STAAD.Pro Member Properties: Sections, Materials and Assignment Workflow

A STAAD.Pro member without a property is a line. A member with the wrong property is a confident line. Section tables, prismatic definitions, tapers, user tables and material grades decide whether the analysis is talking about the steel you will buy. Assignment is therefore a workflow: group members, assign once, print the list, and make that list the parent of the drawing schedule.

PEB work makes this sharper. A tapered built-up rafter is not an IPE from a European table. If the model uses a prismatic substitute, the drawings and the shop must know that — or, better, the model should carry the taper the portal frame will use. Copying last job’s user table is how a flange thickness from another building survives.

This article covers sections, materials and assignment discipline. It does not quote yield strengths or catalogue properties as if they were universal. Use the mill certificates, manufacturer data and the standard named in the design basis. Geometry of the members themselves is in nodes and coordinates. Whole-file QA is in model checking.

Why property errors are expensive

Wrong I or area changes forces only modestly on a statically determinate beam and a lot on a frame that redistributes. Wrong material density changes self-weight. Wrong steel design parameters change ratios without touching analysis stiffness. The 3D view will still look like a warehouse. Catch properties in tables, not in orbit mode.

When geometry is later sent to CAD through Staad2CAD, often only the centreline travels. The property list is then the only honest source of depths. If that list is wrong, CAD annotation will be wrong even if conversion was perfect.

Sections: tables, prismatic, tapers and user libraries

Pick the definition that matches what will be fabricated. Do not use a catalogue I-section as a quiet stand-in for a welded plate girder unless you have documented the substitute and checked that its properties bound the real member in the way the reviewer accepted.

Catalogue sections

Confirm the table matches the marketplace (region, designation, units). A similarly named section from another table is not “close enough” without a property comparison.

Prismatic and user-defined

You are responsible for the numbers you type. Have a second person check a sample against a property calculation or manufacturer sheet. Axis convention — which is major — must match how the member is placed, including beta angle.

Tapers

Taper definitions must use the same stations as the PEB frame elevation. A taper that ends short of the haunch is a different member.

Materials and design parameters are not decorations

Material objects carry modulus, Poisson, density, and may carry grade identifiers used by design modules. Design parameters (ky, ly, unsupported lengths, code selections) can govern ratios more than the section does. They must come from this project’s basis, not from a template. This article will not list parameter values; those are job-specific.

An assignment workflow that does not rely on clicking members one by one

Create groups: rafters, exterior columns, interior columns, braces, struts. Assign properties to groups. When a special crane column exists, it gets its own group, not a leftover typical. After assignment, print a member-property table sorted by group and read it like a drawing.

• Groups named after the drawing marks, not only after STAAD numbers.
• One property name per intended section; avoid duplicates like W12A and W12_A.
• Unused properties deleted so they cannot be assigned by autocomplete.
• User tables stored with the project, not only in a personal library path.
• Beta angles checked on sloping members after property assignment.
• A size list exported for CAD and for the PEB approval schedule.

Keeping properties aligned with drawings and PEB classification

Primary versus secondary members should be visible in grouping. If secondaries are omitted from STAAD, the property list should not pretend they are there. If they are included, their properties must be cold-formed or hot-rolled as specified, not “whatever channel was in the table.”

When a checker asks “what is member 2047?”, the answer should be a mark and a section, not a shrug. Stable numbering plus groups make model to drawing possible.

Assigning STAAD properties on a steel or PEB frame

Properties after clean geometry, before you trust ratios.

1. Finish the geometry skeleton.
2. List intended sections from the design, including tapers and specials.
3. Create property names and materials for this job; do not inherit a dirty library.
4. Group members to match drawing identity.
5. Assign properties and relevant design parameters from the basis.
6. Print the property table and spot-check a rafter, a column, a brace.
7. Export the size list that CAD will be required to use.
8. If a size changes, change the property and the list together; do not edit only CAD.

Engineering tips

• Name properties after the mark series (RF_TaperA) so reports are readable.
• If two members share a property but not a mark series, that is fine; if they share a mark series but not a property, it is not.
• Watch unit conversion when pasting properties from a spreadsheet.
• For built-up sections, store the plate sketch with the project, not only Ix in a field.
• After changing beta, glance at local-axis display on one sloping rafter.
• Delete trial sections before someone assigns them from a dropdown.

Property mistakes that look like analysis insight

Using a mill section because the tapered property was tedious

Then issuing PEB shop drawings with tapers. The stiffness and the steel are different objects.

Swapping major and minor axes on a built-up I

The frame is suddenly flexible in the strong direction. Check I values against a hand estimate of a known shape.

Leaving another project’s steel grade on the material object

Design ratios move; drawings still say the specified grade. Procurement and analysis diverge.

Assigning properties by clicking in a crowded 3D view

You will miss the back-side brace. Use groups and tables.

Member-property review checklist

Perform on the printed property table, not only on the renderer.

• Every member has a property.
• Property names are unique and meaningful.
• Catalogue tables match the specified marketplace.
• Taper stations match frame elevations.
• Materials match the specification, including density for self-weight.
• Design parameters for this job, not the template, are assigned where used.
• Groups map to drawing marks.
• Unused properties removed.
• User tables live in the project archive.
• Size list issued for CAD matches this table.
• Special members (crane, stepped) are not on typical properties.

Frequently asked questions

Can I analyse a PEB taper as a prismatic member of average depth?

Only as a documented approximation accepted by the responsible engineer. It is not a substitute for the tapered geometry you intend to fabricate. If you approximate, say so on the analysis notes and still draw the real taper.

Where should the official member-size list live — STAAD or CAD?

In the analysis property table for that revision, exported to a human-readable list that CAD must follow. CAD should not be allowed to become the size master. See model to drawing.

Do I need to model purlin properties if purlins are only loads on the frames?

No, if they are truly omitted as members. You still need their layout for restraint parameters and for drawings. If you later add purlins as members, assign proper cold-formed properties, not leftover mill channels.

How do I check that Ix and Iy are not swapped?

Compare the reported values to an independent property calculation or a catalogue for a similar shape, and confirm local axes on a member with obvious orientation (a deep rafter). Do not rely on the 3D extrusion if the renderer uses a generic stick.

The property table is a drawing

STAAD.Pro member properties are the steel. Tables, tapers, user definitions and materials have to match what will be bought and drawn. Group, assign, print, export the list, and forbid CAD from inventing sizes. Leftover properties from another job are not a shortcut; they are a different specification.

Continue with model checking before you run issue analysis. Strengths, catalogue dimensions and design parameters remain project-specific. StruTools does not supply section databases or replace manufacturer data.