Tutorial 4 of 7 · Intermediate · about 25 minutes

Member design and optimisation

With the loads and combinations in place, this tutorial checks every steel member to AISC 360-16, reads the governing check, lets the optimiser propose lighter sections, and shows the concrete, wood and masonry design.

1. Set the design parameters #

Select the members and open their design parameters in the properties panel:

• Unbraced lengths for flexure and for compression in each direction, or the bracing points along the member.
• Effective length factors, when you are not using the direct analysis method.
• Moment gradient for lateral-torsional buckling: worked out from the moment diagram, or entered.
• Member type: beam, column or brace, which sets the deflection limits used for serviceability.

Members that share the same parameters can be set together; select them with Groups & select by… on the Model tab.

2. Check the steel members #

1. On the Design tab, click Steel (AISC 360). The design runs as a background job over every combination.
2. The 3D view colors each member by its governing ratio: green well below one, amber close to it, red over it. Turn Utilization colours on or off on the Results tab.
3. The design table lists every member with its section, its governing ratio, the check that governs (for example flexure, compression, or combined forces), the load combination and the clause of AISC 360-16.

3. Read one member in detail #

Click a member. The details show every check of that member, each with the required strength, the available strength, the ratio, the combination and the clause. Slender-web plate girders are checked by Chapter F5. A check that falls outside what the program covers is marked as not covered, never as a pass.

4. Stability: the direct analysis method #

For frames where second-order effects matter, run a P-Delta analysis with the reduced stiffness and notional loads of the direct analysis method, then design with effective length factors of one. ILX Structures records which analysis the design is based on.

5. Optimise for least weight #

1. Select the members to optimise (all the beams of a floor, for example) or a group.
2. Click Optimize members. Choose the target ratio, the shape family (W shapes, HSS and so on) and any depth limits.
3. ILX Structures tries the candidate sections, re-analyses the model where the stiffness changes, and lists the lightest section that works for each member, with its ratio and the weight saved.
4. Review the list and apply it. One Undo takes it all back.

6. Seismic frames to AISC 341-22 #

For members of special moment frames, special concentrically braced frames and eccentrically braced frames, set the frame type in the design parameters. The design adds the AISC 341-22 checks: width-to-thickness limits for highly ductile members, the strong-column weak-beam check, brace slenderness, link rotation and the expected-strength forces.

7. Concrete, wood and masonry #

• Concrete (ACI 318): give the members their reinforcement (bars, stirrups, cover) and design beams, columns and shear walls to ACI 318-19.
• Wood (NDS): give the members their species, grade and adjustment factors (load duration, wet service, temperature, size) and check beams and columns to NDS 2018.
• Masonry (TMS 402): walls under axial load and bending, with the unit, grout and reinforcement.

Each code has its own results table and colors the model the same way.

Next #

Print it all in a report: Reports and hand-off.

Screens in the app may differ slightly from the words here as the app gains features; the steps stay the same. Questions: services@ilxstudio.com.