隔震结构地震反应分析的实用计算方法

根据上部结构和隔震单元特性对隔震结构反应的影响,提出了可用于隔震结构反应分析的简易方法,避免从数学上求解耦联的非线性方程.将隔震层的恢复力模型等效线性化,以结构动力响应的Duhamel积分为基础,提出了一种新的结构动力响应的数值计算方法.     

平面非规则隔震结构性能参数对地震反应的影响

本文提出了考虑内部刚度分布层单元构造方法。该法将楼板视为剪切弯曲深梁,并用单元平均刚度、刚度偏心距和弹力半径来构造侧移刚度分布。以U型和L型结构为算例,用反应谱方法和时程分析方法计算分析了隔震体系性能参数对非规则结构的局部变形的影响。     

考虑楼板变形时非规则隔震结构的计算方法研究

建立了考虑楼板变形时的隔震结构动力计算方法,并针对非规则结构中几种需要考虑楼板变形的情况,进行了隔震前后的动力性能计算分析研究。     

基于隔震结构Benchmark模型的隔震层刚度分布分析研究

在隔震结构Benchmark模型的基础上,建立了相应的动力反应计算方法及计算程序,并在理想化隔震层刚度布置的情况下研究了隔震层水平刚度分布对基础隔震结构地震响应的影响.通过针对Benchmark模型设计的3种隔震方案的计算结果比较表明:当隔震层刚度中心靠近结构质心时,能显著降低结构的扭转反应,但同时增大了水平位移分量.文中在隔震结构Benchmark模型上建立的计算方法和结论为隔震体系计算和隔震方案设计提供了可靠的依据和途径.     

隔震结构"小震不坏"的动力可靠度分析

本文探讨叠层橡胶隔震体系在“小震不坏”条件下的动力可靠度分析。基于等效线性化的隔震工程设计参数,建立非比例阻尼隔震结构模型。采用双过滤白噪声功率谱模型描述地震动,并用林家浩虚拟激励法进行随机响应分析。以各层的最大层间位移响应作为控制指标,取结构的弹性位移限值作为位移极限值,建立功能状态方程。根据一次二阶矩方法,用串联模式计算体系的总体可靠度。文末选用了一个7层隔震框架作为数值算例,探讨了隔震阻尼、寒冷环境、节点构造误差所引起的隔震层刚度上升,以及场地土类别等对体系动力可靠性的影响。     

钢筋-沥青隔震层非线性震动特性研究

为了研究钢筋-沥青隔震层的材料与几何非线性震动特性,对钢筋-沥青隔震结构进行了振动台试验,分析了结构在不同加速度幅值输入时的隔震性能。同时,在钢材的应力-应变关系基础上,考虑构件竖向力的二次矩效应,提出了钢筋-沥青隔震层骨架曲线的计算方法,并结合双线型恢复力模型的滞回规则,建立了相应的恢复力模型。利用建立的恢复力模型,编制程序进行了弹塑性时程分析,并与试验结果作对比。结果表明:当钢筋-沥青隔震层的受力钢筋进入弹塑性阶段时,隔震层能够吸收大部分地震能量,显著降低上部结构的地震反应;弹塑性时程分析结果与试验结果吻合较好,由此建立的恢复力模型准确并且适用,可为钢筋-沥青隔震层的工程设计与非线性地震反应分析提供参考。     

大震下被动与智能隔震结构动力可靠度的对比

对被动及智能隔震结构在“大震”条件下的动力可靠度进行探讨。将被动及智能隔震体系均取作弹塑性模型,并用退化Bouc-W en滞变模型描述上部结构的恢复力,用非退化Bouc-W en模型描述隔震层的恢复力。采用虚拟激励法计算结构的随机响应,根据我国抗震规范中“大震不倒”的设防目标,采用各层最大层间位移峰值响应和累积滞变耗能构造双参数的随机疲劳累积损伤指数,作为功能状态指标。假定各层失效相关,用串联系统计算体系动力可靠度。通过数值算例,对比了被动隔震、智能隔震与非隔震体系的条件失效概率,从动力可靠度角度显示了智能隔震体系的减震优势。     

单轴平扭耦联基础隔震结构动力简化分析

为了建立单轴平扭耦联基础隔震结构的动力简化分析方法,探讨了影响结构扭转反应的参数取值规律,首先基于层单元模型,通过假定上部结构楼层回转半径、偏心距、弹力半径相等,推导了单轴平扭耦联基础隔震结构线性化的动力计算方程;其次,运用该简化分析方程,通过一算例进行了动力响应的参数分析。结果表明:调整隔震层刚心使其与上部结构质心位置接近,可显著降低偏心隔震结构扭转反应;增大隔震层刚度半径及阻尼半径可有效减少或抑制结构扭转反应;所建简化分析方程能有效模拟偏心隔震结构动力响应。     

