Distinct Element Modelling of Unreinforced Masonry Wall Under Seismic Loads with and without Cable Retrofitting

To retrofit and strengthen existing unreinforced masonry (URM) structures to resist the potential earthquake damages has become an important issue in Australia.In order to secure the performance of URM under seismic loading in the future,a research project was carried out aimed at developing a simple and high strength seismic retrofitting technique for masonry structures.A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted.The results indicated that both the strength and ductility of the tested specimens were significantly enhanced with the technique.An analytical model which is based on Distinct Element Method (DEM) has also been developed to simulate the behaviour of URM walls before and after retrofitting.The model is then further developed by applying a seismic wave to the wall to simulate the wall behavior under earthquake loads before and after retrofitting.     

Modelling of URM Walls Retrofitted with Cable：A Comparison Between a Basic Mechanical Model and Distinct Element Method

The Australian love of ＂heritage＂ buildings （most of them are unreinforced masonry （URM） ） means that greater attention is required to secure their performance under seismic or impact loading in the future. A research project has been carried out to develop a new, economic and high strength retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. In this paper, an analytical model which is based on distinct element method（DEM） is developed to simulate the behaviour of retrofitted walls, in DEM, a solid is represented as an assembly of discrete blocks. Joints are modelled as interface between distinct bodies. It is a dynamic process and specially designed to model the behaviour of discontinuities. In order to assist the practising engineers to design this new retrofitted wall system, a simple mechanical model was also developed to predict the strength of the retrofitted walls. The results obtained from this simple mechanical model are compared with those from both experiments and distinct element model.     

Distinct Element Modelling of Unreinforced Masonry Wall Under Seismic Loads with and without Cable Retrofitting

To retrofit and strengthen existing unreinforced masonry (URM) structures to resist the potential earthquake damages has become an important issue in Australia. In order to secure the performance of URM under seismic loading in the future, a research project was carried out aimed at developing a simple and high strength seismic retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. The results indicated that both the strength and ductility of the tested speci-mens were significantly enhanced with the technique. An analytical model which is based on Dis-tinct Element Method (DEM) has also been developed to simulate the behaviour of URM walls be-fore and after retrofitting. The model is then further developed by applying a seismic wave to the wall to simulate the wall behavior under earthquake loads before and after retrofitting.     

基于离散元的沥青路面压实作业参数研究

鉴于沥青混合料的压实机理复杂、影响因素众多等特点,本文采用离散单元的方法,在不同作业参数下,对沥青路面碾压的过程进行数值模拟,并对压实的响应进行分析。从而寻求最佳的施工工艺和使用性能,为路面压实施工提供必要的理论依据。     

经验方法和修正的Feltcher算法选取阻尼因子的介质重构比较

对在TM简谐波照射下的目标重构，从散射的积分方程出发，采用矩量法离散该积分方程，对所得的非线性方程组采用L-M方法求解，数值比较了对阻尼因子选取采用修正的Feltcher算法和经验方法重构的结果。     

车辆专业有限元课程教学改革实践探索

有限元法已成为工程分析中强有力的数值分析工具。根据有限元理论与技术发展的特点,针对传统有限元课程教学体系中存在的数学、力学理论起点高,学生难于掌握等问题,对建立课程新的内容体系,通用有限元软件应用和与实际工程问题的教学内容、方法以及课程安排进行改革。实践证明,通过教学改革,对学生理论基础与实际操作能力的提高起到了积极的作用。     

Stress and Displacement Distribution of Soft Clay Slope with 2D and 3D Elastoplastic Finite Element Method

Based on elastoplastic model, 2D and 3D finite element method (FEM) are used to calculate the stress and displacement distribution in the soft clay slope under gravity and uniform load at the slope top. Stability analyses indicate that 3D boundary effect varies with the stress level of the slope. When the slope is stable, end effect of 3D space is not remarkable. When the stability decreases, end effect occurs; when the slope is at limit state, end effect reaches maximum. The energy causing slope failure spreads preferentially along y-z section, and when the failure resistance capability reaches the limit state, the energy can extend along x-axis direction. The 3D effect of the slope under uniform load on the top is related to the ratio of load influence width to slope height, and the effect is remarkable with the decrease of the ratio.     

一类带参数的两步方法及其A-稳定的条件分析

本文首先给出了常微分方程数值方法的一些基本概念,然后借助阶的等价条件,构造了一类带参数的两步方法,最后得到了这类两步方法 A-稳定的条件。     

Testing Students with Special Needs: A Model for Understanding the Interaction Between Assessment and Student Characteristics in a Universally Designed Environment

This article presents a model of assessment development integrating student characteristics with the conceptualization, design, and implementation of standardized achievement tests. The model extends the assessment triangle proposed by the National Research Council ( Pellegrino, Chudowsky, & Glaser, 2001 ) to consider the needs of students with disabilities and English learners on two dimensions: cognitive interaction and observation interaction. Specific steps in the test development cycle for including students with special needs are proposed following the guidelines provided by Downing (2006) . Because this model of test development considers the range of student needs before test development commences, student characteristics are supported by applying the principles of universal design and appropriately aligning accommodations to address student needs. Specific guidelines for test development are presented.     

基于特征值的零构件疲劳可靠性统计方法

在零构件疲劳失效的分布规律的基础上,对多种零构件疲劳强度可靠性实验数据进行统计分析,充分利用疲劳S-N曲线的对数线性关系,通过引入静态机械性能参数断裂真应力和疲劳循环基数两个特征值点,较好地实现了零构件制造工艺性能参数与疲劳特性结合,获得一种零构件疲劳可靠性工程评价方法。本文还报告了在连杆、转向节、混凝土道路小样零构件的疲劳强度可靠性评估工作中的试验、统计、应用情况。本文方法具有简单、实用、易于推广的特点。     

基于灰色关联度与TOPSIS法的养老机构评价模型分析——以合肥市为例

随着老龄化趋势加重,社会对养老机构的需求不断增加,养老机构的选择成为一个核心问题。文章在分析养老机构影响因素的基础上,构建了养老机构评价指标体系,并利用灰色关联度与TOPSIS相结合的方法,建立了养老机构评价模型。以合肥市8家养老机构为例进行模型验证,结果表明,利用模型能够选择出综合条件最优的养老机构,并且灰色关联度法与TOPSIS法联合使用比两种方法单独使用评价结果更准确可靠。