Study On Seismic Performance Of Steel Box Basket-type Arch Bridge Based On Multi-scale Finite Element Analysis

As the infrastructure of the national economy,bridges are the lifeline engineering for the survival of people.They are easily damaged in earthquakes,and once the bridges damaged,it is difficult to repair in time.This will affect the disaster relief work after the earthquake,and miss the best time for the disaster relief.The steel arch bridges are widely used,not only because they have good spanning capacity,large bearing capacity,good seismic performance,they are also beautiful and economical.With the application of steel arch bridge more and more widely,the related researches on its seismic performance is attracting a lot of scholars.But the researches little concentrate on the basket-type arch bridges,and computer simulation is used in the seismic study of the whole bridge.Most of the current researches on the finite element method are beam element models,although the model has the advantages of fast computation and simple data sorting,it will cause large errors.Therefore,the multi-scale modeling method is applied in this paper.In order to improve the calculation accuracy,the multi-scale modeling method is applied in this paper,and the seismic performance analysis was carried out on the half through basket-type arch bridges.This paper applies the finite element method to establish a multi-scale model of a half through steel box basket-type arch bridge based on a practical engineering(whose leaning angle is 4 degree).and the dynamic time history analysis was carried out.The results of the multi-scale model are compared with the conventional beam element model to explore the difference between them.Secondly,in order to explore the influence of the leaning angle on the seismic performance,the multi-scale models of arch bridge with 7 degree and 0 degree were established,and the dynamic time history analysis was carried out under transverse and longitudinal seismic waves,respectively.Through the comparisons between the results of 7 degree,4 degree models and 0 degree model,to find influence of the leaning angle on seismic performance.The results are as follows:(1)Based on a practical engineering,the multi-scale model of the half through basket-type arch bridge was established,and the finite element software ABAQUS was used to analyze the eigenvalue analysis.The dynamic characteristics of the arch bridge such as basic period,frequency,the vibration modes and so on are obtained.And the first 15 modes of vibration are analyzed.(2)The beam element model and multi-scale model of the arch bridge were established,and the dynamic time history analysis was carried out on them under the seismic waves,respectively.And the displacement and internal force responses of the two models were compared.The results show that the multi-scale model is in good agreement with the beam model.The arch springing enters the yield state under 1.5 times earthquake,and the stress-strain hysteresis curves obtained from the two models have a large deviation.It shows that the beam element can not take into account the problem of local yield and stress concentration.Therefore,in the analysis of seismic performance,the multi-scale modeling method should be considered for the parts that need selective analysis and the local yield occur easily.(3)The multi-scale models of arch bridge with 7 degree and 0 degree were established,then the dynamic time history analysis was carried out and the results were compared.According to the comparison,it is finded:the leaning angle of arch rib increases the lateral stability of the arch bridge.(4)The dynamic time history analysis on the three arch bridge models were carried out under the transverse and longitudinal seismic waves,and compared their displacement and internal force responses and the stress-strain hysteretic curves of the plastic parts.Through the comparisions we can find that the basket-type arch bridge can reduce the transverse displacement of vault effectively,the 4 degree arch bridge model has reduced 2.99%-14.9%,and the 7 degree arch bridge has reduced 1.79%-20%;but has little influence on the displacement response under the longitudinal earthquake;under the transverse earthquake,bending moment and shear force responses of 1/4 arch rib and vault are less than that of the 0 degree arch bridge,the 4 degree arch bridge model has the best improvement effect,has reduced 5.9%-58.7%,7 degree model has reduced 3.7%-45.2%;under the longitudinal earthquake,the axial force and shear force of the key sections are getting smaller and smaller as the arch rib is inclined inward.In conclusion,the multi-scale finite element analysis of half through steel box basket-type arch bridge can take into account the problem of local instability and stress concentration,it has high precision.And with the leaning angle of the arch bridge increases,the seismic performance of the bridge is improved,but in the design of bracing structure need for seismic reinforcement.