Wind Speed Structural Damage Risk Calculator

ANA›Life Services Authority›National Calculator Authority›Wind Speed Structural Damage Risk Calculator

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Wind Speed Structural Damage Risk Calculator

Estimates structural damage risk and expected damage level based on wind speed, building characteristics, and site exposure using ASCE 7 wind load principles and Beaufort/Saffir-Simpson damage correlations.

Design Wind Speed (mph)

3-second gust speed at 33 ft (10 m) above ground

Building Type

Residential (Wood Frame) Light Commercial (Metal/Masonry) Engineered Commercial (Concrete/Steel) Essential Facility (Hospital/Emergency)

Exposure Category

B – Suburban/Wooded (Kz=0.70 at 33 ft) C – Open Terrain (Kz=0.85 at 33 ft) D – Coastal/Open Water (Kz=1.03 at 33 ft)

Building Height (ft)

Mean roof height above ground

Risk Category

I – Low Hazard (Importance Factor = 0.87) II – Standard (Importance Factor = 1.00) III – Substantial Hazard (Importance Factor = 1.15) IV – Essential Facility (Importance Factor = 1.15)

Building Age (years)

Older buildings may have lower resistance

Calculate Risk Results will appear here.

function winCalc() { var resultDiv = document.getElementById('win-result');

// --- Inputs --- var V = parseFloat(document.getElementById('win-windspeed').value); var bType = parseInt(document.getElementById('win-building-type').value); var expCat = document.getElementById('win-exposure').value; var h = parseFloat(document.getElementById('win-height').value); var I = parseFloat(document.getElementById('win-importance').value); var age = parseFloat(document.getElementById('win-age').value);

// --- Validation --- if (isNaN(V) || V 300) { resultDiv.innerHTML = 'Please enter a valid wind speed between 1 and 300 mph.'; return; } if (isNaN(h) || h 2000) { resultDiv.innerHTML = 'Please enter a valid building height between 5 and 2000 ft.'; return; } if (isNaN(age) || age 200) { resultDiv.innerHTML = 'Please enter a valid building age between 0 and 200 years.'; return; }

// --- Exposure Velocity Pressure Coefficient Kz (ASCE 7-22 Table 26.10-1) --- // Kz = 2.01 * (z/zg)^(2/alpha) // Exposure B: alpha=7.0, zg=1200 ft // Exposure C: alpha=9.5, zg=900 ft // Exposure D: alpha=11.5, zg=700 ft var alpha, zg; if (expCat === 'B') { alpha = 7.0; zg = 1200; } else if (expCat === 'C') { alpha = 9.5; zg = 900; } else { alpha = 11.5; zg = 700; }

var z = Math.max(15, h); // minimum z = 15 ft per ASCE 7 var Kz = 2.01 * Math.pow(z / zg, 2 / alpha); Kz = Math.min(Kz, 1.80); // cap per ASCE 7

// --- Topographic Factor Kzt (assume flat terrain = 1.0) --- var Kzt = 1.0;

// --- Ground Elevation Factor Ke (sea level = 1.0) --- var Ke = 1.0;

// --- Velocity Pressure qz (ASCE 7-22 Eq. 26.10-1) --- // qz = 0.00256 * Kz * Kzt * Ke * V^2 (lb/ft²) var qz = 0.00256 * Kz * Kzt * Ke * V * V;

// --- Design Wind Pressure p = qz * G * Cf * I --- // G = gust factor = 0.85 (rigid structure, ASCE 7 Section 26.11) // Cf = force coefficient (simplified: 1.3 for enclosed rectangular building) var G = 0.85; var Cf = 1.3; var p = qz * G * Cf * I; // lb/ft²

// --- Building Resistance Capacity (lb/ft²) by type --- // Based on typical design pressures for each construction type var capacityBase; if (bType === 1) capacityBase = 20; // Wood frame residential else if (bType === 2) capacityBase = 35; // Light commercial else if (bType === 3) capacityBase = 60; // Engineered commercial else capacityBase = 75; // Essential facility

// --- Age Degradation Factor --- // Capacity reduces ~0.3% per year due to material aging, max 30% reduction var ageFactor = Math.max(0.70, 1.0 - (age * 0.003)); var capacity = capacityBase * ageFactor;

// --- Demand-to-Capacity Ratio (DCR) --- var DCR = p / capacity;

// --- Risk Score (0–100) --- // Normalized sigmoid-like mapping of DCR to risk percentage var riskScore = Math.min(100, Math.max(0, (DCR / 2.0) * 100));

// --- Damage Level Classification --- var damageLevel, damageColor, damageDesc; if (DCR = 1.15) ? 130 : 115;

// --- Output ---
resultDiv.innerHTML =
'### Wind Structural Damage Risk Results
' +
'' +
'Velocity Pressure Coefficient (Kz)' + Kz.toFixed(3) + '' +
'Velocity Pressure (qz)' + qz.toFixed(2) + ' lb/ft²' +
'Design Wind Pressure (p)' + p.toFixed(2) + ' lb/ft²' +
'Building Resistance Capacity' + capacity.toFixed(2) + ' lb/ft² (age-adjusted)' +
'Demand-to-Capacity Ratio (DCR)' + DCR.toFixed(3) + (DCR >= 1.0 ? ' ⚠️ EXCEEDS CAPACITY' : ' ✅ Within Capacity') + '' +
'Risk Score' + riskScore.toFixed(1) + ' / 100' +
'Wind Speed Context' + windContext + '' +
'' +
'' +
'Damage Level: ' + damageLevel + '' +
'' + damageDesc + '' +
'' +
'Recommendation: ' +
(DCR >= 1.0
? 'Wind loads exceed structural capacity. Consult a licensed structural engineer immediately. Consider wind-resistant retrofitting or evacuation during high-wind events.'
'Structure appears adequate for this wind speed. Ensure regular maintenance and inspect connections, roof fasteners, and cladding annually.') + '

' + 'Note: This is a simplified risk estimate. A licensed structural engineer should perform a full ASCE 7 analysis for design or safety decisions.

'; }

#### Formulas Used

Velocity Pressure Coefficient (ASCE 7-22 Eq. 26.10-1): Kz = 2.01 × (z / zg)2/α

Velocity Pressure: qz = 0.00256 × Kz × Kzt × Ke × V²  (lb/ft²)

Design Wind Pressure: p = qz × G × Cf × I  (lb/ft²) where G = 0.85 (gust factor), Cf = 1.3 (force coefficient), I = importance factor

Demand-to-Capacity Ratio: DCR = p / Capacityadjusted Capacityadjusted = Capacitybase × (1 − 0.003 × Age), min 70% of base

Risk Score: Risk = min(100, (DCR / 2.0) × 100)

#### Assumptions & References

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