The Study On Rapid Reinforcement Technology Of Concrete Bridge Piers

The rapid development of bridge in China,various kinds of bridge damage have appeared due to its service time and growth of traffic in China.The lower part of the bridge,such as bridge pier and pile foundation,is directly related to the durability and bearing capacity of the bridge.The weakening of their bearing capacity and durability will seriously weaken the safety performance of bridges,and result in many security risks.Traditionally,the underwater structure strengthening technology needs drainage and water blocking treatment which consumes a large amount of time and cost because of the cofferdam,foundation seepage control and drainage of foundation pit.Moreover,during construction,the channel space is occupied which makes great social influence.To overcome those problems,this thesis puts forward the rapid reinforcement technology of concrete bridge piers.First of all,this thesis puts forward a kind of proportion of the self-stressing of non-dispersible underwater concrete.Then,a series of experimental study was conducted on rapid reinforcement of concrete bridge piers.Finally,the key parameters influencing the reinforcement effect were summarized through the experiment and finite element simulation,thus theoretical calculation model and the design suggestions were made.The main contents are as follows:(1)Orthogonal test of four factors and three levels was employed to develop the self-stressing of non-dispersible underwater concrete(SNDC).The experimental data shows that the 28-day strength can reach 32.4Mpa,14-days limit expansion rate can reach 0.038%at the water cement ratio of 0.41,the sand rate of 40%,the amount of expansion agent admixture of 10%,the amount of anti-dispersant agent by adding water,and the dosage of water reducing agent of 1.5%.And the performance of anti-dispersion,mobility and so on of the concrete are in line with the requirements of the specification(2)Experimental study was conducted on rapid reinforcement of concrete bridge piers.Through the comparison and analysis,the peak load and the peak displacement of the reinforced specimens are obviously increased,compared with the unreinforced specimens.The failure modes were also changed from brittle failure to ductility.The peak load of the reinforced specimen using SNDC as filling material is 1.22 times of the reinforced specimen without using SNDC as filler which is proved the SNDC can effectively improve the reinforcement effect of the reinforcement technology.(3)Based on the analysis of the test results and the process,the key factors influencing the reinforcement effect of the concrete bridge piers are:the self-stress value of SNDC,the concrete strength of SNDC and the concrete segment strength.Using ABAQUS finite element analysis software for further analysis,it is concluded that the self-stress value of SNDC has a linear correlation with peak load,and increasing the strength of SNDC or improve the strength of concrete segment can raise the peak load to a certain extent.However,if the strength difference between the SNDC and the concrete segment is too large,the influence of the strength on the peak load will not be obvious.(4)On the basis of experimental study and finite element simulation,this thesis presents a theoretical model for calculating the peak load of concrete bridge piers.It is found that the theoretical model has good applicability through the verification of the relevant experimental data.(5)Based on the experimental results and the results of the data,this thesis puts forward the relevant design and construction suggestions in order to provide references for the following demonstration projects.