Cable Force Optimization And Stability Analysis Of Extroverted Steel Tube Arch Bridge

The arch ribs of an extroverted steel tube arch bridge are gradually narrowed from the middle of the span to the foot of the arch,and multiple arch rib plates intersect at sharp angles in turn.The connecting boom between the arch rib and the main beam is arranged at an angle with the change of the arch rib.After the load on the main beam is transferred to the arch ribs by the boom,the structure is subjected to complex forces.The optimization of cable force and stability analysis for extroverted steel tube arch bridge is of great engineering guidance.In this study,a finite element model is established using Midas Civil to solve for the formed cable force and the construction stage cable force of an extroverted steel tube arch bridge as a background.The bridge was solved for the bridge forming cable force and the construction stage cable force,and the influence of the structural parameter changes on its stability was analyzed.The correlation degree of the structural parameter changes on its stability was evaluated by using the gray correlation theory to provide a reference for future construction and design optimization of such bridges.The main research contents and conclusions of this study include the following.(1)The finite element model of the extroverted steel tube arch bridge was established by Midas Civil,and the construction stages were simulated and analyzed.The line and stress data collected in each construction stage were compared with the design and simulated values,and the results showed that the measured values in each construction stage were in good agreement.(2)Using the finite element model,the minimum bending energy method,the rigid support continuous beam method,the rigid boom method and the unknown load coefficient method were used to solve the initial cable force of the bridge,and the equal frequency method was introduced to optimize the cable force of the bridge.The results show that the value of the boom cable force of the rigid support continuous beam method has negative values,which is not suitable for the solution of the cable force of the three-span continuous beam.The initial cable force solved by the unknown load factor method is relatively more uniform,and the force of the structure is more reasonable,which is more in line with the actual force of the structure after the optimization of the cable force.(3)The influence of the boom tensioning sequence on the internal force of the main beam and main arch is analyzed,the optimal tensioning scheme is determined,and the iterative method of positive loading and inverted dismantling-positive loading are used to solve the initial tension of the boom during the construction process.The results show that the initial tension of the boom is calculated by the iterative method of inverted dismantling-positive assembly,and the boom is tensioned symmetrically from the quarter point of the arch rib to the middle of the span and then to the quarter point of the arch rib,and finally the boom at the foot of the arch is tensioned to meet the safety and economy of construction.(4)Using the finite element model,the stability of the outward-facing steel tube arch bridge was analyzed under different working conditions,and the effects of changes in structural parameters such as boom parameters,arch rib parameters,sagittal-to-span ratio and cross bracing parameters on the stability of the bridge were discussed.The results show that the stability of the structure is mainly influenced by the constant load,and after considering the nonlinear factors,the stability of the structure is reduced to a certain extent,but still in a safe state.The structure has high stability when the angle of camber of the arch rib is 15 degrees and the sagittal-span ratio is at 1/3.5 to1/4.When the thickness of the arch rib is 23 mm to 25 mm,the stability of the structure is improved more obviously.(5)The gray correlation theory is used to evaluate the correlation degree between parameter changes on structural stability,and the correlation degree between different change factors and stability coefficients is as follows: boom arrangement angle > risespan ratio > arch rib thickness > arch rib camber angle > arch rib section form > cross brace form.For cambered steel tube arch bridges,it is usually difficult to optimize the rise-span ratio of the arch ribs and the angle of the boom arrangement,and the thickness of the arch ribs and the camber angle of the arch ribs should be optimized to improve their stability.