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Title:	Square concrete-filled steel tube columns longitudinally strengthened with carbon fibre reinforced polymer sheets under eccentric axial loading
Authors:	Mohammad Ansari (P63121)
Supervisor:	Wan Hamidon Wan Badaruzzaman, Prof. Dato' Ir. Dr.
Keywords:	Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	30-Apr-2021
Description:	Applying Carbon Fibre Reinforced Polymer (CFRP) is the most convenient and practical method for strengthening and retrofitting Concrete-Filled Steel Tube (CFST) columns. The CFRP sheets can be applied easily to the surface of the steel tube with epoxy adhesive after concrete casting, which, unlike welding and drilling, does not have any destructive effect on the concrete and steel. CFRP sheets are mostly applied in the circumferential direction to prevent or delay the outward buckling of the steel tube and provide additional confinement effect to the infilled concrete. The earlier researchers have confirmed that applying CFRP sheets in the circumferential direction can improve the axial load capacity of the CFST column. However, limited improvement in the moment capacity of CFST beam-columns was achieved by the circumferential wrapping of CFRP sheets. Since the moment capacity of the column is the main factor for strong column-weak beam criteria, enhancing the moment capacity of CFST columns using CFRP is still a concern for researchers. Recent studies have confirmed that the moment capacity of the CFST beam under pure bending was enhanced by applying the CFRP sheet in the longitudinal direction. The CFRP sheets applied in the longitudinal direction provide additional reinforcement to the tube tensile flange, which leads to increasing the flexural stiffness and moment capacity of the CFST beams. However, the behaviour of the CFST columns longitudinally strengthened with CFRP sheets has not been studied. Thus, the main objectives of this study (1) to investigate experimentally the axial load and moment capacity of square CFST columns strengthened with unidirectional CFRP sheets in longitudinal direction subjected to eccentric axial loading, (2) to identify finite element models based on the tested specimens, (3) to numerically study the influence of various parameters on the axial load and moment capacity of CFRP-strengthened square CFST columns, and (4) to develop a theoretical method to predict the axial load and moment capacity of the CFRP-strengthened CFST columns. Three specimens including a control specimen and two CFRP-strengthened specimens with 3 and 4 layers of CFRP were experimentally tested under eccentric axial loading. The results of the experimental tests were used to develop and verify FE models. A total of 156 FE models were developed using ABAQUS software to investigate the other parameters, which had not been studied in the experimental test, such as steel tube size, concrete strength, load eccentricity ratio, more layers of CFRP, and the percentage of the column web's depth wrapped with CFRP. It was concluded that the CFST columns achieved higher axial load and moment capacity when the number of CFRP layers increased. The predicted optimum number of CFRP layers is 4. The CFRP strengthening approach is more significant when the load eccentricity ratio is beyond 30%. Moreover, CFRP sheets was more efficient for the models with lower concrete strength. The increase in the ultimate axial loads and moments of the models is more significant when the CFST beam is wrapped up to 50% of the CFST section's depth with CFRP sheet. In addition, theoretical formulae were developed to predict the ultimate axial load and moment of the CFRP strengthened CFST columns. The results also showed that the average predicted axial and moment capacities of the models was 11% lower than those obtained from FE analysis, which confirmed the validity of the suggested theoretical formulae.,Ph.D.
Pages:	178
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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