The Influence Of Strain Gradient On Creep And Ultimate Compressive Strain Of The Edge Compression

In the engineering structure,There is always strain gradient on the section of beams and columns because of the uneven distribution of stress.Conceptually,when the stress of the edge of eccentrically compressed member is the same as that of the axial compressive member,the creep development of the eccentrically compressed member is smaller than the axial compressive member because of the strain gradient.The ultimate compression strain of the compression edge after creep development is greater than that of short-time loading failure.The purpose of this paper is to study the creep development law and the ultimate compression strain of the compressive edge with strain gradient,and thus providing theoretical foundation for the compression design methods of the highstrength(500Mpa,600Mpa)hot-rolled steel bar in the compressive region of eccentrically compressed members and bending members.In order to study the effect of strain gradient on the creep of concrete subjected to compression edge compression,16 beams are designed.The strength grades of concrete are C30,C40,C50,C60,C70 and C80,the relative compression region height is 0.15,0.25,0.35 and 0.45,The height of the section is 150 mm,300mm,450 mm and 600 mm,loading level of 0.3,0.4,0.5,0.6,0.7.12 beam are replenished for the comparison of shrinkage.The sectional dimension,concrete and experimental environment of the 12 comparison beams are the same as the 16 experimental beams.During the 3 month of experiment,the creep on different measuring points and deflction of the beams are measured and recorded.According to the experimental data,the following research work is completed:(1)The development laws of the concrete in the edge of compression region under the influence of 4 parameters(concrete strength,loading level,height,relative compression region height);(2)The development laws in the midspan of beams in consist of 4 parameters(concrete strength,loading level,height,relative compression region height).In order to investigate the development of the ultimate compression strain of the compression edge concrete creep development,experimental data of 15 beams are collected.We tried to find the law between the creep of concrete in the compression region,the relative compression region height,and the ultimate compression strain of the compression edge.Finally,an equation consisting of those three variables are presented.