Structural Fire Resistance of Concrete

A method is presented for calculating the structural fire endurance of concrete members under various conditions of axial and bending restraints. Included is the calculated temperature distribution during a fire within concrete sections. Practical illustrative examples are given. Conclusions were: (1) Temperature distributions can be calculated for various cross sections and aggregate types, and from these data and information on temperature-strength relations, the material strength can be obtained at any time during a fire; (2) equilibrium conditions at collapse, considering bending and axial restraint simultaneously, were obtained and show that time of collapse depends on the axial restraining force, its line of action, and member deflections; (3) axial restraining forces increase fire resistance; (4) for interior bays, fire resistance is independent of the restraining force location; (5) equilibrium conditions are independent of deflections whenever axial restraining forces are neglected; and (6) members in concrete structures can develop substantial restraining forces.