Experimental Investigation Of Material Properties Of 400mpa And 500mpa Steel Bars Under Temperature

At present 200Mpa and 300Mpa level steel bars have been eliminated basically in the international community, in fact 400Mpa level steel bars become the universal application , but intensity of steel bars has achieved 500Mpa level or is higher at the developed country . It is precisely because of this, the strength and deformation behaviours of 400 Mpa and 500 Mpa steel bars which commonly will be used in structural engineering under high-temperature are studied in this thesis. The electrical furnace and deformation measuring are specially designed and produced. The main testing results are as follows:Yielding strength, ultimate strength, stress-strain relationship, the Yang's modulus and strain caused by temperature of two steel bars of every grade ranging of 20℃to 800℃. Two steel bars are measured under different temperatures.Comparisons are also made between the results measured from steel bars of the same diameters.Two different paths of stress-temperature are adopted in the tests: elevated before loading and loading before elevated. And then, the test results from both testing paths are compared and some conclusions are drawn .The coupling action between stress and temperatures is also studied. The influences of temperature to the strength and deflection of the steel bars are discussed as well.According to the test results, the equations describing the mechanic performance of two bars under high-temperature are given in this thesis, which can be applied to concrete structures under high-temperature cases and can be used as fire reinforced concrete structure to assess the use of detection.