LH-Series Joist Deflection and Stress Analysis Calculator

LH-Series Joists

  • LH, Longspan Steel Joists
  • Designations: 18LH02 to 48LH17
  • Depths: 18 to 48 in.
  • Types: Parallel Chord, Single Pitch, Double Pitch; Underslung or Bottom Chord Bearing
LH-SERIES JOIST ANALYSIS
For Uniformly Loaded, Longspan Steel Joists
Using Steel Joist Institute (SJI) Standard Load Tables
Variables:
Joist Designation (Size) =
Joist Span, L =??
LH-series Joist Span Criteria for Load Table
Size Min. Span Max. Span
18LH 21' 36'
20LH 22' 40'
24LH 28' 48'
28LH 33' 56'
32LH 38' 64'
36LH 42' 72'
40LH 47' 80'
44LH 52' 88'
48LH 56' 96'

ft.
Joist Spacing, S =
LH-series Joist
Maximum Joist Spacing for Horizontal Bridging
Bridging Angle Size
Section 1x7/64 1-1/4x7/64 1-1/2x7/64 1-3/4x7/64 2x1/8 2-1/2x5/32
Numbers r=0.20" r=0.25" r=0.30" r=0.35" r=0.40" r=0.50"
02,03,04 4'-7" 6'-3" 7'-6" 8'-9" 10'-0" 12'-4"
05,06 4'-1" 5'-9" 7'-6" 8'-9" 10'-0" 12'-4"
07,08 3'-9" 5'-1" 6'-8" 8'-6" 10'-0" 12'-4"
09,10 4'-6" 6'-0" 7'-8" 10'-0" 12'-4"
11,12 4'-1" 5'-5" 6'-10" 8'-11" 12'-4"
13,14 3'-9" 4'-11" 6'-3" 8'-2" 12'-4"
15,16 4'-3" 5'-5" 7'-1" 11'-0"
17 4'-0" 5'-1" 6'-8" 10'-5"

LH-series Joist
Maximum Joist Spacing for Diagonal Bridging
Bridging Angle Size
Joist 1x7/64 1-1/4x7/64 1-1/2x7/64 1-3/4x7/64 2x1/8
Depth r=0.20" r=0.25" r=0.30" r=0.35" r=0.40"
18 6'-6" 8'-2" 9'-10" 11'-6"
20 6'-5" 8'-2" 9'-10" 11'-6"
24 6'-4" 8'-1" 9'-9" 11'-5"
28 6'-2" 8'-0" 9'-8" 11'-5"
32 6'-1" 7'-10" 9'-7" 11'-4" 13'-0"
36 7'-9" 9'-6" 11'-3" 12'-11"
40 7'-7" 9'-5" 11'-2" 12'-10"
44 7'-5" 9'-3" 11'-0" 12'-9"
48 7'-3" 9'-2" 10'-11" 12'-8"
ft.
Unif. Dead Load, w(DL) = psf
Unif. Live Load, w(LL) = psf
Deflect. Factor, DF(LL) =
Results:
Required Loads:
Dead Load, W(DL) = plf W(DL) = w(DL)*S
Live Load, W(LL) = plf W(LL) = w(LL)*S
Total Load, W(TL) = plf W(TL) = W(DL)+W(LL)
Reactions, RL & RR = lbs. RL = RR = W(TL)*L/2
For Joist Selected
In joist size designations, the digits to the left of "LH" represent the total joist depth, while the digits to the right of "LH" represent the section number, 02 through 17.
Joist
Joist
The approximate moment of inertia of the joist is:
Ix = 26.767*W(LL)*(L-0.33)^3/1000000
where: W(LL) = uniform live load based on deflection of
1/360 of span from Joist Load Table (plf)
L = joist span from center to center of supports (ft.)
(Note: joist design length = L-0.33'.)
Joist
Allowable Loads and Stress Ratios
Maximum Spans for Rows of Bridging for LH-series Joists
* Section Number of Rows
Number 1 2 3 4 5 6
02 22' 33' 40' --- --- ---
03 22' 33' 44' 48' --- ---
04 22' 33' 44' 48' --- ---
05 24' 36' 48' 56' --- ---
06 24' 36' 48' 60' 64' ---
07 26' 39' 52' 65' 72' ---
08 26' 39' 52' 65' 80' ---
09 28' 42' 56' 70' 84' 88'
10 28' 42' 56' 70' 84' 96'
11 32' 48' 64' 80' 96' ---
12 32' 48' 64' 80' 96' ---
13 32' 48' 64' 80' 96' ---
14 32' 48' 64' 80' 96' ---
15 42' 63' 84' 96' --- ---
16 42' 63' 84' 96' --- ---
17 42' 63' 84' 96' --- ---
* Last digits of joist designation shown in load table.
# Rows
Size Weight Inertia, Ix
W(TL) = total allowable distributed load capacity (plf)
(from Joist Standard Load Table)
W(TL)
The Flexure Ratio = Req'd. W(TL) / Allow. W(TL).
where: Req'd. W(TL) = W(DL)+W(LL)
Allow. W(TL) = from Joist Standard Load Table
Flexure
W(LL) = distributed live load which produces
deflection of 1/360 of span (plf).
(from Joist Standard Load Table)
W(LL)
The Deflection Ratio = Req'd. W(LL) / Allow. W(LL).
where: Req'd. W(LL) = w(LL)*S
Allow. W(LL) = from Joist Standard Load Table
Deflect.
of
(plf) (in.^4) (plf) Ratio (plf) Ratio Bridging
Total Load Deflect. Live Load Deflect.
D(TL)
Deflection Factor for total load may be determined from formula:
DF(TL) = (L-0.33)*12/D(TL)
DF(TL)
D(LL)
Deflection Factor for live load may be determined from formula:
DF(LL) = (L-0.33)*12/D(LL)
DF(LL)
(in.)
(in.)
D(TL) = 1.15*5*W(TL)*(L-0.33)^4*(12^3)/(384*29000000*Ix)
D(LL) = 1.15*5*W(LL)*(L-0.33)^4*(12^3)/(384*29000000*Ix)
?? Determine Equivalent Unif. Dead and Live Loads for Input from Detailed Analysis:
Equiv. Load, W(TL) = plf
Equiv. Load, w(TL) = psf w(TL) = W(TL)/S
Load Ratio, DL/TL =
DL/TL = W(DL)/W(TL)
Unif. Dead Load, w(DL) = psf w(DL) = w(TL)*(DL/TL)??
Unif. Live Load, w(LL) = psf w(LL) = w(TL)-w(DL)
Notes: 1. OSHA is interpreting Section 29CFR-1926.751(c)2 to mean all joists whose length
>= 40' require bolted diagonal bridging in place before slackening of hoisting lines.??
2. For point loads on LH-series joists, the magnitude and location of load should be
indicated on the design drawings and "SP" must be added to the joist designation.??????????????