Pre/Post Earthquake Damage Assessment for Infilled RC Frame Buildings

该项目计划对一座现有的两层钢筋混凝土框架建筑进行现场动态测试，该建筑填充了未配筋的砖墙。这座位于加利福尼亚州埃尔森特罗的建筑建于20世纪20年代，是那个时代加州建筑实践的典型代表。具有类似特征的建筑位于地震活动频繁的地区，如洛杉矶、旧金山、地中海地区和拉丁美洲。这类建筑通常具有历史意义，但事实证明，它们很容易受到地震的影响。对工程师来说，理解和改善他们的行为一直是一项具有挑战性的任务。这项研究中选择的建筑在1940、1979、1987和2010年的地震中遭受了破坏，这些地震都是近距离记录的。该建筑在前三次地震后进行了修复和翻新；然而，考虑到该地区的经济情况，2010年地震期间造成的破坏不能以具有成本效益的方式修复。因此，该结构计划拆除。这为使用移动振动器测试现实生活中的建筑提供了独特的机会。测试将是渐进的，预计将使建筑处于倒塌的边缘。来自现场的独特的实验数据将加深我们对这些结构的复杂行为及其破坏机制的了解，它将为参与地震工程的研究人员和实践者提供基准数据，对于未来的分析和实验室振动台研究将是有用的。拟议研究的目的是开发一个框架，用于可靠地评估现有的填充了砖墙的钢筋混凝土框架的损坏情况。现场测试获得的数据将用于验证有限元模型和损伤识别技术。这两种工具的组合将允许推导出可用于识别结构在极端事件之前或之后的状态的破坏指数。重点是对结构的三维行为进行建模，包括填充墙的平面外行为。此外，还将开发简化模型，并用详细分析模型的结果进行验证。之所以选择将成为这项实验和分析研究的焦点的建筑，是因为它因近距离记录的四次历史地震而遭受了相当大的破坏。从建筑物的强迫振动中获得的数据也将用于验证分析工具。总而言之，拟议的研究包括：将损伤结构进一步推向非线性行为的全尺寸试验；捕捉填充物和边界框架之间面内和面外相互作用的有限元模型；用试验获得的数据验证模型，以及用以前地震的数据验证；以及开发和验证系统和损伤识别技术，以量化真实结构的损伤。

This project plans to dynamically test in the field an existing two-story reinforced concrete frame building infilled with unreinforced masonry walls. The building, located in El Centro, CA, was built in the 1920s and it is typical of the construction practice in California in that era. Buildings with similar characteristics are located in regions with high seismicity such as Los Angeles, San Francisco, the Mediterranean region, and Latin America. Such buildings often have historical significance but they have proved vulnerable to earthquakes. Understanding and improving their behavior has been a challenging task for engineers. The building selected in this study has sustained damage during earthquakes of 1940, 1979, and 1987 and 2010 which have been recorded in close proximity. The building was repaired and retrofitted after the first three earthquakes; however, the damage induced during the 2010 event cannot be repaired cost-effectively considering the economy in the area. Hence, the structure is scheduled to be demolished. This provides a unique opportunity to test a real life building using mobile shakers. The testing will be incremental and it is expected to bring the building on the verge of collapse. The unique experimental data from the field will enhance our understanding of the complex behavior of these structures and their failure mechanisms, and it will be useful for future analytical, as well as laboratory shake-table studies since it will provide benchmark data for researchers and practitioners involved with earthquake engineering. The aim of the proposed research is to develop a framework for the reliable assessment of damage in existing reinforced concrete frames infilled with masonry walls. The data obtained from field testing will be used to validate finite element models and damage identification techniques. The combination of the two tools will allow the derivation of a damage index that can be used to identify the state of a structure prior or after an extreme event. Emphasis will be given in modeling the three-dimensional behavior of the structure including the out-of-plane behavior of the infill walls. Moreover, simplified models will be developed and validated with the results of the detailed analytical models. The building that will be the focal point of this experimental and analytical study was selected because it has sustained considerable damage due to four historical earthquakes that have been recorded in close proximity. The data obtained from the forced vibrations of the building will be also used for the validation of the analytical tools. In summary, the proposed research includes full-scale tests that will push a damaged structure further into the nonlinear behavior; finite element models to capture the in- and out-of-plane interactions between the infills and the bounding frame; validation of the model with data obtained from the tests, as well as validation with data from previous earthquakes; and development and validation of a system and damage identification techniques for the quantification of damage in a real structure.