Research On Base Isolation Of V-type Rigid Frame And Arch Composite Bridge

As one of the most critical lifelines,if the bridge is damaged in the earthquake,it will hinder the rescue work of medical staff and firefighters in the disaster area,resulting in many secondary disasters.In recent years,the construction of steel arch bridge in the number and quality of the main aspects of rapid development,not only beautiful appearance,with a high bearing capacity of CFST arch bridge also has a good strength ratio.In this paper,taking Nian chu river bridge as the background,Midas Civil finite element software is used to build the whole bridge model,friction pendulum bearing and high damping rubber bearing are used as the isolation device and the bearing friction is considered.The research contents as follows:(1)Under the condition of reading a lot of documents,the development status,structural forms and seismic damage characteristics of beam arch composite bridges at home and abroad are introduced.According to the development of seismic isolation design,this paper analyzes the classification of seismic isolation bearings,and introduces several main seismic analysis methods of bridges.(2)Based on the analysis of the mechanical characteristics of the bridge in this background,the Midas Civil finite element software is used to establish the calculation model of the whole bridge without considering the pile-soil action.The comparison of the natural vibration characteristics of the model with friction pendulum bearing and the model with high damping rubber bearing is made with that of the model without isolation.Through the comparison and analysis of the changes of the period and frequency before and after adding the isolation bearing,the research shows that the natural period of the isolation model is more than 1.4 times of that of the non isolation model,which shows that the friction pendulum isolation bearing and the high damping rubber bearing can extend the low-order period of the structure to a certain extent,but the impact on the high-order period is relatively small.(3)Under the action of frequent ground motion,the seismic wave input mode is longitudinal bridge and transverse bridge.The dynamic characteristics of two isolation models and non isolation models are compared and analyzed.The influence of two bearings on the displacement response and internal force response of the bridge is discussed,and the isolation effect of two bearings is analyzed.The research shows that: in most cases,the two kinds of bearings can damage the bridge structure under the action of frequent earthquakes.In some cases,the internal force of V-shaped pier outer inclined leg will increase after the addition of the seismic isolation bearings.In the design,it should be considered that not all cases are partial to safety.(4)In the case of rare ground motion,the nonlinear dynamic time history analysis of the model before and after isolation is carried out under the same input mode as that of frequent earthquake.The results show that the moment value of the main part of the V-pier decreases in different degrees,both in the transverse and longitudinal directions,comparedwith the case of larger bending moment of outer diagonal leg in the case of frequent earthquake,the performance of vibration reduction isolation bearing plays a greater role in the case of rare earthquake,which is conducive to reducing the damage of structure by earthquake.