Study On The Performance Of Damaged Beams Strengthened With Carbon Fiber Sheet Under Different Unloading Degree

The aspects of overload,environmental changes and construction defects etc.can lead to different degree of damage during the bridge service.The bridge should be reinforced in order to ensure safety.Pasting carbon fiber reinforce ploymer is widely used with high strength,convenient construction,corrosion resistance and improve effectively the bearing capacity.Second loading problems affects the internal force of structure reinforcement,it can reduce effectively the influence of second loading by unloading before reinforcing.This thesis is mainly about reinforcing damaged beams by using carbon fiber reinforce ploymer.The main contents of this thesis are the following:(1)On the basis of reading the relevant norms and literature,this thesis summarizes the current research status of carbon fiber cloth reinforcement technology and the existing research results,the research thought is conceived.(2)The section ratio of reinforcement,layers of carbon fiber reinforce ploymer,width of carbon fiber reinforce ploymer,concrete grade are chosen as variable,the ultimate bearing capacity,stress and deflection of reinforced concrete damaged beams after pasting carbon fiber reinforce ploymer are theoretical calculated,and the thesis summarizes the calculation of carbon fiber reinforce ploymer reinforcement.The theoretical results show that the flexural capacity can be improved effectively by pasting carbon fiber reinforce ploymer,which improves higher with the greater degree of unloading,and it improves greater with increasing of the number and the width of the carbon fiber cloth;With the degree of structure unloading increasing,the deflection and stress of steel reduce under the same load.(3)By using the finite element software to model and analysis,draw the load-deflection diagram and the load-stress diagram,the calculation results show that the finite element modeling results are consistent with the theoretical results;Before the steel yield,the stress of carbon fiber cloth increases steadily,and the degree of unloading is larger,the deflection is smaller under the same load,the stress of steel is smaller after CFRP participating in the force.The stress of carbon fiber cloth increases sharply after the yield of the steel bar.This paper demonstrates a conclusion that the structure should be unnstalled,and the second loading shouldn’t be ignored,it provides refernce and basis in bridge reinforence to promote carbon fiber reinforce ploymer reinforcement technology.