我国现行抗震设计规范中场地评定方法的比较和评述

目前，我国抗震设计规范中采用的场地评定方法主要有两种：一是建筑抗震设计规范（ＧＢＪ１１－８９）采用的场地分类的方法，一是构筑物抗震设计规范（ＧＢ５０１９１－９３）和电力设施抗震设计规范采用的场地指数法。前者是把场地影响按照场地分类指标划分成若干场地类别，因此，确定的地震荷载是不连续的，跳跃变化的。后者是一种以模糊推论的综合评判方法导出的场地指数为指标进行连续评定的新方法，在这种方法里，场地性质的差     

珠江三角洲通信系统震害预测

基于珠江三角洲通信建筑物的调查资料，对典型的通信建筑物做了时程地震反应分析和单体震害预测；对另一些建筑物做了群体震害预测；并就通信设备震害预测问题做了简单评述。     

Field of vertical crustal deformation in North China and the feature of its dynamic evolution

ＦｉｅｌｄｏｆｖｅｒｔｉｃａｌｃｒｕｓｔａｌｄｅｆｏｒｍａｔｉｏｎｉｎＮｏｒｔｈＣｈｉｎａａｎｄｔｈｅｆｅａｔｕｒｅｏｆｉｔｓｄｙｎａｍｉｃｅｖｏｌｕｔｉｏｎ王若柏，洪汉净，许忠淮，耿世昌，孙东平，韩月萍Ｒｕｏ－ＢａｉＷＡＮＧ；Ｈａｎ－ＪｉｎｇＨＯＮ...     

梁板分离式分层隔震结构减震原理研究

为了拓宽隔震技术的应用范围,提出了梁板分离式分层隔震结构概念,其核心思想是将框架结构或框架剪力墙结构中的所有楼层或某些楼层的全部或部分楼板通过橡胶隔震支座支承于梁上。建立了分层隔震结构的动力分析模型,利用自编程序按时程分析法和振型分解反应谱法分别计算了不同工况下分层隔震结构的地震反应,运用隔震技术的基本原理和振型分析法分析了刚度比和场地条件等因素对减震效果的影响。发现了刚度比变化过程中分层隔震结构的两个极限状态,并利用其中之一初步判断减震效果。     

Use of a derived distribution approach for flood prediction in poorly gauged basins: A case study in Italy

A derived distribution approach is developed for flood prediction in poorly gauged basins. This couples information on the expected storm scaling, condensed into Depth Duration Frequency curves, with soil abstractions modeled using Soil Conservation Service Curve Number method and hydrological response through Nash’s Instantaneous Unit Hydrograph. A simplified framework is given to evaluate critical duration for flood design. Antecedent moisture condition distribution is included. The method is tested on 16 poorly gauged Mediterranean watersheds in Tyrrhenian Liguria, North Western Italy, belonging to a homogeneous hydrological regions. The derived flood distribution is compared to the regional one, currently adopted for flood design. The evaluation of Curve Number is critical for peak flood evaluation and needs to be carefully carried out. This can be done including local Annual Flood Series data in the estimation of the derived distribution, so gathering the greatest available information. However, Curve Number influence decreases for the highest return periods. When considerable return periods are required for flood design and few years of data are available, the derived distribution provides more accurate estimates than the approach based on single site distribution fitting. A strategy based on data availability for application of the approach is then given. The proposed methodology contributes to the ongoing discussion concerning PUB (Prediction in Ungauged Basins) decade of the IAHS association and can be used by researchers and practitioners for those sites where no flood data, or only a few, are available, provided precipitation data and land use information are at hand.     

