Local buckling of steel plates in concrete-filled thin-walled steel tubular beam-columns

The availability of high strength steels and concrete leads to the use of thin steel plates in concrete-filled steel tubular beam-columns. However, the use of thin steel plates in composite beam-columns gives a rise to local buckling that would appreciably reduce the strength and ductility performance of the members. This paper studies the critical local and post-local buckling behavior of steel plates in concrete-filled thin-walled steel tubular beam-columns by using the finite element analysis method. Geometric and material nonlinear analyses are performed to investigate the critical local and post-local buckling strengths of steel plates under compression and in-plane bending. Initial geometric imperfections and residual stresses presented in steel plates, material yielding and strain hardening are taken into account in the nonlinear analysis. Based on the results obtained from the nonlinear finite element analyses, a set of design formulas are proposed for determining the critical local buckling and ultimate strengths of steel plates in concrete-filled steel tubular beam-columns. In addition, effective width formulas are developed for the ultimate strength design of clamped steel plates under non-uniform compression. The accuracy of the proposed design formulas is established by comparisons with available solutions. The proposed design formulas can be used directly in the design of composite beam-columns and adopted in the advanced analysis of concrete-filled thin-walled steel tubular beam-columns to account for local buckling effects.     

General behaviour and effect of rigid and non-rigid end post in stainless steel plate girders loaded in shear. Part I: Experimental study

To better understand the response of stainless steel plate girders loaded in shear, an experimental campaign was carried out at UPC as a part of extensive research on shear behaviour of stainless steel girders.A total of 8 stainless steel plate girders were tested. The primary design variables were, apart from the aspect ratio and slenderness of the web panel, the rigid or non-rigid condition of the end post. In parallel, a numerical model was developed in code ABAQUS [Hibbit, Karlsson and Sorensen Inc., ABAQUS/Standard, Version 6.3. User’s manual. Rhode Island (USA); 2002]. The tests results served as a basis for calibration of numerical models and furthermore for the development and verification of a new approach to structural stainless steel design.Different responses and modes of failure in shear were observed and special attention was taken of the effect of the rigidity of the end post during the analysis of results. The comparative analysis of the experimental results with current codes’ approaches clearly shows that shear design procedures included in Eurocode 3 Part 1.4 [European Committee for Standardisation. ENV 1993-1-4. Eurocode 3: Design of steel structures. Part 1.4: General rules—supplementary rules for stainless steel. Brussels; 1996], which specifically deals with stainless steel structures, are overly conservative.     

轻骨科混凝土局压承载力研究

轻骨料混凝土较适合于大跨径桥梁，但在预应力轻骨料混凝土桥梁端锚处必然会遇到局压问题。分析认为骨料混凝土局压提高系数比普通混凝土低，但国内外此方面的研究很少，无法给出较确切的计算值，本文在29个试验的基础上研究了轻骨料混凝土局压破坏的规律，并分析得出其局压强度提高系数公式。     

对建筑形式的思考——地域文化与现代文化同台共舞

本文试图通过对带有地域特色的现代建筑作品的分析,探讨一些较为感性化的设计思维。     

局部热源法在建筑节能现场检测中的应用

提出了采用局部常功率热源法现场检测墙体传热系数的方法。介绍了使用该方法进行传热系数稳态检测的理论依据,设计了实验测试系统。编制了三维稳态导热程序,模拟了多组不同边界条件下的墙体传热过程,并建立了用于墙体传热系数辨识的神经网络,辨识结果与理论值吻合较好。     

A study into optimization of stiffeners in plates subjected to shear loading

A great deal of attention has been focused on plates subjected to shear loading over the past decades. One main fact in design of such elements, which fall in the category of thin-walled structures, is their buckling behavior. Plate girders and recently shear walls are being widely used by structural engineers, as well as ship and aircraft designers. The role of stiffeners is proved to be vital in design of such structures to minimize their weight and cost.In this work, by using ANSYS finite element method of analysis, some 1200 plates are analyzed in order to study the role of stiffeners and to come up with some limits for an optimized design procedure. This eigenvalue method of analysis is first validated with the theoretical calculations and known cases for a wide range of typical panel geometries.The results show that the number of panels produced by intermediate transverse stiffeners should not be less than the value of plate's aspect ratio. In other words, the transverse stiffeners should divide the length of the plate to portions equal or less than its width.It is also shown that the optimum geometric properties of the stiffeners correspond to the point when the buckling shape of a plate changes from the overall mode to local mode. Furthermore, all stiffened plates, with a similar aspect ratio and number of stiffeners, have a specific value of EI_s/aD, for which the critical shear stress is optimal. In addition, some expressions to predict these properties are presented.     

Is the association between temperature and mortality modified by age, gender and socio-economic status?

Background

A number of studies have examined the relationship between high ambient temperature and mortality. Recently, concern has arisen about whether this relationship is modified by socio-demographic factors. However, data for this type of study is relatively scarce in subtropical/tropical regions where people are well accustomed to warm temperatures.

Objective

To investigate whether the relationship between daily mean temperature and daily all-cause mortality is modified by age, gender and socio-economic status (SES) in Brisbane, Australia.

Methods

We obtained daily mean temperature and all-cause mortality data for Brisbane, Australia during 1996-2004. A generalised additive model was fitted to assess the percentage increase in all deaths with every one degree increment above the threshold temperature. Different age, gender and SES groups were included in the model as categorical variables and their modification effects were estimated separately.

Results

A total of 53,316 non-external deaths were included during the study period. There was a clear increasing trend in the harmful effect of high temperature on mortality with age. The effect estimate among women was more than 20 times that among men. We did not find an SES effect on the percent increase associated with temperature.

Conclusions

The effects of high temperature on all deaths were modified by age and gender but not by SES in Brisbane, Australia.     

海绵城市建设在旧城区改造工程设计中的应用

通过雨水的合理收集、利用与适时补充地下水,达到缓解水资源紧张和保护生态环境的目的,海绵城市建设在城市旧城区改造工程中的应用,有着重大现实而长远的意义。济南市舜园小区的海绵城市设计思路是以"渗""滞"为主、"蓄""用"结合,设施分散、就地消纳雨水。建设模式彰显了雨水的自然积存、自然渗透和自然净化,是一种绿色可持续的雨水排放模式。设计人员从汇水分区入手,完善排水系统,结合LID设施提升场地设计到优化路面及改造微地形,秉持了低影响、低成本、因地制宜及特色创新的设计原则,在改善济南市人民群众居住环境的同时,打造出海绵城市建设的亮点,彰显了示范作用。     

大气浑然的时代建筑:记福建省博物馆创作

福建省博物馆是福建省近年来最重要的大型文化项目之一，本文就该馆的设计，从自然性、文化性、地方性、标志性等几个方面做了深入浅出的阐述，同时也论述了其设计的主要手法和风格。     

绿屋面系统对比研究

本文对欧洲和北美绿屋面系统的分类方法进行了介绍,对生态屋面与普通屋顶花园在建造成本、资源占用、对城市生态环境的影响等多方面进行了对比,提出应根据绿建筑评估标准(LEED)来进行绿屋面选型,并加强生态屋面系统技术的基础研究工作。