Performance Factor: 1.52x better than TDW L/480 standard
Deflection Analysis (Girder)
PASS
TDW GIRDER STANDARD (L/1000)
≤ 0.600"
PASS
MID-TIER (L/800)
≤ 0.750"
PASS
MINIMUM ACCEPTABLE (L/600)
≤ 1.000"
Performance Factor: 1.00x better than TDW Girder L/1000 standard
CAPACITY UTILIZATION (vs L/1000) — by load source0%
050%75%90%100% (limit)
Load Source
ASCE 7 ASD Load Combination
Total lbs on Girder
Defl Contribution
% of L/1000
TOTAL:
0 lbs
0.000"
0%
Member Details
Member
Size
Quantity
Length
Weight
Top Chords
HSS 1×1×0.125"
2
600 in
131.02 lbs
Bottom Chords
HSS 1×1×0.125"
2
600 in
131.02 lbs
Diagonal Struts
HSS 1×1×0.125"
20 pairs
33.54 in
146.49 lbs
Vertical Struts
HSS 1×1×0.125"
10 pairs
30.00 in
65.51 lbs
Gussets
Grade 100 Plate
40
Various
42.54 lbs
TOTAL
516.59 lbs
Capacity Analysis
Top Chord Axial:15.31 lbs
Bottom Chord Axial:15.31 lbs
Struts Axial:45.94 lbs
Gussets Axial:750.00 lbs
Panel Width:5.00 ft
Diagonal Length:2.80 ft
Diagonal Angle:45°
Total Panels:10.00
SJI JOIST PARAMETERS
Warning: SJI calculations reflect PUBLISHED values. Actual field capacity may be 40-55% lower due to re-cert A36, MIG HAZ damage, and eccentric load paths.
JOIST SELECTION
GEOMETRY
LOADING
REALITY FACTORS
Apply Re-Cert A36 Factor (-28%)
Apply MIG HAZ Damage (-15%)
Apply Eccentric Load Path (-8%)
Reality Check Applied
The following real-world factors reduce published capacity:
Re-Cert A36: -28%
MIG HAZ: -15%
Eccentric: -8%
Total Reduction: 44%
Joist Weight
850 lbs
Joist Depth
24"
Actual Capacity
259 plf
Required
500 plf
SJI Joist Diagram
■ Top/Bottom Chords (Double Angles)■ Web Members (Crimped Single Angles)⚠ Welded Tabs (Failure Point)
Capacity Analysis
Published (SJI Tables)
INADEQUATE
460 plf
Based on Grade 50 material, perfect welds, concentric loads
Actual (Real-World)
INADEQUATE
259 plf
Accounts for re-cert A36, MIG HAZ, eccentric loads
CAPACITY EXCEEDED This joist is 93% overstressed under real-world conditions.
Deflection Analysis
DESIGN STANDARD
L/240
SJI Code Minimum
ALLOWABLE
2.500"
ESTIMATED ACTUAL
L/221
Warning: SJI joists are designed to L/240 - the bare minimum allowed by code. This provides no margin for error, load underestimation, or dynamic effects.
Connection Warning
SJI joists use welded tab connections:
Tabs are MIG welded to joist ends
Joist sits ON TOP of bearing (gravity only)
No positive connection against uplift
Wind reversal can wrench tabs off
Amazon St. Louis (Dec 10, 2021): 6 workers killed when joist tabs wrenched off under wind uplift. Roof lost diaphragm action. Walls collapsed inward.
STRUCTURAL COMPARISON
TDW VS SJI
Same span, same loading - different results
□ SELECT FROM SUMMARY
□ COMPARISON PARAMETERS
□ TDW TRUSS SYSTEM
WINNER
4
Trusses Required
12.5'
Spacing O.C.
Deflection Ratio:L/388
Actual Deflection:1.548"
Weight per Truss:1378 lbs
Total Steel Weight:5510 lbs
Steel Grade:Grade 70-100
Weld Type:Laser (1/8" HAZ)
Connection:Embedded Saddle
□ Cannot fail without wall destruction
□ SJI JOIST SYSTEM
INFERIOR
9
Joists Required
6.25'
Spacing O.C.
Deflection Ratio:L/240
Actual Deflection:2.500"
Weight per Joist:900 lbs
Total Steel Weight:8100 lbs
Steel Grade:Re-Cert A36
Weld Type:MIG (1"+ HAZ)
Connection:Welded Tabs
□ Tabs wrench off under wind uplift
□ TDW ADVANTAGE SUMMARY
56%
Fewer Members
4 vs 9
1.6×
More Rigid
L/388 vs L/240
2-3×
Material Strength
Gr100 vs Re-Cert A36
8×
Less HAZ Damage
Laser vs MIG
□ THE CRITICAL DIFFERENCE
TDW Embedded Saddles
Truss is CAPTURED in wall structure. Cannot separate without destroying the wall itself. Building stays standing.
SJI Welded Tabs
Joist sits ON TOP of tabs. Wind uplift wrenches tabs off. Roof loses diaphragm action. Walls collapse. People die.
"Amazon St. Louis, December 10, 2021: 6 Dead"
MEMBER LIBRARY
DESIGN SUMMARY
Trusses and girders designed and ready for building assembly
TRUSSES
No trusses designed yet. Design a truss in TDW Calculator and click "Add to Summary"
GIRDERS
No girders designed yet. Design a girder in TDW Calculator and click "Add to Summary"
DECK
No deck assigned yet. Assign deck types in Assembly tab
ACCESSORIES
No accessories placed yet. Place accessories in Assembly tab
BUILDING PLAN
Building plan not assembled yet. Configure in Pre-Build and Assembly tabs
TOTALS
Category
Count
Weight (lbs)
Weight (tons)
Trusses
0
0
0.00
Girders
0
0
0.00
Deck
0 SF
0
0.00
Bridging
0 pcs
0
0.00
Accessories
0
0
0.00
Columns
0
0
0.00
TOTAL STEEL
—
0
0.00
QUOTE BUILDER
Project & Customer Information
PSF
Stress Scale
No LoadFailure
□ NASG TDW TRUSS — FEM ANALYSIS
NO LOAD
—
Deflection Ratio
—
Max Deflection
0%
Utilization
□ SJI STANDARD JOIST — FEM ANALYSIS
NO LOAD
—
Deflection Ratio
—
Max Deflection
0%
Utilization
—
× Stiffer (TDW vs SJI)
—
TDW Deflection Ratio
—
SJI Deflection Ratio
L/480 vs L/240
Selected Standards
SJI PUBLISHED LOAD TABLE AUDIT — Math Verification
Selects the joist currently active in the SJI Calculator tab and verifies published capacities against first-principles engineering using
the official SJI Ix formula: Ij = 26.767 × W × (L − 0.33)³ × 10⁻⁶ where W = the published L/360 deflection load.
Reality factors (recertification, eccentric loading, HAZ) are then applied to show effective capacity.
Parameter
Published / Input
Calculated
Delta
Status
ASSEMBLYAssign trusses, girders, deck, then place accessories