B. Ahmed

Prediction of initial stiffness and available rotation capacity of major axis composite flush endplate connections

Abstract Knowledge of the initial rotational stiffness of a connection is important for the global elastic analysis of frame structures. Based on a simple force transfer mechanism and consideration of the behaviour of individual components, a method has been developed to predict the initial stiffness of composite flush endplate connections. The approach is compatible with that proposed earlier to predict moment capacity for several types of composite connection. In order to apply plastic analysis to frame structures a knowledge of the available and the required rotation capacities is necessary. A simple technique to determine the available rotation capacity of composite flush endplates is described herein. Taken together, the two methods represent key steps in the development of an approach to predict the main measures of the behaviour of composite endplate connections. Used in conjunction with the moment capacity and failure mode prediction method developed earlier by the authors, they provide a complete representation of the design properties of composite flush endplate connections.

Unified classification system for beam-to-column connections

A new classification system for beam-to-column connections is proposed, in which the stiffness and strength characteristics of the connections are considered simultaneously. Using this method, it follows that a connection is classified into a unique category, thereby clarifying the position for design engineers. Since connection stiffness and strength are considered simultaneously, new terms have been proposed for defining the connection categories; these are: fully-connected, partially-connected, pin-connected and non-structural. Compared with the properties of the connected beam as well as the adjoining columns, a fully-connected connection should have high strength and high stiffness; a partially-connected connection has moderate strength and stiffness, a pin-connected connection has either low stiffness or low strength and non-structural connections are those that cannot meet either the strength or the stiffness or the ductility requirements for the other three types of connections. Numerical examples have been included which demonstrate the validity of this classification system. Its basis is that the overall performance of the frame at both the serviceability and ultimate limit states should closely accord with that predicted by the associated method of analysis; this is particularly important when either of the standard approaches assuming pinned or rigid connections is used.

Effect of high shear on the moment capacity of composite cruciform endplate connections

Abstract Present design approaches for determining the moment capacity of composite connections do not properly consider the influence of changes in the shear to moment ratio, although there is evidence from the few available tests that there is some effect. Through the use of simple mechanics equations are developed that can address the problem with reasonable accuracy. Finite element methods are used to verify the validity of the developed equations. Finally. a design method to predict the actual effect—in particular, the calculation of moment capacity in those situations for which changes to the shear to moment ratio become important—is presented. Use of the design method is illustrated by means of a worked example.

Modelling composite connection response

Publisher Summary This chapter discusses a finite element model to simulate the structural behavior of composite flush endplate beam to column connections. This model has been validated against test results and compared with a simplified calculation method; both checks demonstrate its accuracy. Parametric studies using the model to investigate variations in: reinforcement ratio, degree of shear connection and shear-span/moment ratio are also described. For successful numerical modeling of any composite connection the following items must be properly represented: reinforcement, shear studs (considering slip between the slab and the beam, and also the percentage of shear interaction provided), steel beam and column (including buckling and plasticity), bolts (including slip), separation and closure at the interface of the endplate and the column flange and load introduction.

Effect of column axial load on composite connection behaviour

Abstract The design methods currently available for composite joints do not allow for possible reductions in moment capacity due to the presence of axial load in the column. Using a previously validated FE model developed by the authors, joint behaviour under varying, levels of column axial load for both symmetric and non-symmetric joints has been studied. It was established that the level of column axial load does not significantly affect moment capacity for symmetric joints, whereas non-symmetric joints have their momen capacity reduced by the presence of high axial load in the column. The reason was found to be directly related to the type of failure of the non-symmetrically loaded joints, which is controlled by the effective resistance of the column web in shear. Both theoretica and FE results are then used to develop a design method for the non-symmetric joints that allows for the influence of a varying level of column axial load, including the beneficial effect of the possible presence of some level of moment on the other side of the connection. The method is illustrated by worked examples.

Design of composite finplate and angle cleated connections

Abstract A design method for composite finplate and angle cleated connections is described. The method covers both symmetric and non-symmetric connections and allows for the presence of axial compression in the column. It is similar to that developed by the authors for flush endplate connections. Verification against all available test results demonstrates the methods ability to accurately predict the moment capacity of finplate and angle cleated connections. A worked example for the angle cleated connection is used to illustrate the methods application.