HEAVY TIMBER 



If a stiff floor with a limited deflection is desired, the fol- 

 lowing formula may be used to find the amount of deflection 

 due to a uniformly distributed load on a floor of a given thick- 

 ness, span between beams or girders, and kind of timber : 



The value of D is commonly limited to 1/30 of an inch per 

 foot of length of span where a plastered ceiling is to be used, 

 or 1/25 of an inch per foot when ceilings are left without 

 plastering. 



Girders and The design of the girders used in a structure 

 Beams will depend upon the manner in which the loads 



are supported by these girders. In mill con- 

 struction buildings where laminated or standard mill floors are 

 used, the load is distributed unif ormily along the length of the 

 girders ; but in cases where intermediate beams supporting the 

 floor extend from girder to girder, the loads are concentrated 

 at the ends of the girder and at one or more equally spaced 

 intermediate points. These different methods of support cause 

 different effects in bending and deflection. Formulas for 

 bending, shear, and deflection will be given for three of the 

 common cases. 



LOAD UNIFORMLY DISTRIBUTED 

 Bending 



Shear 



W= 



3 

 Deflection 



870 W I 8 



ONE CONCENTRATED LOAD AT CENTER OF GIRDER 

 Bending 



m 



<* 



Page fifty-eight 



