Research On The Key Technology Of Swivel Monitoring Of Long Span Steel-Concrete Composite Beam Adjacent To The Railway

Because of its light weight,high bearing capacity and excellent span capacity,steel-concrete composite beams have been more and more used in beam bridges,and the use of rotation construction is the common method of this type of bridge.For the steel-concrete hybrid beam constructed by turning,the structural system is frequently transformed and the stress is complex during the construction process.In addition,the vibration induced by the adjacent train can not be ignored.Therefore,it is of great significance to develop the rotation monitoring technology of the long-span steelconcrete hybrid beam bridge near the railway.Based on the construction of a large span steel-concrete hybrid beam bridge,the key technology research of the construction monitoring is carried out based on theoretical analysis,numerical simulation and field test.The main work and conclusions are as follows:(1)The fine refinement finite element model of hybrid beam is established by Midas/FEA.Through the in-depth analysis of construction process,the study on the stress characteristics of the whole construction process is carried out.The research shows that the main girder is under good stress during the whole construction stage,in which the low level tensile stress appears in the concrete roof during the construction stage of the rotation,and the steel beam stress level is high,so the turning construction stage is the most unfavorable condition in the whole construction process of the bridge.(2)Through the theoretical analysis and field measurement,the research on the rotation monitoring technology of the large-span hybrid beam bridge near the railway is carried out.The results show that based on the results of finite element analysis,the monitoring content and monitoring method of the bridge are determined,and a set of methods for the construction monitoring of the steel mixed continuous rigid frame bridge are formed.(3)Through the contact nonlinear analysis of the weak link steel-concrete joint section of the hybrid beam during the construction of the transition,the research on the mechanical properties and the transmission mechanism of the steel-concrete joint is carried out.The results show that the internal force can be transferred smoothly in the steel-concrete joint section,and the stress concentration occurs at the intersection of the stiffener and the pressure plate.The main stress of the concrete in the joint section exceeds the design value of the axial tensile strength.(4)Through the field measurement of the train induced ground vibration and the beam end vibration of the rotating bridge under the action,the influence of train induced vibration on the stability of the bridge is analyzed.The results show that the train induced ground vibration decreases with the increase of the distance of the vibration source.The frequency of the ground vibration near the ball joint is mainly between 5Hz and 35Hz.The lateral amplitude of the beam end of the bridge under the trial running condition is significantly higher than that of the beam end under the standing alone condition.