SSI效应对粘弹性阻尼结构减震效果的影响分析

本文以一单跨7层框架结构为研究对象,对不同场地和地震波输入条件下的粘弹性阻尼结构进行了二维有限元时程分析,探讨了SSI(土-结构动力相互作用)效应对粘弹性阻尼结构减震效果的影响。分析结果表明:①在硬土和稍硬土地基条件下,SSI效应明显降低了结构的楼层位移峰值,若在抗震设计中对客观存在的SSI效应加以考虑,设置较少数量的阻尼器(与刚性地基假定条件下确定的阻尼器数量相比)就能使结构的实际地震位移反应满足基于刚性地基假定的地震位移控制目标;②粘弹性阻尼结构的减震效果与场地条件、输入地震动特性密切相关;③与刚性地基相比,SSI效应使粘弹性阻尼结构的减震效果明显降低,且地基越软,降低幅度越大。因此,在实际的工程设计中,应当充分考虑SSI效应,对粘弹性阻尼结构的减震控制效果进行合理的评价,并针对不同的场地条件选用合适的阻尼器类型和性能参数,才有可能达到预期的减震控制效果。     

Comparative assessment of sustainable development in South American countries on the basis of the Sustainable Society Index

This study reports an overview of the economic, social and environmental performance of the main South American countries (SAC) as measured by the Sustainable Society Index. This is a well-known composite indicator, composed of 21 indicators, grouped in seven categories, covering environmental, social and economic wellbeing dimensions. Thirteen European countries recently incorporated into the European Union (NEUC) are considered as a reference. The study covers the period 2006–2016. The South American Region features significant natural resources and plays an important role in the global economy. However, there is concern about the long-term sustainability of social and economic development, given the high rate of economic growth based on the production of low added-value primary products. Sustainable development requires reasonable balance between economic, social and environmental performance, as well as a sustained and balanced increase in performance associated with those fundamental dimensions. Moreover, it is important to agree on minimum performance levels for all performance indicators, taking into account particular social, economic and environmental realities. SAC feature a clear imbalance in some categories affecting the economic, social and environmental wellbeing dimensions, showing either stagnation or significant decrease in recent years. It can be concluded that in the light of findings reported here, South American countries are far from being on the pathway towards sustainable development.     

土-桩-框架结构非线性相互作用的精细数值模型及其验证

利用有限元软件ABAQUS,建立了土-桩-框架结构非线性相互作用(SSI)的二维精细有限元模型,分别采用记忆型粘塑性嵌套面模型和损伤塑性模型模拟土体和混凝土材料,采用梁单元和rebar单元模拟RC桩基及其内部纵筋,采用接触面对法模拟桩土接触效应,取得了良好的计算效果。将自由场、框架、土-桩-框架结构模型的分析结果和其它成熟的计算软件进行对比,验证了数值模型的有效性。分析发现:桩基外侧靠近承台处的土体的非线性反应很强烈,而桩基内部土体的非线性反应较小,很大程度上只是跟随群桩一起运动。由于桩土动力接触,桩顶的加速度反应可能超出上部结构,并且桩顶的加速度时程曲线上有非常明显的"针"状突变。随着地震动强度的增加,上部框架逐渐表现出单自由度体系的动力特征,加速度反应谱有从多个波峰退化为单一波峰的趋势。     

基于应力-强度干涉理论的可靠度点估计研究

研究了基于应力-强度干涉理论(SSI)的可靠度点估计的一般模型,进而给出了应力和强度均服从单参数指数分布和双参数指数分布时可靠度估计值计算公式,给出其与样本值之间的定量关系。对于应力和强度服从其他分布的情况,采用分布类型变换将其变换为指数分布,然后利用指数分布类型的研究结果给出可靠度估计值计算式,简化了计算。     

Accumulation and relationship of metals in different soil aggregate fractions along soil profiles

Different aggregates vary in their ability to retain or adsorb metals in soil. Five soil profiles were sampled from different soil horizons and grouped, and the concentrations of Al, Mg,Ca, Fe, Mn, Cd, Cu and Pb were determined in six sizes of aggregates(> 2, 2-1, 1-0.6, 0.6-0.25,0.25-0.053, < 0.053 mm). Significantly high(p < 0.05) structural stability indexes(SSI) and aggregate stability indexes(ASI) were recorded in the topsoil horizon, which may be attributed to the high soil organi...