PRACTICAL 

 STRUCTURAL DESIGN 



CHAPTER I 



External Forces 



A STRUCTURE is a combination of parts designed to hold 

 in equilibrium definite forces and in this book the word 

 "structure" is limited to buildings. 



The intention being to give a modern treatment in the plainest 

 possible manner, it is necessary to settle upon a definite termin- 

 ology > that is, upon a system of shorthand symbols to use 

 for it is best to present rules in a condensed manner in order that 

 every step in an operation may be quickly apprehended. A rule 

 thus written becomes a formula. Formulas are merely mathe- 

 matical shorthand, and when a formula is seen it is not algebra. 

 Algebra is useful in deriving a formula, but when the formula is 

 presented it requires only the use of common arithmetic to solve it. 

 Let W = a uniformly distributed load. 



Let w = a unit of a distributed load. On a panel w is the load 

 per square foot. On a beam or girder w is the load per 

 lineal foot. Then it follows that W = w multiplied 

 by the span. 



P = a concentrated load. When several concentrated 

 loads are used the different loads are designated by 

 subscripts, as P, P n P, P n etc. 

 S - clear span between supports. 



L - length of span used for obtaining a bending moment. 

 That is, a beam may extend from one support to another 

 with a span, S, measured from face to face of sup- 

 port, and this will be used in obtaining W, the total 

 load on the span. To find the bending effect of the 

 load it is necessary to use a length measured from 

 center to center of supports, or from points back of 

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