Towards a direct collapse–load method of design for concrete frames subjected to severe ground motions

Most current methods of design for concrete structures under earthquake loads rely on highly idealized ‘equivalent’ static representations of the seismic loads and linear‐elastic methods of structural analysis. With the continuing development of non‐linear methods of dynamic analysis for the overload behaviour and collapse of complete concrete structures, a more direct and more accurate design procedure becomes possible which considers conditions at system collapse. This paper describes an evaluation procedure that uses non‐linear dynamic collapse–load analysis together with global safety coefficients. A back‐calibration procedure for evaluating the global safety coefficients is also described. The aim of this paper is to open up discussion of alternative methods of design with improved accuracy which are necessary to move towards a direct collapse–load method of design. Copyright © 2002 John Wiley & Sons, Ltd.     

超高层建筑设计地震动参数的研究

本文以沈阳市世纪华丰文化广场工程场地为例,在地震危险性分析的基础上,进行土层地震反应分析,对超高层建筑设计地震动参数的确定进行研究,为抗震设计提供可靠依据。     

重力波在中层大气温度波导中的传播模式研究

本文给出了重力波在中层大气温度波导中的导制传播模型,并在此模型的基础上详细讨论了重力波部分导制传播下的对称模式与非对称模式,导出了不同模式下相应的特征函数和色散方程,进一步用离散的方法对两类色散方程进行了求解;同时还利用二维全隐欧拉格式（FICE）对重力波在温度波导中的传播进行了模拟,模拟的结果也成功地展现了对称与非对称两种传播模式.研究表明,下边界的扰动能量在向上传播进入波导区域后被俘获,形成导制传播.不同周期的初始扰动,在波导内均会形成对称与非对称形式两种模式的导制传播,由于两者的行进速度不一致,最终会引起两种不同模式的分离.数值模拟中重力波的水平行进速度与线性模型预测值非常接近.波导中不同模式下重力波的水平波长与初始扰动的水平波长非常一致,然而波导区域内重力波的频率与初始扰动的频率无关,频率不同的初始扰动会激发出相同频率的重力波对称与非对称导制传播模式.这表明在确定的温度波导中,水平波数才是决定重力波传播特性的决定因素.进一步的分析显示,初始扰动的水平波数-频率分布越接近完全导制传播的色散关系时,温度波导中更易于生成以该种模式部分导制传播的重力波.     

单层带支撑异形柱框架的高温性能研究

针对单层异形柱框架,通过高温数值分析,考察了支撑设置和受火位置对结构高温变形及内力的影响。研究结果表明：对于单层多跨异形柱框架,当只有一端有支撑跨时,会在一定程度上增大另一端的边节点水平位移和边柱侧向变形,对结构整体抗火不利;当左、右两端均有支撑跨时,非支撑跨在火灾作用下的梁轴力比很大,升温后期可能因梁跨中竖向位移急剧增大而发生破坏。基于上述研究结果,给出了4类单层带支撑异形柱框架火灾行为的初步判定方法。     

邹城地震台地电场观测数据分析及干扰排查

简要介绍了山东邹城地震台大地电场观测系统,分析总结了其观测数据的日变化特征,并对一些引起数据变化的干扰因素进行了分析。     

混沌遗传算法在高层结构风振控制优化中的应用研究

将混沌遗传算法(Chaos Genetic Algorithm,简称CGA)引入高层结构的风振控制优化中,对采用黏弹性阻尼器来控制风振响应的高层结构进行参数优化;用Matlab语言编制了均布法、迭代法、简单遗传算法(Simple Genetic Algorithm,简称SGA)和混沌遗传算法的风振控制优化分析程序;对9个高层结构进行风振控制优化,对比了算法程序的计算效率以及无控、均布、迭代、SGA和CGA工况下的结构风振响应。研究结果表明:混沌遗传算法可以应用于高层结构风振控制优化之中;混沌遗传算法的计算效率比简单遗传算法最高提升了29%;经混沌遗传算法优化后,黏弹性阻尼器附加给结构的附加阻尼比与均布和迭代相比最高分别提高了61%和22%,CGA工况的顶层加速度响应与均布和迭代法相比最高分别减小了14%和12%。为高层结构风振控制优化研究提供了新思路,具有一定的理论价值和实际意义。     

永安地震台数字地震观测系统常见故障的分析及排除

论述了永安地震台数字地震观测系统的组成单元及各单元的作用与功能,总结、分析日常观测中常见的各类故障,并详细分析仪器运行过程中典型故障的产生原因及排除方法,可为其他相关地震台站提供借鉴。     

渗流作用下河岸深基坑支护结构稳定性分析

河水径向渗流会对河岸基坑稳定性及支护结构内力产生显著影响。以某深基坑工程为背景进行了三维流固耦合数值模拟分析,研究了渗流对深基坑土体及支护结构受力与变形的作用规律。研究结果表明：1初始水位时,渗流作用对土体水平应力与土体剪应力的影响较小,但水位上升后,坑底处土体水平应力明显增大,在坑壁拐角处应力集中现象突出,土体剪应力在开挖面以下的底脚处最大;2土体水平位移与竖向位移均在水位上升时呈递增趋势;3桩身弯矩与剪力在水位上升初期有较大增加,之后增长速度减小;4上层、下层锚杆的自由段和锚固段轴力在水位上升初期均有明显增加,但之后增加幅度很小;5安全系数在水位上升初期降低较多,之后以较小速度呈线性减小。     

Deformation characterization of a regional thrust zone in the northern Rif (Chefchaouen,Morocco)

This paper provides the structural analysis of the Chefchaouen area in the northern Rif. Here the Dorsale Calcaire superposes, by means of an excellently exposed thrust fault, onto the Predorsalian succession in turn tectonically covering the Massylian Unit. Hanging wall carbonates of the Dorsale Calcaire Unit form a WSW-verging regional fold with several parasitic structures, deformed by late reverse faults in places indicating an ENE vergence. A 200 m thick shear zone characterizes the upper part of the Predorsalian succession, located at footwall of the Dorsale Calcaire Unit. Here the dominantly pelitic levels are highly deformed by (i) C′ type shear bands indicating a mean WSW tectonic transport and (ii) conjugate extensional shear planes marking an extension both orthogonal and parallel to the shear direction. The Massylian Unit is characterized by a strain gradient increasing toward the tectonic contact with the overlying Predorsalian succession, where the dominantly pelitic levels are so highly deformed so as appearing as a broken formation. Such as the previous succession, conjugate extensional shear bands and normal faults indicate a horizontal extension parallel to the thrust front synchronous with the mainly WSW-directed overthrusting. The whole thrust sheet pile recorded a further shortening, characterized by a NW–SE direction, expressed by several reverse and thrust faults and related folds. Finally strike-slip and normal faults were the last deformation structures recorded in the analyzed rocks. A possible tectonic evolution for these successions is provided. In the late Burdigalian, the Dorsale Calcaire Unit tectonically covered the Predorsalian succession and together the Massylian Unit. The latter two successions were completely detached from their basement and accreted in the orogenic wedge within a general NE–SW shortening for the analyzed sector of the northern Rif. At lithosphere scale the thrust front migration was driven by roll back and slab tear mechanisms producing a synchronous arching and related counterclockwise rotation of the tectonic prism along the African margin. Radial displacement involved extension parallel to the thrust front well-recorded in the analyzed rocks. The NE–SW shortening, probably acting in the Tortonian–Pliocene interval, was related to the final compression of the Rif Chain resulting in out-of-sequence thrusts affecting the whole orogenic belt.