| Orthotropic steel deck(OSD)has the characteristics of light weight and high strength.It is widely used in bridge engineering,and has good application prospects.However,the fatigue crack phenomenon of OSD structure has always existed,which has reduced the applicability and safety of the bridge.cutout is one of the important part of OSD structure.since people began to systematically study fatigue cracking of OSD structure,it has always been a problem of experts and scholars.In order to improve the fatigue performance of the OSD,the steel-UHPC(Ultra-High Performance Concrete)light-weight composite deck was proposed in recent years.By using 35~65mm UHPC layer,the stiffness of bridge deck can be increased and the stress of fatigue detail in OSD structure can be reduced.Theoretically,this structure can significantly reduce the stress of fatigue details on OSD structure,but test data of real bridge structure are few.In order to study the improvement of the stress state of the cutout after laying the UHPC layer on the light-weight composite deck.In this paper,stress state of cutout are analyzed by finite element calculation and counted by field test.The main contents are as follows.(1)A large span self-anchored suspension bridge was chosen Finite element models were built for the OSD with/without the UHPC layer The traditional simplified loading method and the response surface loading method were used in the finite element analysis to obtain the relationship between stress displacement distributions and vehicle axle loading positions.The distribution of stress in cutout is understood.Then the cause of peak tension stress and peak compressive stress at the cutout was revealed by analyzing the deformation characteristics of the cutout.And the maximum stresses of the cutout were found.This research shows that the regularities of stress distribution of the cutout are basically the same for the OSD with/without the UHPC layer.And the in-plane stress is dominant relative to the out-of-plane stress.A large portion of the transverse influence line of the cutout is in tension and a small portion is in compression.The compressive stress is mainly caused by the load right above the cutout,whereas the tensile stress is mainly generated by the load that deviant from the position of the cutout.However,it is difficult to obtain the accurate peak tensile stress of the cutout by using the traditional simplified loading method.And it may produce a smaller stress range.Therefore,the response surface loading method is recommended.(2)A field test was carried out by loading vehicle,in which the stress responses of the cutout with different lateral loading position were measured for the OSD with/without the UHPC layer,the maximum/minimum stress of each point are obtained..Based on the experimental data,the measured results show that it has a similar law with the calculated results: the UHPC layer has a reduction in the peak stress of cutout;when the vehicle partial load,there are tensile stress around cutout,when the vehicle acts on the cutout,there are compressive stress around cutout;The in-plane stress is the main part of peak stress of cutout.Thereafter,fatigue evaluation of cutout after laying UHPC layer is carried out.The results show that the fatigue life of cutout meets the requirements of standard.(3)Three different types of the cutout was considered in extra theoretical calculation with the loading method of response surface.T he response surface and influence line of stress are obtained.the peak stress of cutout before construction of UHPC and after was compared.It is found that the UHPC layer has obvious effect on the reduction of peak stress.And the regularity between stress and load location of three different cutouts is similarly.Futhermore,our research also shows that the fatigue performance of the cutout,which used in the self-anchored bridge,is the best among those cutout forms.In summary,the UHPC layer solution could be used as an effective scheme for improving the fatigue performance of the OSD. |
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