Experimental and analytical investigation of vanadium micro-alloyed concrete-filled tube-concrete footing connections: Fid-Bau Portal

Experimental and analytical investigation of vanadium micro-alloyed concrete-filled tube-concrete footing connections

Kingsley, A.M. / Williams, T.S. / Lehman, D.E. / Roeder, C.W.

Use of high-strength steel structural members can reduce the material required for a given quantity of resistance. However, reduced sections can be susceptible to local instability and result in increased deflections. In concrete-filled tube (CFT) columns, the full tensile strength of the steel can utilized because the concrete fill restrains buckling of the tube and reduces member deflections. An ongoing research study was initiated to develop reliable connections for CFT columns constructed using for high-strength, vanadium micro-alloyed steel (CFVST) columns. The current research investigates the performance and constructability of embedded-type CFVST column-concrete footing connections. The experimental results indicate that the connection contributes significantly to the global response. To verify the results, nonlinear finite element models were developed, which included material nonlinearities and damage to the concrete in the footing and joint. The analytical and experimental results were used to develop preliminary recommendations for analysis and design of CFT column-to-footing connections. An analytical model which can accurately predict the nonlinear response of the experimental connections is a valuable tool in assessing and developing design recommendations for an adequate column-footing connection. The inelastic finite element studies performed provided adequate qualitative predictions of the experimental connection behavior and progression of damage. However, the accuracy of the numerical results in predicting the full experimental response is still under investigation. The current test series represent a limited study regarding the relationship between the D/t ratio, the steel strength and the required embedment depth ratio. Because these parameters determine the tension force demand, which in part determines the embedment length requirements, a thorough study of these parameters is required.