398 NOTE TO CHAP. XTV. [APPENDIX. 



A comparison of the above with the same case hinged at 

 the ends of the lower rib, shows a decided gain. The effective 

 bright is increased, being now 20 ft., in place of 19.5; in 

 addition to which both ribs under total load bear their proper 

 proportion. If, then, we wish the arch continuous at crown, 

 both ribs should butt against an end plate, pivoted in the 

 centre. This is preferable to hinging the lower rib at its ex- 

 tremities, and removing the end flanges A. 



25. Temperature Strains. For the strains due to tem- 

 perature, we may take, as before, the thrust H = 25 tons, and 

 find thus 



A = 11.2 B = +- 13.2 C = +" 29.4 D = +~ 37.6 



E = 27.0 P = 45.5 G = 56.4 H = 59.2 



12 =T 17.8 23=13.9 3 4 = q= 9.8 45= 11.3 



5 6 = +- 2.8 6 7 = 8.1 7 8 = 4.3 



all somewhat less than in the previous case, as they should be, 

 since the point of application is at the centre between the 

 flanges. 



We have then from the preceding table the total maximum 

 strains : 



A = + 135.7 B = + 135.2 C = + 144.3 D = + 155.5 



E- *-1582 F _ + 176.7 r _ + 173.9 +172.3 

 > 8 ' 2 -- 7.2 G ~- 19.2 H= - 25.5 



+49.0 oo_ + 33.4 q ,+28.5 ,,+24.8 

 - 44.1 2 d - - 33.0 - - 25.4 = -26.1 



7 . +33.0 

 --28.5 ~_30.7 78 = -34.7 



26. Arch continuous at Crown and fixed at the Ends. 



From our table, Art. 160, we have directly for a = 25 45', 

 and h = 20, y being now measured above the horizontal tangent 

 at crown of centre line, 



for = 0, y = 0.209 h = 4.18 ft. 



= 0.2a, y = 0.208 h = 4.16 



/3 = 0.4a, y = 0.206 h = 4.12 



/9 = 0.6a, y = 0.201 h = 4.02 



/3 = 0.8a, y = 0.198 h = 3.96 



/3 = 1.0a, y = 0.189 h = 3.78 



