| With the rapid development of economy in our country, the traffic volume has increased exponentially. Some of the existing motorways have been in the saturated state and even the phenomena of traffic congestion appear. Therefore, there is a tremendous need to widen and rebuild them. In the course of the expansion of the line, because of its long construction period, technical difficulty, great influence on the environment along the line, bridge widening has become the focus and difficulty of the entire expansion project.In this paper the following research works about splicing method and related parameters of widening bridges are given:(1) Study on the load and internal force transverse distribution of new and existing bridge when using different widening methods.Taking a simply supported T beam as example, the bridge model is built by the finite element analysis software MIDAS/Civil. The transverse load distribution and the horizontal distribution of internal forces after widening according to different splicing methods are calculated. The analysis results show that the transverse distribution of the existing bridge is more uniform after widening, and the rigid connection mode is more conductive to the overall stress of the bridge.(3) Calculation and analysis of transverse distribution coefficient before and after wideningThe typical simple supported beam bridges (16m slab beam,20m box girder,30m T beam) and continuous bridges (4×20m box girder and 4×25m Tbeam) are chosen. The existing bridges are widened from two lanes to four lanes and beam lattice models are respectly established.The transverse distribution coefficient of the main beams of the bridge before and after widening is calculated by the numerical method and MATLAB program. By comparing the corresponding vehicle load of the original General Specifications for Design of High Bridges and Culverts(JTJ021-89) used in the design of the existing bridge and the current General Specifications for Design of High Bridges and Culverts(JTGD60-2015), and considering that the impact factor changes, the maximum allowable value of transverse distribution coefficient of each beam after widening is proposed, which is taken as the criterion to check calculation value of each beam of the existing bridge in order to determine the existing beam of the typical bridges needed to be strengthened. The calculation results show that all the existing bridges need to be strengthened, and all of them are outside.(2) Analysis of the applicability of lateral reduction coefficient in widening bridgeBased on the G6 of Beijing Tibet expressway as the line of bridge widening, by seting different conditions in view of the above five kinds of typical bridges,action effects of key sections of the bridges under actual vehicle (general motorcade and congested motorcade) partial load are calculated to compare with effects calculated under standard load in order to analyse the applicability of the four lane lateral reduction factor 0.67 and the safety in widening bridge.The results show that only the new bridge of continuous T beam is unsafe when the lateral reduction coefficient is taken as 0.67. Through calculation the recommended value is 0.80.Finally, combined with the calculation results, measures should be taken to avoid heavy traffic congested motorcade being loaded to the right two lanes at the same time, and the existing bridge should be reinforced timely after widening to ensure the safe operation and service life of the bridge after widening. |
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