← Back to All Tools
🏗️

Structural Steel I-Beam Deflection & Bending Stress Calculator

Calculate simply supported structural steel beam maximum bending moment, flexural stress, and center deflection (L/360 and L/240 limits) under uniform distributed loads.

Includes Dead Load (DL) + Live Load (LL) + Beam Weight
e.g., W10x30 = 170 in⁴, W12x26 = 204 in⁴, W14x30 = 291 in⁴

Calculation Results

Midspan Maximum Deflection: 0.424 inches Span Ratio: L / 509 (Passes L/360 Code)
Maximum Bending Moment: 34,425 ft-lbs
Maximum Flexural Stress (fb): 12,368 PSI Stress Ratio: 24.7% of 50 ksi yield
End Reaction Load (Each Support): 7,650 lbs

About This Calculator

Calculate simply supported structural steel beam maximum bending moment, flexural stress, and center deflection (L/360 and L/240 limits) under uniform distributed loads.

Frequently Asked Questions

What is the L/360 deflection limit in building codes?

L/360 is the International Building Code (IBC) maximum allowable live load deflection for floors. For an 18-foot span (216 inches), maximum deflection cannot exceed 216 / 360 = 0.60 inches to prevent drywall plaster cracking and bouncy floors.

What is the difference between Moment of Inertia (Ix) and Section Modulus (Sx)?

Moment of Inertia (Ix, in⁴) measures a cross-section's resistance to bending deflection and sag. Elastic Section Modulus (Sx, in³) measures the beam's geometric resistance to yield stress and structural failure.

What does W12x26 mean for a wide-flange steel beam?

In AISC designation, 'W' indicates a wide flange I-beam shape, '12' represents the nominal depth of the beam in inches (approximately 12 inches deep), and '26' denotes the weight in pounds per linear foot (26 lbs/ft).

What modulus of elasticity (E) is used for structural steel?

Structural steel has a constant Young's modulus of elasticity (E) of approximately 29,000,000 PSI (29 x 10^6 psi or 200 GPa), regardless of whether it is A36, A572, or A992 grade steel.