Research On The Material Design Of Square Expansive Concrete-Filled Steel Tubular Members

Square concrete-filled steel tube (SCFT) with simple structure nodes is more suitable to bear bending press, because of large section inertia moment. The SCFT has more excellent integrate properties. But compared with circle concrete-filled steel tubes, the core concrete of SCFTs have lower reinforcement effect. In order to solve this problem, filling expansive concrete in square steel tube is a better way to form a composite structure. The core concrete of this structure form has high density. And the steel tube provides lateral stress at initial period to make up the defect that constraining force comes up too late.First the effect of expansive agent addition on the material properties of moderate-strength and high-strength expansive concrete is studied. The results indicate that there are some different properties between moderate-strength and high-strength concrete. But in common there is a reasonable expansive agent scale to make expansive rate and compressive strength develop with coordination.Second, according to the results above, the basic mixture ratio of moderate-strength and high-strength concrete is decided. And the stub, square expansive concrete-filled steel tube columns are prepared to do axial compression experiments. The effects of expansion addition and steel ratio on specimens are researched by measuring extreme strength and load-strain curve. At last an excellent composite material used for square expansive concrete-filled steel tube is discussed.The results show that adding expansive agent could increase the bearing capacity of square moderate-strength and high-strength expansive...