Analysis For Seismic Performance Of Abnormal Joints With Variable Cross-Section Column And Column Effective Lengh In Steel Frame

Along with further use of steel structure and the development of large industrial buildings and high-rise civil buildings, abnormal joints arise at the historic moment. For abnormal joints, there are no specified formulas and construction measures in our country’s standard used right now, only relying on the engineering practical experience. In recent years, there are some researches about the seismic behavior of abnormal joints with variable cross-section beam, but the seismic behavior of abnormal joints with variable cross-section column remains to be studied.For this purpose,at first the article uses ANSYS to establish finite element model of abnormal joints and makes them compared with the test results to verify the rationality of the test results and the feasibility of finite element simulation. At the same time six stress paths are set up to analyze the stress distribution of abnormal joints. Then on the basis of experiment, a series of abnormal joints are established with axial compression ratio, intensity of steel, column height ratio as control parameters to study the three control parameters on the influence of the bearing capacity of abnormal joints. Besides, The steel intensity and column height ratio impacted on the bearing capacity of abnormal joints is considered, when the same vertical load is loaded on the top of column. The analysis of this part extends the influence of test control parameters.The paper also deduces the formula of equivalent stiffness for variable cross-section column in steel frame with abnormal joint, and amends the formula of effective length factor for the lateral steel frame column. Finally, the effective length factors of steel frame column with different column height ratios are compared, as well as standard effective length factor.Research shows that the finite element simulation analysis is accurate and effective, and the abnormal joint which is applicable to practical engineering has better seismic performance. The effect of control parameters on the bearing capacity of abnormal joints is that the bearing capacity of abnormal joint is reduced with the increase of axial compression ratio, and the bearing capacity of the column height ratios is not a linear relationship under the same axial compression ratio,also the declining value of bearing capacity of abnormal joints in high strength steel is much greater than the lower steel strength with the increase of axial compression ratio. Revised μ. of steel frame with abnormal joints and the corresponding corrected critical force P_cr is less different from standard calculated value,which can explain that irrespective of P-Δ effect,the overall stability analysis of lateral steel frame with abnormal joint about variable cross-section column can be directly analyzed according to the steel frame with common joint.