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Xu J.,Guangxi University | Chen Z.,Guangxi University | Xue J.,Key Laboratory of Disaster Prevention and Structural Safety of China Ministry of Education | Su Y.,Key Laboratory of Disaster Prevention and Structural Safety of China Ministry of Education
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2013

In order to reveal the interaction failure mechanism of bond performance at the interface of recycled aggregate concrete filled circular steel tubes (RACFCST), a total of 15 RACFCST short column specimens were designed for push-out test. Three test parameters of replacement rate of recycled coarse aggregate (RCA), concrete strength grade and length to diameter ratio were considered to research their influences on bond behavior of RACFCST. Load-slip curves, distribution laws of bond strain and bond load for RACFCST specimens were obtained. For contrastive computation, practical formulas for bond strength of concrete filled steel tube (CFST) were used to calculate that of the RACFCST. The regression bond strength formula was put forward. The results show that the initial slip at the loading end develops earlier than that at the free end. The longitudinal strains of steel tube in the early and late loading stages respectively exhibit a negative exponent distribution and linear distribution. Along with the increasing of the ratio of length to diameter, the bond load of RACFCST will be increased to some extent. The development of interfacial bond damage can be advanced with the increasing of RCA replacement rate. At the same time, energy dissipation of bond slip is much better along with the increasing of interface embedded length.


Xu J.,Guangxi University | Chen Z.,Guangxi University | Chen Z.,Key Laboratory of Disaster Prevention and Structural Safety of China Ministry of Education | Xia K.,China Electric Power Research Institute
Journal of Natural Disasters | Year: 2012

In order to reveal the bearing capacity and failure mechanism of CFRP strengthened existing reinforced concrete poles with corrosion steel collar joints, three poles from a road section of Southwest line in the Southern Power Grid were selected to conduct flexural capacity test research. Two pole specimens were pasted with double vertical CFRP and one pole specimen was pasted with single vertical CFRP. The whole process of forcing and failure mode of all specimens was observed by the test, and the important indicators, such as curves of load-deflection, curves of stiffness degeneration and ultimate bearing capacity, were obtained. Results indicated that the strengthened poles with connection joints were mainly bond failure between concrete and the external CFRP, the damage process is very fast, and the failure feature is brittle. These specimens' cross-sectional strains conform to the assumption of plane cross-section. Also, bearing capacity and stiffness of the strengthened specimens are much larger than those without CFRP. The bearing capacity of specimens pasted with double CFRPs is larger than that of the specimen with single CFRP. Comparing the initial stiffness and elastic-plastic stiffness, it is seen that the ones with double CFRPs are a little higher than the one with single CFRP. Weighting the cost-effective effect, it is determined that pasting single-layer CFRP longitudinally is more economical and reasonable. The results can provide a reference to the same type of existing reinforced concrete poles for reinforcing design.


Chen Z.,Guangxi University | Chen Z.,Key Laboratory of Disaster Prevention and Structural Safety of China Ministry of Education | Ying W.,Guangxi University | Ying W.,Tongji University | And 2 more authors.
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2015

In order to reveal the mechanical properties of short age recycled coarse aggregate concrete under tri-axial compression, 14 cylinder specimens were designed for tri-axial compression test. Aging time and lateral confinement were considered as variables in the test. Failure patterns of specimens were observed, peak stress, peak strain, elastic modulus and stress-strain curves were obtained. Based on the experimental data, the influence of aging time and lateral confinement on the mechanical properties of short age recycled coarse aggregate concrete under tri-axial compression were analyzed; the strength calculation methods were discussed; the formulas of elastic modulus, peak strain, peak stress and stress-strain constitutive equation were put forward. Results show that: aging time has a great influence on peak strain and elastic modulus; on the other hand, peak stress, peak strain and elastic modulus of recycled coarse aggregate concrete are significantly influenced by lateral confinement. The calculated results by CEB-FIP(1990) are in good agreement with experimental data. © 2015, Tongji University. All right reserved.

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