Section properties describe geometry. Area, centroid location, moment of inertia, section modulus, plastic-modulus prompts, and radius of gyration help organize beam, column, connection, and machine-frame review, but they do not determine design acceptability by themselves.
The ToolGrit section screen keeps idealized shape formulas, cached W-shape rows, transformed-section prompts, source pointers, and qualified-review warnings visible. Current AISC database rows, AISC 360 design provisions, ACI/IBC adoption, material grade, bracing, load combinations, fabrication details, connection behavior, and PE review still control real design use.
Key Geometry Properties
Area (A): total cross-sectional area. It is a geometry input for later axial, shear, weight, or cost review, not a capacity result.
Moment of inertia (I): second moment of area about an axis. It is a stiffness-related geometry term that later deflection or buckling checks may use after load, material, support, and bracing assumptions are sourced.
Section modulus (S): S = I / c, where c is the distance from the neutral axis to the extreme fiber. It is a geometry term for later bending-stress review, not a bending-strength approval.
Plastic modulus prompts (Z): simplified geometry rows for selected shapes. Compactness, material grade, bracing, load combinations, and code provisions remain outside the screen.
Radius of gyration (r): r = √(I/A). It helps frame slenderness questions, but column capacity requires current design provisions, effective length, bracing, end conditions, and member data.
Section Properties Calculator
Moment of inertia, section modulus, plastic modulus, and radius of gyration for rectangles, circles, hollow sections, I-beams, channels, angles, and tees. AISC W-shape lookup included.
Local Shape Formulas Are Idealized
Rectangles, circles, tubes, I-shapes, channels, angles, tees, and custom rectangular components are useful for reviewing idealized geometry and unit consistency. Those formulas can also make it obvious when a dimension is entered in the wrong unit system or a component centroid is misplaced.
Real rolled, formed, welded, and fabricated sections may include fillets, tapers, corner radii, tolerances, holes, copes, welds, corrosion loss, reinforcement, or composite behavior that an idealized rectangle model does not capture. Cached W-shape rows should be checked against the current AISC Shapes Database and project source before use.
Parallel Axis Review
For built-up rectangular components, the screen uses the standard parallel-axis relationship:
I_total = sum(I_local + A * d^2)
That is enough to check the geometry bookkeeping for simple composite sections. It is not enough to approve a built-up member, welded reinforcement, composite beam, or repaired section.
Before relying on a composite result, verify component dimensions, material compatibility, connection transfer, welds or fasteners, shear flow, local buckling, construction-stage loading, concrete cracking or transformed-section assumptions, and any applicable AISC, ACI, IBC, or owner requirements.
Where The Geometry Stops
The app output can be a useful input to a later beam, column, connection, machine-frame, or fabrication review, but the app does not build load combinations, determine material strength, choose phi or omega factors, classify compactness, compute lateral-torsional buckling, verify bracing, size welds, check bolts, assess fatigue, or approve construction.
Use high sensitivity, unexpected centroid shifts, weak-axis radius-of-gyration concerns, transformed-section warnings, or catalog mismatches as reasons to open the current source and involve the responsible designer.