K-Series Joist Deflection and Stress Analysis Calculator

K-Series Joists Specifications

  • Designations: 8K1 to 30K12
  • Depths: 8 to 30 in.
  • Standard Seat Depth (Height): 2.5 in.
  • Span Range: 8 to 60 ft.
  • ASD Load Range: 127 to 550 plf
  • LRFD Load Range: 190 to 825 plf
  • Maximum Span/Depth Ratio: 24
K-SERIES JOIST ANALYSIS
For Uniformly Loaded, Open-Web Steel Joists
Using Steel Joist Institute (SJI) Standard Load Tables
Variables:
Joist Designation (Size) =
Joist Span, L =??
K-series Joist Span Criteria for Load Table
Size Min. Span Max. Span
8K 8' 16'
10K 10' 20'
12K 12' 24'
14K 14' 28'
16K 16' 32'
18K 18' 36'
20K 20' 40'
22K 22' 44'
24K 24' 48'
26K 26' 52'
30K 30' 60'
ft.
Joist Spacing, S =
K-series Joist
Maximum Joist Spacing for Horizontal Bridging
Bridging Material Size
Round Rod Equal Leg Angles
Section 1/2" Dia. 1x7/64 1-1/4x7/64 1-1/2x7/64 1-3/4x7/64 2x1/8 2-1/2x5/32
Number r = 0.13" r=0.20" r=0.25" r=0.30" r=0.35" r=0.40" r=0.50"
1 thru 9 3'-3" 5'-0" 6'-3" 7'-6" 8'-7" 10'-0" 12'-6"
10 3'-0" 4'-8" 6'-3" 7'-6" 8'-7" 10'-0" 12'-6"
11 & 12 2'-7" 4'-0" 5'-8" 7'-6" 8'-7" 10'-0" 12'-6"

K-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
Depth r=0.20" r=0.25" r=0.30" r=0.35"
12 6'-6" 8'-3" 9'-11" 11'-7"
14 6'-6" 8'-3" 9'-11" 11'-7"
16 6'-6" 8'-2" 9'-10" 11'-6"
18 6'-6" 8'-2" 9'-10" 11'-6"
20 6'-5" 8'-2" 9'-10" 11'-6"
22 6'-4" 8'-1" 9'-10" 11'-6"
24 6'-4" 8'-1" 9'-9" 11'-5"
26 6'-3" 8'-0" 9'-9" 11'-5"
28 6'-2" 8'-0" 9'-8" 11'-5"
30 6'-2" 7'-11" 9'-8" 11'-4"
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 digit(s) to the left of "K" represent the total joist depth, while the digit(s) to the right of "K" represent the section number, 1 through 12.
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 K-series Joists
* Section Number of Rows
Number 1 2 3 4 5
1 16' 24' 28' --- ---
2 17' 25' 32' --- ---
3 18' 28' 38' 40' ---
4 19' 28' 38' 48' ---
5 19' 29' 39' 50' 52'
6 19' 29' 39' 51' 56'
7 20' 33' 45' 58' 60'
8 20' 33' 45' 58' 60'
9 20' 33' 46' 59' 60'
10 20' 37' 51' 60' ---
11 20' 38' 53' 60' ---
12 20' 39' 53' 60' ---
* Last digit(s) 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)
D(TL) = 1.15*5*W(TL)*(L-0.33)^4*(12^3)/(384*29000000*Ix)
(in.)
(in.)
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 w(TL)??
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 K-series joists, the magnitude and location of load should be
indicated on the design drawings and "SP" must be added to the joist designation.??????????????