09-10-2014, 02:36 PM
The secondary effects due to axial load in the design of frame columns are incorporated through additional moments estimated using their effective lengths. The current design methods to account for the secondary effects are based on various assumptions which may not even be realized in practice. A recent study to identify the critical parameters that are omitted, or incorrectly considered, in the current design methods has also proposed a simple yet general method for determining the effective length of frame members. In the current study, this method is improved and extended to include the effect of shear deformations. Further, simplified closed-form implicit expressions is provided which can be directly coded in a computer program. Convenient design charts are proposed for elastic-end restraints to calculate the effective length factor. Approximate explicit expressions for effective length factors are also provided. A closed-form expression for moment modification factor which also takes into account the shear deformations is provided. The effect of shear deformations