Pre/Post Earthquake Damage Assessment for Infilled RC Frame Buildings

本项目计划在现场对一座现有的两层钢筋混凝土框架建筑进行动态测试，该建筑填充有未配筋的砌体墙。该建筑位于加利福尼亚州的埃尔森特罗，建于20世纪20年代，是那个时代加州典型的建筑实践。具有类似特征的建筑物位于地震活动频繁的地区，如洛杉矶，弗朗西斯科，地中海地区和拉丁美洲。这些建筑通常具有历史意义，但它们已被证明容易受到地震的影响。了解和改善它们的行为一直是工程师的一项具有挑战性的任务。本研究中选择的建筑物在1940年、1979年、1987年和2010年的地震中遭受了破坏，这些地震都有近距离记录。该建筑在前三次地震后进行了修复和改造;然而，考虑到该地区的经济状况，2010年地震造成的破坏无法以具有成本效益的方式修复。因此，该结构计划拆除。这为使用移动的振动器测试真实的生活建筑物提供了独特的机会。测试将是渐进式的，预计将使建筑处于倒塌的边缘。来自现场的独特实验数据将增强我们对这些结构及其失效机制的复杂行为的理解，并且它将对未来的分析以及实验室振动台研究有用，因为它将为参与地震工程的研究人员和从业人员提供基准数据。建议的研究的目的是开发一个框架，在现有的钢筋混凝土框架填充砌体墙的损坏进行可靠的评估。从现场测试中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导出可用于识别极端事件之前或之后的结构状态的损伤指数。重点将在建模的三维行为的结构，包括平面外的行为填充墙。此外，将开发简化模型，并利用详细分析模型的结果进行验证。之所以选择这座建筑作为这次实验和分析研究的重点，是因为它在近距离记录的四次历史地震中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。总之，拟议的研究包括全尺寸试验，将推动受损结构进一步进入非线性行为;有限元模型，以捕捉填充物和边界框架之间的面内和面外相互作用;验证模型与试验获得的数据，以及验证与以前的地震数据;以及开发和验证一个系统和损伤识别技术，用于量化真实的结构中的损伤。

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.