Finite Element Analysis On Shear Lag Effect Of Prestressed Concrete Curved Box Girder Under Seismic Loading

As a important type of modern bridge,curved bridge has been widely used and its cross section is usually box-shaped.The study found that ignoring the shear lag effect of box girder in the design often leads to unsafety of structures.Bending-torsion coupling effect of curved box girder makes the shear lag effect of curved box girder more complex than that of the straight box girder.There is a substantial research on shear lag effect of the curved box girder under static load,but the study of shear lag effect of curved box girder in particular prestressed concrete(PC)curved box girder under seismic action is relatively less.In order to solve these problems,the following work has been done in this paper:(1)The concept of shear lag effect and prestress degree was elaborated,the finite element theory and method of calculating seismic action was introduced;(2)Finite element models of PC curved box girder of 5 different prestress degrees were established in ANSYS,shear lag coefficient under EL Centro wave,Tianjin wave and Tangshan wave was calculated.The results show that the change laws of shear lag effect of nodes on the mid-span section with prestress degree under three seismic waves are the same,shear lag effect of nodes located at the junction of topplate and inner web and the inner edge of flange gets less significant with prestress degree decreasing,changing prestress degree has little influence on the shear lag effect of the junction of topplate and baseplate.When prestress degree is higher than 0.5,shear lag effect of nodes located at outer edge of flange gets less significant with prestress degree decreasing,shear lag effect of node at the junction of baseplate and web gets stronger with prestress degree decreasing;when prestress degree is no higher than 0.5,nodes located at the outer edge of flange and the juntion of baseplate and inner web gets stronger with prestress degree decreasing,shear lag effect of node at the juntion of baseplate and outer web gets weaker with prestress degree decreasing.(3)Comparative analysis of shear lag effect of mid-span section of simply supported and clamped supported curved box girder was undertaken.The results show that theshear lag coefficient distribution in topplate and baseplate is the same under two boundary conditions;the change law of shear lag effect of same node with prestress degree under two boundary conditions is also the same;changing boundary conditions will significantly influence shear lag effect of node located at the edge of flange plate;shear lag effect of node located at edge of flange of clamped supported box girder is more significant than that of simply supported box girder.