Dynamic response of URM buildings with flexible diaphragms

As seismic awareness increases, especially in traditionally non-seismic regions, there is an ever-increasing need to evaluate the lateral resistance of existing structures. Unreinforced masonry (URM) structures are perceived to be seismically unsafe due to dramatic media coverage of these structures following earthquakes. However, well-built URM structures can possess substantial seismic resistance, although quantifying this strength can be difficult. Through a combination of experimental and analytical investigations, the overall objective of the study is to provide recommendations for the evaluation and rehabilitation of URM buildings.To accomplish this objective, the study was broken down into three primary tasks: (1) an experimental investigation, (2) the development of a simple dynamic model, and (3) a review of current analysis methods. The experimental investigation consisted primarily of the construction and dynamic testing of two, two-story, URM buildings with flexible floor and roof diaphragms on the University of Illinois shaking table. The two buildings were subjected to a total of nine simulated earthquakes. Experimental results indicated that (first-story) pier rocking was a ductile mode of response.Based on experimental results, a simple (3-DOF), nonlinear elastic model was developed. This model, in conjunction with a nonlinear time-step integration program, was used to estimate peak displacements during the rocking portions of the later earthquake simulations.The third task was a review of existing static and dynamic methods for analyzing URM structures. The static methods studied included two design codes, two rehabilitation codes, finite element modeling, and a pushover analysis. Dynamic methods included an elastic time-step integration, response spectra analysis, equivalent frame modeling, and finite element modeling.After a thorough examination of the measured results from the dynamic testing and a comparison between these results with those calculated during the analytical studies, a number of recommendations for the evaluation and rehabilitation of unreinforced masonry buildings with flexible diaphragms were made.U of I OnlyETDs are only available to UIUC Users without author permissio