Performance And Strengthening Of Reinforced Concrete Beams Fire Resistance Test

In this paper, based on reinforced concrete beams as research objects, the dint properties of structure after strengthen have been studied in the tests, and its fire-resistance behaviors and dint behaviors of augmented section are analyzed and discussed with the method of theoretical analysis and numerical calculation together. The main contents include:(1)Considering the thermal properties of concrete, the finite difference equation and formula are built for the temperature of reinforced concrete beams with safeguard under three side exposing to fire. The program is developed to compare with the test results. The computer results shows that, the safeguard can reduce the speed of thermal transfer to the concrete and rebar, delay the time of heightening temperature and reduce intensity, then enhance its fire-resistance behaviors.(2)The experiments of seven reinforced concrete beams under fire and one beam in common temperature are accomplished. The deformation characteristic and damage form of members are investigated through the tests. The influences for its fire-resistance behaviors of constant loads and times exposed to fire are researched and discussed.(3)The tests of two reinforced concrete beams under loads after fire have been carried out. The macroscopical phenomena,damage features and deformation rules of the members are studied, and the drop degree of the bearing capacity is compared and analyzed.The results shows that the concrete beams was damaged serious by fire, and the damage is serious with bigger loads and longer time exposed to fire.(4)Five concrete beams damaged by fire are strengthened with self-compacting concrete. The experiments of the beams after repaired are accomplished, the influences for its dint behaviors of constant loads and repairing thickness are researched and discussed. The bearing capacity of the strengthened reinforced concrete is compared and analyzed with the method of section grid. A simplified method for calculating the residual bearing capacity of the strengthened reinforced concrete flexural members after exposed to high temperature through increasing section area from their single surface is presented.