis is applied to two different types of earth-rock dams. The results indicate that the rigorous lower and upper bounds are very close even for rockfill materials with large internal friction angles. The failure surfaces are easily predicted using the contour of the yield function and the displacement field obtained by the limit analysis method. In addition, the pore water pressures are modelled as external forces in the limit analysis to assess the seismic stability of earth-rock dams in the reservoir filling stage.     

Seismic stability of concrete gravity dams

Linear finite element analyses are commonly used to simulate the behaviour of gravity dam—foundation systems. However, the foundation is generally unable to develop any significant tensile stresses. Therefore any tension occurring in the vicinity of the dam—foundation interface is largely fictitious. Moreover, the traditional overturning and sliding stability criteria have little meaning in the context of the oscillatory response of dams during earthquakes. In this study, time domain analyses using non-linear contact elements located at the dam—foundation interface have been used to determine the dynamic sliding and uplifting response of gravity dam monoliths considering various elastic foundation properties. The magnitudes of the relative interface displacements, of the percentage of base not in contact (PBNC) and of the compressive stresses at the heel or toe of the dam have been used to monitor the seismic stability. The numerical results have shown that the non-linear behaviour of the dam—foundation interface reduces the seismic response of the system, indicating the possibility of more rational and economical designs. The PBNC was identified as the critical seismic stability response parameter for all analyses except for very flexible foundation conditions where the maximum values of relative interface displacements need to be considered.     

Seismic fracture analysis of concrete gravity dams

A numerical procedure for evaluation of the fracture process of gravity dams during strong earthquakes is presented. The BEM is used to discretize the dam reservoir system including the crack surfaces, and stress intensity factors at the crack tip are employed in a stage by stage procedure which simulates the crack extension. For each stage of constant crack length the mode superposition technique is applied; this is made possible by simulating the impact process of crack closing by a load pulse applied at the contact points which permits the structural stiffness to be assumed unchanged. To verify the proposed procedure, a cantilever beam model structure made of gypsum was tested on a shaking table. Good correlation with the numerical results was obtained, from which it is concluded that the procedure can be employed for evaluation of the crack propagation process in concrete structures subjected to dynamic loadings.     

Seismic stability of concrete gravity dams strengthened by rockfill buttressing

Rockfill buttressing resting on the downstream face of masonry or concrete gravity dam is often considered as a strengthening method to improve the stability of existing dam for hydrostatic and seismic loads. Simplified methods for seismic stability analysis of composite concrete-rockfill dams are discussed. Numerical analyses are performed using a nonlinear rockfill model and nonlinear dam-rockfill interface behavior to investigate the effects of backfill on dynamic response of composite dams. A typical 35 m concrete gravity dam, strengthened by rockfill buttressing is considered. The results of analyses confirm that backfill can improve the seismic stability of gravity dams by exerting pressure on the dam in opposition to hydrostatic loads. According to numerical analyses results, the backfill pressures vary during earthquake base excitations and the inertia forces of the backfill are the main source for those variations. It is also shown that significant passive (or active) pressure cannot develop in composite dams with a finite backfill width. A simplified model is also proposed for dynamic analysis of composite dam by replacing the backfill with by a series of vertical cantilever shear beams connected to each other and to the dam by flexible links.     

边坡地震稳定性分析探讨

传统的拟静力法和安全系数时程分析法在评价边坡地震稳定性时存在一定的局限性。在提出准确的评价边坡地震稳定性必需因素的基础上,建议对边坡地震稳定性分析方法重新进行分类。根据动力分析得到的边坡在地震作用下的破坏机制和破裂面的性质和位置,提出基于拉-剪破坏的动力时程分析法和强度折减动力分析法。第一种方法将FLAC计算得到破坏时刻的动应力施加到静力情况下边坡上,采用动力分析得到的拉-剪破裂面,结合极限平衡法求解边坡地震安全系数,是一种改进的动力有限元时程分析法;第二种方法考虑了拉-剪破坏的FLAC强度折减动力分析法,是完全动力的方法。最后通过算例分析验证了新方法的可行性,为边坡地震安全系数计算提供了一种新的思路。     

Seismic performance sensitivity and uncertainty analysis of gravity dams

Uncertainties in structural engineering are often arising from the modeling assumptions and errors, or from variability in input loadings. A practical approach for dealing with them is to perform sensitivity and uncertainty analysis in the framework of stochastic and probabilistic methods. These analyses can be statically and dynamically performed through nonlinear static pushover and IDA techniques, respectively. Of the existing structures, concrete gravity dams are infrastructures which may encounter many uncertainties. In this research, probabilistic analysis of the seismic performance of gravity dams is presented. The main characteristics of the nonlinear tensile behavior of mass concrete, along with the intensity of earthquake excitations are considered as random variables in the probabilistic analysis. Using the tallest non‐overflow monolith of the Pine Flat gravity dam as a case study, its response under static and dynamic situations is reliably examined utilizing different combinations of parameters in the material and the seismic loading. The sensitivity analysis reveals the relative importance of each parameter independently. It will be shown that the undamaged modulus of elasticity and tensile strength of mass concrete have more significant roles on the seismic resistance of the dam than the ultimate inelastic tensile strain. In order to propagate the parametric uncertainty to the actual seismic performance of the dam, probabilistic simulation methods such as Monte Carlo simulation with Latin hypercube sampling, and approximate moment estimation techniques will be used. The final results illustrate the possibility of using a mean‐parameter dam model to estimate the mean seismic performance of the dam. Copyright © 2014 John Wiley & Sons, Ltd.     

