Research On The Optimization Of Bridge Expansion Joint Slot Structure And The Preparation Of High Performance Concrete

The ratio of diseases caused by the failure of bridge expansion joints to meet their service period increases year by year,which has great influence on the overall performance of bridge structure.The repair and replacement of bridge expansion joints after damage is not only high cost,but also easy to cause traffic congestion.Based on the field investigation of the diseases of the expansion joints of the bridges in service in mountainous areas of Guizhou Province,it is found that the unreasonable structural design of the expansion joints and the poor performance of the concrete in the anchorage zone of the expansion joints are the main reasons for the failure of the expansion joints.In order to solve the above problems,this paper takes Guizhou Yu ’an Expressway Sandu Section Jiaogui Bridge as an example,based on numerical simulation and test,combined with existing research,to carry out structural optimization of bridge expansion joint groove and preparation of high performance concrete.Research shows that :(1)This paper analyzes the stress characteristics of concrete in the anchorage zone when the depth of the beam beam embedded in the slot is 8cm,10.8cm,13.6cm,15.8cm and 18.6cm.It is suggested that the reasonable slot size of expansion joint should be 20cm-40 cm in depth direction and 40 cm-50 cm for the width of the slot.(2)The influence of different fiber materials and different fiber content on the performance of the prepared concrete was studied by triangle orthogonal design.According to the experimental research and analysis,for the single fiber,0.3 % PP fiber concrete has the worst comprehensive performance,followed by 0.3 % PVA fiber concrete.Basalt fiber concrete shows good comprehensive performance,and steel fiber concrete has the best comprehensive performance.(3)The effect of different cementitious materials on the autogenous shrinkage of concrete is obviously different.The autogenous shrinkage of concrete is reduced by54.8 % with 30 % fly ash,and the autogenous shrinkage of concrete is reduced by18.5 % with PVA fiber and short steel fiber.The self-shrinkage of concrete was reduced by 9.9 % by adding 30 % mineral powder alone.In terms of reducing the autogenous shrinkage of concrete,30 % fly ash alone is the best choice.(4)The crack resistance,compressive strength,fracture toughness and impact resistance of concrete after optimization of mix proportion are greatly improved,and meet the engineering requirements;The 28 d fracture toughness of the prepared concrete is 14 ～ 53 % higher than that of the original concrete,and the 28 d impact resistance of the concrete is-19 ～ 81 % higher.The incorporation of fly ash reduces the compressive strength of concrete,but has little effect on the fracture toughness and impact resistance of concrete.The compressive strength,fracture toughness and impact resistance of concrete are improved by adding mineral powder.