Estimation method for normal section load-bearing capacity of concrete members subjected to fire

For a critical section of slab whose tensile region surface is subjected to fire, change of concrete strength in the compressive region is neglected, and change of tensile reinforcement strength under high temperature is taken into account. For a critical section of slab whose compressive region surface is subjected to fire, a reduced value of the effective height of the section is applied, hence change of residual concrete strength and tensile reinforcement strength is neglected and change of compressive reinforcement strength under high temperature is taken into account. Likewise, for an axially compressive concrete square column subjected to fire on four surfaces, reduced value of the section dimension is applied, hence change of residual concrete strength is neglected and change of reinforcement strength under high temperature is taken into account. Based on the above thoughts, estimation methods for the normal section load-bearing capacity of slabs subjected to fire and axially loaded concrete square columns subjected to fire on four surfaces are established and can serve as a reference when checking fire resistance of concrete structures.