Fatigue Reliability Assessment Of Light-weighted Steel-UHPC Composite Bridge Deck Structure

Attributed to its advantages of the light self-weight,high strength,good economic performance,and short construction period,the orthotropic steel deck(OSD)has been widely applied to various types of long-span bridges.However,due to the repeated impact of vehicle load,the OSDs in operation are easily damaged either in the bridge deck or in the asphalt pavement.Plenty of works have been done in this field,and methods such as,increasing the thickness of steel bridge deck,changing the weld penetration and choosing the rational floor-beam web cutouts shapes were proposed though unpractical.For this purpose,a researching group at Hunan University led by Shao Xudong innovatively introduced the reinforced UHPC(ultra-high performance concrete)into OSD,producing a new configuration called"light-weighted steel-UHPC composite bridge deck(LCBD)".The new configuration has been validated both theoretically and experimentally that it can largely solve the fatigue problem of steel bridge deck.The fatigue performance of the LCBD structure has been analyzed mainly through the deterministic analysis method,but few studies have considered the influence of random factors,such as vehicle load,construction error and environmental corrosion.The above factors make it inaccurate to calculate the fatigue life of a bridge in service with the deterministic analysis method.Therefore,the fatigue life calculation based on fatigue reliability theory will be more reliable,which also provides the theoretical basis for the normal service of the LCBD structure under the fatigue reliability target index.This thesis will focus on the analysis the fatigue reliability of the LCBD structure.The main works were summarized as follows:(1)This thesis systematically summarized the fatigue reliability assessment method for steel bridge based on the traditional fatigue theory,stated the basic theories of fatigue stress,S-N curve and Miner linear cumulative damage criterion,and introduced the standard fatigue vehicle load in the United States,Europe,the UK and China.(2)The fatigue reliability of the LCBD was evaluated based on the fatigue reliability theory.A finite element model for a girder segment of the Humen Bridge in Guangdong Province was established.The fatigue reliability indexes of typical fatigue-prone details of the LCBD and the asphalt concrete pavement bridge deck were calculated and compared.The influence of a few parameters,including the UHPC layer thickness,traffic volume growth,vehicle overloading on the fatigue life of LCBD was investigated.(3)The fatigue reliability of the headed stud in the LCBD was analyzed based on the fatigue reliability theory.The fatigue rules for the shear stud in different specifications were summarized.The finite element model for a girder segment with headed studs was established in ANSYS,and the fatigue reliability indexes of headed stud were calculated.The influence of a few parameters,including the stud spacing,traffic volume growth,vehicle overloading on the fatigue life of the headed stud was investigated.(4)The bending and tension fatigue life of the UHPC in the LCBD structure was preliminarily estimated.The background information of UHPC was introduced in detail,and the regulations of UHPC in relevant criteria were presented.The tensile stress of UHPC layer was extracted by finite element analysis,the fatigue life of UHPC was preliminarily estimated,and the influence of reinforcement ratio on the fatigue life of UHPC was studied.