| In the past 50 years,several major earthquakes caused severe damage to the bridge structure,especially major earthquakes in or near the city,such as the Great Hanshin Earthquake,the Loma Prieta Earthquake,and the Wenchuan Earthquake.Earthquake damage surveys indicate that structural or structural damage is one of the main causes of severe damage to the bridge,such as the Hanshin high-speed line viaduct in the Hanshin Earthquake and the Cypress Street double-deck viaduct in the Loma Prieta earthquake.As one of the common bridge types in urban traffic,due to the special distribution of mass and stiffness of double-storey viaducts,the beams and piers are closely adjacent to each other,and the seismic response is more complex.Among them,the collisions between the lower deck deck and pier columns and the upper main beams and the stoppers are particularly Severe,especially the collision of the lower deck and the pier will cause serious damage to the joints of the lower horizontal beam and the pier,shearing of the pier and the collapse of the upper deck directly to the lower deck.In this paper,the collision of two-story viaducts in earthquakes is studied.Numerical simulation and parametric sensitivity analysis methods are used to comprehensively study the influence of parameters such as impact stiffness,initial clearance,recovery coefficient,and friction coefficient of bearings on the impact of bridges.The double collision effect between the upper bridge deck and the block,the lower bridge deck and the pier column was studied,and the effectiveness of the high damping rubber cushion as a measure for collision reduction was proposed and analyzed.Thesis research shows:(1)Most of the collision force between the lower deck and the pier is absorbed by the lower traverse.The transverse beam then transfers the axial force to the pier,resulting in a large shear change at the junction of the pier.It is very unfavorable for the nodes of the horizontal beam and the horizontal beam and the pier column.This is also in line with the damage of the double-deck viaduct in the past and the earthquake damage of the bridge surface collapse.The impact of the collision on the seismic shear and bending moment of the upper pier is affected.Larger,but less impact on the lower pier column,the reason for this is that most of the energy of the collision is absorbed by the transverse beam when the pier passes from top to bottom.(2)The shear force response,bending moment response,axial beam axial force response and collision force of the pier are directly proportional to the impact stiffness;changing the clearance between the lower main beam and the pier column does not effectively prevent the collision between the two,because Under the action of earthquake,the main girder still has large displacement after the failure of the bearing.As long as the main girder collides with the pier,the impact of the impact on the internal force of the pier is enormous;the collision effect under different recovery coefficients The influence of the internal force of the pier has little difference.Although the energy loss during the collision is different,once the collision between the lower girder and the pier will lead to a sudden increase in the internal force response of the pier and horizontal beam;change the bearing friction coefficient The effect of time collision on the internal force of the lower pier has a small difference,and the upper pier is relatively large.The friction coefficient of the support has little effect on the impact force and the number of collisions.(3)When the lower main beam collides with the pier column,the quality of both is very large,and the collision force is also large.However,the collision between the upper main beam and the block is due to the small mass of the block and the strength of the weak block.The block is directly damaged and the collision force is small.Therefore,the collision effect between the lower girder and the pier has a greater impact on the internal force of the pier.The impact of the upper girder and the block on the internal force of the pier is relatively Small;the collision effect of the lower layer caused the increase of the bending moment of the pier,and the collision of the upper layer reduced the bending moment of the pier.The impact of the upper and lower collisions had opposite effects on the pier.When the high strength stopper was set,it was effective.Control the lateral displacement of the main beam,protect the bearing and counteract the force of the lower collision on the pier column,but the lateral momental impact force of the main beam under the high-intensity block is also larger,and the small box beam side plate has a larger instantaneous pressure.Under stress,cracking of the beam may occur.(4)According to the collision effect between the lower bridge deck and the pier column,a high-damping rubber mat was used as a device for reducing collision by parametric analysis.It was found that a high-damping rubber gasket was installed between the main beam and the pier column and the main beam.After the instantaneous impact force is applied to the rubber mat,the rubber mat converts a large part of the impact energy into deformation potential energy,and then slowly releases it.The rubber mat energy absorption can greatly reduce the impact of the impact on the pier and horizontal beam earthquakes.Response to the adverse effects;Through the rubber pad thickness and area of the parameter analysis found that the rubber pad area and thickness of the greater,the better the reduction effect,when the rubber pad area of 0.6m2,the rubber pad thickness of 8cm,has been able to achieve more Good reduction effect,high economical and practical.(5)The collision effect between the lower girder and the pier will lead to a significant reduction in the bending capacity/demand,shear capacity/requirements and tensile strength/demand of the horizontal beam of the piers,and the rubber pad reduction device It can significantly improve the seismic performance of pier columns and horizontal beams. |
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