Effect of the water/cement ratio on concrete behavior under extreme loading

This study focuses on identifying concrete behavior under severe triaxial loadings (near field detonation or ballistic impacts). In order to reproduce high stress levels with well‐controlled loading paths, static tests have been carried out on concrete samples by mean of a very high‐capacity triaxial press (stress levels on the order of 1 GPa). It is a longstanding fact that the water/cement ratio (W/C), upon entering the concrete composition, is a major parameter affecting the porosity and strength of the cement matrix of hardened concrete. The objective of this article is to quantify the effect of this ratio on concrete behavior under conditions of high confinement. From the composition of a reference ‘ordinary’ concrete (i.e. W/C=0.6), two other concretes have been produced with W/C ratios equal to 0.4 and 0.8, respectively. This article presents experimental results and their analysis regarding the effect of water/cement ratio (W/C) on concrete behavior under high confinement. It shows that when placed under high confinement, concrete behaves like a granular stacking composed of concrete without any influence from the level of cement matrix strength. Copyright © 2009 John Wiley & Sons, Ltd.     

云南地区地震的桥梁震害

收集了云南地区从１６２４～１９８８年遭受地震破坏的各类桥梁６７座的震害资料,并给出了桥梁的震害、建造年代、场地等情况及破坏程度的划分,根据云南地区地震对桥梁的破坏,石拱桥占的数量较多,钢筋混凝土桥较少。章主要对石拱桥及钢筋混凝土桥的构件震害表现进行分析探讨,认为在一般场地地质条件下,当受到不大于Ⅷ度地震的作用,桥梁受力构件基本不会产生明显破坏;而在场地不利情况下,Ⅵ、Ⅶ度地震都可能会遭受破坏。     

应用碳纤维布增强钢筋混凝土柱抗震能力的研究

本文通过8根钢筋混凝土柱在周期反复荷载作用下受力性能的试验研究,验证了使用碳纤维布包裹钢筋混土柱来提高其延性这种补强加固方法的有效性,本文分析了轴压比,混凝土强度,碳纤维布强度以及碳纤维布的包裹范围,包裹层数等因素对抗震加固效果的影响,最后,还对碳纤维布加固钢筋混凝土柱使其延性提高的机理进行了分析。     

钢管混凝土短柱隔震装置的试验与隔震结构仿真分析

本文阐述了钢管混凝土短柱装置的工作原理,给出了装置的构造,对隔震装置的试验结果进行了详细分析,并对传统结构模型与隔震结构模型的对比实验作了仿真计算与分析．从计算结果可知,钢管混凝土基底隔震装置具有良好的隔震性能和推广使用价值。     

摩擦-钢管混凝土短柱复合隔震支座性能试验与隔震分析

作者在钢管混凝土柱支座隔震房屋实验研究中发现,隔震支座中上盖与底座的接触无论如何处理,摩擦力总是存在的．因此,隔震支座实际上是摩擦耗能与钢管混凝土耗能复合减震系统。本文通过对单个和一组隔震支座的实验研究,确定了短柱支座的恢复力模型,采用了高阶单步算法分析了装有此类支座隔震结构的地震反应,验证了复合隔震支座良好的隔震性能及隔震效果。     

钢筋混凝土有边框带双层暗支撑剪力墙抗震性能试验研究

通过两个模型的试验研究,分析了有边框带双层暗支撑剪力墙的抗震性能,建立了力学模型,计算结果与实测值符合较好。     

抗震结构时变抗力及其动力可靠度研究

研究了抗震结构的动力反应以及结构的随机性与时变性 ,提出了结构的抗力时变模型以及相应的结构时变可靠度的分析方法。该方法对结构维护与评估具有广泛的应用价值。     

A rate‐dependent cohesive crack model based on anisotropic damage coupled to plasticity

In quasi‐brittle material the complex process of decohesion between particles in microcracks and localization of the displacement field into macrocracks is limited to a narrow fracture zone, and it is often modelled with cohesive crack models. Since the anisotropic nature of the decohesion process in separation and sliding is essential, it is particularly focused in this paper. Moreover, for cyclic and dynamic loading the unloading, load reversal (including crack closure) and rate dependency are essential features that are included in a new model. The modelling of degradation is based on a ‘localized’ version of anisotropic continuum damage coupled to inelasticity. The concept of strain energy equivalence between the states in the effective and nominal settings is adopted in order to define the free energy of the interface. The proposed fracture criterion is of the Mohr type, with a smooth transition of the failure and kinematics (slip and dilatation) characteristics between tension and shear. The chosen potential, of the Lemaitre‐type, for evolution of the dissipative processes is additively decomposed into plastic and damage parts, and non‐associative constitutive equations are obtained. The constitutive equations are integrated by applying the backward Euler rule and by using Newton iteration. The proposed model is assessed analytically and numerically and a typical calibration procedure for concrete is proposed. Copyright © 2006 John Wiley & Sons, Ltd.     

高压旋喷桩内插预应力钢筋混凝土方桩围护体系的设计与施工

在充分分析比较传统深基坑围护体系优劣的基础上,将高压旋喷止水帷幕与预应力钢筋混凝土方桩相结合,设计创新出一种新型的围护体系,且将之运用于工程实例中,大大降低了工程成本,创造了巨大的经济效益。     

深基坑地下水对钻孔灌注桩施工的影响及对策

在城市高层及超高层建筑中,先开挖基坑后施工钻孔灌注桩的方案已被广泛应用。当原地下水位高于基坑开挖面或桩长范围内有承压水层时,就会对钻孔灌注桩施工产生不利的影响甚至造成不良后果。在分析深基坑地下水对钻孔灌注桩的不利影响的基础上,提出了相应的预防及解决措施,总结得出的经验可供类似工程参考。