| With the rapid development of society,the rapid development of concrete filled steel tube composite arch bridge in the field,because of the good cooperation between the steel tube and the concrete,the CFST with compressive resistance,good fire resistance,good toughness and ductility.Concrete filled steel tube material applied for the first time in the 1880 s British Severn railway bridge pier,but the CFST in bridge in real development in our country,so far,the concrete-filled steel tube arch bridge have been built in our country and the construction of the more than and 300 seat,and towards the direction of large span development,then the stability of rib arch it appears,because the main arch rib is compressed structure,especially the arch plane stability problem,through a large number of experiments and theoretical analysis that the lateral stiffness of the arch rib is smaller than the vertical stiffness,that is very easy to get out of plane instability before the in-plane instability.At the same time,CFST arch bridges exposed some problems during operation,one of the more prominent problem is the problem of separation between steel and concrete,the problem of disengaging the confining effect between steel tube and concrete failure,the influence of different degree of bearing capacity of CFST arch bridge,prevention measures at the present stage of the CFST arch rib cavity problem and many solutions,but the concrete creep and shrinkage caused by the separation is inevitable.The separation of concrete is inevitable,and it is more likely to be out-of-plane instability in the process of CFST arch rib.So this paper studies the influence of outof-plane stability of separation on concrete filled steel tube arch rib.Modeling and analysis of concrete filled steel tubular arch ribs by large scale software ANSYS,the finite element model is established by taking the single arch rib test of Chen Baochun as the research object,and compared with the experimental results,after verifying the correctness and reliability of the established finite element model,studying on the influence of slenderness ratio,steel ratio,ratio of rise to span and hoop coefficient on the out-of-plane stability bearing capacity of the CFST arch rib in the case of separation.Research shows: the bigger the slenderness ratio,the smaller the ultimate bearing capacity of arch rib,on the contrary,the ultimate bearing capacity of arch ribs increases with the increase of steel ratio,steel strength grade and concrete strength,the ultimate bearing capacity of arch ribs increases first and then decreases with the increase of the ratio of rise to span,and the optimal span ratio is between 0.25-0.3.When the separation of arch rib,the ultimate bearing capacity of arch rib greatly decrease with the increase of separation ratio and separation length,should pay enough attention to this.Separation location and loading way have a great influence on the ultimate bearing capacity of arch rib,the ultimate bearing capacity of arch rib under symmetric load is obviously higher than unsymmetrical load.Based on the study of the parameters of the arch rib,studying on the calculation formula of the member space force in GB50936-2014,viod reduction coefficients are introduced in Kn and Km in the case of considering the separation,by summarizing the data of each parameter and fitting simplified void reduction coefficient calculation formula,compared with the results of finite element calculation,the error between the two formulas is about 10%,which shows that the formula has good accuracy and can be used as reference for practical engineering. |
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