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来加强。然而，这种加固可以将更多的荷载转移到基础上。本研究将探讨这种结构-基础体系的地震易损性。该研究将回顾地震荷载下建筑物加固和修复的主要方法。本文将评估这些修复方法对基础的要求，并确定常用基础系统的典型缺陷。一系列的基础修复方案包括：A)使用额外的桩；b)在建筑物周围提供额外的基础；c)用额外的混凝土和钢材加固现有的基础和桩帽；以及d)改善结构与基础的连接。改进后的连接可能包括将短期超载安全地传递给土壤的机制，或者可能允许将结构的某些部分与基础暂时分离，以防止对关键元件的损坏。这项研究将包括对各种结构和基础系统和土壤的广泛分类的分析。几个地震诱发加速度记录将被用作分析和评价的基础激励。分析研究将与过去地震期间建筑物和基础的性能相关联。重点将是为中等高度（大约4至20层）的建筑物制定选择地基修复技术的准则和建议。结果将在最终报告和专业出版物中进行总结。

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.