etabs-analysis

name

etabs-analysis

description

ETABS analysis and modeling behavior — element formulations (frame, shell/area, link, tendon), load cases (static linear/nonlinear, modal eigen/Ritz, response spectrum, time history direct/modal, nonlinear staged construction, hyperstatic, buckling), automatic lateral loads (seismic & wind per code), P-Delta, modal participation, diaphragms, constraints, meshing, mass source, materials & hinges, and soil-structure springs. Use to explain WHY ETABS produces a result or how a modeling feature behaves. Triggers on "load case", modal/Ritz, response spectrum, time history, P-Delta, staged construction, auto seismic, auto wind, diaphragm, hinge, nonlinear, damping, mass source, eigenvalue, story drift behavior, meshing, or rigid/semi-rigid. Points into the CSI Analysis Reference Manual, Lateral Loads Manual, and technical notes in reference/.

ETABS Analysis & Modeling

This skill explains how ETABS models and analyzes structures — the theory and documented behavior behind results. The authoritative sources are the vendor manuals in reference/ at the repo root. Cite the specific manual

• section rather than answering from general FEM knowledge, since ETABS has documented formulations and defaults.

Primary references (paths under reference/)

• CSI Analysis Reference Manual.pdf — the main reference. Element formulations (frame, shell/area, link/support, tendon, cable), coordinate systems & joints, constraints (diaphragm, body, equal), materials, sections, load patterns vs load cases, all analysis case types (linear/nonlinear static, modal eigen & Ritz, response spectrum, direct & modal time history, nonlinear staged construction, buckling, hyperstatic, moving load), P-Delta & large displacement, damping, mass source, modal participation, and output conventions. This is the first place to look for why ETABS does X.
• Lateral Loads Manual.pdf — automatic lateral load generation: seismic (auto base shear, story forces per ASCE 7, IBC, Eurocode 8, NBCC, IS 1893, NTC, etc.) and wind (ASCE 7, etc.), including auto load pattern parameters. Pairs with the OAPI cAutoSeismic interface and the wind auto-load functions.
• Introductory Tutorial.pdf, User's Guide.pdf, Welcome to ETABS.pdf — workflow orientation and menu-level behavior.
• CSiXRevit Manual.pdf — ETABS ↔ Revit interoperability (BIM round-trip).

Technical notes (reference/Technical Notes/)

Focused deep-dives — read the matching one for these topics:

File	Topic
S-TN-MAT-001.pdf	Material stress-strain curves (all material types)
S-TN-MAT-002.pdf	Modified Darwin-Pecknold 2-D reinforced concrete material model
S-TN-ECS-001.pdf	Material time-dependent properties (creep/shrinkage/aging)
S-TN-HNG-001.pdf	Parametric P-M2-M3 (interacting) plastic hinge model
S-TN-WHM-001.pdf	ETABS wall hinge models (nonlinear shear wall hinges)
S-TN-LNK-001.pdf	High-damping rubber isolator link property
S-TN-LNK-002.pdf	Sumitomo viscoelastic damper link property
S-TN-SSI-001.pdf	Auto point-spring supports from soil profiles & column footprints
S-TN-VIB-001.pdf	Floor vibration analysis
S-TN-IFC-001.pdf	IFC4 import and export

Verification examples (reference/Verification/Analysis/)

Example 01.pdf … Example 15.pdf — closed-form / textbook problems solved in ETABS with the independent solution, to validate analysis features. Use to confirm a formulation or reproduce expected results.

Mapping behavior to the API

Each analysis concept has an OAPI counterpart (drive it via the etabs-oapi skill; method lists in .claude/skills/etabs-oapi/reference/api/):

• Load cases: cCaseStaticLinear, cCaseStaticNonlinear, cCaseStaticNonlinearStaged, cCaseModalEigen, cCaseModalRitz, cCaseResponseSpectrum, cCaseDirectHistoryLinear/Nonlinear, cCaseModalHistoryLinear/Nonlinear, cCaseHyperStatic.
• Loads & functions: cLoadPatterns, cLoadCases, cCombo, cAutoSeismic, cFunction, cFunctionRS.
• Run & read: cAnalyze, cAnalysisResults, cAnalysisResultsSetup.
• Modeling: cConstraint, cDiaphragm, cGenDispl, cPropLink, cPropMaterial.

How to answer an analysis question

1. Pin down the feature (which load case type / element / modeling option).
2. Read the relevant CSI Analysis Reference Manual section (target the chapter — it's a large PDF; use the pdf skill / Read with a page range), or the matching technical note / Lateral Loads Manual.
3. If a number must be reproduced, use a Verification example.
4. If it must be scripted, hand the driving to etabs-oapi.

Related skills

For FEM theory from first principles, anthropic-skills:fem-mechanics-expert. For nonlinear/seismic modeling and OpenSees comparison, anthropic-skills:quake-research and anthropic-skills:opensees-expert.