Alignment Analysis Of Steel-Concrete Composite Beam Bridge Main Beam Besed On Unstressed Status Method

With the continuous development of the national economy and science and technology,the bridge span has become longer and longer,and the construction difficulty has become more complicated.Therefore,how to properly control the alignment has become the key points and difficulties of construction control.Current stage bridge structure construction is usually constructed with the methods of cantilever assembly and segmented lifting and other construction methods,whose structure alignment at the bridge-forming stage are closely related to the construction methods adopted and the construction process.Therefore,once the construction process changes,the alignment will be affected.The theory of construction by stages which considers the unstressed state quantity of each unit(the final state of the structure is independent from the construction)just provides the theoretical basis for the solution of the above problems.Using the theory of staged construction based on stress-free state method,the most important step is to calculate the unstressed fabrication length of each segment of the project,and based on this,strictly control the fabrication precision in the fabrication process,to ensure the structure alignment at the final bridge-forming stage fits the structure alignment of the one-time formed bridge.This paper takes an steel-concrete composite beam bridge in Zhejiang Province as the engineering background,primarily determines the main beam construction segment fabrication length of the fore-stage based on the unstressed state method,and analyzes the main factors which may appear and have an influence on the alignment change during the late on-site construction process.The main contents of the thesis are as follows:(1)Based on the unstressed state method,the control elements of the segmented lifting process are derived,an contrastive analysis of the difference in the alignment of the bridge formed under different construction schemes is made and the optimal position of the closed joint is determined.(2)Based on the tangential initial displacement method,formal analysis of construction process is made by establishing finite element model,which calculates the unstressed fabrication alignment of the bridge main beam.In addition,by deriving the size correction formulathe corresponding corrections were made to the fabrication dimensions of each beam segment.(3)Based on the parameter sensitivity analysis of alignment in fabrication stage,the influencing factors which may deviates during the fabrication are analyzed,and the degree of their influence on alignment under the conditions of single parameter and multi-parameter combinations is correspondingly obtained.And according to the sensitivity of different parameters,the corresponding adjustment measures are taken.(4)Combined with this bridge construction example,the influence of external temperature on the main beam structure alignment of steel-concrete composite beam bridge is researched during the installation stage.And the finite element model is established by ANSYS to make simulation analysis of temperature effect at different installation stage,so the influence degree of temperature variation at each installation stage on the main beam alignment is obtained.