| Engineered Cementitious Composites(ECC)is a novel type of high performance material,which obtained higher compressive strength,tensile strength,ductility and better crack control ability compared with normal concrete.In order to promote the further application of this novel material in structural reinforcement,and improve the overall performance of the strengthened RC columns under small eccentric compression and improve its brittle damage pattern.structure after improving the RC column,experimental research and theoretical analysis on RC column reinforced by ECC under the small eccentric compression were carried out in this paper.The eccentric compression mechanism,cracks distribution characteristics,ductility performance and failure model were analyzed and discussed in detail based on the test results,which provide obvious theoretical significance and great value for the practical application.The main research contents and conclusions of this paper are as follows:(1)Considering the influence of the thickness of reinforced layer and eccentric distance,four strengthened RC columns and one RC column as reference were designed and tested under the small eccentric compression load.The test results showed that ECC reinforced small eccentric RC columns exhibited showed multiple-cracking pattern,and ductility failure model,ECC and concrete crushing.Compared with the unreinforced RC columns,the cracking load,peak load and ductility of strengthened columns were increased by 108%to 233%,45%～159%,44.9%～49%,respectively.(2)Based on the test results,the typical load-span deflection curve of RC columns strengthened with ECC under small eccentric compression was drawn,and the influence rules of eccentricity and reinforcement layer thickness on the cracking load and peak load,strain of ECC and reinforcing bars,ductility and cracking-control ability were studied.The compression mechanism analysis of ECC reinforced RC small eccentric compression column demonstrated that the ECC reinforcement layer has obvious hoop effect on strengthened RC columns,which can effectively improve the brittle damage of small eccentric compressed RC column and improve its ductility.(3)Based on the section enlargement method,the constraint mechanical mechanism and the basic principle of concrete structure,the bearing capacity of RC columns strengthened with ECC is analyzed theoretically,the bearing capacity calculation assumption of RC columns strengthened with ECC is put forward and the calculation formula is established.The calculation results are in good agreement with the measured test value.Based on the standard short-term stiffness calculation formula,the short-term stiffness calculation formula of the cross-section ofRC columns strengthened with ECC is suggested.The load value corresponding to the serviceability limit state of ECC reinforced RC column under small eccentric compression is determined,thus the span deflection is calculated,which is in good agreement with the test results. |
