Skip to main content

Inelastic Seismic Story Drift & Drift Ratio Calculator

Story drift controls structural damage, ensures P-delta stability, and protects non-structural facades and piping during earthquake shaking.

Calculated Result
32.00 mm

Inelastic Design Drift (Δ)

Story Drift Ratio

0.80%

Code Limit Compliance (≤ 2.0%)

PASS (Compliant)

Calculation Breakdown

  1. Amplify elastic drift to account for inelastic pushover yielding Δ = Cd · δ_e / IeΔ = (4 * 8) / 1 = 32.00 mm
  2. Compute drift ratio relative to floor-to-floor story heightRatio = (32.00 / 4000) * 100% = 0.80%

Drift Ratio vs Elastic Deflection

Interactive visualization based on your current inputs

Ratio (%)
0.00.51.01.52.05 mm10 mm15 mm20 mm (Limit)δe (mm)Drift Ratio (%)

What Is the Inelastic Seismic Story Drift & Drift Ratio Calculator?

Story drift controls structural damage, ensures P-delta stability, and protects non-structural facades and piping during earthquake shaking.

How Does the Inelastic Seismic Story Drift & Drift Ratio Calculator Work?

The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.

Inelastic Seismic Story Drift & Drift Ratio Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

\Delta = \frac{C_d \cdot \delta_e}{I_e}, \quad \text{Drift Ratio} = \frac{\Delta}{h_{sx}} \times 100\%

Elastic analytical deflections must be amplified by Cd to capture severe plastic hinges and ductile inelastic yield mechanisms.

How to Use the Inelastic Seismic Story Drift & Drift Ratio Calculator

  1. Enter your primary measurements in the input fields above.
  2. Select your preferred units (e.g. metric or imperial) if applicable.
  3. Review or adjust operational assumptions such as field efficiency.
  4. Click Calculate to instantly generate the full results breakdown and visual chart.
  5. Use the Reset button at any time to clear the form and test a new scenario.

Step-by-Step Example Calculation

Commercial Office 4m Floor Height

Input Values:

elasticDriftMm:8
deflectionAmplificationCd:4
importanceFactorIe:1
storyHeightMm:4000

Understanding Your Result

Your calculated result represents the realistic operational capacity or baseline output under the specified conditions. Comparing theoretical and effective outputs reveals the direct impact of turns, overlap, and practical downtime.

Factors That Affect the Result

Field terrain, operator experience, equipment maintenance, overlap margin, and weather conditions can significantly influence real-world output.

When Should You Use This Calculator?

Use this calculator whenever you need quick, verified estimates for job planning, budgeting, equipment sizing, or project timelines.

Assumptions & Limitations

  • Includes the Cd/Ie inelastic amplification factor required by ASCE 7 Chapter 12.

Frequently Asked Questions

Calculation Accuracy & Reference Note

This calculator implements verified, deterministic mathematical equations based on published standards. Results should be treated as professional engineering estimates; always verify critical operations with local equipment manuals and site inspections.

Explore more tools and calculators in Math Calculators