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Glass fiber‐reinforced plastics (GFRP) tube‐concrete‐steel tube double‐skin tubular beam (DSTB) is composed of an outer GFRP tube and an inner steel tube, with concrete sandwiched between two tubes. It possesses numerous advantages, including excellent ductility and corrosion resistance, lightweight, and convenient construction. Current research on DSTBs is primarily focused on the GFRP tube with an approximate ±90° fiber angle (the angle between the fiber direction and the longitudinal axis of DSTB). An experimental study on DSTBs with ±45°, ±56°, ±68°, and ±80° fiber angles was conducted under bending load. Experimental results show that the ultimate bearing capacity and deformation ability of DSTBs increases with the increase of fiber angle, the ultimate moment capacity of DSTBs with ±56°, ±68°, and ±80° fiber angles were 2.61%, 6.69%, and 6.74% higher than that of DSTB with ±45° fiber angle, respectively, the deformation ability of DSTBs with ±56°, ±68°, and ±80° fiber angles were 23.03%, 32.04%, and 38.48% higher than that of DSTB with ±45° fiber angle, respectively. However, the cracking strain decreases with the increase of fiber angle. [ABSTRACT FROM AUTHOR]

Elliptical concrete-filled steel tubular (CFST) column is a new form of CFST columns, consisting of an outer elliptical tube filled with concrete. Although the study on mechanical performance of the elliptical CFST members is receiving more and more attention, they have been limited to static behavior. Against this background, an experimental study on elliptical CFST columns was carried out under combined axial compression and cyclic lateral loading. The failure modes, hysteretic curves, skeleton curves, load carrying capacity, deformability, stiffness degradation, and energy dissipation ability was obtained and discussed. The test results indicated that the elliptical CFST columns possess excellent seismic performance and ductility. Valuable experimental data were provided for the formulation of the theoretical hysteresis model of the elliptical CFST columns. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubular columns are widely used in structural systems, and elliptical concrete-filled steel tubular columns are receiving more and more attention. An experimental study on cold-formed elliptical concrete-filled steel tubular stub columns was carried out under monotonic and cyclic axial compression. The failure modes, axial load–displacement curves, ultimate loads, hoop strain–axial strain behavior, strength deterioration, and residual deformation were obtained and discussed. Complementary finite element models considering the complex non-uniform confinement between steel tube and concrete were developed and validated by experimental results. Then, the validated FE model was used to study the influence of aspect ratio, yield strength of steel, and compressive strength of concrete on the axial capacity of elliptical concrete-filled steel tubular stub columns. Finally, a relatively simple superposition method was put forward to predict the axial bearing capacity of elliptical concrete-filled steel tubular stub columns. Compared with the test data, both the numerical method and superposition method can generate accurate predictions. [ABSTRACT FROM AUTHOR]