Research On Key Technology Of Demolition Of Single Arch Rib Cfst Arch Bridge

With the continuous development of the city,the traffic volume and heavy-duty vehicles have increased dramatically,as well as the aging of bridge components and the improvement of design standards,resulting in more and more bridges facing demolition due to insufficient carrying capacity or not meeting the current urban development.At present,most of the research on the demolition of arch bridges is aimed at concrete arch bridges.There are few related studies on the demolition of CFST arch bridges,and few practical cases for the demolition of single-arch rib CFST arch bridges in complex environments.Therefore,based on the Jianhu Bridge,this paper studies the key technologies for the demolition of single-arch rib CFST arch bridges in complex environments.The main work of the paper is as follows:(1)Summarize the methods of demolition of bridges at home and abroad,and make a comprehensive comparison of the structural characteristics and the technical difficulties at demolition of single-arch rib CFST arch bridges.Finally,the gantry crane dismantling method is selected to dismantle the single-arch rib CFST arch bridge,and the specific dismantling steps are explained.(2)The overall finite element model of the arch bridge is established,the mechanical characteristics of the whole process of the arch bridge demolition are analyzed,the theoretical value is compared with the measured value.At the same time,the influence of the material strength and temperature on the displacement and stress of the whole process of the arch bridge demolition is analyzed.The study found that the most unfavorable position of compressive stress in the demolition of a single-arch rib CFST arch bridge is at the arch foot,and the most unfavorable position of tensile stress is at the beam;the stress and displacement fluctuate the largest during the demolition process of the web,and are proportional to the length of the cantilever;the theoretical value is smaller than the measured value;the stress and displacement of the arch bridge are inversely proportional to the material strength and proportional to the temperature.(3)Do local modeling for the arch foot part which is the most complex in the demolition process.Analyze the distribution characteristics of its displacement,and study the influence of different prestressed reinforcement arrangement,mesh division and temporary support position of main beam on stress distribution at arch foot.The analysis shows that the local stress concentration is mainly distributed at the contact surface of each component.The different prestressed reinforcement arrangement,the mesh division and the temporary support position of main beam have a great influence on the stress distribution at the arch foot.(4)Model the foundation support of the single-row gantry crane with the largest span currently used,analyze its stability under different working conditions,and analyze the effects of Bailey beam stiffness,initial imperfections,steel tube column diameter and wall thickness on its stability.Finally,based on the above research conclusions,the support is optimized.The analysis shows that when the gantry crane operates at both ends of the support,the stability of the support is the worst,and the Bailey beam is the first to be unstable.The stiffness of Bailey beam and initial imperfections have a great influence on the stability of the support;the diameter and wall thickness of the steel pipe column have a great influence on the stability of the stent within a certain range;after the support is optimized,its vertical displacement is effectively reduced.