High Temperature Behavior Of Bonded Prestressed Concrete Beam With Steel Corrosion Under Partial Heating Condition

The material properties variation of the prestressed concrete(PC)under high temperature have siginificant effect on the overall structural mechanical properties.The collapse of PC structrues when exposed to fire was occurred frequently.In the meantime,the factors affecting the behavior of structures at elevated temperature are complex,such as heating rate,highest temperature,heating time,heating area,the load level,concrete cover thickness,the reinforcement ratio,corrosion rate of the steel bar,and the initial stress value of the prestressed reinforcement.The location subjected to fire on the structures are often random and partial.Therefore,there is no mature theory and method to evaluate the fire resistance of the structure.In this thesis,the bonded prestressed concrete(BPC)beams with partial length exposure to high temperature are investigated experimentally.The crack distribution and growth,deformation characteristic,failure pattern and the temperature field distribution of the BPC beams under and after elevated temperature are recorded and discussed.The efforts in the thesis include:(1)Static load tests of two BPC beams after elevated temperature is conducted.By comparison with the identical study under normal temperature,the coupling effects of elevated temperature and steel corrosion on the failure pattern and mechanical performance of BPC beam are investigated systematically.(2)Static load tests of eight BPC beams under high temperature is conducted.The entire test includes two phases: a constant load is applied on the beam with temperature elevating and the applied load is increasing until the beam is failure with temperature decreasing.The effect of steel corrosion,initial stress of prestress strand,and pre-load level on the failure pattern and mechanical performance of beams under elevating temperature are investigated systematically based on the test results.(3)Based on the thermal theory,a three-dimensional thermal transient structure analysis model is established in ANSYS to solve the temperature field distribution inside the beams.The analyzed results are verified by the test results.According to the high temperature creep mode,constitutive relation of materials,the theory of normal temperature static load model and the ANSYS thermal analysis results,an ansys program is produced to solve problems according to the results of the temperature field distribution.Then,the development of deformation with differentparameters under different conditions is investigated systematically,which provides theoretical basis for fire resistant design.