Stress Characteristics And Experimental Study Of Support System Of Giant Beam In Layered Pouring Construction

With the development of urban construction,the use of land in urban areas is becoming more and more tense.The need for secondary development and construction of large-scale projects in the upper part of the completed underground structures(tunnels,underground stations,subways,etc.)is becoming more and more urgent.In the second development,in order to obtain a large space for use,giant cross-section girders often appear in the structural design.When a giant beam is used for construction,the weight is transmitted to the underground structure through the support system once,because the load is too large,it often causes Cracking or destruction of the structure,causing serious engineering accidents.In order to avoid this kind of thing,the giant beam is layered and poured,and the partial weight of the giant beam is shared by the precast pouring beam to reduce the load on the underground structure,and the underground structure is not cracked or cracked during the construction of the giant beam.A necessary choice.This paper takes the development of the upper cover of the Donggang depot of the Lanzhou Rail Transit Line 1 project as the background,and uses the Midas/gen to establish the pouring beam,support and the application of the cover of the girders.Using the spatial finite element model of the collaborative work of the library framework,the force of the library structure under different construction stages of layered pouring is studied.The influence of the different layer height of the giant beam on the force of the library structure is analyzed.The most favorable stratification height ratio of structural forces is proposed.The application scheme of the stratified pouring of the Donggang depot is proposed.The axial force variation of the supporting poles during the construction process is monitored and compared with the numerical simulation results.At the same time,the bonding performance of the horizontal construction joint formed by the secondary casting was analyzed,and the following conclusions were obtained:(1)The stratified pouring of the giant beam can reduce the force of the lower beam of the library frame beam and column;under different layer height ratios,the effect of using the library structure to reduce the force is different.When ?h=0.6~0.7,the application library is used.The frame is most beneficial;(2)The proportion of pre-casting beams sharing the construction load during the second casting increases with the increase of its own height.When ?h=2/3,the precast pouring beam can bear 85% of the secondary casting construction load;(3)The layered pouring of the giant beam can effectively reduce the axial force of the lower support pole.The axial force of the pole at different positions is different than that of the whole casting.The axial force near the pole near the bearing decreases more.;(4)The difference between the simulated value and the measured value of the axial force of the girders under the giant beam is within 15%,indicating that the simulated value is close to the measured value,and the calculation model can reflect the true force of the supporting system;(5)The weak part of the overall work of the giant beam at the layered pouring interface is mainly caused by the weak mechanical bite force.The viscosity of the new and old concrete interface can be improved by increasing the interface roughness,applying the interface agent and setting mechanical joints.Knot performance.