Investigation of Foundation Rehabilitation Strategies

不符合现代抗震设计要求的现有建筑可以通过增加钢支撑或钢筋混凝土剪力墙进行加固。然而，这种加固可以将更多的荷载传递到基础上。这项研究将检查这种结构-基础系统的地震易损性。这项研究将回顾加固和修复建筑物以应对地震荷载的主要方法。评估这些修复方法对基础的要求，找出常用基础系统的典型缺陷。当局会考虑一系列的地基修复计划，包括：(A)使用额外的桩柱；(B)在建筑物周边加建一个基础；(C)用额外的混凝土和钢材加固现有的地基和桩帽；以及(D)改善结构与地基的连接。改进的连接可以包括用于安全地将短期超载传递到土壤的机构，或者可以允许结构的部分与基础临时分离，以防止对关键元件的损害。这项研究将涉及对各种结构和广泛类别的基础系统和土壤的分析。几个地震加速度记录将被用作分析和评估的基本激励。分析研究将与建筑物和地基在地震中的过去表现相关联。重点将是制定准则和建议，为中等高度(约4至20层)的建筑物选择地基修复技术。结果将在最后报告和专业出版物中总结。

Existing buildings which do not satisfy modern seismic design requirements may be strengthened by the addition of steel bracing or reinforced concrete shear walls. This strengthening, however, can transfer more loads to the foundation. This research will examine the seismic vulnerability of such structure-foundation systems. The study will review the major methods of strengthening and rehabilitating buildings for seismic loading. The demands of these rehabilitation methods on the foundation will be evaluated and typical deficiencies of commonly used foundation systems will be ascertained. A range of foundation rehabilitation schemes including: a) use of additional piles, b) provision of an additional footing around the perimeter of the building, c) reinforcement of existing footings and pile caps with additional concrete and steel, and d) improvement of structure-foundation connections will be considered. The improved connections may include mechanisms for safely transmitting short duration overloads to the soil or may allow temporary separation of parts of the structure from the foundation to prevent damage to critical elements. The study will involve analyses of a variety of structures and broad categories of foundation systems and soils. Several earthquake induced acceleration records will be used as base excitations for analysis and evaluation. The analytical studies will be correlated with past performance of buildings and foundations during earthquakes. The emphasis will be on developing guidelines and recommendations for selecting the foundation rehabilitation techniques for buildings of intermediate height (approximately 4 to 20 stories). The results will be summarized in a final report and professional publications.