Study On Mechanical Properties Of RC Flexural Members Which Are Strengthened By HPFL After High Temperature

High performance ferrocement laminate(HPFL) using steel as reinforced material and high performance cement mortar as the base material of thin layer structure.Compared with traditional repair methods of reinforced concrete structure, HPFL has strong compatibility with concrete structure, and is of good ductility, good fire resistance performance to high temperature, does not affect the original structure space height,environmentally safe, etc. Study on bending capacities of RC slabs and bending stiffness of RC beam slab assemblies which are strengthened by HPFL after high temperature. The main contents and conclusions are as follows:(1)Summarizes the researches of the domestic and foreign scholars about mechanical properties and thermal performance of the steel and concrete after high temperature. At the basic of which came up with simplified calculation models about strength and elastic modulus of steel and concrete after high temperature on this basis.(2)Use finite element analysis software ANSYS to simulate the temperature field of RC slabs under high temperature. Then determine the location of 300 ℃ isotherm and 800 ℃ isotherm within the RC slabs. Using thermal-stress coupling to couple stress field of RC slabs which are strengthened by HPFL after high temperature.(3)Make equivalent section according to the simulated temperature filed isotherm height of RC slab after high temperature. Derive the remaining capacity calculation formula of RC slab after high temperature, bending bearing capacity calculation formula of RC slab strengthened by HPFL after high temperature and bending bearing capacity calculation formula of RC slab strengthened by HPFL after high temperature on secondary load. Using the static equilibrium method, energy method and improved yield line method based on double shear yield criterion respectively to derive the ultimate bearing capacity formula of RC slab strengthened by HPFL after high temperature. Considering tension membrane effect to derive the ultimate bearing capacity formula in cases of large deflection. The analysis results show that the derived calculation formula is of more precision compared with existing test data. The examples in combination with engineering examples show that the reinforcement effect is perfect, which can be used for reinforcement engineering after high temperature.(4)Use finite element analysis software ANSYS to simulate the temperaturefield distribution of two-dimensional beam section under 5400 s high temperature.Make equivalent section of damaged RC beams section after high temperature. Put forward the remaining bending stiffness calculation formula of the RC beam after high temperature and derive RC beams and slabs’ short-term stiffness calculation formula strengthened by HPFL after high temperature on secondary load. Put forward the short-term bending stiffness effect coefficient which RC slabs applied to RC beam on secondary load in the RC beam slab assemblies. The RC beams’ short-term stiffness calculation formula strengthened by HPFL after high temperature on secondary load was amended. Carry on the on-site loading tests to verify the RC beams’ short-term stiffness calculation formula strengthened by HPFL after high temperature on secondary load. The comparison of the test value and the calculated value show that the RC beams’ short-term stiffness calculation formula strengthened by HPFL after high temperature on secondary load is of high precision.