Study On Effective Length Coefficient Of Three-stepped Columns In Semi-rigid Connection Gabled Portal Rigid Frames

The beam-to-column connection is an important complicated content in the steel framedesign. The reliability and effectiveness of connection has very important effect on the wholeframe behavior. In traditional steel frame analysis, the behavior of beam-to-columnconnections is usually treated as either pinned or rigid joints. In fact, its behavior is betweenthe two situations, it’s called semi-rigid connection. It’s unsafe if the connection is assumedfully rigid one; also, the beneficial effect would be neglected if assumed absolutely pinconnection. So the special character of semi-rigid connection has become a popular subject ofstudy in recent years, attracted the attention of both domestic and foreign researchers.As the processing technology becomes more complex, the industrial workshop,whichassembles three-order crane has been used in industrial buildings more and more. Thecode(GB50017-2003)and(CECS102:2002) do not provide the calculation ways of theeffective length coefficient of three-stepped columns, then there was no standard code forcivil engineers when they designed this kind of industrial buildings, so its use was limted.Based on the research of the former scholar, the effective length coefficient ofthree-stepped columns in portal semi-rigid frames was analyzed systematically by the ways oftheoretical formula and numerical methods, some useful conclusion and new ideas wereobtained. The main work and conclusions are as follows:First, the characteristic﹑development and code in several countries of semi-rigidconnection were introduced. The moment and rotation angle relationship of semi-rigidconnection was nonlinear and it was usually researched by establishing function model anddatabase. Obtaining accurate value of initial rotational stiffness has great significance, bycomparison, an integrated approach which included several factors was obtained.Second, several FE-programe elements related to portal rigid frame model wereintroduced, the portal rigid frame model whose beam-to-column connections were pinned﹑semi-rigid﹑fully rigid was established by ANSYS programe, the internal force of rigidframe was obtained with different rotational stiffness, it was changed with the rotationalstiffness of semi-rigid connections and the reasons were analyzed. The structural stabilitytheory related to FE was introduced, including the establishment of stable characteristicequation and the derivation process of semi-rigid element stiffness matrix. Several mainfactors about effective length coefficient of rigid frame column were proposed, it could becalculated newly refering to linear rigidity ratio of beam and column, the result was that buckling analysis of portal rigid frames of three-stepped columns could be solved by ANSYSappropriately. The effective length coefficient of three-stepped columns in rigid frame whichhad tapered beams or semi-rigid connections was obtained by ANSYS. the result was thatthese two factors could make the coefficient increase.Third, depending on a practical example, the effective length coefficient of three-steppedcolumns in rigid frame which had tapered beams﹑semi-rigid connections and linear rigidityratio of beam and column was obtained, in contrast to the result gained through traditionalmethods,the error could not be negligible, so more attention should be paid to in structuraldesigning.Finally, the dissertation put forward the limitations, and pointed out the research focusand following work to be done.