Chapter 8 Long/Slender Columns PDF

LONG/SLENDER COLUMNS CHAPTER 8  CHAPTER 8: LONG/SLENDER COLUMNS 8.0 NOTATIONS AND SYMBOLS  CHAPTER 8: LONG/SLENDER COLUMNS 8.0 NOTATIONS AND SYMBOLS  CHAPTER 8: LONG/SLENDER COLUMNS 8.1 INTRODUCTION  A column is said to be slender...

LONG/SLENDER COLUMNS CHAPTER 8  CHAPTER 8: LONG/SLENDER COLUMNS 8.0 NOTATIONS AND SYMBOLS  CHAPTER 8: LONG/SLENDER COLUMNS 8.0 NOTATIONS AND SYMBOLS  CHAPTER 8: LONG/SLENDER COLUMNS 8.1 INTRODUCTION  A column is said to be slender if its cross-sectional dimensions are small compared with its length.  Most columns are subjected to bending moments producing lateral deflection of a member between its ends and may result in relative lateral displacement of joints associated with secondary moments that are added to the primary moments and that  CHAPTER 8: LONG/SLENDER COLUMNS 8.1 INTRODUCTION  A slender column may be defined as a column that has significant reduction in its axial load capacity due to moments resulting from lateral deflections of the column.  When column bends or deflects laterally an amount Δ, its axial load will cause additional moment applied to the column equal to PΔ. This moment is called secondary moment or P-Delta  CHAPTER 8: LONG/SLENDER COLUMNS 8.2 SLENDERNESS EFFECTS  It is important to determine whether the effects of slenderness need to be considered or to be neglected in the design of any column because second- order effects can have a significant influence on design strength.  The degree of slenderness is generally expressed in terms of the slenderness ratio (kLu/r), where Lu is the unsupported length of a  CHAPTER 8: LONG/SLENDER COLUMNS 8.2 SLENDERNESS EFFECTS  If slenderness effects are considered small, then columns are considered “short” and can be designed as short columns.  However, if they are “slender”, the moment for which the column must be designed is increased or magnified. Once the moment is magnified, the column is then designed using the increase moment. An approximate  CHAPTER 8: LONG/SLENDER COLUMNS 8.2 SLENDERNESS EFFECTS  CHAPTER 8: LONG/SLENDER COLUMNS 8.2 SLENDERNESS EFFECTS  If bracing elements resisting lateral movement of a storey have a total stiffness of at least 12 times the gross lateral stiffness of the columns in the direction considered, it shall be permitted to  CHAPTER 8: LONG/SLENDER COLUMNS 8.2 SLENDERNESS EFFECTS 8.3 ALIGNMENT CHART - Procedure used for estimating effective lengths - The primary design aids to estimate the effective length factor k is the Jackson and Moreland Alignment Chart