Experimental Investigation And Nonlinear Finite Element Analysis Of The Behaviors Of Unbonded Prestressed Concrete Slabs Under Fire

In this thesis, behaviors of unbonded prestressed concrete slabs including 4 simply-supported slabs and 9 continuous slabs are investigated under fire, based on the elevated temperature curve accord to the ISO standard fire curve.The main factors including concrete cover and prestressing levels which may have influence on the fire resistance of the simply-supported slabs are examined. The deflection and prestress are presented. From the results of tests, the fire endurance of the simply-supported slabs are given. The general regularity of prestress and cracks are analyzed.The main factors including prestressing levels, length of negative moment reinforcement and fire case which may have influence on the fail modes of the continuous slabs are examined. Fire case which include end span under fire, middle span under fire and end-middle span under fire simulate different room catch fire. The regularity of deflection, prestress and reactions are presented. Fail modes which are influenced by prestressing levels, length of negative moment reinforcement and fire case are proposed. From the test results, suggestion that negative moment reinforcement should run through the specimens to postpone the crack's appearance and improve the specimens' fire endurance are also proposed. The general regularity of prestress, cracks and reaction are analyzed.Programs are developed to analyses the sectional temperature field. Regard yield function as temperature and plastic strain's function, the deflection of simply-supported slabs under fire are analyses by coordinate finite element. The computing results show in good agreement with the results of tests. It is demonstrated that the method and the computer programs are reliable.