StructureCalcsHSS18X18X3/4
Square HSS · AISC Shapes Database v15.0 · United States
HSS18X18X3/4 is a square hollow structural section 457 × 457 mm with a 19.1 mm wall, weighing 254.7 kg/m. The dimensions below are the published AISC Shapes Database v15.0 values; the drawing is generated from them.
Square HSS give equal stiffness both ways with flat faces for simple welded connections — a standard column and brace choice in US practice.
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Published dimensions
| Property | Metric | Imperial |
|---|---|---|
| Overall depth, d | 457 mm | 18.00 in |
| Overall width, b | 457 mm | 18.00 in |
| Wall thickness, t | 19.1 mm | 0.750 in |
| Mass per metre | 254.7 kg/m | 171.2 lb/ft |
| Area, A | 30,387 mm² | 47.10 in² |
| Second moment, Ix | 965,656,908 mm⁴ | 2,320.0 in⁴ |
| Second moment, Iy | 965,656,908 mm⁴ | 2,320.0 in⁴ |
Derived section properties
Integrated from the section's own outline including its outside corner radii, whose arcs are integrated analytically rather than approximated by facets. For HSS18X18X3/4 the computed area agrees with the published value to 0.17% and Ix to 0.25%. Where a value is also published, the published one above is the one to quote.
AISC tabulates hollow-section properties on the design wall (tdes = 0.93 tnom, per AISC 360), while the published mass reflects the nominal wall — which is why mass and area here differ by about 7% by convention, on every AISC hollow section.
| Property | Value |
|---|---|
| Elastic modulus, Sx | 4,213,486 mm³ |
| Elastic modulus, Sy | 4,213,486 mm³ |
| Plastic modulus, Zx | 4,953,494 mm³ |
| Plastic modulus, Zy | 4,953,494 mm³ |
| Radius of gyration, rx | 178.2 mm |
| Radius of gyration, ry | 178.2 mm |
S is the elastic modulus and Z the plastic modulus, following AISC 360. Australian and British practice reverse the letters.
Neighbouring sizes
Where these numbers come from
Published AISC Shapes Database v15.0 values. How StructureCalcs verifies its numbers · Understanding steel section properties · Query this section over the API