Study On Mechanical Properties Of Short-headed Studs Embedded In High Performance Composite Deck Considering Damage Effect

Orthotropic steel bridge decks are widely used in domestic and overseas bridge projects because of their good mechanical properties and lighter weight.However,it is prone to fatigue cracking and pavement damage under repeated loading of partial wheel load.Considering the outstanding advantages of ultra high performance concrete(UHPC),such as high strength and good durability,etc,on account of this,the original steel-concrete composite bridge deck concrete layer is replaced by the UHPC structure layer.An innovation composite bridge deck composed of orthotropic steel deck with large longitudinal throughs and UHPC layer(abbreviation: high-performance composite bridge deck)is proposed to solve the two major problems faced by steel bridge panels.In order to ensure the cooperation between the steel bridge deck and the UHPC structural layer,short-headed studs are usually used to achieve effective connection between the two.Compared with the stud-type shear connectors in the conventional steel-concrete composite structure,the stud in the UHPC structural layer of the high-performance composite bridge deck is shorter,and the length-to-diameter ratio of the shear nails don’t meet the requirements of the steel structure design specification.On the other hand,the performance of the structural layer also has a significant effect on the stress state of the shear pin.In this paper,through the in-depth analysis of the mechanism of short studs in combined deck structures,the introduction of short studs and UHPC material damage constitution,and the static and fatigue properties of short studs are studied.The main contents and conclusions are as follows:On the basis of analyzing the force mechanism of short studs in the UHPC structure layer of high performance composite bridge deck,the UHPC structure is equivalent to a linear spring system with large supporting stiffness,and the calculation formula for the shear stiffness of short-headed stud elastic phase is introduced,this paper further put forward the three line model to describe the load slip curve of short-headed stud.Based on the explicit dynamic solution technique,the pseudo static analysis of the short stud static test numerical analysis model was carried out.The ductile damage constitutive model of short stud and the plastic damage constitutive model of UHPC were introduced in the model,The whole process curve of the load-slip relationship of short studs was obtained,and the damage evolution of UHPC structural layers and short studs was studied.The Broown-Miller multi axis fatigue evaluation criterion was introduced to evaluate the shear fatigue performance of short studs,and compared with the test results,the applicability of the Broown-Miller multiaxial fatigue evaluation criterion was verified.The damage evolution of UHPC layer and short stud under cyclic loading is further analyzed,and the effect of stress ratio and short stud diameter on the shear fatigue performance of short studs is discussed.The results show that the stress ratio has a great influence on the fatigue performance of short studs in the high performance composite bridge panel.With the increase of stress ratio,short fatigue life of the studs value also increased,and the increase is larger.Increase the fatigue performance of short stud diameter of short studs had improved,but the effect is not significant.