Experimental Research On Eccentric Compressive Properties Of Mould-Bag Fiber Concrete Columns

The application of concrete filled steel tubular arch frame in deep roadway support not only gives full play to its superior support ability,but also exposes the problems of huge workload in transportation and assembly of steel arch frame,complex installation of connecting parts of components,easy corrosion of steel tube and high processing cost.In order to solve the support problems faced by deep roadways and to seek a new type of support for replacing CFST arches,a flexible and economical mould-bag fiber concrete arch frame was developed.In order to improve the mechanical properties of the arch structure,based on the previous indoor experiments of the mould-bag fiber concrete arch structure under axial compression and pure bending,the experimental research on the biasing mechanical properties of the arched frame is studied in this paper.The research work is of great significance to the establishment of the theoretical system of mould-bag fiber concrete arch support.Taking eccentricity,strength of core concrete,the number of CFRP confined layers and type of matrix material as variables,the eccentric compression experiments of CFRP confined concrete cylinder were carried out,and the eccentric compression failure characteristics and load-bearing characteristics of CFRP confined concrete cylinder were analyzed.The results show that under eccentric compression,the concrete in the compression zone of CFRP-confined concrete cylinder components is crushed and peeled off with CFRP.CFRP breaks circularly because the expansion deformation of concrete reaches the limit strain.The decrease of the height of compression zone leads to the increase of the vertical tension of CFRP on the tension side until it breaks,and ultimately the matrix cracks and the specimens are destroyed;In terms of bearing capacity,the ultimate load of components with eccentricity of 0.2,0.4 and 0.6 decreased by 22.47%,41.51%and 65.51%compared with component with eccentricity of 0;The ultimate load of components with core concrete strength of C30 increased by 19.49%and 32.53%respectively;The number of CFRP confined layers increased from 0 to 3,and the ultimate load increases by 15.03%,48.79%and 65.62%respectively.The bearing capacity of components could be increased by adding steel fibers into the matrix,but only 8.43%;Eccentricity and number of restraint layers were important factors affecting eccentric compression bearing capacity of CFRP,followed by strength grade of core concrete,while the influence of steel fiber on bearing capacity was the smallest.The effects of eccentricity,matrix strength,volume fraction of steel fiber and carbon fiber restraint on the eccentric compression deformation and load-bearing characteristics of steel fiber concrete columns were studied by means of eccentric compression experiments.The results show that under eccentric compression,the bond strength between steel fiber and matrix of steel fiber reinforced concrete circular cylinder specimens decreases gradually until it disappears,and the relative displacement between the two results in partial or total pull-out of the steel fiber.The concrete in compression zone is crushed and the components are damaged.Compared with the component with eccentricity of 0.2,the ultimate load of components with eccentricity of 0.4 and 0.6 decreased by 21.97%and 47.95%,the ultimate load of components with matrix strength grades of CF40 and CF50 increased by 10.59%and 19.71%respectively,and the ultimate load of components increased by 3.15%,6.62%and 10.06%from 0 to 3%,respectively.The ultimate load of fiber cloth restrained component was 18.01%higher than that of unconstrained component.Eccentricity was the key factor affecting the bearing capacity of specimens,followed by CFRP restraint and matrix strength,while steel fiber volume ratio had the least influence.When the volume ratio of steel fibers was less than 3%,the larger the volume ratio,the slower the change of deformation stage after peak of load-deflection curve of components,and the toughness of specimens increased accordingly.