Issue 46

W. Hao et alii, Frattura ed Integrità Strutturale, 46 (2018) 391-399; DOI: 10.3221/IGF-ESIS.46.36 394 was also getting larger. Before the specimen failed, usually it was the pressure side that showed bending first and the final failure form was the local bending deformation of the steel tube. The failure forms of the specimens are shown in Fig. 3. Figure 3: Failure forms of specimens. When the slenderness ratios and eccentricities of the specimens were the same, if the steel ratios were different, the bent parts would also be different. For example, when the steel ratio α=0.11, the bent part of the RPC filled square steel tubular column was about 1/10 of the length from the top of the column; and when the steel ratio α=0.22, the bent part of the specimen was almost close to the mid-span of the specimen. This was because when the eccentrically loaded column was being compressed, the bending was extended from its two ends to the middle. The larger the steel ratio, the stronger the deformation resistance of the specimen is. Load-displacement curves of specimens Fig.4 shows the load-span lateral displacement curves of the specimens. It can be seen that the load-displacement curves of the RPC filled square steel tubular specimens can be roughly divided into three stages: the linear elastic stage, the elastic- plastic stage and the descending stage. In the linear elastic stage, the load-displacement curve of the column is basically linear. The descending section of the curve is relatively flat, which shows that the specimen had good ductility and ability to maintain load in the later stage. As the slenderness ratio and eccentricity of the specimen increased, the ultimate bearing capacity of the column was gradually decreased, and the lateral displacement was increased gradually. When the eccentricity e=40mm, for a RPC filled square steel tubular column with a slenderness ratio of λ=10.39, 20.78, 27.71 and 34.64, the ultimate bearing capacity was 480kN, 450kN, 410kN and 382kN, respectively. When the eccentricity e=20mm, for a RPC filled square steel tubular column with a slenderness ratio of λ=10.39, 20.78, 27.71 and 34.64, the ultimate bearing capacity was 708kN, 694kN, 573kN and 588kN, respectively. The steel ratio and the confinement coefficient also had great effects on the ultimate bearing capacity and mid-span lateral displacement of the specimen. When the confinement coefficient ξ=0.65, 0.92 and 1.13, under the load with an eccentricity of e=40mm, the bearing capacity of the specimen was 382kN,