CORRUGATED BAR COMPANY, INC. 



In the case of restrained beams, the first stirrup or the point of bending down of bar 

 should be placed not farther than one-half of the depth of beam away from the face 

 of the support. 



It is important that adequate bond strength or anchorage be provided to develop 

 fully the assumed strength of all web reinforcement. 



Low bond stresses in the longitudinal bars are helpful in giving resistance against 

 diagonal tension failures and anchorage of longitudinal bars at the ends of the beams 

 or in the supports is advantageous. 



It should be noted that it is on the tension side of a beam that diagonal tension 

 develops in a critical way, and that proper connection should always be made between 

 stirrups or other web reinforcement and the longitudinal tension reinforcement, 

 whether the latter is on the lower side of the beam or on its upper side. Where nega- 

 tive moment exists, as is the case near the supports in a continuous beam, web rein- 

 forcement to be effective must be looped over or wrapped around or be connected with 

 the longitudinal tension reinforcing bars at the top of the beam in the same way as 

 is necessary at the bottom of the beam at sections where the bending moment is 

 positive. 



Inasmuch as the smaller the longitudinal deformations in the horizontal reinforce- 

 ment are, the less the tendency for the formation of diagonal cracks, a beam will be 

 strengthened against diagonal tension failure by so arranging and proportioning the 

 horizontal reinforcement that the unit stresses at points of large shear shall be rela- 

 tively low. 



It does not seem feasible to make a complete analysis of the action of web rein- 

 forcement, and more or less empirical methods of calculation are therefore employed. 

 Limiting values of working stresses for different types of web reinforcement are given 

 in the section on "Working Stresses." The conditions apply to cases commonly met 

 in design. It is assumed that adequate bond resistance or anchorage of all web rein- 

 forcement will be provided. 



When a flat slab rests on a column, or a column bears on a footing, the vertical 

 shearing stresses in the slab or footing immediately adjacent to the column are termed 

 punching shearing stresses. The element of diagonal tension, being a function of the 

 bending moment as well as of shear, may be small in such cases, or may be otherwise 

 provided for. For this reason the permissible limit of stress for punching shear may be 

 higher than the allowable limit when the shearing stress is used as a means of com- 

 paring diagonal tensile stress. The working values recommended are given in the 

 section on "Working Stresses." 



Columns. By columns are meant compression members of which the ratio of 

 unsupported length to least width exceeds about four, and which are provided with 

 reinforcement of one of the forms hereafter described. 



It is recommended that the ratio of unsupported length of column to its least width 

 be limited to fifteen. 



The effective area of hooped columns or columns reinforced with structural shap>es 

 shall be taken as the area within the circle enclosing the spiral or the polygon enclos- 

 ing the structrual shapes. 



Columns may be reinforced by longitudinal bars; by bands, hoops, or spirals, to- 

 gether with longitudinal bars; or by structural forms which are sufficiently rigid to 



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