Behavior And Modeling Of Semi Rigid Steel Beam To Column Connections.

In most steel frame designs the beam to column connections are assumed to be rigid orrnpinned. Rigid joints, where no relative rotation occurs between the connected members,rntransfer not only substantial bending moments, but also shear and axial forces. On thernother extreme, pinned joints are characterized by almost free rotation movement betweenrnthe connected elements that prevent the transmission of bending moments. Despite thesernfacts, the great majority of joints doesn’t exhibit such idealized behavior.rnA substantial effort has been made in recent years to characterize the behavior of semirnrigid connections. Most design codes included methods and formulas to determine bothrntheir resistance and stiffness. EC3 and EC4, for instance, allow the use of springs attachedrnto the end of the beams at both sides of the joints. In order to account for the panel shearrndeformation the code allows the use of interaction parameter, called the β factor. Butrnsince the definition of the β factor implies an approximation of internal forces at thernjoint, it requires an iterative process at the time of the global analysis of the structure.rnIn order to avoid this iterative process various researchers proposed new elementsrnaccounting for various deformation modes of the connections. Although the new proposedrnelement by Bayo et.al accurately characterizes the behavior of semi-rigid connectionsrnbased on the EC component method it is not appropriate to use in commonly availablernsoftware.rnIn this thesis a new component-based two-node-connection element is proposed. By usingrnthe proposed two-node element the static and dynamic response behaviors of a semi-rigidrnframe as compared to a rigid frame of the same geometry and cross section are studiedrnusing a general purpose finite element package ANSYS.rnThe study showed that connection flexibility tends to increase vibration periods and hencernreduces the internal stresses due to a given earthquake action in the frame elements asrncompared to those in rigid frames.rn12rnCHAPTER ONErn1.1. INTRODUCTIONrnTraditionally, steel frame design assumes that beam-to-column joints are rigid or pinned.rnRigid joints, where no relative rotations occur between the connected members, transferrnnot only substantial bending moments, but also shear and axial forces. On the otherrnextreme, pinned joints are characterized by almost free rotation movement between thernconnected elements that prevents the transmission of bending moments. Despite thesernfacts, it is largely recognized that the great majority of joints doesn’t exhibit suchrnidealized behavior. This is explained by the fact that in semi – rigid frames the internalrnforce distributions, lateral displacement magnitudes, collapse modes are functions of jointrnflexibility.rnExtensive studies have been carried out over the past twenty five years to estimate thernactual behavior of such joints. Innumerable studies have been produced on composite andrnsteel semi-rigid connections, covering the state of the art [1], numerical studies andrnexperimental tests [2 - 8].rnThe fundamental results of these investigations led to code specifications that providedrnstructural engineers with adequate procedures to evaluate the moment rotationrncharacteristics of semi rigid connections. A good example of this new design trend isrnavailable in Eurocode3 [17]. Despite the substantial increase in structural designrnknowledge, the semi-rigid connection design is still facing resistance from structuralrnengineers. This is explained by:rn1. Lack of detailed information on the advantages of semi-rigid design philosophy.rnSemi-rigid frame design has many advantages. These include:rna. Economy

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