Modeling of mechanical damage in traditional brickwork walls after fire exposure

The paper addresses the issues of fire behavior of masonry walls made of traditional/historical component materials (bricks and mortar).There are reasons for coupling investigations on the residual mechanical properties to fire resistance data, aiming at a more complete knowledge of the behavior of a masonry member during and after fire exposure. The paper proposes a numerical approach via FEM to the problem of residual mechanical performance of load-bearing fire-separating masonry walls after insulation failure. The goal is to establish relationships between fire resistance ratings under exposure and decay in mechanical properties after exposure; the parameter of wall thickness is especially investigated. This is performed by means of FEM analysis, simulating a standard ISO 834 fire resistance test followed by a mechanical compressive failure test on each investigated type of wall. First, a preliminary transient heat flow analysis gives a numerical prediction of fire resistance after violation of I (Insulation) criterion; then, a staggered heat flow - stress analysis repeats the heating of the wall up to insulation failure and calculates the thermal strain accounting for cracking; finally, a ‘cold’ structural analysis in compression is performed on the thermally-deformed model after cooling. The comparison of numerical outcomes to available experimental information allows to judge the reliability of the numerical approach in reproducing the residual behavior of a masonry wall after fire exposure.