Draft
3.7Joists 73
3.7 Joists
43 Steeljoists,Fig. 3.8looklike shallow trusses(warrentype) andaredesignedassimply
supporteduniformlyloadedbeamsassumingthattheyarelaterallysupportedonthetop(to
prevent lateraltorsionalbuckling).Thelateralsupportis oftenpro dedby theconcreteslab
it suppors.
44 Thestandardopen-webjoistdesignationconsistsof thedepth,theseriesdesignationand
thechordtype. Threeseriesareavailablefor
oor/roof construction,Table3.3
Series Depth(in) Span(ft)
K 8-30 8-60
LH 18-48 25-96
DLH 52-72 89-120
Table3.3:JoistSeriesCharacteristics
4"4"4"Span[Design Length = Span – 0.33 FT.]Figure3.8:prefabricatedSteelJoists
45 Typicaljoistspacingrangesfrom2 to 4 ft,andprovidesanecient useof thecorrugated
steeldeck which itselfsupportstheconcreteslab.
46 For preliminaryestimatesof thejoistdepth,a depthto spanratioof 24canbe assumed,
therefore
dL= 2 (3.5)
wheredis in inches,andLin ft.
47 Table3.4listtheloadcarryingcapacity of openweb,K-seriessteeljoistsbasedona amxi-
mumallowablestressof 30ksi. For each span,the rstlineindicatesthetotalsafeuniformly