Research On Mechanical Behavior And Slip Characteristic Of Main Cable Of Long-span Suspension Bridge

The long-span multi-tower suspension bridge is widely used in the construction of river and sea crossing bridges.The sliding state of main cable and main saddle is directly related to the anti-sliding safety of main cable and the structural safety of suspension bridge.In the operation process,the main cable of suspension bridge is subject to the coupling action of dead load,wind load and live load for a long time,which easily leads to the unbalanced force of the main cable on both sides of the main saddle,and then causes the phenomenon of "layered sliding" between the main cable strand and steel wire,and the sliding phenomenon between the main cable strand and the saddle groove.When the unbalanced force is greater than the ultimate friction between main cable and main saddle,slip accident between main cable and main saddle will occur,which will lead to structural instability and even collapse accident of suspension bridge.Therefore,it is of great theoretical significance to study the mechanical behavior and slip characteristic of the main cable of long-span suspension bridge to ensure the structural safety of suspension bridge.Established a long-span suspension bridge static model and wind-vehicle-bridge coupling dynamics model,and explored the influence of suspension bridge design parameters on the load and displacement of the main cable on both sides of the main saddle.Established the three-dimensional contact finite element model between the main cable strand and the saddle,which is used to study the influence of loading force,friction coefficient of different contact pairs and the number of strands on the stress and slip characteristics of strands.A three-dimensional contact finite element model of the main cable steel wire and the saddle groove is established,revealing the influence of the loading force,the friction coefficient of different contact pairs and the number of steel wires on the stress and slip characteristics of the steel wire.The static sliding test rig for main cable strand and saddle is developed.The influence of tension difference between two ends of main cable strand and the number of strands on the sliding characteristics of main cable strands is revealed through the sliding test of main cable and saddle.The results show that: the axial force of main cable decreases with the decrease of vertical span ratio;the lateral and vertical displacement in the middle of main cable span increases with the increase of wind speed and wind attack angle.The maximum slip distance and axial stress difference of cable strand increase with the increase of initial tension,friction coefficient between cable strands,friction coefficient between cable strand and saddle.The maximum slip distance of steel wire relative to saddle decreases with the increase of initial tension and steel wire number,while axial stress difference increases.The maximum slip distance of the steel wire relative to the saddle increases with the increase of the friction coefficient between the steel wires and the friction coefficient between the steel wire and the saddle,which improves the antisliding ability of the steel wire bundle relative to saddle;With the increase of the loading force,cable strand slip distance increases linearly at first and then increases in an arc shape,and the cable force difference increases linearly at first and then gradually slows down with the increase of loading force;With the increase of the number of strands,the overall anti-sliding ability of strands is improved.