近断层地震作用下设备-结构耦合隔震体系动力响应分析

建立设备-结构耦合隔震体系模型,选取近断层脉冲型和非脉冲型地震波各50条,计算耦合隔震体系的动力响应。分析表明,近断层脉冲型地震动对耦合隔震体系的影响大于非脉冲型地震动,且对主体结构的影响大于对设备的影响;近断层脉冲型地震作用下的隔震层位移、层间位移、楼层加速度、设备加速度和设备位移的平均响应分别达到非脉冲型地震作用的2.25倍、2.17倍、2.24倍、1.17倍和1.20倍。进行设备-结构耦合隔震体系设计时,需考虑近断层地震动脉冲作用的影响,同时需注意引起主体结构和设备最大响应的地震动不一定相同。     

近断层地震动作用下隔震结构的优化设计

首先讨论了近断层脉冲型地震动的特点,并以台湾集集地震实际脉冲型近震记录为地震动输入,应用含潜在约束策略的序列二次规划算法,对安装铅芯橡胶隔震支座的钢筋混凝土框架隔震结构的隔震器参数和上部结构构件截面几何尺寸进行一体化优化设计,然后输入E l Centro(1940)、Taft(1952)地震波对优化后的隔震结构进行地震反应分析。计算结果表明,对考虑脉冲型近断层地震动作用的隔震结构进行参数优化设计后,该隔震结构能同时满足脉冲型和普通非脉冲型近震作用的结构设计需求。     

不规则场地上基础的动阻抗及其在入射波作用下的输入运动

本文根据边界元方法建立了位不规则场上刚体的动阻抗和在入射平面波作用下的有效输入运动的分析模型，分析模型考虑了不规则场地和基础对入射波的散射作用以及土与基础的相互作用，通过验证确认了本方法的正确性，文中计算了凹陷，高地和盆地三种不规则场地土不同条件基础的动阻和有效输入的运动，并与半空间地基上相应基础的情况作了对比，计算表明，当基础尺寸与不规则场地范围可比时有必要用本文模型分析不规则场地的影响和土一结     

Three-dimensional reflectivity method for complicated irregular formations

The reflectivity method for complicated irregular formations has been extended to three-dimensional irregular (layered) topography. The Aki-Larner technique is generalized to solve the integral equations for 3-D boundary conditions, and propagator matrices are enlarged to express the total wave-field. The formulation in terms of the propagator matrix has been applied to horizontal layers included in the irregularity. The model can simulate more complex, layered, topography. Frequency responses on the surface of 2-D and 3-D layered soft basins are calculated for incident plane waves. They compare favorably with the results of another boundary method. Transfer function versus dimensionless frequency has been also calculated for the 2-D layered soft basin. Significant differences between the layered model and the homogeneous model have been observed; therefore it is necessary to consider the complicated irregular formations at the actual site.     

Calculation of Ground Vertical Displacements,Tilts and Their Distribution Characteristics around an Irregular Load

Based on the load model of a uniform isotropic semi-infinite elastic medium,we deduced a calculation of vertical displacement and tilt and proposed a method of calculation of vertical displacements and tilts caused by irregular load on the ground or underground at a certain point with two-dimensional and three-dimensional shapes. We compared the difference between the simplified model and the irregular model. Finally,the vertical displacements near the irregular load and the distribution of horizontal tilt are presented.The results show that,compared with the point simplified model,the irregular load model has certain advantages for describing the near field. The establishment of a twodimensional irregular load model can help with the calculation of the modal vector superposition after load scattering. The three-dimensional irregular load model can redistribute load through different weights given to the scattered points after the load scattering,and then obtain displacement with the vector calculation method. The results of vector superposition calculation from the scattered irregular load both in two-dimensions and three-dimensions are all convergent obviously as grids become denser,and it is shown that the calculation method is correct and feasible.     

复杂地表的单程波动方程地震叠前正演

作者基于数学检波器和等时叠加原理,实现了复杂地表的单程波动方程地震叠前正演模拟。该方法采用虚拟的数学检波器接收地下的反射地震信号,灵活地将接收点布置在地表的任何地方,从而满足地表起伏的要求。此外,根据等时叠加原理, 该方法采用单程波动方程进行波场延拓和成像,计算简单快速。通过复杂正断层的数值模拟,得到了高信噪比的共炮集地震记录,并采用适用于起伏地形的深度偏移方法对该共炮集地震记录进行了叠前深度偏移,较好地实现了地震波的偏移归位,从而证明了这里提出的起伏地表的单程波动方程地震叠前正演方法是正确和有效的。     

Dynamic behaviour and identification of non-uniform ground by the discrete wave number method

Powell's method for minimizing a function of several variables without calculating derivatives is applied to recorded earthquake motion on the ground surface to identify ground characteristics that have irregular profiles. The identifications are made by designating the shear wave velocity depth and width of the irregularity of surface ground as unknown parameters and are based on the least square fit between the amplitude of the transfer function determined from accelerograms recorded at two observation sites and the corresponding transfer function calculated from the response analysis of a ground model. The discrete wave number method is used to analyze the response of ground with a non-uniform profile for the incidence of SH waves. The effect of the initial assumed values on the convergence is studied by evaluating the square error between the theoretical transfer function and that calculated from the parameters identified. The dispersive trend found for the accelerograms is explained by the calculated response of a ground model with a non-uniform profile.     

