ANALYSIS OF STEEL BEAM-TO-COLUMN MOMENT CONNECTIONS
Abstract
Research investigations of structural steel Beam-To-Column moment connections have been presented in this dissertation. An analytical study of both beam-to-column flange connections as well as web connections is carried out. Results of tests carried out at Lehigh University are used as a bench mark to validate the analytical procedure. A finite element formulation has been used extensively in this study. An analytical procedure involves modelling of connection using finite element technique for predicting the behavior of the connection. A NONlinear Structural Analysis Program (NONSAP) is used for the analysis purpose. For flange moment connections, full scale assembly has been considered for the study and is modelled with the help of 2-dimensional isoparametric finite elements in the planes of the webs of beams and column. Type of web connections considered in this study is unsymmetrical connection where there is only a beam on one side of the column. The flange connection plate which is used to join beam flange and column has been isolated with suitable free body and is modelled with 2-dimensional isoparametric elements in the plane of the beam flange. In case of flange moment connections, an analytical procedure has been developed to predict the overall behavior of the connections. Connections studied herein are having details of fully welded, only flange welded, and fully bolted moment connections. In case of fully bolted connections, bolts are modelled with suitable bar elements. Calibration of finite element model of bolted joint was carried out using pilot test on the same joint to justify the model. Analysis results of load-deflection behavior, the stress distribution in the panel zone, and spread of yield zones at different stages of loading were compared with test results. It is shown that the connection behavior can be predicted analytically. In case of web moment connections, the flange connection plate area is analyzed with the help of nonlinear finite element method taking suitable free body out of the connection assemblage. Three different hypothetical beam-to-column assemblages are used representing the one used in lower stories, middle stories and higher stories of a multi story frame for the analysis purposes. In this type of connection, failure will occur at the junction of beam flange and flange connection plate. The high stress concentration occurs at this notch and fracture starts at the notch. The fracture criteria are proposed to determine the place of the fracture and the direction of the crack. The design guidelines are presented for the design of flange connection plate. Through the study of stress distribution in flange connection plate, the weld required to join flange connection plate to the column can be determined. It is proposed that for a connection having the ratio of beam flange width to the column depth higher than 0.8, the flange connection plate need not be welded to the column web for the full length but the weld of 30 to 40% of the length of column web depth in the middle of column web depth is sufficient. For connection having the ratio of beam flange width to the column depth less than 0.8, the connection strength can be achieved without welding flange connection plate to the column web. However tack welding may be needed to maintain stiffness of the connection intact.
Degree
Ph.D.
Subject Area
Civil engineering
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