Pre/Post Earthquake Damage Assessment for Infilled RC Frame Buildings

本项目计划在现场对现有的两层钢筋混凝土框架建筑进行动态测试，该建筑填充了无筋砌体墙。该建筑位于加州埃尔森特罗，建于20世纪20年代，是当时加州建筑实践的典型代表。具有类似特征的建筑物位于洛杉矶、旧金山、地中海地区和拉丁美洲等地震活动频繁的地区。这些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。理解和改进它们的行为对工程师来说是一项具有挑战性的任务。本研究中选择的建筑在1940年、1979年、1987年和2010年的地震中遭受了近距离的破坏。在前三次地震后，这栋建筑得到了修复和翻新；然而，考虑到该地区的经济状况，2010年地震造成的损失无法经济有效地修复。因此，该建筑计划被拆除。这提供了一个独特的机会来测试一个真实生活中的建筑使用移动振动器。测试将是渐进的，预计将使建筑物处于倒塌的边缘。来自现场的独特实验数据将增强我们对这些结构的复杂行为及其破坏机制的理解，并且它将有助于未来的分析，以及实验室振动台研究，因为它将为研究人员和从业者提供基准数据参与地震工程。提出的研究目的是开发一个框架，以可靠地评估现有的钢筋混凝土框架砌筑墙的损伤。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。这两种工具的结合将允许推导出一个损伤指数，该指数可用于识别极端事件之前或之后的结构状态。重点将放在结构的三维行为建模，包括填充墙的面外行为。此外，将开发简化模型，并与详细分析模型的结果进行验证。之所以选择这座建筑作为实验和分析研究的重点，是因为它在历史上近距离记录的四次地震中遭受了相当大的破坏。从建筑物的强制振动中获得的数据也将用于分析工具的验证。总之，提出的研究包括全面的测试，将推动一个损坏的结构进一步进入非线性行为；有限元模型，以捕捉在平面内和平面外的相互作用之间的填充和边界框架；用从试验中获得的数据以及以前地震的数据对模型进行验证；并开发和验证了一种用于实际结构损伤量化的系统和损伤识别技术。

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.