Research And Application Of Stress-free State Method In Concrete-filled Steel Tubular Arch Bridge

At present,the calculation methods for the reasonable construction state of the bridge structure in phased construction mainly include the inverted dressing iterative method,the dressing iterative method and the stress-free state method.It is easy to be affected by factors such as temporary load and temperature load when the inverted assembly and iterative method and the dressing iteration method are used to determine the reasonable construction state,and the subsequent boom tensioning process is cumbersome.The stress-free state method performs construction control with a relatively stable amount of stress-free state,which makes the installation of the boom easier during construction.However,the research and application of the current stress-free state method are mostly concentrated in cable-stayed bridges,and are rarely used in concrete-filled steel tubular arch bridges.This paper mainly studies the application of stress-free state method in concrete-filled steel tubular tied arch bridges.The main research contents are:(1)Based on the principle of minimum potential energy,the mechanical equilibrium equation of the plane beam element and the space beam element of the geometric linear staged construction is derived,and the mechanical equilibrium equation of the plane element unit and the plane beam element of the geometric nonlinear staged construction is derived,and the mechanical equilibrium equation is used to explore the influencing factors of the internal force and displacement of the final state of the staged construction structure;The construction method of one-time forming and staged forming is used to verify the principle of the stress-free state method.The structural system is the same,only the external loads is different,intermediate construction process of the single-span suspension arch bridge with is verified stress-free state principle second.The idea of construction control stress-free state in concrete-filled steel tube arch bridge is proposed.(2)Based on the rigid support continuous beam method,the rigid suspension method and the bending energy minimum method,the bridge boom force is solved separately,the reasons for the different boom strength obtained by the three methods are compared.(3)The shrinkage and creep of the concrete and the stiffness characteristics of the arch rib section are not considered.The stress-free length of the boom under the dead load is solved.Comparing the state of the concrete-filled steel tube arch bridge,formed by the step-bystep with stress-free length of boom and one-time forming.analysis of the effectiveness of the stress-free state on the construction of the concrete-filled steel tube arch bridge.The iterative method is used to modify the stress-free length of the boom under constant load considering the shrinkage and creep of the concrete and the stiffness characteristics of the arch rib section.how to determine the stress-free length of the boom(4)Explain the concept of several types of arch ribs,analyze the difference between the manufacturing line shape and the installation line shape during the construction of the fullframe support,the influencing factors of the arch rib pre-camber,and the several distribution modes of the arch rib pre-camber,through the construction process accurate simulation,solving the total deflection during arch rib construction;analyzing the influencing factors of the precamber of the beam,accurately simulating the construction process,and solving the total deflection of the control sections of the girders;analyzing how to solve the ribs and systems the stress-free line of the beam.(5)The stress-free state method is used to determine the intermediate ideal construction state.The construction process in which the boom is installed in the post and no longer tensioning in the construction process;the safety of the reasonable construction state determined by the stress-free state method during the construction process is analyzed;Comparing the state of bridge formation obtained from the reasonable construction state determined by the inverted dressing iterative method,the dressing iterative method and the stress-free state method,the effect of the bridge state of the concrete-filled steel tubular tied arch bridge obtained by the stress-free state method is analyzed.