Research On The Reinforcing Performance After Secondary Loading Of RC Frame’s Beam&column In Structure Underpinned And Column Removed Project

Based on a structure underpinned and column removed engineering project inYuping county, Guizhou province, the thesis attaches some resistance strain gauges in2RC columns strengthened with externally bonded steel frame and2RC beamsstrengthened with reinforced concrete around three areas. During the project, beforeremoving column, we use jacks to offload by steps and then, remove columns bydrilling hole in it, which makes RC structure’s beam&column get secondary loading.The thesis makes research on the secondary loading of strengthened RCbeam&column in the bracket girder and removed column project, measures the strainof them during the loading by steps. What’s more, the finite element numericalsimulation of RC columns strengthened with externally bonded steel frame and RCbeams strengthened with reinforced concrete around three areas are carried out usingthe finite element software ANSYS. The followings are the main research work in thethesis:(1)It describes the characteristics and research status of RC columnsstrengthened with externally bonded steel frame and RC beams strengthened withreinforced concrete. It’s very meaningful to do research on them.(2)In the strengthening and rebuilding engineering of frame office building inYuping county, Guizhou province, the strain data have been measured by attachingsome resistance strain gauges in the2RC columns strengthened with externallybonded steel frame and the2RC beams strengthened with reinforced concrete aroundthree areas, which is near the removed columns, during the loading by steps. Thencalculate internal force at every step and establish a relationship between the internaland the strain in reality.(3) In order to do the finite element analysis with ANSYS and study theirperformance after secondary loading, chose the element types、material props andsome other parameters of the strengthened RC column and RC beam. Compared thedata from references with the results of finite element analysis, we can draw aconclusion that the method used to do finite element analysis is reasonable.(4)Analyze the performance after secondary loading of the2RC columnsstrengthened with externally bonded steel frame in the strengthening and rebuildingengineering with ANSYS. Then compare the result of finite element analysis with the data from the experiment test. Mainly focus on the eccentric distance and the initialstress level, the characteristic of20RC columns strengthened with externally bondedsteel frame after secondary loading is analyzed. We can draw the conclusion that inthe practical engineering, the new externally bonded steel frame and original membercan work in coordination, but no matter in the practical engineering or in theory, theuse ratio of new externally bonded steel frame is less than0.9, which is specified bythe design code for strengthening concrete structure. It means that the evaluation ofthe code is too large.(5)Analyze the performance after secondary loading of the2RC beamsstrengthened with reinforced concrete around three areas in the strengthening andrebuilding engineering with ANSYS. Then compare the result of finite elementanalysis with the data from the experiment test. Mainly focus on the initial stress leveland the increase of depth or breadth, the characteristic of16RC beams strengthenedwith reinforced concrete around three areas after secondary loading is analyzed. Wecan draw the conclusion that no matter in the practical engineering or in theory, thenew reinforced concrete and original member can work in coordination, and the useratio of new rebar is larger than0.9, which is specified by the design code forstrengthening concrete structure. It means that the evaluation of the code isreasonable.(6)According to the strain test and the finite element numerical simulation on RCcolumns strengthened with externally bonded steel frame and RC beams strengthenedwith reinforced concrete around three areas, we can draw the conclusion that aftersecondary loading is still in elastic stage and the research on the secondary loading ismeaningful to provide guidance to the engineering practice.