Construction Monitoring Of Long-span Rigid Frame-continuous Composite Beam Bridge And Simulation Analysis Of Hanging Basket Structure

Long-span rigid frame-continuous composite girder bridge has been widely used in engineering because of its excellent spanning capacity.However,due to its large span,large deflection and high precision requirements,reasonable construction monitoring is essential.In this paper,taking a high-speed railway（61+3×108+61）m rigid frame-continuous composite girder bridge as the engineering background,the influencing factors existing in the construction monitoring process are analyzed.In this paper,the basic theories of rigid-frame continuous beam,bridge construction monitoring,hanging basket cantilever casting and construction monitoring are summarized at first,and then the general engineering situation of（61+3×108+61）m rigid frame-continuous composite girder bridge is introduced.On this basis,the whole process of modeling with Midas/Civil software is given in detail,and the simulation results under design parameters are analyzed.At the cantilever casting stage of rigid-frame continuous beam,the variation law of deflection,internal force and stress of the beam body is analyzed.Then,the influence of the hanging basket simulation method,concrete elastic modulus,creep calculation specification,steel tendon prestress and live load on the bridge alignment is discussed.When modeling,the hanging basket load is equivalent to a vertical force,which has little influence on the alignment result,but the simulation result is more accurate when the hanging basket load is equivalent to a vertical force and a bending moment.The deflection results calculated by the creep model of the new highway concrete code are quite different;The static and live load of the train has great influence on the alignment.Through sensitivity analysis of four influencing factors: concrete elastic modulus,prestress,channel deviation coefficient and channel friction coefficient,it is concluded that the main factors affecting the finished shape of long-span rigid frame-continuous composite beams are concrete elastic modulus and prestress.Combined with the actual construction parameters obtained from the bridge field test and the adjustment of parameter error by the least square method,the re-calculated construction pre-camber results are applied to the bridge elevation adjustment.By analyzing the monitoring data of alignment,stress and temperature,the completed alignment of the rigid frame-continuous composite beam bridge in this paper is smooth,and the closure deviation and the completed elevation deviation are within a reasonable range,which meet the design requirements.The measured stress is relatively consistent with the calculated stress,and the deviation is within 2MPa.The concrete at the end of cantilever section before closure is greatly affected by temperature,which is consistent with the change trend of atmospheric temperature.Finally,the structural safety of rhombic hanging basket used in the construction of rigid frame continuous beam and the results of hanging basket preloading are analyzed to ensure the safety of bridge construction and the accuracy of construction monitoring elevation control.The conclusions at the end of this paper can provide some reference for the construction monitoring of similar bridges.