Study On The Seismic Behavior Of Diaphragm-through Connection Between Box Column And I-beam In Steel Frames

Joint in the steel structure is the key part of the communication of horizontal andvertical component. Safely and reliably designed joint is of great importance to thestructure to form an effective lateral system. Box cross-section column is commonly usedfor its bi-axial equal stability in plane and high tensional stiffness. It is more suitable forbidirectional lateral resistance steel structure framework compared with the H sectioncolumn. Steel frames composited by box columns and I beams is becoming a new trend.Test and finite element analysis on the connection are carried out to investigate theinfluence of the extend length and the thickness of diaphragm on the mechanical property ofjoint. Analysis is also made to get the reasonable value range of the parameters. Four specimensare fabricated respectively. The diaphragm thickness of JD1and JD2is8mm but the extendedlength of them is25mm and50mm respectively. Meanwhile, the diaphragm thickness of JD3and JD4is10mm but the extended length of them is25mm and50mm respectively. Theperformance of steel structure connection with box section column and H beam is analyzedbased on the low cyclic loading test. Through the analysis of test data, hysteretic behavior, load-carrying capacity, energy dissipation, the rule of strength and the stiffness degradation areanalyzed. The general finite element software ANSYS is used to establish eight finite elementmodels. Four of the models are the same as the one used in test, another four with theconsideration of the difference of axial pressure ratio. Geometric nonlinear and materialnonlinear are also considered to simulate pseudo-static test so as to illustrate the mechanicalproperties of joint under low cycle load and the stress distribution of them. Comparativeanalysis shows that the finite elements results can well coincide with the test result.Test and finite element analysis results show that the steel structure of box sectioncolumn and beam of rigid connection by bolts has good seismic performance and the force transmission is clear. The degradation of bearing capacity and stiffness is steady andductility coefficient is not less than3.The viscous damping coefficient ranges from0.161to0.215. Diaphragm is a major force transmission parts which has a significant impact onmechanical properties of connection. With diaphragm thickness increased by8mm to10mm, the node’s load improved by about30%.But when the extended length increased from25mm to50mm, the bearing capacity of the connection only rose by6%.The outer partof the extended diaphragm is always in a low stress state. It is unnecessary to design theconnection with large extended diaphragm, which may also takes up architectural space.Axial pressure ratio has little effect on the performance of the joint. As is shown in thisstudy, the thickness should be enough and it is recommended be larger than the thicknessof the flange of beam to ensure the reliability of the connection. The increase of extendedlength of diaphragm can be help to the capacity of joint with smaller degree. To avoid weldheat affected zone, the extended length designed more than25mm is reasonable but not toomuch. The section of diaphragm weakened by the bolt hole is supposed to the higheststress level and its strength should be ensured.