A numerical study of piled raft foundations

Abstract

This paper presents raft‐pile‐soil interaction for a vertically loaded flexible piled raft on layered subsoil using a two‐dimensional finite difference numerical tool. The subsoil is modeled as a linear elastic material and the raft is modeled as a beam structure under plane strain. In addition, the piles are simulated by a series of pile elements considering the pile/soil interface behavior. In the simulations, the required input parameters of soil, pile and interface are determined by back analyses of pile loading tests. Settlement, bending moment, both in pile and raft, as well as effects of raft flexibility for vertical uniform loading in the subsoil were examined. It is found that even though for vertical uniform loading, a relatively high bending moment may be induced in the piles due to lateral displacement of the stressed subsoil. For the case of a piled raft placed over a soft clay layer at ground surface the contact pressure at the raft‐soil interface is merely 4 ～ 6% of that developed in the unpiled raft. Nevertheless, the contact pressure may reach 15 ～ 25% of that of the unpiled raft if the piled raft is resting on a sand layer at the ground surface. This implies that the loading carried by the pile group could be reduced by almost 1/4 of the design load and it could eventually reduce the cost of pile group construction to a certain extent.     

Quantile regression of indoor air concentrations of volatile organic compounds (VOC)

There are many factors determining the concentration of volatile organic compounds (VOCs) in indoor air. On the basis of 601 population-based measurements we develop an explicit exposure model that includes factors, such as renovation, furniture, flat size, smoking, and education level of the occupants.As a novel method for the evaluation of concentrations of indoor air pollutants we use quantile regression, which has the advantages of robustness against non-Gaussian distributions (and outliers) and can adjust for unbalanced frequencies of observations. The applied bi- and multivariate quantile regressions provide (1) the VOC burden that is representative for the population of Leipzig, Germany, and (2) an inter-comparison of the effects of the studied factors and their levels.As a result, we find strong evidence for factors of general impact on most VOC components, such as the season, flooring, the type of the room, and the size of the apartment. Other impact factors are very specific to the VOC components. For example, wooden flooring (parquet) and new furniture increase the concentration of terpenes as well as the modifying factors high education and sampling in the child's room. Smokers ventilate their flats in an extent that in general reduces the VOC concentrations, except for benzene (contained in tobacco smoke), which is still higher in smoking than in non-smoking flats. Very often dampness is associated with an increased VOC burden in indoor air.An investigation of mixtures emphasises a high burden of co-occurring terpenes in very small and very large apartments.     

Incidence and risk factors of severe traumatic brain injury resulting from road accidents: a population-based study

A population-based study was carried out in 1996-2001 to provide the incidence and to identify the risk factors of severe traumatic brain injury (TBI) resulting from a road accident. The severe TBI was defined as an injury to the brain or the skull, excluding scalp injuries, with an abbreviated injury scale (AIS) severity score greater than 2. The severe TBI of 1238 patients were described. The annual incidence and mortality of severe TBI were, respectively, 13.7 per 100,000 and 5.3 per 100,000. The fatality rate increased from 20% in childhood to 71% over 75-year-old. Compared to restrained car occupants, the odds ratio for having a severe TBI was 18.1 (95% confidence interval, CI=12.8-25.5) for un-helmeted motorcyclists, 9.2 (95% CI=7.5-11.3) for pedestrians, 6.4 (95% CI=4.7-8.8) for un-helmeted cyclists, 3.9 (95% CI=3.1-4.8) for unrestrained car occupants and 2.8 (95% CI=2.2-3.5) for helmeted motorcyclists. Even after adjustment for several severity factors, male gender and age above 55 were both risk factors. Prevention programs aiming at improving the head protection should be promoted. The circumstances of the accident should be taken into account to predict a severe TBI.     

演绎国药形象——广州国际医药港首期建筑设计概念

对传统的演绎的确需要很高的审慎度,判断的标准在于对传统元素的“变形”能力的研究。本文以具体设计项目为载体,讨论了设计团队如何从功能、形式与材料剖析传统建筑元素,以现代科技为根基体现传统国药形象。     

FEM COUPLING FIELD ITERATION AND ITS CONVERGENCE FOR A GMM ACTURATOR

The coupling iteration (CI) of the finite element method(FEM) is used to simulate the magnetic and mechanical characteristics for a GMM actuator. The convergent ability under different prestress and different load types is investigated. Then the calculated deformations are compared with the experimental values. The results convince that the CI of FEM is suitable for the simulation of energy coupling and transformation mechanism of the GMM. At last, the output deformation properties are studied under different input currents, showing that there is a good compromise between good linearity and large strain under the prestress 6 MPa.     

Load duration curve: A tool for technico-economic analysis of energy solutions

Accuracy and relevance of energy solution analysis for a customer could be greatly improved when considering the relationship between the electric power demand and time, information which is usually not readily available. In an attempt to fill this gap, the concept of customer load duration curve (LDC) has been investigated. A six parameters relationship has proven to be able to accurately represent measured annual and monthly LDC of 332 commercial, institutional and industrial customers. Plotted against the load factor, the values of each of the six parameters are shown to be constrained within specific ranges. This characteristic has lead to the development of an algorithm for the generation of realistic synthetic LDC. This kind of algorithm can be implemented in a technico-economic model for population studies or risk management through Monte Carlo simulations. Here we present some results for the assessment of a peak shaving application in commercial and industrial markets using Monte Carlo simulations.     

产品设计与企业CI

CI战略越来越受到企业的重视,针对有的企业因此而忽视产品设计与开发的偏差,从产品设计与CI的三大构成要素及CI的导入形式两方面阐述了产品设计与CI战略相辅相成、互相促进、不可分割的紧密联系,强调了产品设计与开发在企业经营战略中的重要地位.     

CI战略与思想政治工作

CI战略与思想政治工作两者之间有着相同点,也有着不同点.我们要使用CI战略,找准其与思想政治工作的契合点,这对于现代企业开展新时期的思想政治工作、推进人本管理是很有指导意义和借鉴意义的.     

基于CI的智能检测与虚拟仪器诊断系统研究

通过对计算智能的智能诊断方法的研究和在故障特征提取中的分析与探讨,并结合VC++和MATLAB的优点,采用两者混合编程的方法开发了机械传动损伤检测与故障分析的虚拟仪器诊断系统;在VC++环境下完成了系统界面的设计,利用MATLAB软件实现试验数据的分析计算、信号处理及图形显示等任务,通过接口软件完成了在VC++下调用*.m文件转换后的程序,从而成功研制出具有不同种类多种功能的齿轮故障分析诊断软件系统;该软件系统包括机械传动齿轮振动信号的采集导入、信号分析处理、特征提取、图形可视化显示、故障检测与诊断和检测与监控等功能;通过测试验证表明,该系统能够很好地对齿轮进行故障检测与诊断,从而实现了虚拟仪器诊断系统的应有功能。