Unistrut Load Capacity Calculator

Unistrut Load Capacity Calculator

P1000 (12 Gauge – 1-5/8″ x 1-5/8″) P1100 (14 Gauge – 1-5/8″ x 1-5/8″) P3300 (12 Gauge – 1-5/8″ x 7/8″) P5500 (12 Gauge – 1-5/8″ x 2-7/16″)

Uniformly Distributed Load (UDL) Center Point Load

Calculation Results:

Maximum Allowable Load: 0 lbs

Deflection at Max Load: 0 inches

Note: Calculations are based on beam orientation (open side up) and standard carbon steel properties.

function calculateUnistrutLoad() { var profile = document.getElementById('channelProfile').value; var span = parseFloat(document.getElementById('spanLength').value); var loadType = document.getElementById('loadType').value; var safetyFactor = parseFloat(document.getElementById('safetyFactor').value); if (isNaN(span) || span W = (8 * Fb * S) / L // W is total load in lbs maxLoad = (8 * Fb * S) / span; // Adjustment for Safety Factor (Fb is usually already adjusted in tables, // but we apply it here for customization) maxLoad = maxLoad / (safetyFactor / 1.67); // Deflection = (5 * W * L^3) / (384 * E * I) deflection = (5 * maxLoad * Math.pow(span, 3)) / (384 * E * I); } else { // M_max = (P * L) / 4 => P = (4 * Fb * S) / L maxLoad = (4 * Fb * S) / span; maxLoad = maxLoad / (safetyFactor / 1.67); // Deflection = (P * L^3) / (48 * E * I) deflection = (maxLoad * Math.pow(span, 3)) / (48 * E * I); } document.getElementById('maxLoadResult').innerText = maxLoad.toLocaleString(undefined, {maximumFractionDigits: 2}); document.getElementById('deflectionResult').innerText = deflection.toFixed(4); document.getElementById('resultsArea').style.display = 'block'; }

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Understanding Unistrut Load Capacity

Unistrut (strut channel) is a standardized structural system used in the construction and electrical industries for light structural support. Knowing the load capacity is critical for the safety and integrity of trapeze supports, seismic bracing, and equipment racks.

Key Factors Influencing Capacity

• Span Length: The distance between support points. As the span doubles, the load capacity generally halves for uniform loads and reduces significantly for point loads.
• Profile Dimensions: Deep channels like P5500 have a much higher Moment of Inertia (I) and Section Modulus (S) compared to shallow channels like P3300, allowing for much greater spans.
• Load Type: A Uniformly Distributed Load (UDL) spreads weight evenly across the entire span, whereas a Center Point Load concentrates all weight at the weakest part of the beam (the middle).
• Material Gauge: Standard Unistrut is 12-gauge steel. Thinner 14-gauge or 16-gauge channels have lower capacity even if the outer dimensions are the same.

Technical Reference Table

Series	Size (Inches)	Area (in²)	Weight (lb/ft)
P1000	1-5/8 x 1-5/8	0.555	1.89
P3300	1-5/8 x 7/8	0.334	1.16
P5500	1-5/8 x 2-7/16	0.723	2.47

Calculation Examples

Example 1 (Uniform Load): A P1000 channel with a 48-inch span. Using the standard allowable stress, it can support approximately 840 lbs of weight spread evenly. If that same 840 lbs is concentrated in the center, the channel may fail or exceed safety limits.

Example 2 (Deflection): For aesthetic and functional reasons, many engineers limit deflection to 1/240th or 1/360th of the span. For a 120-inch span, a deflection of 0.5 inches (1/240) is often the maximum permissible, even if the metal is not yet near its breaking point.

Safety and Standards

This calculator uses basic beam formulas. In real-world applications, always consult the official Unistrut Engineering Catalog. These calculations assume the beam is simply supported and lateral bracing is sufficient to prevent twisting (torsional-flexural buckling). Always use a safety factor (typically 1.67 per AISC) to account for material variations and unexpected dynamic loads.