Research On Response Of Self-anchored Suspension Bridge Under Static And Dynamic And Explosive Shock Waves

In recent years,bridge explosions caused by accidents or terrorist attacks have occurred sometimes,which seriously affecting social stability and national security.It is urgent to conduct anti-explosive research on bridges under explosive shock waves to improve their antiexplosive performance.In this paper,the self-anchored suspension bridge was studied.The finite element method was used to analyze its static and dynamic characteristics,and the internal law of the dynamic response of the explosion shock wave to the structure under different working conditions was discussed.The main contents and conclusions are as follows:1.The suspension bridge was modeled separately according to its structure.The suspender cable force and the displacement of the main cable at the suspending point were used as control indicators.The calculation model of the finished bridge state was obtained by adjusting the initial stress on the main cable and the suspender multiple times.2.Static calculation under design load and natural vibration analysis were carried out.The results show that the maximum increase of the displacement and bending moment of the main beam appears in the third span.The suspender cable force has the largest increment on both sides of the third span.The mid-span main cable has the smallest increase in tensile force in the middle.The increase in the tension of the main cable at the side span decreases as the height of the suspension point decreases.The internal force and deformation of each component under the design load meet the design requirements.The first-order vibration period is longer than that of ordinary beam bridges,which is consistent with the flexible characteristics of suspension bridges.The first-order vibration mode conforms to the characteristics of a full-floating system,and the last four modes are common modes of suspension bridges.The numerical solution of the first-order antisymmetric vertical bending vibration frequency is in good agreement with the existing analytical solution.3.The explosive center of the explosive was set above the center of symmetry of the bridge deck.The dynamic response of the explosive shock wave was simulated,and the effects of explosive equivalent and explosive height were discussed.The results show that under the effect of instantaneous impulse,the deformation of the suspension bridge spreads from the center of the bridge to both sides.The response process is divided into an unsteady state and a steady state stage.And the maximum internal force of each component appears in the unsteady state.With the increase and decrease of explosive equivalent and explosion height,the maximum value of the internal force and displacement of the main beam and the suspender cable force changes greatly,but the maximum tension of main cable does not change significantly.The maximum internal force and displacement of the main beam appear in the third span under each working condition.This section is a dangerous section.4.The blast centers were set at 1m above the center of the symmetry of the bridge deck,the bridge deck in the center of 2 lanes and 4 lanes in the third span respectively,and the dynamic responses of the structure under transverse symmetric and asymmetric instantaneous impulses were calculated numerically.The minimum explosive equivalent of the bridge structure under different explosion conditions was obtained.And according to this,the antiexplosion design of similar structure was put forward.The results show that along the horizontal bridge,as the burst center deviates from the central axis of the bridge,the internal force and maximum deformation of each member increase except for the maximum compressive stress of the main beam.When the position of the burst center is different along the horizontal bridge,the main beam will break firstly,and the suspender is the second one.When the explosion center is set above the bridge deck in the center of 4 lanes,the explosive equivalent that caused the structure to be destroyed is the smallest,and the value is 891.8 kg.It is recommended that in the design of similar structures,the main beam structure of the dangerous section be partially strengthened,a damper should be provided at the position of the main longitudinal beam,and the cross-sectional area of the suspender on both sides of the dangerous section should be appropriately increased to improve the anti-explosion performance of the structure.