A Methodology to Assess Seismic Risk for Populations of Unreinforced Masonry Buildings

A regional risk/loss assessment methodology that utilizes easily obtainable physical properties of clay brick unreinforced masonry buildings is developed. \nThe steps of the proposed risk/loss assessment methodology are based on comprehensive sensitivity investigations that are conducted on building as well as region specific parameters. From these investigations, the most significant factors for regional risk/loss estimations are \nidentified and the number of essential parameters that is required by the proposed \nmethodology is reduced. \nParameter distributions for global and local properties of unreinforced masonry buildings at urban regions of the United States are defined. From these distributions building populations are generated and they are used in sensitivity investigations. A simple analytical model representing dynamic haracteristics of unreinforced masonry buildings is utilized to carry out the sensitivity investigations. A procedure that utilizes response estimates from analytical \ncalculations is laid out to evaluate building damage for in-plane and for out-of-plane actions. An example building evaluation is provided to illustrate the steps of the proposed procedure. \nThe developed regional risk/loss assessment methodology is demonstrated on a small town in Italy that was recently shaken by two moderate size earthquakes. From data collection to utilization of generated hazard-loss relationships, the steps of the methodology are demonstrated from the perspective of a stakeholder. Estimated losses are compared with the field data. \nAnalytical investigations have shown that due to total risk/loss concept, hazard-loss \nrelationships that are unacceptably cattered for individual building loss calculations can be utilized to estimate risk/loss at regional level. This statement is proven to be valid especially for building populations that possess low-level correlation in terms of their dynamic response characteristics. Furthermore, sensitivity investigations on biased building populations have shown that among investigated parameters, 1) ground motion categories, 2) number of stories, \n3) floor aspect ratio and 4) wall area to floor area ratio are the most significant parameters in regional risk/loss calculations.