Friday, June 22, 2007

Luck of the Irish one year too late...

Ha!


















The 5, 2 die roll at Northridge was good for us, but we tested in house, with a 4,4 and got an Agg. of about 0.52", so maybe we just managed to ride that fine light of unwavering stiffness just right. Or perhaps we were a little bit lucky. The chords were designed to eliminate the (5,6)/(1,2) die rolls, so I guess they did their trick. This was similar to the 2005 design strategy with the three different loading spots, stiff in the middle, and let the deck & overall depth keep it stiff closer to the piers.

Design improvements for 2007? Maybe sacrifice some overall depth, leave the tension chords shorter on the compression chord extension, and consolidate the 4 extra bolts there to one at each node rather than 2 at each node like we had to deal with (right Rishi?). Better speed, slightly better lightness, sacrifice maybe 0.07" of deflection on average.

Section size wise - 1.5/8.cir.0.035 instead of 1.3/4.cir.0.035 for the truss with matching crank zones at 0.049 wall, 7/8 or 3/4" chords perhaps, though we subtracted 4 chords after regionals and the 1" chords seemed reasonable for the NSSBC structural system we used. 3/16" cir. 0.028" wall on all lateral truss webbing rather than 0.035", some definite weight savings for a not so critical element zone. Truss out the piers and make them lighter. Other than just making the bridge lighter as a whole, I think what we came up with wasn't too bad. 141 lbs. final weight in lab - Everybody was about 10 lbs heavy correct? We sure were. Ha!

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