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