Finite Element Study On Fatigue Cracking Of OSD Rib-to-deck Detail Reinforced With CFRP

OSD has significant structural prorerties and has been successfully applied to thousands of bridges in the world,but its structure is complex and stress concentration is significant.The fatigue cracking of the structural details is more serious under wheel load.Therefore,it has the engineering significance to strengthen the structural details of the existing OSD with fatigue cracks.In order to discuss feasibility of CFRP in application to reinforcing rib-to-deck details cracking on OSD,the ABAQUS was employed to build the multi-scale finite element model of OSD,and the extended finite element method was used to model the rib-to-deck welding surface cracks,the three-dimensional solid element method was used to simulate OSD reinforced with CFRP,the main research contents and conclusions of this paper are listed as follows:First of all,in order to study the feasibility of the extended finite element method and the three-dimensional solid element method,on the one hand,to discuss reliability of extended finite element method,this paper establishes axial tension plate model and pure shear plate model,the stress intens ity factor is calculated by the extended finite element method,then compared with analytical solution.The results show that it is feasible to use the extended finite element method to calculate the stress intensity factor value of the crack tip,but we shoud pay attention to the contour integration number and mesh density.On the other hand,this paper established a axial tension plate model reinforced with CFRP,so as to dicuss the reliability of three-dimensional solid element method.The fatigue life growth calculated by the three-dimensional solid element method was similar to papers’ value,this shows that the method is reliable for CFRP reinforcement simulation.Afterwards,in order to study the feasibility of CFRP in application to reinforcing rib-to-deck details with cracks on OSD,this paper bulided the multi-scale finite element model.Based on the most critical loading location in bridge transverse direction,the range of stress intensity factor before and after applying the CFRP on the cracked rib-to-deck weld detail was analyzed and compared.It was found that the CFRP reinforcement can effectively reduce stress intensity factor range at crack tip,and thereby can reduce the fatigue crack propagation rate.And by comparing the stress distribution before and after CFRP reinforcement,it was found that the strengthening effects of CFRP are recognized not only in reducing the stress concentration at the weld toe,but also in providing the bridge effect in the split zone.Finally,this paper established a series of multi-scale finite element models by changing the number of CFRP layers,the longitudinal CFRP length,the CFRP width of the transvers and the longitudinal direction,and the adhesieve thickness to analyze the influence of each parameter on the reinforcement effect.The results indicated that strengthening effect of CFRP can be improved by increasing numbers of CFRP layers,the length and the width of CFRP,but would be reduced by increasing the adhesieve thickness.While the length and the width of CFRP are greater than a certain value,its strengthening effect is not significant.