基于非规则网格声波正演的时间域全波形反演

全波形反演是地震资料处理中速度建模的有力工具,相比层析成像等速度建模方法它能够得到速度场的更高频成分.本文给出了基于声波方程格子法正演的时间域全波形反演方法,该方法用非规则、非结构化的三角网格来离散计算区域及模型参数,能实现网格粒度与反演分辨率在空间上的自动匹配,内存需求少,计算效率高;采用L-BFGS优化方法,以分频段变网格的方式实施多尺度反演.以二维Overthrust模型进行了速度反演数值测试,显示了该方法的高效性和潜力.     

Influence of irregular topography and random soil properties on coherency loss of spatial seismic ground motions

Coherency functions are used to describe the spatial variation of seismic ground motions at multiple supports of long span structures. Many coherency function models have been proposed based on theoretical derivation or measured spatial ground motion time histories at dense seismographic arrays. Most of them are suitable for modelling spatial ground motions on flat‐lying alluvial sites. It has been found that these coherency functions are not appropriate for modelling spatial variations of ground motions at sites with irregular topography (Struct. Saf. 1991; 10 (1):1–13). This paper investigates the influence of layered irregular sites and random soil properties on coherency functions of spatial ground motions on ground surface. Ground motion time histories at different locations on ground surface of the irregular site are generated based on the combined spectral representation method and one‐dimensional wave propagation theory. Random soil properties, including shear modulus, density and damping ratio of each layer, are assumed to follow normal distributions, and are modelled by the independent one‐dimensional random fields in the vertical direction. Monte‐Carlo simulations are employed to model the effect of random variations of soil properties on the simulated surface ground motion time histories. The coherency function is estimated from the simulated ground motion time histories. Numerical examples are presented to illustrate the proposed method. Numerical results show that coherency function directly relates to the spectral ratio of two local sites, and the influence of randomly varying soil properties at a canyon site on coherency functions of spatial surface ground motions cannot be neglected. Copyright © 2010 John Wiley & Sons, Ltd.     

SH波地表散射的局域边界元模拟

本文提出了一种计算不规则起伏地形中SH波散射的有效方法——局域边界元法.本方法基于传统边界元法,为计算复杂地表散射问题提供了一种更加高效的解决方案.根据地震波满足的边界积分方程中牵引力格林函数的特性,我们将自由边界分解成水平部分和起伏部分.通过公式推导,可将水平部分的位移由起伏部分的位移通过格林函数线性叠加表示,因此只需对起伏部分的位移进行直接求解,从而极大地减少了待求解的未知数个数,显著提高了计算效率.通过与半圆形山谷SH波平面波入射的解析解比较,验证了方法的正确性.数值模型比较显示,局域边界元模拟结果与传统边界元数值解完全吻合,但是大幅提高了计算效率.因此,局域边界元法可以作为模拟不规则地形中地震波散射的有效工具.     

Fast practical evaluation of soil–structure interaction of embedded structures

A simple and fast evaluation method of soil–structure interaction (SSI) effects of embedded structures is presented via a cone model. The impedances and the effective input motions at the bottom of an embedded foundation are evaluated by means of the cone model. Those quantities are transformed exactly to the corresponding values at the top of the foundation. The evaluated quantities are combined with the super-structure at the top of the foundation. The transfer function amplitude of the interstory drift of a single-degree-of-freedom super-structure is computed for various cases, i.e. no SSI, SSI without embedment, SSI with shallow embedment, SSI with deep embedment. Soil properties are also varied to investigate in more detail the SSI effects of embedded structures. It is found that, while the transfer function amplitude is reduced by the increase of embedment in general, the characteristics of the transfer function amplitude for a very small ground shear wave velocity and large embedment are irregular and complicated.     

Nodal domain integration model of two-dimensional advection-diffusion processes

The nodal domain integration method is applied to a two-dimensional advection-diffusion process in an anisotropic inhomogeneous medium. The domain is discretised into the union of irregular triangle finite elements with vertex-located nodal points and a linear trial function is used to approximate the governing flow equation's state variable in each element. Non-linear parameters are assumed quasi-constant for small durations in time in each element. The resulting numerical model represents the Galerkin and subdomain integration weighted residual methods and the integrated finite difference method as special cases. Both Dirichlet and Neumann boundary conditions are accommodated in a manner similar to the Galerkin finite element approach.