Seismic diagnosis of railway substructures by using secondary acoustic emission

One difficult task for the seismic diagnosis of existing structures is how to nondestructively evaluate the damage degree of invisible substructures, such as embedded foundations. To diagnose substructures efficiently, a method for nondestructive inspection is developed by applying acoustic emission (AE) technique. As a newly proposed method, characteristics of secondary AE induced by train operations were investigated, and experiments using model piles and in-situ AE monitoring of in-service railway bridges conducted under railroad traffic, from which it was demonstrated that the proposed method is practicable enough to detect invisible defects in structures. A new index, known as RTRI (ratio of Repeated Train load at the onset of AE activity to Relative maximum load for Inspection period) is proposed for structural damage qualification based on the results of in-situ AE monitoring.     

Effects of soil–structure interaction on the dynamic properties and seismic response of piled structures

This paper presents a simple and stable procedure for the estimation of periods and dampings of piled shear buildings taking soil–structure interaction into account. A substructuring methodology that includes the three-dimensional character of the foundations is used. The structure is analyzed as founded on an elastic homogeneous half-space and excited by vertically incident S waves. The strategies proposed in the literature to estimate the period and damping are revised, and a modified strategy is proposed including crossed impedances and all damping terms. Ready-to-use graphs are presented for the estimation of flexible-base period and damping in terms of their fixed-base values and the system configuration. Maximum shear forces together with base displacement and rocking peak response are also provided. It is shown that cross-coupled impedances and kinematic interaction factors need to be taken into account to obtain accurate results for piled buildings.     

Evaluation of substructuring method for seismic soil-structure interaction analysis of bridges

This paper evaluates the commonly used substructuring method for analysis of bridge systems where the bridge is divided into two sub-systems: the bridge superstructure and the substructure including the pile foundations, abutments, and soil. Modeling of the soil-structure interaction (SSI) in the system is simplified by replacing the pile foundations, abutments, and soil with sets of independent equivalent linear springs and dashpots at the base of the superstructure. The main objective of the paper is to examine how well the substructuring method simulates the seismic response of a bridge system. The baseline data required for the evaluation process is derived from analyzing a fully-coupled continuum bridge model, already validated for the instrumented two-span Meloland Road Overpass. The same bridge system is also simulated using the substructuring method. The results from both approaches are compared, and it is shown that the differences between them can be significant. The substructuring method consistently overestimates the pier base shear forces and bending moments and the pier top deflections. Moreover, the spectral response of the bridge structure is mispredicted. The analyses are repeated for a three-span bridge system subjected to several ground motions, leading to a similar observation as before. Hence, the current state of practice for simulating seismic SSI in bridges using the substructure model is shown to be too simplified to capture the major mechanisms involved in SSI.     

用三维半解析边界元的子结构法分析凸起山包对地震波的散射

本文建立了一种三维半解析边界元子结构法。这种方法可在频域就三维轴对称凸起山包对地震波的散射进行分析。这种方法节省存储空间、计算工作量小。另外还叙述了拐角的处理方法。     

The Distances of Subclusters in the Virgo Area

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SMW围护桩在上海地区的开发和应用

概述了国外和上海地区SMW工法的开发和应用情况，概要讨论了SMW工法施工中水泥土配合比，型钢水泥土复合桩的形式，设计强度计算，型钢起拔技术研究等问题，简单介绍了自制的四轴深层搅拌机及几个SMW工法工程应用实例。     

A numerical solution to seepage problems with complex drainage systems

Seepage problems with complex drainage systems are commonly encountered in civil engineering, with strong non-linearity. A numerical solution based on the Finite Element Method combining the substructure technique with a variational inequality formulation of Signorini’s type is proposed to solve these problems. The aims of this work are to accurately characterize the boundary conditions of the drainage systems, to reduce the difficulty in mesh generation resulting from the drainage holes with small radius and dense spacing, and to eliminate the singularity at the seepage points and the resultant mesh dependency. Numerical stability and robustness of the proposed method are guaranteed by an adaptive procedure for progressively relaxing the penalized Heaviside function associated with the formulation of the discrete variational inequality. Two challenging numerical examples are presented to validate the effectiveness and robustness of the proposed method.     

多点地震动输入下的拟动力实验方法

本文将拟动力实验方法应用于多点地震输入下的结构响应研究中,采用子结构技术解决了结构在多点地震输入下的实验问题。针对不同类型结构和不同方向的地震动输入,文中给出了相应的似动力实验的数值积分方法。最后采用两点地震动输入对所提出的方法进行了实验验证,证明该方法的有效性。     

A REVIEW OF THREE-DIMENSIONAL CHEMICAL STRUCTURE RETRIEVAL SYSTEMS

This paper presents a review of the rapid developments that have taken place over the last few years forthe searching of databases of three-dimensional(3D)molecules.The geometric arrangement of the atomsin a 3D molecule is described by an interatomic distance matrix.This is a form of labelled graph thatcan thus be searched using the subgraph-isomorphism algorithms that are widely used for searchingdatabases of two-dimensional(2D)molecules.Several in-house and commercial systems have beendeveloped for 3D database searching that are based on such techniques.These systems are reviewed andtheir effectiveness demonstrated by examples of their use in the discovery of novel,biologically activemolecules.Current systems represent a molecule by one or a small number of low-energy conformationsand there is hence much interest in the development of representational techniques and searchingalgorithms that account for ihe full set of geometric arrangements that can be adopted by a flexiblemolecule.     

Substructure Method of Three-Dimensional Semi-Analytic Boundary Element and Its Application to Seismic Scattering of Hill Topography

In this paper,a substructure method of three-dimensional semi-analytic boundary element is established.The seismic scattering by three-dimensional topography of a hill can be analyzed by the method in frequency domain.Using this method,the computational effort and storage space are reduced considerably.Finally,analytic results are given.