Evaluati̇on of reducti̇on i̇n web of beams on performance and capaci̇ty of thei̇r connecti̇ons to columns

Following the Northridge Earthquake (1994) and subsequent extensive research, various types of connections were examined so as to optimize their capacities and strengths. One of the results of these investigations was invention of reduced web/flange section connections. In reduced beam section (RBS) connections a local decrease in the beam section near the column reduces concentration of stress on the connection. As a result, the point of formation of the plastic joint is moved from the connection to a beam section near the column. In the present research, a finite element parametric analysis was carried out on a type of RBS connection with a locally reduced web section. In this state, shears are created locally on the web at a very slight distance from the column side on the beam section to reduce the beam's bending capacity at the site. Consequently, a plastic joint is created inside the beam away from the beam column connection and failure at the connection and the welded beam-column flange is prevented. The objective of the present research was to conduct a parametric analysis on a new type of reduced connection. This connection is in the form of a beam with shears on its web. One of the advantages of this new form as compared to the reduced beam flange form is that it increases plasticity of the section and its compression. In this state, due to the considerable torsional stiffness of the beam, the section shows more resistance to torsional lateral buckling. In this investigation, the advantages and disadvantages of this connection as well as its behavior under reciprocating, seismic, and statistic loadings were examined. To this end, step-wise changes were made to the local shearing parameters of the beam to create the connection. The variation in the connection performance caused by variations in the shearing records applied to the connection was also depicted by diagrams and assessed. For this purpose, first a mid-rise structure with a special steel moment frame and characteristic acceleration of the records was exposed to time history analysis. Afterwards, the laboratory setup of the frame connections, which properly represents their performance in a building frame (i.e. the connection site and half of the beam and column connected to it) was modeled in ABAQUS and was analyzed through a time history analysis of the shearing in the frame floor holding the connection. In addition, the capacity curve and cyclic loading curve for this connection were prepared to determine the connection's performance levels. First, the performance levels of the connection were determined using a proper criterion with regard to connection failure. Afterwards, failure curves were obtained based on the performance levels determined for the connection. The resulting failure curves were compared to the connection's rotation moment curve and cyclic loading curve, which were obtained under nonlinear static loading and cyclic loading. The connection under study demonstrated satisfactory performance in keeping the plastic joint away from the connection, and it also showed high levels of ductility, high energy loss, and satisfactory strength. Keywords:RBS , Northridge Earthquake , Buıldıng frame , plastic joint , Hıgh energy spend