Structural Workbench Preview 16 — dynamic response, slabs on columns, steel bracing points

Dynamic response (M15), slabs on columns (M10) and steel bracing points (M07)

Preview 16 adds the M15 dynamic-response numerical family, column supports for slab panels with a link to the frame model, and per-segment lateral-torsional buckling checks for steel members braced along their length. Nothing here is a code seismic or vibration check: code design spectra need a seismic standard (R-SEISMIC-CODE), and the M10, M12 and M15 parents stay blocked on their code resources.

• Dynamic response (response-v1). Everything runs on the M14 modal model.
  • Harmonic response: steady-state sweeps with Rayleigh damping (entered as ratios at two frequencies, or as coefficients), solved by a sparse complex-symmetric LDLᵀ. Results include amplitude and phase plots and tables at any node.
  • Response spectrum: user-defined spectra (periods from 0, Sa in m/s² or g, stated damping), combined by SRSS or CQC. Results include base reactions, peak support reactions, member actions and displacements, with a mass-participation target.
  • A Response tab, a report section and schema 1.6.0 (responseSpectra). 1.5.0 projects migrate by version.
  • Validation:
    • Closed-form SDOF amplitude, phase and spectrum values, and SRSS and CQC on a shear frame, within 1e-9.
    • A spatial frame against OpenSees K and M solved in complex arithmetic, within 1e-6.
• Slabs on columns (plate-v1).
  • Supports: a slab panel can sit on pinned, fixed or spring point supports.
  • Link to the frame model: the columns can be derived from the model (springs kz = EA/L and krx, kry = 4EI/L, or 3EI/L when the far end rotates). The column reactions can then be applied back to the frame as nodal loads.
  • Validation: a 12 × 10 m flat slab on six columns matches OpenSees ShellMITC4 with zeroLength springs within 1e-6 (deflections, moments and column reactions).
  • The link is one-way; it is not a coupled frame–shell model.
• Steel bracing points (ADR 0024).
  • A member can be braced at points along its length. Each segment is checked with its own Lb and its own F1-1 Cb, taken from exact quarter-point moments. A segment ending at an unbraced free end takes Cb = 1.0.
  • AISC Example F.1-2B, modelled as one member braced at its thirds, reproduces the three-member model (Cb 1.46 / 1.01 / 1.46) within 1e-9.
• Fixes:
  • Second-order analysis no longer double-counts member-load equivalents in the reactions. Member-load end moments now reach released (hinged) ends.
  • The package check passes again.

Verified publication

The Pages workflow (run) passed the locked Rust tests, security, build and contract checks, and deployed.

The live site (Build 23b9a004e7b9) was checked with an automated browser script:

• Harmonic: a 41-point sweep matched the closed form within 1.6e-13.
• Spectrum: the SRSS base shear matched the oracle within 3.1e-14.
• Slab: the panel with an opening reproduced OpenSees within 9.6e-13.
• Column: the 37° column case gave utilisation 0.8 at the oracle's M_Rd within 1e-9.
• No page errors.

The check used Playwright Chromium with SwiftShader software WebGPU, so it is not hardware-GPU evidence.

• Source commit 2564a05. Source hash c1d2a431… matches the tested source.
• The hosted build 23b9a004… is a Linux rebuild. The same two files as in Previews 14 and 15 (the WASM binary and the generated UKR01 example) differ from the local build b53b4d67…; the cause is not established.

Local corpus on the tested build: the M07 parent and LTB, M09 parent, M14 parent, M10-PLATE, M12-COLUMN and M15-RESPONSE gates pass; 262 Rust tests; 54 unit and security tests; full browser suite 123/123. The publication JSON, the hosted build.json, the smoke result and screenshots are attached.

This is a prerelease preview.