Study On The Construction Control Mechanism And Measures Of Long Span PC Continuous Rigid Frame Bridge

In recent years,China's transport industry has been developing rapidly,and the importance of bridge as the key project in transportation system is obvious.Continuous rigid frame bridge was developed with increasing traffic volume and longer span requirements.The bridge is popular for its good structure,strong bearing capacity,strong anti-seismic performance and fast construction speed.Most of a long-span PC continuous rigid-frame bridge construction by the cantilever method,belonging to the statically indeterminate structure for many times,this kind of construction method is more uncertainty,will bring more complex internal force and displacement change,are easy to appear the final design and the situation of the state,therefore,continuous rigid frame bridge construction control has become the important content of construction tasks.In this paper,relying on the Longtandu Bridge as the engineering background,Longtandu Bridge instead of 55 + 100 + 55 m prestressed concrete continuous rigid frame bridge,with the help of a large general software Midas/Civil finite element numerical calculation of the bridge construction process,and according to the calculated results of longtandu ridge,the main research content of this article is as follows:(1)The development of continuous rigid frame bridge and the characteristics and construction methods of continuous rigid frame bridge are introduced.The construction control mechanism is introduced in detail,including the task,contents,methods and influence factors of construction control.(2)The camber of the bridge includes the camber of the construction and the camber of the finished.Through the simulation results of finite element software,the construction camber of Longtan Bridge is extracted,and the camber is set up after the cosine curve method and the two parabola curve method are compared to the final selection cosine curve method.The normal compressive stress of the section of each construction phase is extracted by the model,and the ANSYS software is used to check the hanging basket for the cantilever construction to ensure the safety of the hanging basket.(3)Introduce the concept of grey neural network,train the neural network through the toolbox of MATLAB,and predict the height error produced in linear control.Only using BP neural network can not get perfect result.Finally,the prediction method based on the combination of BP neural network and grey system theory has achieved an perfect prediction effect in the construction control work.(4)The monitoring scheme of line shape,stress and temperature are introduced.The height change trend of each cantilever section is analyzed dynamically in three stages,and the structure of the bridge is in a safe and stable state according to the trend of stress and temperature.According to the gap between the measured value and the theoretical value,the construction state of the bridge is judged and the possible causes are analyzed.(5)Through the analysis of the roof of the box beam,the influence of the structural deformation and stress on the three conditions of weight,moving load and temperature is analyzed by changing the thickness of the roof.Through the comprehensive evaluation method,the concrete dosage ratio,compressive stress ratio and deformation ratio in different roof thickness are obtained,and the optimum thickness of the top plate of the continuous rigid frame bridge with the main span of 100 m is determined to be between 28cm~32cm.