Fragility functions for low aspect ratio reinforced concrete walls

Low aspect ratio reinforced concrete walls are widely used in buildings and infrastructure to provide resistance to earthquake shaking. Future performance assessment of such structures, which will focus on repair cost and business interruption rather than component checking per ASCE 41, will utilize fragility functions that relate the probability of exceeding one or more damage thresholds to an efficient response (demand) parameter.Fragility functions are developed here for low aspect ratio reinforced concrete walls to enable future performance assessment of buildings and other structures incorporating these common structural components. The functions are developed by review and statistical evaluation of data from tests of rectangular, barbell and flanged walls. Story drift is used as the demand parameter. Experimental data are interpreted using damage states and methods of repairs. Documents that provide guidelines for repair of reinforced concrete walls, observations from experimental programs, previous research on retrofit of reinforced concrete walls, and expert opinion are used to identify the most appropriate damage states and their corresponding methods of repair. Damage states are characterized in most instances by direct indicators of damage such as cracking and crushing of concrete cracking, residual displacements due to sliding, and reinforcement buckling and fracture. Each of these damage states is linked with one of four methods of repair in increasing order of repair cost, namely, cosmetic repair, epoxy injection, partial wall replacement, and wall replacement. An ordered sequence of fragility functions is provided for each wall cross section. The statistical evaluation of the data do not support the development of fragility surfaces to accommodate widely used design variables such as axial force, rebar ratio and aspect ratio.