南京江心洲大桥主桥的地震反应谱分析

以南京江心洲大桥主桥为研究对象,采用大型有限元分析软件ANSYS建立了该独塔自锚式悬索桥的三维有限元模型,采用子空间迭代法对该桥模型进行了自振特性的分析,在其中考虑了几何非线性的影响。对该桥模型进行模态分析。在此基础上运用反应谱法计算了该桥的纵向、横向、竖向、纵向＋竖向以及横向＋竖向的地震响应,并针对其主要截面位置进行分析。结果表明,横向地震下的塔底应力比纵向、竖向输入下大,竖向地震作用下主梁地震应力要比横向、纵向地震作用下的大,塔顶位移在纵向＋竖向地震动输入时的位移值最大等。研究结果对同类桥型的工程抗震研究具有参考意义。     

Response spectral amplification ratios from 1- and 2-dimensional nonlinear soil site models

In order to determine the effect of geometry on the ground response of 2-dimensional (2-D) basins filled with soils that can develop nonlinear response, we use three basin models with width/depth ratios 3, 6 and 10. The three basins are subjected to a suite of rock site records with various magnitudes and source distances. We compute response spectral amplification ratios at four locations on the surface of the 2-D basins, and determine the average variation of the amplification ratios with respect to excitation spectra, for peak ground acceleration (PGA) and 3 spectral periods of 0.2, 0.5, 1 s. Similarly, we compute the average response spectral amplification ratios for two 1-dimensional (1-D) nonlinear models, one having the soil profile at the basin centre and the other having a soil profile at half the depth of the basin. From the relationship between the average amplification ratios and excitation spectra, we determine the cross-over point in terms of excitation spectral values that separate the amplification range from the deamplification range. Our results show that the cross-over point varies significantly from one location to another on the ground surface and from one basin to another, in a range of 0.3–1.1g for PGA. The effects of basin geometry are very strong at weak and moderate excitation, but decrease with increasing excitation spectra in a significant portion around the basin centre. Our results provide some justification for using 1-D models for 2-D basins with a width/depth ratio ?6 if the soil site is subjected to strong ground shaking.     

Random vibration analysis of long-span structures subjected to spatially varying ground motions

On the basis of the pseudo-excitation method (PEM), a random vibration methodology is formulated for the seismic analysis of multi-supported structures subjected to spatially varying ground motions. The ground motion spatial variability consists of the wave passage, incoherence and site–response effects. Advantages of this method are that less computation effort is required and that the cross-correlations both between normal modes and between excitations are automatically included. Random seismic responses of a realistic long-span bridge due to the wave passage, incoherence and site–response effects are extensively investigated. It is shown that all these effects have significant influence on the seismic response of the structure.     

Nonlinear dynamic analysis of Meloland Road Overpass using three-dimensional continuum modeling approach

This paper presents a three-dimensional (3D) continuum nonlinear analysis of the Meloland Road Overpass (MRO) near El Centro, California. The modeling methodology and the computational tools are discussed in detail. The performance of the computational model is evaluated by comparing the computed responses with the responses recorded at the bridge site during the 1979 Imperial Valley and 2010 El Mayor-Cucapah earthquakes. Amongst the recorded earthquake events at the bridge site, these two events caused the strongest shaking. The comparison shows that the 3D model is potentially an effective tool for detailed analysis of a full bridge system including foundation soils, pile foundations, embankments, supporting columns, and the bridge structure itself in a unified system without relying on any ancillary models such as Winkler springs. Additional response parameters such as displacements, rockings, and bending moments are also evaluated although none of these was measured during the seismic events.     

Winkler model for dynamic response of composite caisson–piles foundations: Seismic response

A simplified method with a dynamic Winkler model to study the seismic response of composite caisson–piles foundations (CCPF¹) is developed. Firstly, with the dynamic Winkler model, the kinematic response of the CCPF subjected to vertically propagating seismic S-wave is analyzed by coupling the responses of caisson part and pile part. Secondly, a simplified model for the foundation–structure system is created with the structure simplified as a lumped mass connected to the foundation with an elastic column, and through the Fast Fourier Transformation (FFT) this model is enabled to solve transient seismic problems. Thirdly, the proposed method for the seismic response of CCPF-structure systems is verified by comparison against 3D dynamic finite element simulation, in which the Domain Reduction Method (DRM²) is utilized. Lastly, the mechanism and significance of adding piles in improving the earthquake resistance of the foundation and structure is analyzed through an example with different soil conditions. Discovered in this study is that adding piles under the caisson is an efficient way to increase seismic resistant capability of the soil–foundation–structure system, and the main mechanism of that is the elimination of the pseudo-resonance.