SEISMIC RESTRAINTS FOR CLAY BRICK URM PARAPETS VALIDATED USING SHAKE-TABLE TESTING

Unrestrained unreinforced clay brick masonry (URM) parapets are found atop of a large number of vintage URM buildings. Parapets are typically cantilevered wall structural elements that form decorative and ornamental features of the building facades or in case of building side parapets, form a fire barrier. Parapets are considered to be the most vulnerable element that is prone to out-of-plane collapse when subjected to earthquake induced shaking. Due to the elevated location and the extent of the parapets above the main street frontage and main building entrances, unrestrained parapets represent a major risk to passers-by or building occupiers trying to escape from the building during an earthquake. Numerous observations made following recent earthquakes suggested that URM parapets that were previously secured performed below expectations. Subsequently, a comprehensive shake-table campaign was undertaken on 13 full-scale solid clay brick URM parapets, nine of those where then retrofitted and subjected again to dynamic loading. The objective of the study reported herein was to conduct an experimental investigation and develop generic industry-accepted proof-tested retrofit solutions for securing of URM parapets, including steel brace, timber brace, vertical strong-backs and post-tensioning. Results and observations from the experimental study are presented herein.