Experimental and Analytical Studies for the Size Effect on the Axial Strength of High-Strength Concrete Walls with Various Fire-Damaged Areas

The purpose of this study is to investigate the effect of fire-damaged areas associated with wall width on the axial strength of fire-damaged reinforced concrete (RC) walls. Toward that goal, Finite Element (FE) models of RC walls in real scale are generated with various wall widths of (600, 1500, and 3000) mm and number of heated surfaces such as half-surface, single-surface and double-surfaces. For the analyses, experiments are used to obtain temperature distributions inside the walls depending on the fire-damaged areas, and to validate the FE models. The analytical results show that the axial strength of the fire-damaged wall increases linearly with the wall width, except that the ratios of axial force to wall width showed slightly off from the average for the case of walls heated on half of the surface. Using the axial strength data of fire-damaged concrete walls obtained from the current and previous studies, regression analysis is conducted to estimate axial strength reduction ratios of fire-damaged concrete walls, considering various influencing parameters, such as concrete strength, fire-damaged areas, wall width and height. As a conclusion, multiple linear regression formulations from the regressions analyses are able to estimate axial strength reduction ratios of the fire-damaged concrete walls considering various influencing parameters of the wall size, concrete strength and fire-damaged area and the estimations showed good agreements with the data collected from experiments and FE analyses.