Effective Length Estimation for RC Column

Abstract

For stability of any structure, vertical elements and its connections are of prime importance. Vertical elements are categorized as compression member and are principally undergoes buckling failure. Buckling analysis conducted to understand behaviour of the frame warrants effective length of column. Thus, design of the frame in any structure is conducted based on effective length factor of the column. Wood's charts are most widely used in adopted, around the world, to estimate effective length of member in design practices alongside codal stipulation. However, effective length factor is mostly as a geometric property even though many other factors do influence it. Thus, it is important to study effective length estimation in detail and impact on design parameters. In the present study, major focus is on various method to determine effective length of column in the frame. Besides for the frame study is carried out to estimate effective length factor 'k' using Wood's chart and following codal stipulation of IS: 456-2000. Effective length factor 'k' is estimated using commercial software Etabs using P-Δ analysis as well as without P-Δ analysis to realize the impact of later analysis while first analysis one mostly need in design practice leading to non-sway frame mechanism and restricting the value of effective length factor k as a unity. In the last phase of the study, impact of effective length factor on design parameter like axial force, bending moment, percentage of steel in additional to stiffness ratio, slenderness ratio are studied. It has been found that use of P-Δ analysis during design of structure requires careful consideration. Effective length factor is not a geometric parameter alone, but it is affected by various parameters as well as behaviour of whole structure.