
Dead Load 100x75/2 6x50x75/2

= 15000 pounds.
= 9000 pounds = 2400 pounds = 19500 pounds 
The arch will be designed for Dead plus half live, then the maximum moment due to live load should be the same for Dead only, as for Dead plus full live. The thrust will not be as large for the Dead only, so this is not the optimum loading but should be near.
The arch will be analysed for 6 segments each 75/6 = 12.5feet long, horizontally. The slope length is, approximately: so the weight of each segment is: The center load is 6460/2+19500=22730 pounds. These values were entered into the program DFINICU.BAS, and the following coordinates for the arch were obtained for Y: 0,0.00; 1, 7.12; 2 13.39; 3 18.82; 4,23.34; 5,27.28; 6, 30.00. The center coordinate is 18.82, so the rise above the diagonal is 18.8215=3.82. The arch can now be analysed designed, reanalysed, redesigned, etc.
(Use of the program PROPXY.BAS)
A compression member, a 6x6x1/2 is inadequate for compression. The only way ro increase its capacity is to add a plate on the side as shoen in the sketch. The radius of gyration from the AISC Manual is 1.18 inches. What will be the new value of the the radius of gyration?
6,0.5,6, 7,1,6, 8,1,0.0, 9,6.5,0.5, 10,6.5,0 The result for the smaller moment of inertia, I, is 11.01, and for the are, A, is 8.25 si. The radius of gyration is equal to the SQR(I/A) = SQR(11.01/8.25) = 1.16. The only gain has been in the available area.
