Research On The Technology Of Strengthening Box Plate Arch Ring With Steel Box Concrete

This article relies on the reinforced concrete box arch bridge with a main span of150 meters in engineering.Due to insufficient adaptability in bearing capacity,the arch foot section has experienced serious diseases,and the eccentric compression bearing capacity of the arch foot section can no longer meet the requirements of current specifications.To ensure the operational safety of the bridge,it is urgent to treat the diseases in the arch foot section and take structural reinforcement measures to adapt to the increasing traffic load.A series of calculation and analysis were conducted in this article to improve the efficiency of arch bridge structural reinforcement,aiming to innovate reinforcement methods.The main research content is as follows:(1)Based on the actual disease characteristics of the arch ring,in order to enhance the section stiffness and integrity of the arch foot section,share more internal forces generated by live load,and improve the stress of the original structure,enhance the bearing capacity of the original bridge to achieve reinforcement effect.Based on the maturity of the comprehensive reinforcement method,the reinforcement calculation of the equal cross-section increasing cross-section method was first carried out,and the influence of wet weight on the original structure during the reinforcement construction process was studied.The larger the wet weight,the more unfavorable it is to the original structure,but it significantly improves the bearing capacity in the later stage;Then,based on experience,the initial values are formulated and adjusted through continuous trial and error calculations.The dimensionless method is used to balance the size of the increased section,and the optimal size for the increased section method is ultimately determined to be a thickness of 0.52 m for the arch foot section.(2)According to the finite element analysis of the entire bridge and the results of its internal force combination,it can be concluded that the internal force of the arch foot segment is greater than that of the secondary arch foot segment.Considering the actual stress needs,this article proposes an optimization measure of adopting the method of increasing the cross-section with variable cross-section instead of constant cross-section reinforcement.The calculation results show that when using variable cross-section reinforcement to reinforce the arch foot,the arch foot section thickens by 0.55 m,the secondary arch foot section thickens by 0.2m,and the increased dead load decreases by19.2%(20.5 tons).After reinforcement,the safety factor of the original structure increased by 4.9%(0.05),and during the wet weight stage,the safety factor of the original structure increased by 7%(0.1).(3)Due to severe cracking in the arch foot section,the integrity of the section is insufficient.Combined with the widespread application of steel concrete combination in new construction projects,this article utilizes the advantages of steel concrete material combination to further propose a new method of using steel box concrete instead of ordinary reinforced concrete to strengthen the arch foot section;Based on the principle of equivalent stiffness between variable cross-section reinforced concrete and steel-concrete composite sections,a formula for the converted moment of inertia of the composite section is derived to accurately determine the cross-sectional dimensions of steel box concrete;On the premise of achieving the same reinforcement effect,the size of the steel box concrete section is smaller,and its dead load increment is reduced by 21.1%(18.2tons)compared to the reinforced concrete variable section increase section method.At the same time,the steel box can also be used as a permanent formwork for filling concrete,which has higher economy and construction convenience.(4)The synergistic deformation of steel-concrete composite materials is one of the key control factors determining the effectiveness of steel box concrete reinforcement for arch feet.This article first adopts the method of connecting new and old concrete with shear grooves and planting reinforcement.The elastic deformation and shear bearing capacity calculation results of the planting reinforcement on the unit body indicate that the connector is in an elastic working state,avoiding cracking and delamination of the joint surface between the filled concrete and the original arch ring,and ensuring the coordinated deformation of the new and old concrete.Then,a combination of shear keys was used to connect the steel box with the filled concrete,improving the bonding performance of the composite material.It was calculated that the deformation difference between the shear key and the concrete along the shear direction under load was only 10μ m.has good deformation coordination.Analyzed the shear bearing capacity of the combination shear key with welding nails,and then used an optimized combination shear key to anchor the steel box in the concrete arch seat.The maximum tensile stress of the concrete was found to be 0.99 MPa,and the arch seat concrete was in an elastic working state without cracking due to load,ensuring the effective anchoring of the steel box in the concrete arch seat.