Ultimate strength equation for pultruded CFRP plates in fire

Abstract

The paper presents a model for the ultimate strength calculation of fibre-reinforced polymer (FRP) pultruded plates in fire. The model is calibrated from a series of coupon tests on pultruded CFRP plates carried out using steady state and transient state test methods. In the steady state tests, temperatures ranging from ambient to approximately 700℃ were considered. The test specimens were heated to a specified temperature then loaded until failure while the same temperature was maintained throughout the test. Different periods of times of 5 and 30 minutes were maintained to investigate the effect of heating duration. In the transient state tests, the test specimens were loaded to a specified stress level prior to heating, and then the temperature was increased until failure of the test specimens. Three different stress levels applied to the pultruded CFRP plates were considered. Based on the test results, an ultimate strength equation is proposed which has been inspired from a model developed for metallic materials subjected to elevated temperatures. Application of the model is finally demonstrated in a worked example.