Approximate Uniaxial Interaction Diagram For Slender Column Using Second Order Formula From Ebcs2, 1995

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2012-04

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Addis Ababa University

Abstract

In concrete buildings, recently the design of column is increasingly determined by architectural, aesthetic, and economic criteria leading to slender cross-sections of columns. However, slender column design requires rigorous analysis to account second order effect due to deflection of the column. Because the deflection provides additional eccentricity to axial load that induces additional second order moment. If second order effect is not considered adequately, it can cause stability failure, which is catastrophic. Since exact rigorous analysis demands more computational effort, simplified methods have been proposed in building codes such as EBCS_2, 1995, CEB_FIP1990 and ACI code still that involves iterative procedure. Moreover, even recently developed commercial computer programmes such as ETABS and SAP2000 do not consider second order effects due to the deflection of the column between its ends adequately as compared to relative deflection between ends of columns. In this thesis, approximate uniaxial P_M interaction diagram for non-sway slender RC rectangular column is presented based on the simplified method of EBCS_2, 1995-second order eccentricity formula (deflection between two ends of a column) which is rather simple and unsophisticated for design of slender column. For the preparation of the interaction diagram, cross section interaction diagram and column slenderness is used. Since the slender column capacity is smaller than short column capacity, the cross section interaction diagram is modified so that it would have a room for the slenderness effect. This is made by deducting additional moment due to second order and geometric imperfection eccentricity from cross section interaction diagram. Finally, the approximate interaction diagram is checked for its validity and satisfactory result is obtained. Therefore, the interaction diagram can be used as a design aid as well as preliminary cross section capacity estimation since it is very easy and quick method. Moreover, it can be used for checking of computer output

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Formula; from ;Ebcs2

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