6 



Live Loads. 3d. A " live load " on each track, supposed to be moving 

 in either direction, consisting of two 4< consolidation " en- 

 gines, coupled and followed by a train load, distributed as 

 shown on diagram E ; or a special load equally dis- 



tributed on two pairs of driving wheels, spaced six feet, 

 centre to centre, of 100,000 pounds up to class 40; and of 

 120,000 pounds for all classes above E 40. 



For any higher train loading than E 40, all double track 

 bridges with two trusses, for spans 150 feet and over, may 

 be proportioned for the higher train loading on one track 

 and E 40 loading on the second track. 



NOTE. As all the wheel loads in each diagram are made of the same 

 percentages of the driving wheel loads, the strains due to the different 

 engine diagrams will be proportionate to the numerical classes of the 

 engines. 



Any intermediate numbers may be selected, with the understanding that 

 this rule of proportion applies. 



The maximum strains due to all positions of either of the 

 above " live loads," of the required class, and of the " dead 

 loads," shall be taken to proportion all the parts of the 

 structure. 



Lateral Forces. 24. To provide for wind and vibrations from high-speed 

 trains: 



The top lateral bracing in deck bridges, and the bottom 

 lateral bracing in through bridges shall be proportioned to 

 resist a lateral force of 600 pounds for each foot of the span; 

 450 pounds of this to be treated as a moving load, and as 

 acting on a train of cars, at a line 6 feet above base of rail. 



(n.) 



The bottom lateral bracing in deck bridges, and the top 

 lateral bracing in through bridges, shall be proportioned to 

 resist a lateral force of 200 pounds for each lineal foot for 

 spans up to 200 feet, and 25 pounds additional for each 

 additional 50 feet. ( n.) 



25. In trestle towers the bracing and columns shall be 

 proportioned to resist the following lateral forces, in 

 addition to the strains from dead and live loads: 



ist. With either one track loaded with cars onlv, or with 

 both tracks loaded with maximum train load, the lateral 



