Research On Behavior Of Steel Reinforced Concrete (SRC) Beams In Fire

Steel Reinforced Concrete (SRC) structures has been applicated extensively in recent years. The fire resistance of SRC is one of the main researches topic on which researchers pay increasingly attention. Fire-proof experiment can cause environmental pollution, besides it is the waste of time money and resources. This paper mainly analyzed SRC- beam by finite element program ABAQUS. The main research contents and achievements are summarized as follows:1. The finite element analysis models of SRC continuous beam are established to calculation their temperature field distribution rule under ISO-834 standard fire condition. The temperature field distribution rule of 3-face heated SRC continuous beams is obtained: The adjacent span has a little effect on the beam section which is in the middle of the cross, while the cross flank of adjacent cross has almost no influence; The adjacent span and the span flank of adjacent span has little effect on the beam section which is in the support of the beam. The transient temperature field is derived. It will be invoked during the analysis behind.2. First the model's correctness is verified. Then the thermal coupling models for numerical computation of SRC continuous beam are established. Thermal coupling analysis is conducted for SRC continuous beam under five different conditions. Stress-time relationship curves of the concrete at the beam's bottom are obtained. Based on the compared between each stress curve, preliminary obtained that:stress of the concrete at the beam's bottom is linear increased at the beginning of test; Then concrete began to appear stress relaxation due to temperature field; After a modest increase (rises more than that of top concrete's) of stress, stress is continue to reduce until damaged. 3. Analyzing and summarizing numerical results, deflection-time curve of SRC continuous beam can be obtained. The influence of fire position about deflection in the middle of the beam: deflection caused by fire which is at edge span is smaller than that is at mid span; Fire at adjacent span has a little effect on the deflection which is in the middle of the span, while the Fire at span which is flank of adjacent cross has less influence.4. Based on simplify and reasonable assumptions about mechanical properties of materials under high temperature, calculation formulas of SRC beam's equivalent section area under fire are deduced. Two ultimate bearing capacity formulas of steel reinforced concrete beam are established. One is for the beam whose tensile area is under fire, the other is for the beam whose compression area is under fire. It provides theoretical basis for the engineering design.