Seismic sensitivity analysis of reinforced concrete moment frames after a fire

During their useful life, structures are exposed to various loads such as earthquake, impact, fire, etc. Each of these loads causes a different response in the structure and sometimes causes damage. Sometimes a structure may be exposed to successive loads. Earthquake occurrence in buildings that have been exposed to fire load is one of these loads. Changes in parameters such as material specifications, gravity loads, and geometric properties, which are sometimes that the implementation is different from the design, have an effect on the response of structures. In this research, it has been tried to use sensitivity analysis to determine the effect of changes in parameters such as modulus of elasticity and rebar's yield stress, concrete strength, concrete cover, dead and live loads and span length on the performance of a seven-story reinforced concrete frame in the scenario The earthquake happens after the fire. The intended structure is modeled in OpenSees software with mechanical-thermal properties and is first exposed to fire load introduced in EN 1991-1-2 and finally to earthquake. Tornado diagram analysis and Monte Carlo simulation have been used to perform sensitivity analysis of the mentioned variables. The results showed that applying thermal load before seismic load to the structure definitely affects the seismic behavior of the structure and reduces the resistance and increases the dynamic response of the structure. The average drift in the critical floor for the applied records, for the states without fire, one hour of fire, two hours of fire, and three hours of fire, is equal to 0.027, 0.029, 0.033, and 0.036, respectively. Dead load and concrete strength have the highest sensitivity and modulus of elasticity and span length have the lowest sensitivity in the dynamic response of the structure in the scenario of earthquake after fire.