The Anti-overturning Effect Of The Stiffness And Mass Eccentricity Set For Concrete Curved Box Girder Bridges

Due to the beautiful shape,small footprint and other advantages,middle pillar curved beam bridge has been widely used.As the design theory is not perfect,the overall overturn accident of mid-pivoted bearing curved bridge has appeared one after another in many places.In this paper,the anti-overturning stability coefficient of concrete curved beam bridge is studied,because how to ensure the safe operation of the bridge in the design has become an urgent need to solve.Base d on the engineering example,a series of different radius of curvature models is built using ANS YS finite element analysis software to study the influencing factors include asymmetry of guardr ail,asymmetric web thickness,pre-eccentricity of bearing,spacing of end bearing,arrangement of bearing,ultra-high arrangement.The concept of transitional radius is introduced in the modeli ng process:the radius of curvature of middle pillar curved beam bridge when the connection of t he outer end bearing and the middle bearing is overlapped.Based on the calculation results of fin ite element model of concrete curved box girder bridge with different design parameters,the anti-overturning stability coefficient and the internal force and stress of the bridge are compared an d analyzed.The main achievements are as follows:(1)The asymmetric arrangement of the guardrail can significantly improve the uneven force of the outer end bearing of the curve bridge,and the effect of the anti-overturning coefficient of t he curved beam bridge is very significant.The anti-overturning stability coefficient of the curved beam bridge decreases first and then increases with the increase of the radius of curvature,and r eaches the minimum value at the transition radius.Because of the asymmetric arrangement of the guardrail,the anti-overturning stability coefficient of the curved beam bridge is improved from 24.2%of the small radius to 58.9%of the transition radius,and then gradually decreases to 34.9%of the large radius.The asymmetric arrangement of the guardrail causes a certain stress differe nee between the inner and outer sides soleplate of the side span,but at the same time,it can effec tively adjust the shear stress difference between the inner and outer webs,so that the internal and external web shear stress tends to equal.(2)The anti-overturning ability of the small radius curved beam bridge is much better than that of the middle pier pre-eccentricity and the middle-end bearing spacing measures.However,the pre-eccentricity of the middle pier can reduce the normal stress Peak,and can improve the cross-section shear stress distribution.However,the use of torsional support in the pier to improve the anti-overturning capacity is better than other ways,wich can effectively reduce the normal stress of the cross-section,and reduce the internal and external web shear stress difference.Therefore,it should be given priority in the design.(3)The combination of the pre-eccentricity and the non-symmetrical arrangement of the fence is superior to the independent asymmetric guardrail for the anti-overturning performance of the small radius curve bridge.It is better to increase the anti-overturning ability of the large radius curve bridge and increase the effect than to set the asymmetric guardrail separately on the basis of the asymmetric arrangement of the fence.(4)Both the web slab and the pavement will reduce the anti-overturning capacity of the curved bridge,And the pavement to set the bridge cross slope way to reduce the anti-overturning capacity of the curved beam bridge is greater than the height adjustment through the web to set the bridge cross slope way.But the beam rotation slope setting will partly improve the anti-overturning ability of the curve bridge,But comparing with the barrier non-symmetrical layout,the middle of the pier support pre-eccentric and mid-torsion set torsion support way,the effect is minimal.Further,the web made pavement made to the slope and slope settings has increased stress in the outer bottom slab difference.While the beam rotation slope setting has no effect on the section stress of the box girder.(5)The thickening measures of the inner web have a certain improvement over the overturning ability of the curved bridge,but the effect is lower than other measures.The thickness of the inner web is reduced and the stress of the inner web of the beam in the vicinity of the middle pier is reduced,so that the shear stress of the inner and outer webs in this area tends to be equal.