Prediction of the plastic hinge length for square CFST stocky columns: Fid-Bau Portal

Prediction of the plastic hinge length for square CFST stocky columns

Jin, Liu / Liang, Jian / Chen, Fengjuan / Li, Dong / Du, Xiuli

Abstract This paper addresses the problem of plastic hinge length in the evaluation of ductility performance of square concrete filled steel tubular (CFST) column that was largely used in earthquake-resistant structures. Physical tests were conducted on a series of square CFST stocky columns having different cross-section widths ( $B = 200 mm \sim 800 mm$ ). The curvatures of each column were measured, serving as the basic building blocks for establishing the linkage between the plastic hinge length and the cross-section width. From the experiments, it was found that the failure region of all columns is concentrated in the bottom of the CFST columns, which is located in the plastic hinge region. The plastic hinge length of square CFST stocky column increases linearly with the increase of the cross-section width. Meantime, an analytical approach is developed based on the equivalent plastic hinge model and cross-section analysis, by which the analytical formulas of plastic hinge length were proposed. The important parameters involving axial ratio, strengths of concrete and steel plate, slenderness ratio as well as the width-to-thickness ratio on the plastic hinge length of square CFST column were studied. The results indicate that the plastic hinge length tends to increase with the increase of the axial load ratio, however, decreases with the increase of the aspect ratio and the compressive strength of concrete. No significant effects of the width-to-thickness ratio and the steel strength were found on the plastic hinge length of the square CFST column.

Highlights • Experimental tests on square CFST column with different cross-section widths subjected to constant axial and cyclic lateral loading were performed. • The plastic hinge length of square CFST column was measured and analyzed. • An analytical approach for evaluating the plastic hinge length of square CFST column was established based on the equivalent plastic hinge model and cross-section analysis. • A systematic parametric study was carried out for the identification of key parameters in the evaluation of plastic hinge length of square CFST column.