No abstract

L-shaped concrete-filled steel hollow-section (CFSHS) columns have the potential to be widely used as corner columns, and have the advantage of creating larger usable areas in buildings. However, few experimental tests of this kind of column under diagonal cyclic loading have been reported. Tests on eight L-shaped CFSHS columns with equal legs were conducted to study their hysteretic behaviour; the test variables were: loading angle, concrete compressive strength, axial load level and presence or absence of stiffeners. The failure process and modes, stiffness degradation, ductility and energy dissipation were observed, and lateral load–displacement hysteretic curves and envelope curves were plotted. The results show that L-shaped CFSHS columns have generally good hysteretic behaviour and that the displacement ductility coefficients are in excess of 3 in most cases. Columns with a loading angle of 45° have >10% decrease in ultimate strength but a slightly higher ductility than columns with a loading angle of 0°. The ultimate strength, ductility and energy dissipation of columns all decrease with increasing axial load levels. Discontinuously welded stiffeners can improve the ultimate strength and ductility, but the amplitude is limited. Finally, a finite-element model was developed; the predicted results agree well with the test results.

In order to study the seismic performance of recycled steel tubular columns, four round steel tube recycled concrete columns were designed and fabricated, and low-cycle reciprocating tests were carried out. Considering the two parameters of regenerative coarse aggregate replacement rate and axial compression ratio, the whole process and failure mode of the specimen were observed, and the hysteresis curve, skeleton curve and stiffness degradation of the specimen were analyzed. The experimental results show that the failure process and failure modes of the recycled steel tubular columns are similar to those of ordinary circular steel tubular columns. The main performance is the drum bending of the steel pipe at the root of the test piece; the hysteresis curve of the test piece is full, and the replacement ratio of coarse aggregate is opposite. The hysteresis curve of the specimen has little effect, and the axial compression ratio has a great influence on the shape of the hysteresis curve, the skeleton curve, and the stiffness degradation. The recycled steel tubular column has good seismic performance.

In order to study the compressive performance of circular steel tube recycled concrete columns, four circular steel tube recycled concrete columns are designed and manufactured, and subjected to a monotonic static compression test. Consider the eccentricity and the slenderness ratio, this paper observes the whole process of the specimen and the failure mode, and analyses the ultimate bearing capacity, deformation curve, load-deformation relationship, and load-strain relationship. The experimental research shows that the failure process and failure mode of the round steel tube recycled concrete column are similar to those of the ordinary round steel tube concrete column. Similarly, the bearing capacity of the test piece decreases with the increase of the slenderness ratio and eccentricity, and the ultimate failure form is mainly the overall instability failure.