In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially subs...In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distribu- tions and crack propagation of the composite columns in different states of eccentric compressive loading are ana- lyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, com- pressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/ concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate Ioad- carrying capacity of the composite column with small eccentricity.展开更多
The behavior of slender columns under the effect of eccentric loading has always taken the attention of researchers. When investigating the strengthening of reinforced concrete columns, mainly short and circular colum...The behavior of slender columns under the effect of eccentric loading has always taken the attention of researchers. When investigating the strengthening of reinforced concrete columns, mainly short and circular columns are the targeted elements. This is why the data about slender columns with rectangular sections is limited and infrequent specially when loaded eccentrically. This paper aims to increase the available experimental data in this specific area. The experimental program consisted of twenty seven specimens. The specimens were divided into three groups; one control group and two groups strengthened using two strengthening schemes. Scheme 1 implied the use of near surface mounted （NSM） longitudinal steel bars, while in scheme 2, NSM longitudinal steel bars partially wrapped with one ply of carbon fibers reinforced polymers （CFRP） sheets was used. The test specimen had an overall length of 2000 mm and a 100 x 200 mm rectangular cross section. In addition to the strengthening schemes, the test parameters included three ratios for the internal longitudinal steel bars ＂μ＂ 1%, 1.57% and 2.26%. The parameters were extended to cover three stirrups＇ volumetric ratio ＂ρv＂ 0.73%, 0.49% and 0.37%. The specimens were tested under the effect of eccentric loading with eccentricity-to-section height e/h equals 0.25. The research revealed that the strength gain in specimens strengthened with scheme 2 was higher than with scheme 1. Analytical modeling of the stress strain relation of the strengthened RC columns considering the effect of strengthening scheme, internal reinforcement ratio μ, and stirrups＇ volumetric ratio ＂ρv＂ was proposed. Verification was made using available experimental data. The proposed model showed a reasonable agreement with the experimental results.展开更多
基金Supported by the National Natural Science Foundation of China(No.51278118)the Program for Special Talent in Six Fields of Jiangsu Province(No.2011JZ010)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK2012756)the Undergraduate Innovation Program(No.T13052007)
文摘In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distribu- tions and crack propagation of the composite columns in different states of eccentric compressive loading are ana- lyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, com- pressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/ concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate Ioad- carrying capacity of the composite column with small eccentricity.
文摘The behavior of slender columns under the effect of eccentric loading has always taken the attention of researchers. When investigating the strengthening of reinforced concrete columns, mainly short and circular columns are the targeted elements. This is why the data about slender columns with rectangular sections is limited and infrequent specially when loaded eccentrically. This paper aims to increase the available experimental data in this specific area. The experimental program consisted of twenty seven specimens. The specimens were divided into three groups; one control group and two groups strengthened using two strengthening schemes. Scheme 1 implied the use of near surface mounted （NSM） longitudinal steel bars, while in scheme 2, NSM longitudinal steel bars partially wrapped with one ply of carbon fibers reinforced polymers （CFRP） sheets was used. The test specimen had an overall length of 2000 mm and a 100 x 200 mm rectangular cross section. In addition to the strengthening schemes, the test parameters included three ratios for the internal longitudinal steel bars ＂μ＂ 1%, 1.57% and 2.26%. The parameters were extended to cover three stirrups＇ volumetric ratio ＂ρv＂ 0.73%, 0.49% and 0.37%. The specimens were tested under the effect of eccentric loading with eccentricity-to-section height e/h equals 0.25. The research revealed that the strength gain in specimens strengthened with scheme 2 was higher than with scheme 1. Analytical modeling of the stress strain relation of the strengthened RC columns considering the effect of strengthening scheme, internal reinforcement ratio μ, and stirrups＇ volumetric ratio ＂ρv＂ was proposed. Verification was made using available experimental data. The proposed model showed a reasonable agreement with the experimental results.