Seismic response analysis on the stability of running vehicles

The seismometer network of the Japanese expressway system has been enhanced since the 1995 Kobe earthquake. Using earthquake information from the instruments, the expressways are closed if the peak ground acceleration (PGA) is larger than or equal to 80cm/s². The aim of this regulation is to avoid secondary disasters, e.g. cars running into the collapsed sections. However, recent studies on earthquake damage have revealed that expressway structures are not seriously damaged under such‐level of earthquake motion. Hence, we may think of relaxing the regulation of expressway closure. But before doing this, it is necessary to examine the effects of shaking to automobiles since the drivers may encounter difficulties in controlling their vehicles and traffic accidents may occur. In this study, a vehicle was modelled with a six‐degree‐of‐freedom system and its responses were investigated with respect to PGA, peak ground velocity (PGV) and Japan Meteorological Agency (JMA) seismic intensity using five ground motion records. It was observed that the response of the vehicle shows a larger amplitude for the record that has larger response spectrum in the long period range compared to other records. However, similar response amplitudes of the vehicle were observed for all the records with respect to the JMA seismic intensity. The response characteristics of the vehicle model may be very useful for decision‐making regarding the relaxation of the expressway closure under seismic motion. Copyright © 2002 John Wiley & Sons, Ltd.     

南海北部陆坡稳定性定量分析

随着海洋工程的发展,海底滑坡作为一种潜在的地质灾害逐渐成为人们关注的热点.本文采用二维极限平衡法计算并分析了海底斜坡稳定性问题.通过对斜坡模型在各种条件下安全系数的计算,定量分析了斜坡内在因素(如斜坡角度、主要土力学参数)和主要触发机制(地震、快速堆积等)对安全系数的影响.理论计算表明,静态条件下,均质斜坡角度小于20°时,均处于稳定状态;对于含软弱层的斜坡,快速堆积等引起的不排水状态下斜坡安全系数明显降低,斜坡角度大于14°时就会发生失稳.拟静态条件下,当地震动峰值加速度(PGA)小于0.15g时,对于角度小于20°的均质斜坡处于稳定状态,但PGA大于0.25g时,角度大于13°的斜坡即处于失稳状态;对于含软弱层斜坡,PGA为0.1g时,角度大于10°的斜坡即处于不稳定状态;当PGA大于0.3g时,3°以上的海底斜坡即处于失稳状态,发生海底滑坡.结合南海北部陆坡海底地形、地貌特征,在静态条件下,均处于稳定状态;但在地震加载的拟静态下,根据南海北部地震动峰值加速度分布,台湾浅滩段则处于不稳定状态.这解释了该区域大陆坡折带处海底滑坡广泛发育的原因,也表明了地震是引发南海北部滑坡最主要的触发机制之一.     

Seismic displacement analysis of embankment dams with reinforced cohesive shell

Suitable materials for use as shell of embankment dams are clean coarse-grained soils or natural rockfill. In some sites these materials may not be available at an economic distance from the dam axis. The use of in-situ cohesive soils reinforced with geotextiles as the shell is suggested in this study for such cases. Dynamic behavior of reinforced embankment dam is evaluated through fully coupled nonlinear effective stress dynamic analysis. A practical pore generation model has been employed to incorporate pore pressure build up during cyclic loading. Parametric analyses have been performed to study the effect of reinforcements on the seismic behavior of the reinforced dam. Results showed that reinforcements placed within the embankment reduce horizontal and vertical displacements of the dam as well as crest settlements. Maximum shear strains within the embankment also decreased as a result of reinforcing. Furthermore, it was observed that reinforcements cause amplification in maximum horizontal crest acceleration.     

Seismic stability analysis of reinforced slopes

In this paper, the seismic stability of slopes reinforced with geosynthetics is analysed within the framework of the pseudo-static approach. Calculations are conducted by applying the kinematic theorem of limit analysis. Different failure modes are considered, and for each analytical expressions are derived that enable one to readily calculate the reinforcement force required to prevent failure and the yield acceleration of slopes subjected to earthquake loading. Several results are presented in order to illustrate the influence of seismic forces on slope stability. Moreover, a suitable procedure based on the assessment of earthquake-induced permanent displacement is proposed for the design of reinforced slopes in seismically active areas.