Static And Dynamic Behavior Of Box-girder Bridge Strengthened By Prestressed Carbon Fiber Reinforce Plastic Sheet

Since the 21 st century,the traffic volume is increasing with the rapid development of economy as well as the science and technology,and the importance of highway bridges in insuring the steady development of the transportation industry.However,in recent years,a lot of aged bridges can’t meet the requirements of transportation due to different problems which are influenced by the early construction and natural environment,and some of them even have collapsed which has brought great damage to the lives and properties of human beings.T herefore,the reinforcement and transformation of the highway bridges which are with hidden trouble are urgently needed.At present,there are lots of reinforcement methods on bridges,however,which kind of reinforcement methods to be chosen should be based on the local conditions and different bridges.In this paper,post-tensioned and pre-tensioned Carbon Fiber Reinforced Polymer(CFRP)sheets are used in reinforcement of a prestressed concrete box girder bridge(post-tensioned method reinforcement and pre-tensioned method reinforcement for short).And through comparative analysis on effects of two reinforcement methods,it is obtained the best reinforcement method of the bridge.In this paper,the research contents and conclusion are listed as follows:(1)With the finite element software,the bridge model which is before reinforcement is built.CFRP sheets are prestressed by post-tensioned and pre-tensioned methods,and reinforced bridge models are built.The variation law on stresses and displacements which are selected from sections of box girders and bridge piers that are reinforced by post-tensioned and pre-tensioned methods is studied.The results show that the stresses and displacements could be reduced by CFRP sheet,and improved effects of the post-tensioned method on stresses and displacements are better than the pre-tensioned methods.(2)The El-Centro earthquake waves,Tianjin earthquake waves,Lanzhou earthquake waves are utilized to do dynamic finite element analysis on the models which are before reinforce,reinforced by post-tensioned and pre-tensioned methods,and the vertical displacement and acceleration responses of mid-span top plate sections of side span and middle span under the vertical seismic load are studied;the horizontal displacement and acceleration responses of the top of the bridge pier under the horizontal seismic load are studied.The result shows that responses of the bridge are reduced by CFRP sheets,and post-tensioned method is better than pre-tensioned method on control of earthquake responses.(3)Simulating vehicle with the moving load,and considering factors of driving speeds of 60km/h and 90km/h,the variation law on the vertical displacement and acceleration of sections of side span and middle span are studied.The result shows that with the increase of speed,the peaks of horizontal displacement and horizontal acceleration increase;dynamic responses of vehicle-bridge interaction are reduced by CFRP sheets,and post-tensioned method is better than pre-tensioned method on control of dynamic responses of vehicle-bridge interaction.