Reliability-Based Selection of Retrofit Works for Schools under Seismic Hazard

A reliability-based procedure is proposed to assess and compare the economic effectiveness of three retrofit alternatives for actual schools located in three zones with different seismic hazards. The procedure calculates the school failure probability under the damaged conditions, by considering the damages produced by the 2017 earthquake in Mexico, and the failure probability under each retrofit alternative, from the seismic spectra corresponding to the seismic hazard of each site. The best retrofit alternative is the one with the minimum expected life-cycle cost for each school. The global failure probability is calculated according to the Ditlevsen's bounds, and the limit states consist of the event in which the maximum moment exceeds the bending capacity for beams, and the combined axial and bending forces exceed the capacity of the columns; the maximum responses are obtained through nonlinear analyses. The proposed retrofit alternatives are column and beam jacketing with steel angles and plates, increment of the concrete cross sections of columns and beams, and the addition of bracing. The effectiveness of each alternative, in terms of failure probability reduction and expected life-cycle cost, was assessed for each school. The procedure may be used to update the current retrofit specifications for schools.