Issue 46

W. Hao et alii, Frattura ed Integrità Strutturale, 46 (2018) 391-399; DOI: 10.3221/IGF-ESIS.46.36 393 specimens (a round hole was reserved in the cover plate at one end for pouring of RPC), and the prepared RPC was poured into the steel tubes, the experiment was carried out after natural curing for 28 days. Fig. 1 is the specimen of square steel tube. Specimen No. Steel tube wall thickness t/mm Eccentricity e/mm Length of specimen L/mm Slenderness ratio λ Steel ratio α Confinement coefficient ξ 1 3 20 300 10.39 0.11 0.65 2 3 20 600 20.78 0.11 0.65 3 3 20 800 27.71 0.11 0.65 4 3 20 1000 34.64 0.11 0.65 5 4 20 1000 34.64 0.17 0.92 6 5 20 1000 34.64 0.22 1.13 7 3 40 300 10.39 0.11 0.65 8 3 40 600 20.78 0.11 0.65 9 3 40 800 27.71 0.11 0.65 10 3 40 1000 34.64 0.11 0.65 11 4 40 1000 34.64 0.17 0.92 12 5 40 1000 34.64 0.22 1.13 Table 4: Parameters of the Specimens. Figure 1: Specimen of the square steel tube. Figure 2: Experimental set. Experimental equipment The experiment was carried out using a 500t hydraulic servo pressure- testing -machine to load pressure, a DH3818 static strain meter to collect experiment data, an electronic displacement meter to measure the lateral displacements of the specimens, and electronic strain gages pasted in the longitudinal and lateral positions at the mid-span of the specimens to measure the strains of the specimens. The experimental set is shown in Fig. 2. E XPERIMENTAL RESULTS Failure forms of the specimens hrough experimental observations, it was found that the appearances of the RPC filled square steel tubular specimens did not change much until the ultimate load was reached. As the deformation of column gradually increased, the bearing capacity gradually decreased. When the bearing capacity of the column dropped to 95%-85% of the ultimate bearing capacity, the square steel tube showed obvious bending, and the lateral displacement in the mid-span T