ASCE 7-22 Seismic Design Calculator

Estimate seismic design parameters using ASCE 7-22 inputs for site and structure factors.

Calculator

Enter site parameters, structural system, and seismic weight. Fields marked with an asterisk are required.

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Results

\(S_{MS} = F_a \cdot S_s\) —
\(S_{M1} = F_v \cdot S_1\) —
\(S_{DS} = \tfrac{2}{3} S_{MS}\) —
\(S_{D1} = \tfrac{2}{3} S_{M1}\) —
Governing \(C_s\) —
Base shear \(V = C_s \cdot W\) —

Data Source and Methodology

  • ASCE/SEI 7-22 — Minimum Design Loads and Associated Criteria for Buildings and Other Structures. Official overview: ASCE 7-22. This tool implements ELF equations 12.8-1 through 12.8-6, including caps (12.8-3/12.8-4) and minimums (12.8-5/12.8-6).
  • Site Parameters: Use the ASCE Hazard Tool (project location) or your geotechnical report to obtain \(S_s, S_1, F_a, F_v, T_L\).

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

Design spectra:

$$ S_{MS} = F_a S_s,\quad S_{M1} = F_v S_1,\quad S_{DS} = \tfrac{2}{3}\,S_{MS},\quad S_{D1} = \tfrac{2}{3}\,S_{M1} $$

Response coefficient and base shear:

$$ C_s = \min\!\left( \frac{S_{DS}}{R/I_e},\; \begin{cases} \dfrac{S_{D1}}{T\,(R/I_e)}, & T \le T_L \\\\ \dfrac{S_{D1}\,T_L}{T^2\,(R/I_e)}, & T > T_L \end{cases} \right), \qquad V = C_s\,W $$

Minimums:

$$ C_s \ge \max\!\left(0.01,\; 0.044\,S_{DS}\,I_e,\; \mathbb{1}_{S_1\ge 0.6}\cdot \frac{0.5\,S_1}{(R/I_e)}\right) $$

Glossary of Variables

  • \(S_s, S_1\) — Mapped spectral accelerations (short-period, 1-sec).
  • \(F_a, F_v\) — Site coefficients (from Site Class and \(S_s, S_1\)).
  • \(S_{MS}, S_{M1}, S_{DS}, S_{D1}\) — Adjusted MCE and design spectral parameters.
  • \(T\) — Fundamental period (modal or approximate \(T_a\)).
  • \(T_L\) — Long-period transition.
  • \(R\) — Response modification factor (by system).
  • \(I_e\) — Seismic importance factor (by Risk Category).
  • \(W\) — Effective seismic weight; \(C_s\) — response coefficient; \(V\) — base shear.

How It Works: A Step-by-Step Example

Case: Site Class D, \(S_s=1.0\), \(S_1=0.4\), \(T_L=8.0\,\mathrm{s}\), \(T=0.8\,\mathrm{s}\), \(R=8\), \(I_e=1.0\), \(W=25{,}000\,\mathrm{kN}\). Interpolated \(F_a\approx1.10\), \(F_v\approx1.60\).

  1. \(S_{MS}=F_a S_s=1.10\); \(S_{M1}=F_v S_1=0.64\).
  2. \(S_{DS}=\tfrac{2}{3} S_{MS}=0.733\); \(S_{D1}=\tfrac{2}{3} S_{M1}=0.427\).
  3. Base \(C_s=S_{DS}/(R/I_e)=0.0916\); cap \(C_s=S_{D1}/(T(R/I_e))=0.0667\) ⇒ governing \(C_s=0.0667\).
  4. Minimums: \(0.044S_{DS}I_e=0.0323\); \(0.01\); near-fault N/A (\(S_1<0.6\)). Governed by cap.
  5. Base shear: \(V=0.0667 \times 25{,}000 = 1{,}667\,\mathrm{kN}\).

Frequently Asked Questions (FAQ)

Where do I get \(S_s\), \(S_1\), \(F_a\), \(F_v\), and \(T_L\)?

From the ASCE Hazard Tool for your site or from a geotechnical report.

Does the tool apply the near-fault minimum?

Yes — if \(S_1 \ge 0.6\), it applies \(C_s \ge 0.5\,S_1/(R/I_e)\) in addition to other minimums.

What if my site is Class F?

Auto-fill is disabled and a site-specific ground motion procedure is generally required. Enter \(F_a, F_v\) only from a site-specific analysis.

Can I override \(F_a\) and \(F_v\)?

Yes — switch Auto-fill to Off and input values from the Hazard Tool/report.

Does this compute Seismic Design Category (SDC)?

No; this tool focuses on \(V\). Use \(S_{DS}\), \(S_{D1}\), and Risk Category with §11.6 to determine SDC.

Is this enough for final design?

Use results as a professional aid. Final design must follow ASCE 7-22 and local amendments, and be checked by a licensed engineer.

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\]
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Formula (extracted LaTeX)
\[S_{MS} = F_a S_s,\quad S_{M1} = F_v S_1,\quad S_{DS} = \tfrac{2}{3}\,S_{MS},\quad S_{D1} = \tfrac{2}{3}\,S_{M1}\]
S_{MS} = F_a S_s,\quad S_{M1} = F_v S_1,\quad S_{DS} = \tfrac{2}{3}\,S_{MS},\quad S_{D1} = \tfrac{2}{3}\,S_{M1}
Formula (extracted LaTeX)
\[C_s = \min\!\left( \frac{S_{DS}}{R/I_e},\; \begin{cases} \dfrac{S_{D1}}{T\,(R/I_e)}, &amp; T \le T_L \\\\ \dfrac{S_{D1}\,T_L}{T^2\,(R/I_e)}, &amp; T &gt; T_L \end{cases} \right), \qquad V = C_s\,W\]
C_s = \min\!\left( \frac{S_{DS}}{R/I_e},\; \begin{cases} \dfrac{S_{D1}}{T\,(R/I_e)}, &amp; T \le T_L \\\\ \dfrac{S_{D1}\,T_L}{T^2\,(R/I_e)}, &amp; T &gt; T_L \end{cases} \right), \qquad V = C_s\,W
Formula (extracted LaTeX)
\[C_s \ge \max\!\left(0.01,\; 0.044\,S_{DS}\,I_e,\; \mathbb{1}_{S_1\ge 0.6}\cdot \frac{0.5\,S_1}{(R/I_e)}\right)\]
C_s \ge \max\!\left(0.01,\; 0.044\,S_{DS}\,I_e,\; \mathbb{1}_{S_1\ge 0.6}\cdot \frac{0.5\,S_1}{(R/I_e)}\right)
Formula (extracted text)
Design spectra: $ S_{MS} = F_a S_s,\quad S_{M1} = F_v S_1,\quad S_{DS} = \tfrac{2}{3}\,S_{MS},\quad S_{D1} = \tfrac{2}{3}\,S_{M1} $ Response coefficient and base shear: $ C_s = \min\!\left( \frac{S_{DS}}{R/I_e},\; \begin{cases} \dfrac{S_{D1}}{T\,(R/I_e)}, & T \le T_L \\\\ \dfrac{S_{D1}\,T_L}{T^2\,(R/I_e)}, & T > T_L \end{cases} \right), \qquad V = C_s\,W $ Minimums: $ C_s \ge \max\!\left(0.01,\; 0.044\,S_{DS}\,I_e,\; \mathbb{1}_{S_1\ge 0.6}\cdot \frac{0.5\,S_1}{(R/I_e)}\right) $
Variables and units
  • No variables provided in audit spec.
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
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