Creep Stability Analysis Of Long-span Concrete-filled Steel Tubular Arch Bridge With The Influence Of Randomness

CFST arch bridge,as the structural form of long-span bridge,is widely used in the construction of long-span bridge because of its beautiful structure and strong spanning ability.At present,the research on the creep stability of CFST arch Bridges is still in its infancy,and the understanding of the creep of core concrete on the stability of arch Bridges is still unclear.Most of the researches on the stability bearing capacity of arch Bridges do not consider the randomness of the parameters.In the few studies that consider the randomness of parameters,the correlation between parameters is not considered.There is no quantitative conclusion about the creep stability of CFST arch Bridges.Therefore,it is necessary to analyze and study the influence of randomness on the creep stability of long-span concrete-filled steel tubular arch bridge.In view of the existing problems,this paper mainly carries out the following research contents:(1)Deterministic analysis of creep stability of long-span concrete-filled steel tubular arch Bridges.On the basis of the instability theory of arch,the theoretical formula of the critical load of arch bridge is derived,and the contribution of the flexural stiffness,torsional stiffness and transverse coupling stiffness to the critical load of arch bridge is clarified.By using the finite element numerical model,the development law of the creep stability bearing capacity of the long-span concrete-filled steel tubular arch bridge is solved under the deterministic analysis.The instability forms of long-span concrete-filled steel tubular arch Bridges are defined,which are dominated by the control of out-of-plane instability and the joint participation of in-plane instability.(2)Uncertainty analysis of creep stability of long-span concrete-filled steel tubular arch bridge.The randomness of the parameters is introduced into the creep stability of arch Bridges by means of Latin hypercube sampling and matrix transformation.The influence of the randomness of parameters on the creep stability of long-span concrete-filled steel tubular arch bridge is analyzed.The sensitivity of the creep stability bearing capacity to the steel content of the arch section and the creep influenced parameters is given.The results show that the section steel content and the water-cement ratio of core concrete are the important factors affecting the creep stability.Based on the results of sensitivity analysis of arch shaft,the influence of different construction schemes is analyzed and compared.(3)Time-varying reliability analysis and stability factor calculation of creep stability of long-span concrete-filled steel tubular arch bridge.Based on the time-varying reliability analysis theory,the time-varying law of the creep stability reliability of long-span concrete-filled steel tubular arch bridge is analyzed,and the influence of different parameters on the creep stability reliability is studied.It is concluded that with the continuous development of the age of core concrete of arch bridge,the stability and reliability of creep gradually decrease,but it can still meet the requirements of current design specifications after reaching the design life.Therefore,for the long-span concrete-filled steel tubular arch bridge designed according to the current design specifications,creep instability will not be the main reason for bridge failure.(4)The boundary conditions for creep instability of concrete-filled steel tubular arch bridges are defined.The influence factors of arch axis form,rise-span ratio and section stiffness ratio are analyzed,and the boundary of creep instability as the main failure reason of the structure is defined.For concrete-filled steel tubular arch Bridges,the appropriate ratio of rise-span ratio is 1/5.When the ratio of sagittal span deviates from the appropriate one,the problem of creep stability becomes prominent.The section stiffness ratio of the arch rib should be controlled reasonably,and the creep stability problem can be avoided reasonably by controlling the ratio of section inertia moment and polar inertia moment,which should be less than 0.5.It is concluded that parabolic arch is more suitable for arch bridge considering creep stability than arc arch and catenary arch under the same condition.