Research On The Ultimate Load Capacity Of Tubular N-joint

Tubular intersection joint is an important joint in tubular structure. It has many advantages, such as saving the steels, having a large load capacity and so on. At present, the theory on plane circular tubular joints is mature, and there are also some specifications in the code. However, due to little research and experiments focusing on N-joint, it is necessary to do specific research on the ultimate load capacity of N-joint.This experimental research focused on the ultimate load capacity and the reinforcing method of N-joint. We studied the performance and failure modes of four N-joints under static load by both test and finite element method. The finite element method is proved to be accurate according to the comparison between test results and theory analysis results. So the ultimate load capacity of large-scale model is also studied by finite element method. At last, a formula is summarized according to a large number of analysis results to solve some real program problem.Based on the analysis of the test result and theory calculation result, the conclusion is shown as follows: (1) N-joint has good plastic performance and deformation under the static load, and its ultimate load capacity in experiment is much larger than the result calculated by the code. (2) Both the concrete and the planner welded in the chord member in tubular joints will greatly increase the ultimate load capacity of joints. (3) The ultimate load capacity of the N-joints is pertinent to their failure modes, which are greatly influenced by the different load case. (4) The finite element method is effective to analyze the ultimate load capacity of tubular N-joint. (5) The formula of ultimate load capacity of N-joints based on our research can be widely used because it is quite consistent with the test and theory analysis results.