REINFORCED CONCRETE 81 



(d) For slabs or beams, continuous over two spans only, or 

 for concentrated loads, or other unusual conditions, 

 the moments and shears shall be obtained by the 

 " Theorem of Three Moments." 



345 . Resisting Moments : 



(a) In any slab, beam, or girder reinforced for compression 

 the resisting moment of the steel in compression shall 

 equal the compressive value of concrete X 15 X its lever 

 arm. (Par. 3486.) 



(6) In T-beams, where adequate bond between slab and web 

 of beam is provided, the resisting moment of the top 

 flange of the beam may include an adjacent part of 

 the slab. This tributary part of the slab shall be limited 

 as follows : 

 To be available the minimum thickness of slab shall 



be one-thirty-second (fa) of the slab span. 

 The total effective width shall not exceed one-fourth 



() of the span length of the beam, or two-fifths () 



of the slab span, or 8 times the thickness of slab 



plus the thickness of web. 



(c) In T-beams, where the neutral axis falls below the slab, 

 the resistance of the web shall be neglected. 



346. Reinforced Columns. Provision must be made in rein- 

 forced columns for eccentric loading, if any, and for flexure 

 whenever the maximum unsupported length of same exceeds 18 

 diams. (Par. 348, c2.) 



Proper provisions must also be made at the bottom of the 

 columns for tensile stresses, if any, and for the distribution, by 

 means of bearing plates or otherwise, of the compressive stresses 

 borne by the reinforcement. 



The live loads on columns may be reduced according ta 

 provisions in Par. 96. 



347. Temperature Stresses. Temperature stresses shall be 

 calculated, where the structure cannot expand and contract 

 freely, for a variation of not less than 50 F. (Par. 350.) 



UNIT STRESSES 



348. Normal Concrete and Structural Steel. All parts of 

 the reinforced concrete structure shall be so proportioned that 

 the sum of the maximum stresses from all causes shall not exceed 



