Mechanical Characteristics Of High Performance Steel HPS 485W And Bending Behavior Study Of Hybrid Girder

Compared with conventional structural steels used in bridges, high performance steel (HPS) provides higher strength, improved weld ability, enhanced fracture toughness and weathering characteristics. This paper firstly gives an introduction of the developmental history and application all over the world, and then provides a summary of existing research development about HPS. In order to promote the application of HPS and construct cost-effective bridge in China, based on the HPS 485W produced by Wuyang Steel Company using quenching and tempering (Q&T) in China, emphasis of this thesis is on the mechanical characteristic of HPS 485W and bending behavior studies of HPS hybrid girders. All the material mechanical characteristics service as a basis for the further application of HPS in China. In this thesis, the research works are presented as follows:Firstly, a series of mechanical tests were conducted to study the characteristic of HPS 485W. The results of static tensile test and toughness test show that HPS 485W is characterize with higher yield strength, smaller elastic modulus, higher yield ratio, higher toughness and lower brittle-ductile transition temperature. Besides, based on the ductility fracture toughness test, the calculated JIC value is 415.8 kJ/m2 for 18mm thick specimens and 507.79 kJ/m2 for 28mm thick specimens. The function of crack-tip stress-intensity factor range, da/dN versusΔK, is proposed based on the fatigue crack growth rate test, which shows the superior resistance of fatigue crack propergation for HPS 485W.Then, three hybrid girders were designed to study the bending behavior of HPS 485W. All these girders were single point loaded and simple supported. During the test procedure, what should be recorded that the strain and deformation at each load step, and the ultimately failure modes. After the tests, the whole procedure would be analysis in detail. The test results reveal the cost effective of hybrid design girder, and the sepcimen can achieve plastic ultimate bending capacity.After that, using finite element software of ANSYS, the HPS bending girders were molded for both strength and stability analysis. The results of finit element model and tests can fit well. What's more, the finite element molds were revised for bending parameter study, including the dimension of flange and web, and the material in hybrid girder. The resulte revealed that plastic joint can be formed in middle span of compact designed bending girder and local buckling occurred in compression flange with the increase of plastic rotation. For girders with non-compact designed section, after the flange yielding under bending, local buckling would occure and plastic joint cannot be formed.