Effect of temperature on mechanical properties of prestressing bars

Properties of prestressing reinforcement deteriorate with rise in temperature and hence the effect of temperature on mechanical properties is critical for evaluating the fire response of prestressed concrete structures. To develop such temperature dependent properties, a series of steady-state tensile strength tests were carried out on prestressing bar specimens to evaluate tensile strength, elastic modulus and stress-strain response in 20-800 C temperature range. Results from these tests indicate that prestressing bar exhibits slower loss of strength and stiffness than conventional prestressing steel strands and wires throughout the temperature range of 20-800 C. Data generated from tensile strength tests are utilized to develop empirical relations for expressing strength, elastic modulus and stress-strain response of prestressing bar as a function of temperature. The proposed relations can be used as input data in computer models for evaluating fire response of prestressed structures that incorporate prestressing bars.