| At present,in the process of expressway expansion,one of the key problems is to widen and reconstruct existing bridges.Safety assessment before rebuilding existing bridges is a very necessary basic work.It is a precondition for demonstrating the economic and technological feasibility of expressway expansion and reconstruction,and it can provide technical support for project decision-making and construction plan formulation.Besides,evaluating the integrity of existing bridges after expansion,studying the influence of stiffness of new and old bridges on lateral integrity,has important theoretical and practical significance in guiding the design and reconstruction of bridge expansion plans.Based on the summary and comprehensive analysis of the literatures at home and abroad,the work around the safety assessment of the existing bridges and the lateral integrity assessment after the expansion is researched.1.Select four evaluation methods that fit for the characteristics of expressway bridges,and establish a three level evaluation system to make the safety assessment of existing bridges systematized.In the comprehensive assessment of the appearance defect situation,draw lessons from the combination method of bridge component classification and engineering experience,introduce the inspection index of hinges disease,and improve the evaluation of transverse connection of fabricated beam bridge.2.TakeTang-Jin expressway bridges as an example,consider the effect of the transverse connection function attenuation to member resistance,developed a model of time-dependent resistance.In the light of the mechanics model of bending section,considering the three factors that corrosion of reinforcing steel,concrete strength and bond strength decreased and the time-dependent of car load,the calculation program of time-dependent reliability system of concrete girder bridge is organized.The feasibility and effectiveness of the program are verified through an example.3.The lateral distribution coefficient of the precast concrete cellular slab bridges and T beam bridges is calculated by the hinged plate method and the eccentric pressure method and the transverse distribution coefficient is introduced to quantify the lateral integrity.Through the analysis of the transverse distribution of existing bridges before and after the reconstruction,the influence of stiffness of new and old bridges on lateral integrity is researched.And draw the conclusion that when the stiffness ratio is from 0.8 to 1.2,the lateral integrity of the expansion bridge is better. |
