Numerical Analysis For Strengthening Of Bridge By Converting The Bridge System With Steel Fiber Reinforced Self-stressing Concrete

Transportation has developed significantly since the foundation of New China,, after21century, however, due to more and more traffic density and the vehicle load with the rapid development of traffic, many highway bridges in service, especially the prefabricated simply-supported bridges built in the last century, are difficult to meet various requirements either in sevice or in bearing capacity. Among commen methods for strengthening bridge, transforming simply-supported beams into continuous beams is an effective method which is applied widely in strengthening simply-supported bridges with small and midiumspans. The key problem of this reinforcement is the concrete crack in the negative moment area, once the concrete cracking in negative moment area, harmful material such as rainwater will erode the reinforcement in the structure layer of bridge deck which plays serious impact on the durability of bridges after strenghthening. At present, the mechanical prestressed concrete is use in the negative moment region in order to control the cracking of concret. In this paper, a new type of composite material--steel fiber reinforced self-stressing concrete is applied to strenghthen negative moment regioninstead of the the mechanical prestressed concrete.The steel bar and steel fiber reinforced in self-stressing concrete restrict the expansion of concrete to induce chemical prestress, so as to improve the anti-cracking performance of reinforced concrete in the negative moment region.This paper focuses on the mechanics simulation analysis of the bridges before and after reinforcement based on present code for design of highway reinforced concrete and prestressed concrete bridges and culverts JTG D62-2004by a finite element analysis software ANSYS, the main contents are as follows:1. Taking a Shen Loop bridge in Liaoning province for a model based on ANSYS, the bending moment, shear force and the deflection in the control cross section before and after bridge reinforcement are calculatedand bearing capacities of cross section are compared Calculation results show that the cross-sectional bearing capacity has no significant improvement after transfoming the simply-supported structure into continuous structure, but the internal force distribution is more uniform due to the system transforming, the mid-span moment is decreased distinctly, so as to achieved the effect of reinforcement; In addition, the shear force in control section increases after the system changed, so it is necessary to strengthen the shear bearing capacity of the section; deflections of the mid-span is reduced significantly after reinforcement, and meet he requirement of structural deformation.2. Two ways are applied in strengthening negative moment.The first way is using steel fiber reinforced self-stressing concrete in the negative moment region of2-5supports, the other one is only using steel fiber reinforced self-stressing concrete in the negative moment region of2and5supports. After calculating and comparison, it is indicated that the expansion effect of steel fiber reinforced self-stressing concrete can be effectively reduce the negative bending moment at supports due to the effect of shrinkage of the concrete, choosing the self-stressing concrete with the appropriate restrict strain can reduce the negative bending moment of the bearing significantly while the bearing capacity of the T beam after reinforcement satisfy the requirement. In addition, the first way is more appropriate in case that the difference of2-5bearing negative bending moment is not large.