| Recently rib plate composite beam has been widely applied on cable-stayed bridge.However,due to the action resulting from the cable,rib plate composite beam of cable-stayed bridge is a compression-bending member that is distinguished from rib plate composite beam which mainly bears bending moment.As for the factors above,directly adopting the calculated method introduced by existing specifications to calculate the shear lag effect of rib plate composite beam of cable-stayed bridge is inaccurate.Based on cable-stayed bridge with rib plate composite beam,an experiment and finite element analysis has been conducted.This paper analyzes the mechanical behavior and design method of shear lag effect of rib plate composite beam of cable-stayed bridge,which can be used to referred on this kind of bridge.The main aspects and important conclusions are as follows:Firstly,an experiment on a 1:5 scale-model was conducted.In order to adquire the transverse distributed regularity of positive stress on both simple rib plate composite beam and rib plate composite beam of cable-stayed bridge,experiments have been carried out on simple rib plate composite beam and rib plate composite beam of cable-stayed bridge respectively.It is found that the uneven factor of the stress distribution on tested section of rib plate composite beam of cable-stayed bridge is about 1.252 to 1.352,and it will increase by about 20%near the area bearing the equivalent live load.Besdes the shear lag effect of simple rib plate composite beam is 2.034 to 2.154.Secondly,finite element(FE)analysis is carried out by software of ABAQUS to reveal the shear lag effect,and compare the result with those who is obtained from the experiment to check the accuracy of the finite element model.The result shows that the outer flange without main steel rib has little effect on the shear lag effect,and the stress of the bridge deck caused by axial component of the cable force is the linear distribution of 26.8o along the girder.Compared with simple rib plate composite beam,the shear lag effect of rib plate composite beam will increase to 1.401 times due to the action of the verticle component of the cable force.Thirdly,the analysis for the parameters of rib plate composite beam of cable-stayed bridge shows that stress nephogram,positive stress distribution of cross section and shear lag effect of the bridge deck is similar under either dead load or cable force,and although the uneven level of cross-section stress caused by both dead load and the verticle component of the cable force can decrease with the increase of axial component of the cable force,however,it has little influence on shear lag.Besides,the verticle component of the cable force will affect the shear lag dramaticlly,and with the ratio of the verticle component of the cable force to dead load of segment(Pi/G)increasing,the maximum shear lag effect increases first and then decreases,and when the Pi/G is equal to 1,the curve will reach the minimum point.Lastly,the finite element analysis of various verticle component of the cable force points out that when the variation range of Pi/G is 0.8 to 1.2,the increasing factor of shear lag effect on rib plate composite beam of cable-stayed bridge is 1.401 to 1.497 compared with simple rib plate composite beam.Apply segmental linear approximation to obtain the formula that can be used to calculate the increasing factor of shear lag effect on rib plate composite beam of cable-stayed bridge,and establish the practical computing method to calculate the increasing factor of effective width on rib plate composite beam of cable-stayed bridge according to regulation of effective width on simple rib plate composite beam introduced by the existing specifications. |
