Research On The Mechanical Performance Of The Joint In Combination SRC-Steel Truss Web Members

Concrete Filled Steel Tubular (CFST) K-joint with outside steel reinforce concrete in chord is called the joint of SRC-Steel Truss Web Members (The chords with steel reinforced concrete is also called CFST combined column). In order to understand the combination joints mechanical perfomentce, the difference of mechanical performance between CFST-K joints and combination joints, the position factor (ratio of chord diameter and concrete thick) was regarded as the main parameter of this paper, peeling load of outside concrete and joint ultimate bearing capacity were chosen as the research object, the experimental researches and FEM analysis of joints were conducted, the reasonable value of position factor and the formula of bearing capacity were carried out. The main works and conclusions are listed as follows:(1)Comparative trial between CFST-K joint and combination joint was conducted. The results show that, as the same premise of web-chord diameter, the last failure mode of the combination joint is similar to the CFST K-joint after outside concrete was cracked, and the combination joint bearing capacity is littler more of CFST K-joint, the efficiency increases about 5.8%.(2) Based on the position factor, the experiments of combination joints were conducted. The results show that the change of position factor can influence the first-crack load and peeling load, the outside concrete first-crack load and peeling load is smaller as the position factor is bigger, and failure model of combination joint is the CFST K-joint failure model after the outside concrete was cracking.(3) The finite element model of combination joints are established by ABAQUS software, the finite element model is correct through the verification with experimental results; the model was used to do more parameter analysis. The results show that position factor, ratio of stirrup reinforcement ratio, length of stirrup encryption area and outside concrete strength have major impact on peeling load, while they have little influence on joint bearing capacity; ultimate bearing capacity of the combination joint is affected mainly by web-chord diameter.(4) Based on these researches, suggestive value of position factor (about 0.50) in combination joint was put forward through the FEM parametric analysis with the aim of optimizing the peeling load. Based on the existing calculation formula of CFST K-joint, the calculation method of ultimate bearing capacity of the combination joint was proposed. Finally, based on the existing specification, test and FEM calculation results, the construction suggestion of the joint was presented.