Seismic Moment Frame Calculator, AISC 341-16

What it checks

The module designs steel moment frame members for Special (SMF), Intermediate (IMF), and Ordinary (OMF) systems. It performs pure code-equation checks without finite element coupling, relying on demands passed in by the caller. The design method uses LRFD axial demands and expected strengths to verify seismic performance criteria. The sequence of checks begins with beam compactness limits for highly or moderately ductile sections. It then evaluates the strong-column weak-beam ratio for SMF systems, comparing the sum of expected column flexural strengths against the sum of probable beam moments. Finally, the module checks panel zone shear strength and column web thickness requirements.

Inputs

Frame Type - Moment frame classification (SMF, IMF, or OMF).
Material Properties - Yield strength (fy) and strain hardening factor (cpr, typically 1.15 for RBS or 1.10 default).
Column Demands - LRFD axial demand (puc_kips, kips) and unbraced length (lb_ft, ft).
Joint Moments - Sum of expected column flexural strength (sum_mpc, kip-ft) and sum of probable beam moments (sum_mpb, kip-ft).
Story Shear - Story shear at the level (v_story_kips, kips).

What it reports

Compactness Limits - Returns lambda_pf and lambda_pw values from Table D1.1 for beam flange and web compactness.
Strong-Column Ratio - The ratio of sum_mpc to sum_mpb, which must be greater than or equal to 1.0 for SMF; -1.0 indicates the check was not performed.
Panel Zone Shear Demand - Shear demand Vu calculated as sum_mpb divided by beam depth minus story shear, reported in kips.
Panel Zone Strength - Design strength phi_Rn per AISC 360 Eq. J10-11, reported in kips for comparison against demand.
Web Thickness Check - Boolean indicating whether the column web satisfies the thickness requirement tcw >= (dz+wz)/90 per AISC 341 §E3.6e.2.
Flange Plate Requirement - Boolean indicating if plates are not required due to sufficient flange thickness, and the minimum plate thickness in inches if required.
Drift Limit - Allowable amplified story drift delta_a in inches, which the caller compares against Cd*delta_e/Ie.

Code references

The engine cites AISC 341-16 for SMF, IMF, and OMF design criteria, specifically §E3.4a for the strong-column weak-beam ratio and §E3.6e.2 for column web thickness. It also references Table D1.1 for beam compactness limits and AISC 360 Eq. J10-11 for panel zone design strength. System parameters are aligned with ASCE 7-22 Table 12.2-1 and §12.12.1.

Limits

The module does not perform finite element analysis; all demands are passed in by the caller. It assumes negligible axial force for beams (ca=0) when calculating compactness. The strong-column weak-beam ratio check is only performed for SMF systems. Results are engineering aids; the engineer of record is responsible for the design.

This module ships in the desktop app

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