Study On Iocal Impact Factors’ Calculation Method Of Deck Slabs Of Concrete Curved Box-Girder

In recent years,with the rapid development of traffic construction,more and more curved bridges are chosen preferentially.Due to good torsional and flexural performance,box section is widely used in the design of curved bridges.Since the deck slabs of curved box-girder plays an important role in bearing vehicle loads act as local component,the impact effects should be taken into account in the design.However there is no values and calculation method of lacal impact coefficient in our current code.This article mainly study on reasonable values and calculation method of lacal impact coefficient.Paper’s main work and conclusions are as follows:(1)170 domestic concrete curved box-girder had been collected and sorted,and a statistical analysis had been performed on them.After obtaining the common value range of basic design parameters of bridge,a finite element model of single benchmark bridge is built.(2)In light of triaxial three-dimensional vehicle model with 12 degrees of freedom,bridge’s simplified model as multi-degree of freedom system,and consideration of road roughness and its effect of derivative term,the analysis program of vehicle-bridge coupling is compiled by APDL language in ANSYS.(3)By researching the most unfavorable location of vehicle load,the five most unfavorable load location had been found out.This article defines the local impact coefficient of deck slabs of bridge.By analyzing the local impact coefficient of the single benchmark bridge under different speed,the local impact coefficient of transversed bending moment and shear force at the point13,25 and 39 had been found it is close to specification recommends value 1.3,while other critical section impact coefficient is close to 1.It is safe to take the code suggested value 1.3.(4)By building finite element models of different lengths according to the effective beam segments,a minimum length finite element model of 14 m had been built.Considering the road roughness and its effect of derivative term,the analysis program of vehicle-bridge coupling is compiled by APDL language in ANSYS.Factors like radius of curvature,bridge deck roughness,height of box girder,the width of bridge deck slab,thickness of web plate,thickness of top plate and so forth are taken into account.The results show that: road roughness is the main factor affecting local impact effect,and with the deterioration of bridge deck,the deck slab’s impact effect of vehicle on bridge will rise significantly,whereas the influences of other parameters are relatively small.(5)By linear regression analysis of the bridge fundamental frequency and impact coefficient of bridge panel,a simplified calculation formula of local impact coefficient of the most unfavorable position curved box-girder panel is given,which the basis for local impact coefficient calculation.