Seismic Response of Rigid-Block Assemblies: Experimental Studies and Validation of Discreet Element Numerical Tools

最近对葡萄酒桶堆进行的振动台试验揭示了几种位错模式和各种破坏模式，包括整个堆的滑动或摇动、堆上部的滑动或摇摆、顶部桶的升空以及少数情况下堆围绕其垂直轴的明显扭曲。虽然最初的观察显示了一种混沌响应，但对实验结果的进一步检查表明，刚性砌块组件的动态响应可能比最初认为的要有序得多。当块组件的响应与激励的适当参数(而不仅仅是加速度水平)和整个组件以及单个块的配置的适当参数相关时，顺序就出现了。为了提高我们对刚性砌块组件的动态响应的理解，本文提出了这项研究。这笔赠款的主要目的是：(A)通过实验验证关于单个块体摇摆反应的理论结果；(B)验证现有离散和有限元软件在分析刚性块体组件动态响应方面的性能；以及(C)建立一个可靠的程序，工程师可以放心地使用该程序来估计刚性块体组件的地震响应。在这个项目中，我们首先提出了一系列关于独立和锚定块体在地面震动下的摇摆反应的振动台实验，以验证最近的理论结果。这项研究将检验数值工具预测整体位错图案和适当的失效模式的能力，并将证明它们的优势和局限性。最后，最可靠的现有软件将被用来为一系列感兴趣的刚性块组件构建一组漂移、旋转和倾覆光谱。期望本研究能建立一套实用的刚性砌块组合结构地震反应评估方法，并为提高其抗震性能提供实用的改造建议。

Recent shake table tests on wine-barrel stacks have revealed several dislocation patterns andvarious modes of failure including sliding or rocking of the entire stack, sliding or rocking of anupper portion of the stack, lift-off of the top barrels and in few occasions appreciable twisting ofthe stack around its vertical axis. While initial observations suggested a chaotic response, furtherexamination of the experimental results indicate that the dynamic response of rigid-block assemblies might be much more ordered than initially thought. Order emerges when the response of the block assembly is correlated with the appropriate parameters of the excitation (not just the acceleration level) and the appropriate parameters of the configuration of the entire assembly as well as these of the individual blocks. The need to improve our understanding of the dynamic response of rigid-block assemblies motivated the study proposed herein. The main objectives of this grant are: (a) to experimentally verify theoretical findings on the rocking response of single blocks; (b) to validate the performance of existing discrete and finite element software to analyze the dynamic response of rigid-block assemblies; and (c) establish a dependable procedure that engineers can use with confidence to estimate the earthquake response of rigid-block assemblies.In this project we first propose a series of shake table experiments on single free-standingand anchored blocks to validate recent theoretical findings on their rocking response under ground shaking. The study will examine the ability of numerical tools to predict the overall dislocation patterns and the appropriate model of failure and will document their advantages and limitations. Finally the most dependable existing software will be used to construct a set of drift, rotation and overturning spectra for a family of rigid-block assemblies of interest. It is expected that the study will establish a practical procedure for estimating the earthquake response of rigid-block assemblies and provide practical retrofit recommendations for enhancing their earthquake resistance.