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Building Design and Construction Handbook - Merritt - Ventech!

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OPEN-WEB STEEL JOISTS<br />

COLD-FORMED STEEL CONSTRUCTION 8.57<br />

The first steel joist was produced in 1923 <strong>and</strong> consisted of solid round bars for top<br />

<strong>and</strong> bottom chords <strong>and</strong> a web formed from a single continuous bent bar, thus<br />

simulating a Warren truss. The Steel Joist Institute (SJI) was organized to promote<br />

sales of such joists in 1925 <strong>and</strong> has sponsored further research <strong>and</strong> development<br />

since then.<br />

8.28 DESIGN OF OPEN-WEB STEEL JOISTS<br />

Currently, open-web steel joists are still relatively small, parallel-chord trusses, but<br />

hot-rolled steel shapes usually make up the components. (For a time, cold-formed<br />

steel shapes were preferred for chords to utilize higher working stresses available<br />

in cold-formed sections of ordinary carbon-steel grades. Unfavorable fabrication<br />

costs, however, led to a change to the hot-rolled steel chords.)<br />

Joists are suitable for direct support of floors <strong>and</strong> roofs of buildings, when designed<br />

according to SJI ‘‘St<strong>and</strong>ard Specifications, Load Tables <strong>and</strong> Weight Tables<br />

for Steel Joists <strong>and</strong> Joist Girders,’’ Steel Joist Institute, 3127 10th Ave., North Ext.,<br />

Myrtle Beach, SC 29577. Moreover, since 1972, the American Institute of Steel<br />

FIGURE 8.22 Some examples of open-web steel joists.

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