Determination of microscopic parameters of quartz sand through tri-axial test using the discrete element method

A calibration procedure, in which coupled effects of microscopic parameters are considered, is proposed to determine the values of the microscopic parameters in the Discrete Element Method (DEM) for Fujian quartz sand. Laboratory tri-axial tests are conducted to be compared with the DEM simulations and the effects of end restraint in the laboratory tests are eliminated through a digital image measurement system. Sensitivities of the macroscopic behaviour of the specimen to the microscopic parameters are analyzed through DEM simulations. Four coupled effects of the microscopic parameters on the macroscopic behaviour are investigated through a graphic method and then considered in the calibration procedure.     

Estimate of fine sediment deposit dynamics over a gravel bar using photography analysis

Three different methods to analyse fine sediment deposits on a gravel bar using pictures are presented in this paper. A manual digitization and deposits zone delineation are performed as well as two different automated procedures. The three methods are applied on aerial pictures taken in 2006 by a drone from a height around 150 m above the study site. Two other sets of pictures taken in 2010 are also studied: the first set was obtained from the left side bank of the river at approximately 15m above the gravel bar whereas the second one was taken from a helicopter flying 600～m above the ground. These methods were used to estimate the surface of fine sediment deposits before and after flushing events. They yield similar results even if the first automated procedure is able to capture smaller patches of fine sediments. The total surface of fine sediment deposits seems to be similar before and after a flushing event, but the distribution appears quite different. Before a flushing event, a significant amount of fine sediment deposits are mixed with coarser sediments. After the flushing event, one can observe more large fine sediment deposits located on the downstream part of the secondary channel and at the channel margin. Most of the small fine sediment deposit patches were washed out. A short discussion is provided on the possible dynamics of fine sediment deposits over the gravel bar.     

A probabilistic performance‐based approach for mitigating the seismic pounding risk between adjacent buildings

Existing design procedures for determining the separation distance between adjacent buildings subjected to seismic pounding risk are based on approximations of the buildings' peak relative displacement. These procedures are characterized by unknown safety levels and thus are not suitable for use within a performance‐based earthquake engineering framework. This paper introduces an innovative reliability‐based methodology for the design of the separation distance between adjacent buildings. The proposed methodology, which is naturally integrated into modern performance‐based design procedures, provides the value of the separation distance corresponding to a target probability of pounding during the design life of the buildings. It recasts the inverse reliability problem of the determination of the design separation distance as a zero‐finding problem and involves the use of analytical techniques in order to evaluate the statistics of the dynamic response of the buildings. Both uncertainty in the seismic intensity and record‐to‐record variability are taken into account. The proposed methodology is applied to several different buildings modeled as linear elastic single‐degree‐of‐freedom (SDOF) and multi‐degree‐of‐freedom (MDOF) systems, as well as SDOF nonlinear hysteretic systems. The design separation distances obtained are compared with the corresponding estimates that are based on several response combination rules suggested in the seismic design codes and in the literature. In contrast to current seismic code design procedures, the newly proposed methodology provides consistent safety levels for different building properties and different seismic hazard conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

存储过程在天气预警短信监控系统中的应用

为保障天气预警短信接收覆盖面,对预警短信用户短信状态报告的接收情况进行监控,应用存储过程方法设计了状态报告查询模块,实现了预警短信监控系统中短信状态报告的查询、解析功能。利用存储过程设计的查询模块可有效地降低网络负载,平均查询速度提高30%,并能够调取不同的数据结果为后续预警短信操作提供依据。     

Design of controlled elastic and inelastic structures

One of the founders of structural control theory and its application in civil engineering,Professor Emeritus Tsu T.Soong,envisioned the development of the integral design of structures protected by active control devices.Most of his disciples and colleagues continuously attempted to develop procedures to achieve such integral control.In his recent papers published jointly with some of the authors of this paper,Professor Soong developed design procedures for the entire structure using a design-redesign proce...     

偏压连拱隧道优化施工的研究

针对多数连拱隧道修建中存在浅埋地形偏压结构受力状况,结合金丽温高速公路二期工程20多座隧道实际情况,选取有一定代表性浅埋地形偏压覆土厚度,对不同坡度1：1～1：1.5情况下（Ⅱ类取7种、Ⅲ类取3种）偏压连拱隧道结构受力及围岩屈服破坏等进行了施工步骤优化研究。结果表明,一般情况下,连拱隧道施工存在两种偏压效应：一种是因地形偏压引起,称之为“地形偏压”;而另一种则因连拱隧道的分部施工所引起,称之为“施工偏压”。这两种偏压有明确作用方向,产生结果也不相同。对连拱隧道左右洞,按“先外后里”工序施工,能够利用“施工偏压”来部分程度地“抵消”因地形偏压产生的结构偏压受力的不利情况。因此,采用“先外后里”工序施工,实为浅埋偏压情况下连拱隧道最优施工工序。     

八字岭分岔式隧道的三维地质力学模型试验研究

用地质力学模型试验成功地模拟一段分岔式隧道是一项系统工程,它包括确定模型试验模拟的范围和比尺,正确地选择模型试验的相似材料,设计并加工模型试验的台架和模型的制作,开挖与测试。对模型试验这一系统工程做了较为详细的介绍。模型试验结果表明,按照设定的试验工序,试验的新材料适合各类模型试验,试验台架满足试验所需要的刚度,模型易于制作和开挖、测试效果良好。     

桩基-非线性框剪结构相互作用体系(下)-- 相互作用对结构地震反应的影响

本文研究桩基-非线性框剪结构相互作用体系的地震反应。其中上部框架和剪力墙结构分别用门型单元和四弹簧墙单元进行分析;桩基阻抗函数通过单桩阻抗和动力相互作用因于求得。采用频-时域混合法求解体系的动力方程,本文研究了在桩基-框剪结构相互作用体系地震反应分析中,桩基阻抗的频率相关性对结构地震反应的影响,并从土体剪切波速和地震波强度两个方面,研究了土-桩-结构相互作用对框剪结构地震反应的影响。     

A computational procedure for joining separate map sheets

Map sheets have been often used as a basic spatial unit for managing spatial data produced from paper maps. This often results in incompatibility between adjacent map sheets, because spatial objects do not cross the boundaries smoothly and even the boundaries themselves do not match their neighbors exactly. To solve the problem this paper proposes a computational procedure for joining separate map sheets to obtain seamless spatial data. Line objects digitized separately in different map sheets are considered, which are frequently used to represent road networks, gas pipelines, and boundaries of polygon objects. The procedure consists of three steps: (1) extraction of end nodes, (2) detection of matching nodes, and (3) transformation of the map sheet. Each step goes interactively so that unexpected errors can be avoided by human observation. To test the validity of the procedure, map sheets are combined containing the road network data of Tokyo 23-ku area, Japan. This revised version was published online in July 2006 with corrections to the Cover Date.     

隧道施工地质超前预报方法

隧道施工地质超前预报是一项多种方法的综合运用,对预防异常情况及掌子面前方不良地质体的存在具有重要意义,其有利于安全施工、提高效率、缩短工期、避免事故,具有较大的社会效益和经济效益.通过合理组织预报作业流程、采用多种方法和对预测结果进行综合分析,能够提供更为准确的相关信息.