CORRUGATED BAR COMPANY, INC. 



RECOMMENDATIONS ON DESIGN AND WORKING 

 STRESSES IN REINFORCED CON- 

 CRETE CONSTRUCTION. 



(From the Final Report of the Joint Committee on Concrete and Reinforced Concrete, 



July 1, 1916) 



Massive Concrete. In the design of massive or plain concrete, no account should 

 be taken of the tensile strength of the material, and sections should usually be pro- 

 portioned so as to avoid tensile stresses except in slight amounts to resist indirect 

 stresses. This will generally be accomplished in the case of rectangular shapes if the 

 line of pressure is kept within the middle third of the section, but in very large struc- 

 tm-es, such as high masonry dams, a more exact analysis may be required. Structures 

 of massive concrete are able to resist unbalanced lateral forces by reason of their 

 weight; hence the element of weight rather than strength often determines the 

 design. A leaner and relatively cheap concrete, therefore, will often be suitable for 

 massive concrete structures. 



It is desirable generally to provide joints at intervals to localize the effect of con- 

 traction. 



Massive concrete is suitable for dams, retaining walls, and piers in which the ratio 

 of length to least width is relatively small. Under ordinary conditions this ratio 

 should not exceed four. It is also suitable for arches of moderate span. 



Reinforced Concrete. The use of metal reinforcement is particularly advanta- 

 geous in members such as beams in which both tension and compression exist, and in 

 columns where the principal stresses are compressive and where there also may be 

 cross-bending. Therefore, the theory of design here presented relates mainly to the 

 analysis of beams and columns. 



General Assumptions, (a) Loads. — The forces to be resisted are those due to: 



1. The dead load, which includes the weight of the structure and fixed loads and forces. 



2. The live load, or the loads and forces which are variable. The dynamic effect of 

 the live load will often require consideration. Allowance for the latter is preferably 

 made by a proportionate increase in either the live load or the live load stresses. The 

 working stresses hereinafter recommended are intended to apply to the equivalent 

 static stresses thus determined. 



In the case of high buildings the live load on columns may be reduced in accordance 

 with the usual practice. 



(6) Lengths of Beams and Columns. — The span length for beams and slabs simply 

 supported should be taken as the distance from center to center of supports, but need 

 not be taken to exceed the clear span plus the depth of beam or slab. For continuous 

 or restrained beams built monolithically into supports the span length may be taken 

 as the clear distance between faces of supports. Brackets should not be considered as 

 reducing the clear span in the sense here intended, except that when brackets which 

 make an angle of 45 degrees or more with the axis of a restrained beam are built mono- 

 lithically with the beam, the span may be measured from the section where the com- 

 bined depth of beam and bracket is at least one-third more than the depth of the 

 beam. Maximum negative moments are to be considered as existing at the end of the 

 span as here defined. 



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