Design Analysis And Study On Safety And Stability Of Concrete Filled Steel Tube Arch Bridge Under Long Term Partial Load

With the increase of crude oil transportation capacity in China,concrete filled steel tube(CFST) arch bridges are widely used in the oil wharf bridge construction, the steel trestle for oil wharf not only bears the load of oil pipeline, but also bears simple traffic load, two kinds of loads are in lateral asymmetric state, which makes the concrete filled steel tube arch bridge under partial load in a long period of time, which has brought new challenges to design.Therefore, the study on this type of concrete filled steel tube arch bridge has important theoretical and engineering practical significance.Based on a China’s steel trestle for oil wharf arch bridge in Yingkou port as the engineering background, this paper built finite element analysis model by using structural analysis and design software Midas Civil, and the design checking calculation and the dynamic characteristics of the structure were analyzed. Through seismic analysis by inputting the seismic wave in different directions, evaluating its seismic capacity. The influence factors to the stability of the CFST arch bridge was studied, and the transverse brace forms were compared and analyzed for design, and a reasonable layout was put forward to. By comparing the load test data and the theoretical calculated values, proving the safety and reliability of the real bridge structure. All of these analysis, to make effort to provide reference and engineering guiding significance for the design, especially the aspects of safety, reliability and stability,and structural analysis of this kind of bridge.Through the analysis and research, this paper draws the following conclusions and recommendations:(1)After checking, the strength and stiffness of the main structural members,arch rib,tie bar,suspender, and the overall stability all meet the code for design. From the dynamic characteristics and seismic analysis results, it can be seen that the natural vibration characteristics, the dynamic stiffness and the dynamic stress of the structure meet the requirements of the relevant specifications.Under the action of vertical seismic wave, the horizontal displacement of the support abutment is larger, so the suggestion is to set up the block stop against earthquakes.(2)The out-of-plane buckling precedes in-plane buckling for the concrete-filled steeltube arch bridge. Due to the partial load, the instability mode has a tendency to bend to the right or twist to the right.The influence on stability coefficient of arch rib stiffness, tied bar stiffness and suspender stiffness is decreasing in turn.Tied bar stiffness and suspender stiffness mainly influence in-plane stability of the CFST arch bridge, transverse brace mainly influences to the out-of-plane stability of the CFST arch bridge.(3)The influence of "X" type and "K" type transverse brace on the lateral stability of concrete filled steel tube arch bridge is significantly better than that of "I" type transverse brace. The stiffness of the end transverse brace and the arch crown transverse brace has a significant contribution to the stability coefficient. In the design of the CFST arch bridge, the type and position of the transverse brace should be considered comprehensively, only when different types of transverse brace can be applied in combination, the transverse brace can be made full use of.(4)By comparing the calculated value with the measured value of the load test, the results show that under partial load, the stress and deflection of the side of the pipeline are higher than that of the side of the carriageway, the structure is in a biased state. The difference of two sides of deflection value of vibration modal is very small, which shows that two sides of stiffness of the bridge deck system are nearly equal, the Static and dynamic properties of the overall bridge structure are good, the design and calculation method of the bridge is reasonable and reliable.(5)Due to the the partial load in long period time, under the design load, the maximum combined stress of arch rib on the right side is 12.3% larger than the left side, and the maximum displacement of arch rib on the right side is 6.6% larger than the left side;Under the action of earthquake wave, the maximum displacement of arch rib on the right side is 19.3% larger than the left side, the maximum combined stress of arch rib on the right side is 23.5% larger than the left side; Under the the most unfavorable load in the load test, the maximum deflection, strain and the cable force value of the left side and the right side are significant,the cable force maximum value on the right side is 42.4% larger than the left side,the maximum deflection on the right side is 55.6% larger than the left side, the maximum strain on the right side is 65.0% larger than the left side. This bridge is obvious under partial load, it is recommended that two sides of the stiffness of the main structural members of archbridges-arch rib,tie bar,suspender should be different when design for this type of bridges.