Experimental and Numerical Validation of Selective Weakening Retrofit for Existing Non-Ductile R.C. Frames
Experimental and Numerical Validation of Selective Weakening Retrofit for Existing Non-Ductile R.C. Frames
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现有非延性钢筋混凝土选择性弱化改造的实验和数值验证
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发表时间：
2009
期刊：
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通讯作者：
S. Pampanin
中科院分区：
文献类型：
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作者：
W. Y. Kam;S. Pampanin
发展廉价，而有效的和相对非侵入性的结构改造技术，现有的非延性钢筋混凝土（RC）结构仍然是最具挑战性的问题，广泛实施的宏观规模。抗震加固往往被混淆为纯粹的结构加固。作为为期六年的“新西兰多层建筑抗震改造解决方案”国家项目的一部分，坎特伯雷大学基于“选择性弱化”（SW）方法，重点研究了现有易受地震影响的钢筋混凝土框架的反直觉改造策略。概述了SW的概念后，本文提出了一个SW改造策略，地震脆弱的现有钢筋混凝土框架，特别是侧重于外部梁柱（B-C）节点的实验和数值验证。外部b-c节点是许多现有的20世纪70年代前的钢筋混凝土框架中的一个非常脆弱的区域。通过切割底部纵向钢筋和/或向b-c接头添加外部预应力来选择性地削弱梁，可以获得更理想的非弹性机构，从而改善整体抗震性能。在坎特伯雷进行的准静态循环荷载试验中，对四个2/3比例的外部RC b-c节点进行了所谓的SW改造。通过完善的3D有限元（FE）模型和动态时程分析结果的补充，实验结果显示了一种简单、经济、结构高效的结构修复技术的潜力。研究还表明，先进的三维混凝土力学为基础的微平面混凝土建模的潜力，精细有限元分析的非延性钢筋混凝土b-c节点。关键字：选择性削弱、抗震加固/修复、混凝土梁柱接头、模型混凝土、1.0引言和问题说明最近出版的技术指南[11，22]，FEMA 356预标准[10]和国际标准（欧洲规范8-第3部分[8] ASCE-SEI 41标准[2]）代表着重大的进步，并满足了现代城市社会在地震恢复和改造方面的关键需求。人们普遍认为，不详细的非延性钢筋混凝土（RC）抗弯框架对地震区的城市人口构成重大风险。pre 706结构抗震性能研究ATC & SEI 2009改善既有建筑及其他结构抗震性能会议
The development of cheap, whilst effective and relatively non-invasive structural retrofit techniques for existing non-ductile reinforced concrete (RC) structures still remains the most challenging issue for a wide implementation on a macro scale. Seismic retrofit is too often being confused as purely structural strengthening. As part of a six-years national project on “Seismic retrofit solutions for NZ multi-storey building”, focus has been given at the University of Canterbury on the development of a counter-intuitive retrofit strategy for earthquake vulnerable existing rc frame, based on a “selective weakening” (SW) approach. After an overview of the SW concept, this paper presents the experimental and numerical validation of a SW retrofit strategy for earthquake vulnerable existing RC frame with particular focus on the exterior beam-column (b-c) joints. The exterior b-c joint is a critically vulnerable region in many existing pre-1970s RC frames. By selectively weakening the beam by cutting the bottom longitudinal reinforcements and/or adding external pre-stressing to the b-c joint, a more desirable inelastic mechanism can be attained, leading to improved global seismic performance. The so-called SW retrofit is implemented on four 2/3-scaled exterior RC b-c joint subassemblies, tested under quasi-static cyclic loading at the University of Canterbury. Complemented by refined 3D Finite Element (FE) models and dynamic time-history analyses results, the experimental results have shown the potential of a simple and cost-effective yet structurally efficient structural rehabilitation technique. The research also demonstrated the potential of advanced 3D fracture-mechanics-based microplane concrete modelling for refined FE analysis of non-ductile RC b-c joints. Keyword: Selective weakening, seismic retrofit / rehabilitation, concrete beamcolumn joint, modelling concrete, 1.0 INTRODUCTION AND STATEMENT OF PROBLEM The recent publications of technical guidelines [11, 22], FEMA 356 pre-standard [10] and international standards (Eurocode8-Part 3 [8] the ASCE-SEI 41 standard[2]) represent significant progress and address crucial needs in seismic rehabilitation and retrofit for modern urban society. It is widely recognised that poorly detailed nonductile reinforced concrete (RC) moment-resisting frames pose significant risks to urban population in seismic zones. Research on the seismic performance of pre706 ATC & SEI 2009 Conference on Improving the Seismic Performance of Existing Buildings and Other Structures