Unit 29 Moments of Inertia of Composite Areas （惯性单元29时刻复合区域）.pdf

Introduction to Statics .PDF Edition – Version 0.95 Unit 29 Moments of Inertia of Composite Areas Helen Margaret Lester Plants Late Professor Emerita Wallace Starr Venable Emeritus Associate Professor West Virginia University, Morgantown, West Virginia © Copyright 2010 by Wallace Venable Conditions of Use This book, and related support materials, may be downloaded without charge for personal use from www.SecretsOfE You may print one copy of this document for personal use. You may install a copy of this material on a computer or other electronic reader for personal use. Redistribution in any form is expressly prohibited. Unit 29 Moments of Inertia of Composite Areas Frame 29-1 Introduction This unit will teach you how to combine the moments of inertia of simple geometric shapes to obtain the moment of inertia of a composite area. It will also teach you ho not to combine them. Moments of inertia of areas are used extensively in strength to calculate stresses and deflections in beams. In American Customary Units we calculate stress in pounds per square inch (psi) so it is the common practice to use areas (and derived properties) measured in inches. Conveniently, most American drawings have areas dimensioned in inches. In System International (SI) stresses are calculated in Pascals (Newtons per square meter) so it is the common practice to use area areas (and derived properties) measured in meters. For better or worse, cross-sec