12 



web Plates 47. The webs of plate girders must be stiffened at inter- 

 vals, not exceeding the depth of the girders or a maximum 

 of 5 feet, wherever the shearing strain per square inch ex- 

 ceeds the strain allowed by the following formula : 

 Allowed shearing strain = 10,000 75//, 

 where //= ratio of depth of web to its thickness; but no 

 web-plates shall be less than three-eighths of an inch in 

 thickness. 



stiffeners. 48. At any point, the combined stiffeners, fillers and in- 

 closed web, acting together as one column, must be capable 

 of carrying the maximum vertical shear without exceed- 

 ing the allowed unit strain: 



P= 10,000 45 



The stiffeners must connect to the webs by enough rivets 

 to transfer the maximum shear to or from the webs. 

 Roiw Beams. 49. Rolled beams shall be proportioned (31, 45) by 



their moments of inertia. 



counters. 50. The areas of counters shall be determined by taking 

 the difference in areas due to the live and dead load strains 

 considered separately (31); the counters in any one panel 

 must have a combined sectional area of at least three square 

 inches, or else must be capable of carrying all the counter 

 live load in that panel. ( 92.) 



51. Counters shall be provided and proportioned so that 

 either a future increase of 25 per cent, in the specified live 

 load, or the maximum loading E 50, shall not in any case 

 increase the allowed unit strain more than 25 per cent. 



DETAILS OF CONSTRUCTION. 



Detail*. 52. All the connections and details of the several parts of 

 the structures shall be of such strength that, upon testing, 

 rupture will occur in the body of the members rather than 

 in any of their details or connections. 



53. Preference will be had for such details as shall be 

 most accessible for inspection, cleaning and painting; no 

 closed sections will be allowed. 



