| Short section of the bridge prefabrication and cantilever construction is through the "pieces",will be divided into several segments and girder in a factory or construction site to the site after the precast spellers,has many characteristics,such as construction standardization,industrialization and assembly,offers a new way of urban elevated bridge construction,and conform to the state advocates the prefabricated construction and green sustainable development strategy,It has a good development prospect.However,the short-term prefabricated cantilever assembled bridge has very high requirements for linear control accuracy,and the existing construction linear control methods have insufficient accuracy and lack effective methods for deviation analysis,adjustment and prediction.In view of this,this paper,based on the east fourth link segway assembled viaduct of Zhengzhou,studies the alignment control of short prefabricated and cantilever assembled bridge,and gives effective alignment control methods and application suggestions.The main research contents and achievements of this paper are as follows:(1)For the linear control in the prefabrication stage,firstly,based on the linear elasticity theory,the mechanical formula of the initial displacement method of the stress-free tangent line of the cantilever beam is deduced and verified,and the calculation formula of the manufacturing linear shape is given on this basis.Due to the construction technology of short line prefabrication,there will be deflection Angle difference between adjacent segments during prefabrication.Based on the theory of stress-free state control,a segment size correction method for deflection Angle difference is proposed,and a corresponding correction method is proposed considering the influence of bridge internal force state on precast segment size.In addition,for the correct matching to new watering the segmental beam position error caused by translation,rotation and transverse slope error,based on space coordinate transformation and the principle of error correction,considering the local coordinate system with the whole space position misalignment and flat,elevation space coupling effect,put forward in the local coordinate system,the modified matching the translation and rotation error of beam,Then it converts to the global coordinate system to correct the transverse slope error of the matched beam,so as to realize the correction of the prefabricated alignment error.Compared with the existing method,this method is greatly improved,without multiple conversion of the whole and local coordinate system,the calculation is simple,and the control accuracy is high.(2)Aiming at the alignment control in the assembly stage,in order to determine the assembly alignment,based on the theory of linear elasticity,two calculation formulas of the assembly alignment,namely,the zero displacement installation method and the coordinate transformation method,are proposed.In order to ensure the bridge linear eventually meet the accuracy requirement,need to be at the top of the pier 0#block and installed segment coordinates based on the analysis of the deviation and subsequent segment coordinate installation and adjustment are proposed according to both the deviation and deviation prediction method,finally introduces the linear correction measures,thus forming section deviation theory of dynamic analysis of prediction and correction method.(3)In order to obtain reasonable numerical simulation analysis results to guide the alignment control of segmentally-assembled Bridges,taking the(40+66+40)m segmentally-assembled continuous girder bridge of Zhengzhou East Fourth Ring Road as the research object,the simulation mode and precautions of the lower supports were firstly clarified.Finite element software Midas/Civil and Midas/FEA were respectively used to establish models of different element types and grid sizes.By simulating and analyzing the construction process of cantilever assembly,the influences of different element types,grid sizes,boundary condition setting and software functions on bridge deformation were discussed,and a reasonable simulation method with both precision and efficiency was obtained.Determine construction and finished bridge pre-camber data for precast and assembly segments.In addition,Midas/Civil is used to simulate suspension construction and suspension casting construction processes respectively.By analyzing the deformation trend of the two construction processes and the influence of concrete shrinkage and creep on deformation in the two construction processes,the influence of shrinkage and creep on the final line shape is clarified.In addition,the effect of prestress loss on bridge linearity was studied.It provides reference for the alignment control of segmental prefabricated bridge.(4)Monitor the construction of three typical linear short prefabricated and assembled urban viaducts in the prefabricated and assembled stages.The monitoring results show that the alignment deviation of all Bridges meets the requirement of control precision no matter in the stage of prefabrication or assembly,which verifies the correctness of the alignment control method and numerical simulation method proposed in this paper.In addition,the theory and measured coordinate deviation of prefabricated and assembled alignment are analyzed,and relevant comprehensive control measures are put forward for reference of similar projects. |
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