Experimental Study On Fatigue Performance Of Orthotropic Steel-SFRC Composite Bridge Deck

The orthotropic steel-concrete composite bridge deck structure can significantly reduce the fatigue stresses at susceptible details of orthotropic steel decks(OSDs)and effectively improve it’s fatigue performance.At present,the research of concrete layer mainly focuses on high performance concrete.Laying a thick layer of steel fiber concrete(SFRC)can also effectively improve the fatigue performance of OSDs,and it is more economical,but there is a lack of related research at present.In order to study the fatigue performance of the orthotropic steel-concrete composite bridge deck and optimize it’s design,the stress reducing effect of overlay and the governing fatigue failure modes of steel–SFRC composite deck under different design parameters were analyzed by full-scale fatigue tests and numerical simulation.The main research contents and results are as follows:(1)A full-scale model was designed based on the Yibin Lingang Changjiang River Roadrail Bridge.And Through the static tests and fatigue tests to study the fatigue stress and damage of the fatigue details.The results show that after 2 million fatigue load cycles,the OSDs and the stud connectors did not crack,and the crack width of SFRC layer is less than the specification limit,The fatigue performance of orthotropic s steel-SFRC composite bridge deck meets the design service life requirements;The SFRC layer can significantly improve the fatigue performance of OSDs,and the stress of each fatigue detail is reduced by more than30%.(2)In order to study the influence of the concrete layer on the fatigue stress reducing effect of the OSDs,Investigating the relationship between OSD design parameters and the stress reducing effects by parametric analysis using a finite element model.The results show that: the stress reduction effect is mainly affected by the stiffness of concrete layer and steel deck;The stress reduction effect can be estimated according to the stiffness ratio of steelconcrete composite bridge deck through linear equation.(3)The orthotropic steel-concrete composite deck has fatigue failure problems such as concrete layer cracking,steel deck cracking and stud fracture.In order to study the fatigue limit state of the composite deck,the fatigue of the composite deck under different design parameters is analyzed by finite element model,the results show that: the cracking of the concrete layer is the main failure mode of the composite bridge deck structure,and its fatigue performance is mainly determined by the thickness of the steel bridge deck roof,the thickness of the concrete layer and the tensile strength of the concrete,The fatigue strength of orthotropic steel-concrete composite decks can be evaluated by a power function equation controlled by these three parameters.For conventional orthotropic steel-concrete composite deck structure design,if the thickness of the concrete layer is less than 50 mm,it is recommended to use a high performance concrete with a tensile strength of not less than 6MPa.If the concrete material is steel fiber reinforced concrete,the thickness of the concrete layer should not be less than 100 mm.In summary,thick-layer SFRC can effectively reduce the fatigue stress of steel bridge decks,and the fatigue properties of orthotropic steel-SFRC composite bridge decks with reasonable thickness can meet the design service life requirements.The bridge deck design has practical significance and reference value in engineering.