374 



NOTE TO AKT. 124. 



[APPENDIX. 



STRAINS IN FLANGES LIVE LOAD BRIDGE SHUT. 



In the two horizontal lines at bottom, we have the total 

 strains of each kind caused by the live load. 



3d. FLANGES BRIDGE OPEN DEAD LOAD. 



We have next to find the strains due to the dead load when 

 the span is open. 



"We have then 5 tons at each apex, except the ends, where 

 we have P = 2.5 tons. 



These strains are easily found by moments as above, and we 

 have then the following table : 



If now, as should be the case, we suppose the centre sup- 

 ports raised above the level of the ends, so that the ends just 

 bear, then these strains above act even when the bridge is shut. 

 As we have already seen in Art. 131, our formulae for the 

 reactions are not affected by this state of things. The strains 

 due to live load will then be increased by those above, and we 

 thus have for the total maximum strains which can ever occur, 



