| With due rapid development of the city,the undciirouiid tail transit has greatly alleviated the problem of urban road congeslion.However,in Uni acLual.engineering design and construction,it is inevitable that the existing buidings will he suhmierged,resulting in the comflict between the underground rail transit and the existing buitding foundation.Based on xi an bei-airport intereity rail projecl.this paper studies the deformation limits,deformation monitoring and key comstruction technologies of the joists in the pile foundation of the Iarge-axte bridge by constructing the bridge pier 22 of the main line bridge of the T3A terminal building.The main contents are as follows:(1)through the anfilysis of the axial force of bridye pile foundalian undeipinning construction scheme,the underpinning beam construction and stress system transformation in the two stage of the key in the whole construction,due tothe construction site is located in the main bridge TA3terminal under heavy traffic,underground pipelines are more complex surrounding environment,small consliuction site and the factors underpinning beam to the upper bridge transfer vehicle dynamic load uncertainty and other factors,has led to a strict proccss control in construction,strengthen the construction monitoring,guarantee the construction quality and safety.(2)based on the finite element numerical method,the finite-element analysis model of the comples and special-shaped bridge structure on the upper part of the pieris established.By calciilsting and analyzing the most unlavorable load effect combination,the displacoment limit of thebridge pier foundation underpinning process is obtained.Considering the section reinforeement,the maximum displacement of the structure(the vertex position of the pier)and the elastie stress limit of the upper part of the complex bridge are calculated.It provides a scientific basis for deformation detection and displacement control in the construction process scientific basis for deformation detection and displacement control in the construction process of pile base underpinning system.(3)through the observation of the site of the existing bridge,allowable stress value and the bridge structure is the underpinning of bridge settlement has been considered,combined with the results of finite element analysis and construction monitoring results,reference domestic and other active underpinning project,setting the underpinning beam settlement control value.(4)automatic monitoring system based on the underpinning beam settlement,underpinning beam stress and strain of the whole construction process monitoring,so as to obtain the actual internal force and deformation of the structure of the construction phase,tracking control in different construction stages for construction into effect for the upper bridge structure caused by the control of deformation rate,realize the informationization construction,ensure both the safety of the bridge operation,take measures to make it in a safe state. |
