Sections & materials

Steel section library

CivilKit Studio ships a real hot-rolled steel section library covering five regions:

Region	Standard	Designations
Australia / NZ	AS/NZS 3679.1 / 1163	UB / UC, PFC, angles, CHS, flats, round bar (ROD12 to ROD36), Lysaght Cees and Zeds
United States	AISC	W shapes
United Kingdom	BS 4-1 / SCI P363	UB / UC
Europe	EN 10365	IPE / HEA / HEB
Canada	CISC / AISC	W shapes

Open the section library from a member's inspector ("Browse sections") to pick a real catalogue section. Each section carries area, second moments (Ix/Iy), plastic and elastic moduli, and torsion constant J.

Verify before professional use

The catalogues are marked verified: false - they are indicative for early-stage analysis. Every value should be cross-checked against a current manufacturer catalogue and the governing standard before professional use. (An internal consistency check guards the data: Zx = Ix/(d/2), plastic > elastic, and mass = ρ·A all hold across the 275 sections.)

Round bar rods

The Round Bar family (ROD12 to ROD36, Grade 300) covers rod bracing. A rod carries no compression: the shed generators and Add bracing make a rod tension-only by default, and a rod left as an ordinary beam is checked for buckling on a section that cannot provide it. The AS 4100 tension check uses the gross area; the reduced tensile-stress area at a threaded end (AS 1275, about 0.78 A_g for these sizes) belongs to the end connection and is not applied by the member check.

Concrete columns (generic)

Concrete columns aren't a discrete rolled catalogue - the size is continuous - so the library offers them as parametric solid shapes rather than thousands of named rows. In the section library's catalogue dropdown, pick Concrete (generic):

• Rectangular (solid D × B) and Circular (solid ⌀D) columns, with exact A / Izz / Iyy / J computed from the dimensions.
• A preset ladder of common sizes - squares 300→1000, a few blades (200×900, 300×1200), and rounds off the 75 mm formwork ladder (450, 525, 600, 675, 750, 900…). Use the shape family filter to narrow to rectangular or circular.
• A Custom size… row - switch to Rectangular or Circular and type any width × depth or diameter in millimetres.

Assigning a concrete section also sets a concrete material for the member, so the analysis uses concrete stiffness and self-weight - not steel.

Grade follows your region

The Grade picker defaults to the concrete grade for your active design region, and each grade carries that code's elastic modulus:

Region	Default grade	Code	E
AU / NZ	N40	AS 3600	32.8 GPa
Europe / UK	C40/50	EC2 Ecm = 22(fcm/10)^0.3	35.2 GPa
United States	5000 psi	ACI 318 Ec = 4700√f'c	27.6 GPa
Canada	35 MPa	CSA A23.3	28.2 GPa

Change the design region and the default grade (and its E) follows - you never get N40 in a US model. Pick a different grade from the same list to override it.

Section properties in the inspector

Select a member and the inspector shows a compact Section properties readout under the section picker: mass/m, depth, A, Ix (major), Iy (minor), Zx, Sx, J. Values come from the catalogue geometry (in mm units) where available, or are converted from the analysis values for a generic section. It is the quick "what are this section's numbers?" check engineers reach for constantly - and confirms, after solving, that a member is bending about the axis you intended (see Member orientation).

Isolate this section

The member inspector also offers "Isolate this section" - it shows only the members that share the selected section (and their nodes), hiding everything else. It is the fast "show me just the 360UBs" view. Show all (A), or selecting anything, restores the full model. The steel take-off rows are clickable too: a click selects and frames a representative member of that section.

Building custom sections

The Sections module (pick it from the suite bar) is a parametric section builder. Choose a shape, type its dimensions, and it computes the full property set live and draws the profile.

Parametric shapes

Ten shapes are built in:

Shape	Notes
Rectangle, Circle	Solid
CHS, RHS	Hollow circular / rectangular
I-section	With root radius R1, toe radius R2, and flange taper
Channel (PFC)
T-section	Optional root radius
Angle (L)	Equal or unequal, with root + toe radii
Cruciform
Monosymmetric I	Separate top / bottom flange widths (Bt/Bb) and thicknesses

Property readout

The editor shows the full set of computed properties, not just the headline numbers: area, mass/m, centroid, Ix, Iy, product of inertia Ixy, principal I1/I2 and their angle, section moduli Zx/Zy, radii of gyration, torsion J, and warping Iw. For an asymmetric shape (an angle, or a monosymmetric I) the principal axes and Ixy are where the real behaviour shows up.

Property factors

Open Property factors in the editor to scale a section's area, major/minor inertia, or torsion by an independent multiplier (1.0 = unchanged). Useful for a cracked-concrete stiffness knock-down or a built-up member. The factors are saved with the section and restored when you re-edit it.

Families

Custom sections are organised into families. Drag a section from one family onto another to move it, and click a section to load it back into the editor to re-edit (the button becomes Update section). Custom families also appear in the member section picker under Custom.

Materials tab

The Materials tab lists the standard materials (steel, concrete grades, aluminium, timber) with their E, Poisson, density, thermal coefficient and f'c, and lets you add or remove your own custom materials.

Export & import

Export downloads your custom families and materials as a JSON file; Import merges a file back in (existing entries are never overwritten). It is the way to back up or share a library between machines.

Defining a section directly

A section is just its analysis properties (SI):

{ "id": 1, "a": 0.0113, "iyy": 1.43e-4, "izz": 4.85e-5, "j": 3.4e-7 }

izz is the major axis (strong), iyy the minor axis. See the model schema for the full picture.

Materials

{ "id": 1, "e": 200e9, "g": 80e9, "nu": 0.3, "rho": 7850 }

Young's modulus e, shear modulus g, Poisson nu (needed for plate bending), and density rho (self-weight + modal mass). nu/rho default to 0.3 / 7850 if omitted.