Structural Health Study Of Suspension Pipeline Bridge Under The Typical Loads

In the oil and gas transportation process, both long-distance pipelines and gathering pipelines have been inevitably hampered by rivers, valleys, ravines and other similar terrain due to natural conditions. Therefore, suspension pipeline bridge is the most common structure crossing these terrains. Because of the special geographical environment, suspension pipeline bridge has been working in the conditions of high humidity and large temperature difference between day and night, so that its structures have been severely corroded. At the same time, because its structures have the characteristics of ultra-flexible, low damping, long-span ratio and light weight, the suspension pipeline bridge is prone to occur large displacement, large deformation, cracks and other dangerous sources when subjected to the effect of sudden natural hazards and human factors, such as blizzards, earthquakes, construction operations and so on. Once an accident occurs, not only the transportation of oil and gas will be affected, but also the environment is seriously polluted, resulting in huge economic losses and adverse social impacts. Therefore, in order to ensure the safe operation of the suspension pipeline bridge, the suspension pipeline bridge over the Yellow River in the first Shanxi-Beijing natural gas pipeline was taken as the research object in the paper, and the health status study of its structure was carried out under the typical loads.First, aiming at the nonlinear characteristics of large displacement and small strain for the suspension pipeline bridge, a three-dimensional simulation model of the Yellow River suspension pipeline bridge was established by the finite element theory, and according to the field measurement results, the form-finding calculations of cable structures were conducted and the model was modified. On this basis, the stress and displacement response of the pipeline bridge were researched respectively under three kinds of static load:the finished state of the bridge (the weight of the structure), the working state (the weight of the structure and the gas medium), the manned state (the weight of the structure, gas medium and30people). Based on the above simulation results,16potentially dangerous places on the pipeline bridge structure were obtained, in which16pairs of optical fiber grating sensors were arranged, and a remote dynamic monitoring system of the Yellow River suspension pipeline bridge was established. Under the normal working condition, the simulation data and the engineering data were compared to find that the basic deviations were less than20%, which indicated that the model and the simulation method were feasible.Next, the displacement and stress change of each part of the Yellow River suspension pipeline bridge structure were simulated under the four typical loads:snow load (slight snow, moderate snow, heavy snow, blizzard), wind load (low wind speed2.8m/s, high wind speed27m/s), pigging and seismic loads. At different levels of snow load, the occurrence position of the maximum stress and maximum displacement on each structure of suspension pipeline bridge had not changed. With the increase of snow load, the maximum displacement value of all increased, and the maximum stress value of the main cables, slings, towers, bridge truss also increased, but the maximum stress of lanyards, wind cables, stable cables decreased. In the analysis of wind-induced vibration, the response of each suspension bridge structure were compared under the wind speed2.8m/s and27m/s. The displacement value of the top of Baode tower is slightly larger than that of Fugu tower, and for the bridge truss, the main cable, the wind cable, the position of the most severe vibration and the maximum amplitude occurred in1/2of their own structure. In the simulation of a pigging process, the velocity of the pigging ball was2m/s and the cumulative fluid was1m in the internal pipe, the displacement variation at the beginning,1/8,1/4,3/8,1/2,5/8,3/4,7/8and the end of the suspension bridge truss were analyzed, of which the rate of change was greatest at1/2and5/8of the bridge truss. In the seismic load response analysis, the displacement of the connection between the main cable and the tower was smaller under the seismic loads, and the maximum value was only0.01m. The response displacement of the bridge truss, the main cable and the wind cable was larger, and the maximum value was more than1.5m. And the relevant departments should prevent the earthquake with magnitudes above six from damaging the suspension pipeline bridge.Through this research, the health status of the suspension pipeline bridge over the Yellow River in the first Shanxi-Beijing natural gas pipeline was analyzed at the present stage, but also a reference for the risk evaluation and the reliability analysis of other active suspension pipeline bridge was provided at the same time, the technical support was offered for the design and the construction of the similar bridge in future.