Experimental Research On Bond Performance Of Concrete Filled Square Steel Tube

The bond between the steel tube and concrete is the main topic of concrete filled square steel tube; the research in this area has great theoretical significance. Most of research results already have established on push-out test and the main purpose is to determine the interfacial bonding strength, while concrete and steel tube bear load together in the actual project. Three forms of bond state were designed for studying the bond performance between the steel tube and concrete.This paper analyzed the influence of the bond performance on bearing capacity of the concrete filled square steel tube stub column; based on experimental study, nonlinear finite element analysis was carried out. The experimental results were compared with the design specification for the design theory and design considerations.1. Experimental study on axial load capacities of concrete filled square tubular stub columns. Three forms of bond state were designed for research in bear capacity and damage character by setting oiled plastic between concrete and steel tube. Testing result shows that bear capacity and damage character of different specimen is very similar, the difference is very small.2. Experimental study on interfacial bonding strength of concrete filled square tubular stub columns. This paper analyzed bond mechanism between steel tube and concrete. Based on the bond mechanism, critical bond strength was researched. Testing result shows that strain and load is small and ruleless when stress difference between steel tube and concrete achieves the critical bond strength.3. Derivation ultimate bearing capacity. The force between steel tube and concrete is uneven, mechanical model was reduced; the bear capacity of concrete filled square tubular stub columns with different interfacial bond state was investigated based on limit equilibrium theory; it assumed that the steel tube was connected with concrete always for Fujian construction standards " Technical Specification for Concrete Filled Steel Tube Structures" DBJ13-51-2003, while it does not consider the bond strength between the steel tube and concrete for Architectural Institute of Japan "Structural Design and Construction Guidelines for Concrete Filled Steel Tube Structures " AIJ (1997) . Research result shows that the bear capacity of specimens with different interfacial bond status is close basically.4. Nonlinear Finite Element Method (FEM) analysis of axial load capacities of concrete filled square tubular stub columns with different interfacial bond status. Based on the experimental testing, the theoretical analysis using commercial software ANSYS for concrete filled square tubular stub columns is carried out.The curve of theoretical calculation was drawed and comparered with curve of test. Result shows, combined with the theoretical research achievement from this paper, ideal effect have been obtained by using the computer simulation for the course of testing.