huangyhg

custom steel truss connection
i am working on connection detailing of very long custom steel trusses. they are about 168 ft long, 28 ft deep, 8 bays. i use w14-shapes as top and bottom chords, and steel tubes as vertical and diagonal webs. what is the best way to connect them? i am thinking use gussets to connect them, weld gussets to chords, notch ends of steel tubes, use long bolts to fasten them together. the sizes of square tubes about 12". however, i don't think it is good anyway. anyone has better suggestion on the connection or even selection of truss members?
thanks a lot fo any suggestion or idea.
any suggestion on how to break the top and bottom chords is greatly appreciated too. thanks,
for the gusset to hss web connection long bolts are not a good idea. the bolts would be in bending instead of shear. have you considered back-to-back channels for your webs? how heavy are your chord sections? if they are very heavy, bolted gussets may be a better choice to avoid the problems with welding thick sections.
most of the long span steel trusses i have experience with use bolted splice plates to the flanges and webs for chord connections.

for truss size like this, i suggest to use open web tube for all main members, and double channels for secondaries. bolted/riveted connections are preferred. the opening on tube serves as hand hole for bolt installation, air vent, and for drainage and maintenance purposes.
thanks for replies. kslee100, what do you mean an open web tube? my loads are a little big larger. i am afraid of open web tubes are probably not strong enough. i think double chanels for webs is a good way too. my trusses have 9 vertical webs including two ends, and 8 diagonal webs which are symmetrical about the mid span. the maximum axial force of webs is about 700 kips. i am thinking to design it in this way: w14x120s as top and bottom chords, double channels as webs, cutted t-shapes (from a large w-shape)as connectors like gussets, bolt webs, chords and cutted t-shape connectors together, no weld. any comment and new suggestion about this is truly appreciated.

if you are using a w14 member for your chords, they typically have an inside dimension of ~12.5". you may want to consider using w12
i am surprised as to why the 168' deep truss is 28' deep. you could easily get it to work with 14-18 foot depth. is there an architectural reason for it to be 28' deep.
you will also be able to lower your web sizes if you reduce their lengths. a pratt configuration is your best alternative if you don't have uplift to deal with.
slickdeals:
actually the whole length of my trusses is 336 ft long but there are supports at the mid-span of the whole length of 336 ft, either by columns or by other deep trusses. yes, 28 ft deep is for mechanical facilities and duct placements.
i don't like to weld gussets to the flanges of chords. i just feel it is not good especially considering seismic loading.
by the way, the w-shapes of top and bottom chords are placed vertically, not horizontally. if they are set horizontally, then a huge heavy w-shape will be required. this is a not option in my mind anyway.
thanks for your inputs.

are you carrying significant loads that are inducing bending in your chords, that require you to use them vertically as opposed to horizontally?
in addition, you might use intermediate bracing in your web
slickdeals, yes, the chords have got to carry 60-90 psf loads for 28 ft distribtion width. i can't place any intermediate bracing at those webs because mechanical ducts run through those spaces.
i don't have my steel manual at hand now. i'm afraid that standard largest double channels might not be strong enough for the compression of 700 kips for 35 ft long webs.

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