Stress Analysis And Fatigue Crack Propagation Of Orthotropic Steel Bridge Deck

The orthotropic steel bridge deck,which is composed of longitudinal rib,transverse diaphragm and top deck,has the advantages of light weight,high bearing capacity,good seismic performance,short fait construction and so on.It has been widely used in long-span steel and composite bridges.However,as the results of residual stess due to the welding and as the bridge deck is directly loaded by the wheel load,the orthotropic steel deck is also very prone to fatigue cracking.Based on achievements of existing researches,this paper furtuer investigated the hot spot stress,fatigue cracking behaviors of orthotropic steel bridge deck.The main research contents are as follows:(1)The mixed finite element model of orthotropic steel deck structure,by using solid element and shell element is established,and then analyze the static response under wheel load in different positions.The single wheel load’s influence sphere of hot spot stress of deck to rib joint is about 1500 mm in the transverse direction,and no more than 900 mm in the longitudinal direction.The influence of other wheel load could be ignored.The single wheel load’s influence sphere of hot spot stress of deck to rib to diaphragm joint is no more than 1000 mm in the transverse direction,and about 600 mm in the longitudinal direction.The stress level of the welded joint of the rib and diaphragm is very high,and the fatigue crack is easy to appear.(2)The parameters of orthotropic steel bridge deck were optimized and analyzed.Based on the hot spot stress method,the influence of the parameters such as the thickness of the plate,the thickness of rib and the thickness of the diaphragm wall on the mechanical properties is studied.The parametric variation has a great effect on the hot spot stress at the weld toe,but has little effect on the stress concentration factor.(3)Based on the theory of fracture mechanics and finite element theory,the stress intensity factor of the crack front is calculated by Franc 3D and finite element software ABAQUS,and the relationship between the number of load cycles and crack propagation is studied.The results show that the propagation velocity of the crack to the two sides is larger than that in the thickness direction.