Characteristics And Influencing Parameters Of Seismic Response Of Beam-arch Hybrid Bridge

Due to the development of beam-arch composite system bridge have promoted by the improvement of material properties and the innovation of engineering practice technology.As a special form of arch bridge,it will be the main force of the arch and the main moment of the beam together to carry together,give full play Arch and beam their own advantages.At present,although there are many researches concentrated on the static mechanical properties of beam-arch composite bridge at home and abroad,but there is still insufficient about research on dynamic performance,especially earthquake resistance.In view of this paper,it based on a construction project,and carried out seismic response characteristics and structural parameters of the law of the study for the beam-arch composite system bridge,it aimed to provide theoretical and practical reference with the same bridge seismic design.This paper based on the finite element modeling method,considering the interaction of pile-soil-structure,the second-order effect of arch structure,the geometric nonlinear effect of boom and the nonlinearity of boundary nonlinearity,Firstly,it based on the improved LDR method to establish a reasonable finite element dynamic analysis model of beam-arch composite system bridge,and analyzed the dynamic characteristics of the bridge.Then,the seismic response of the bridge is analyzed by nonlinear time-history method,and the seismic performance of the bridge is evaluated according to the failure criterion of bridge structure and component.Thirdly,based on the IDA dynamic incremental analysis method,the seismic response of the beam-arch composite bridge is studied.And it also through IDA curve to study the seismic performance of the bridge is affected by different intensity earthquakes in the future.Finally,the influence of key parameters such as relative stiffness ratio,transverse bracing arrangement and stiffness and span ratio on the seismic response of bridge is studied by parameter sensitivity analysis.Then summarized the seismic performance of beam-arch composite bridge and sensitive design parameters of the reasonable range of values.The paper shows that:(1)Under the action of seismic design,the internal force and displacement response value of the main section of the main arch are smaller,and the bearing is easy to yield and destroy,especially the fixed bearing.The weak link of the whole bridge is bearing and fixed pier,both in the design of the earthquake under the capacity-demand are close to the critical line of seismic performance,and the larger margin for other key components of the seismic capacity.(2)With the increase of the peak acceleration of the ground motion,the seismic moment and shear response of the fixed pier are the most significant,and the values are much higher than the increase of other members.The axial force response is affected by the dead load as other components,and the growth is almost linear.Based on the capability-demand method,the seismic performance of the main pier(1#and 2#pier)began to yield,deterioration and failure state when the peak acceleration of the seismic peak was 0.15g,0.25g and 0.30g respectively.And the displacement demand of unilateral and mutual bearing will be exceed the allowable displacement for the vertical bridge in the seismic when the peak acceleration of 0.65g,destruction,and it will be appear the phenomenon of shear slip move for the fixed direction with fixed and unidirectional bearing in the seismic when the peak acceleration of 0.2g.(3)The sensitivity analysis of the key structural design parameters shows that:?the axial load response of the critical section of the main arch ring increases with the larger of the span ratio,and in addition to the partial cross section,the shear and bending moments increase with the increase of the span ratio,but the magnitude is small.The key moment of the swallows is the smallest when the vector ratio is 1/6,Which has little effect on the seismic response of the critical section of the substructure.?The stiffness of the arch beam has a significant effect on the seismic response of the superstructure and has little effect on the substructure.The internal force response of the critical section of the superstructure increases with the larger of the stiffness ratio for the arch beam.For the substructure,When the earthquake along the longitudinal bridge and the vertical excitation,the critical section of the shear and bending moment response have no obvious change,but the axial force has slight increased trend;when the earthquake along the transverse direction of bridge and vertical excitation,the substructure of the key The internal force response of the section is not changed;?The influence of the stiffness and arrangement of the brackets has a great influence on the internal force response of the critical section of the superstructure.However,the influence of the critical section on the shear force and the bending moment is small.