Study On Construction Mechanical Behavior Of Thin-walled Hollow Pier Steel-wood Composite Formwork Structure

With the perfect ending of the "13th Five-Year Plan" and the smooth implementation of the "14th Five-Year Plan",basic transportation construction such as expressways and bridges has developed in an all-round way.Thin-walled hollow piers,as the main substructure form,are vital to the function of the entire structure.As one of the main forms of thin-walled hollow pier construction,the structural design of steel-wood composite template and the study of force behavior during construction are indispensable.In recent years,there have been many safety accidents caused by the destruction of steel-wood composite template structure.Therefore,under the premise of structural safety,it is very necessary to improve the form of the template and use new building materials and technologies to increase the strength of the structure,speed up the construction process and reduce the project cost.In this paper,the method of on-site testing is used to study the changes in the construction mechanical behavior of the thin-walled hollow pier cantilever climbing steel-wood composite template in the stages of template installation,concrete pouring,and concrete hydration;use numerical simulation to calculate the structural force and compare the test data Analyze and improve the structural design scheme on the basis of the existing structure;and use model tests to study the problems of long duration of high temperature on the surface of the steel-wood composite template in the later stage of the concrete construction of the thin-walled hollow pier and the slow declining speed.To be applied in the project.The main research contents and results are as follows:(1)For the construction of the standard section of the thin-walled hollow pier,the actual construction force and deformation of the steel-wood composite template structure were tested,and the cantilever climbing steel-wood composite template construction process was analyzed to determine the stress and deformation of each part of the template.The overall structure of the thin-walled hollow pier steel-wood composite template and the maximum stress and deformation of each component during the construction of the standard section concrete are obtained near the effective indent height.(2)The law of lateral pressure change is obtained by field test,curve fitting is performed according to the test data,the relevant domestic and foreign codes are referred to,and the force on the steel-wood composite template is also different at different stages of concrete pouring.The calculation formulas for the lateral pressure of the thin-walled hollow pier steel-wood composite template at different stages of the standard section concrete pouring are obtained.(3)Use the finite element software ABAQUS to perform numerical simulation analysis on the steel-wood composite template,and compare the results with the test results and theoretical calculation results.Under the premise of ensuring safety,make full use of the strength of the structure,speed up the construction progress,and reduce the cost of materials.The steel backing of the cantilever climbing template structure of the thin-walled hollow pier is improved,and the model of the pull-screw is designed and improved.The improved structure meets the requirements.At the same time,it reduces the cost of engineering materials.(4)In the process of testing the thin-walled hollow pier standard section steel-wood composite template,the internal mold high temperature duration is long,the temperature difference between the inner and the outer mold surface is large,the temperature difference decreases slowly,and the mold removal time is affected by the laboratory model test analysis.It is obtained that the setting of ventilation holes can effectively solve the problem of the continuous high temperature difference between the inner and outer template of the thin-walled hollow pier.This method shortens the time for mold removal under the premise of ensuring the allowable strength of the concrete,which proves the feasibility of the method in the actual project.