Study On The Performance Of Composite Damper For Beam Falling Proof

China is located in the circum Pacific seismic belt and the Eurasian seismic belt,pushed by the Indian continent,the Indian continent is constantly inserted under the Himalayan crust,and the crust near the Himalayas is active with frequent earthquakes.Earthquake is a kind of natural disaster which will bring great threat to people's life and property.In the past earthquakes,bridges destroyed seriously,the most intuitive damage is the falling of bridge beam,it has the greatest impact on traffic restoration after the earthquake,therefore,it is necessary to take corresponding measures to prevent beam falling accidents.More and more highway and railway projects in China are built in the North-South Seismic Belt.Strong ground motion and fault dislocation are more and more challenging to bridges.Engineers need economical energy dissipation devices to reduce seismic loads and prevent beams from falling.In this paper,a kind of "combined damper system" is developed to meet this need.The effectiveness of the device is verified by theoretical analysis and full-scale experiment.The main achievements are as follows.1.The concept of damper with dual functions of shock absorption and prevent beam falling is put forward,and its feasibility is analyzed theoretically.2.The newly designed damping device is composed of energy dissipation unit and limiting displacement unit in series.When the beam is connected to the pier with damper,the slow relative deformation of the beam and pier caused by temperature is accommodated by the oil damper;the relative deformation caused by a moderate earthquake is restrained by the steel damper;Under the action of a big earthquake,the deformation is very large and there is a risk of beam falling,The oil damper device plays the role of limiting displacement to ensure that the beam will not fall.3.The mechanical parameters of the steel damper and the oil damper are determined by full scale experiments.A case is analyzed with Midas civil software.When the "combined damper system " is used in the simply supported beam bridge,the relative displacement of pier and beam can be significantly reduced under the action of a great earthquake,and the seismic shear force of pier can also be significantly reduced.With the newly designed connection devices,the beam can be prevented from falling through the relative displacement limit of pier and beam.