Understanding Cantilever Beams

Cantilever beams are crucial structural elements that extend beyond their support point, requiring careful engineering consideration.

Load Types Point loads create maximum moment at support. Distributed loads follow parabolic moment curve. Combined loads need superposition analysis. Impact loads need dynamic factor (typically 1.5-2.0).
Stress Analysis Maximum bending stress at support = MC/I. Shear stress varies linearly. Consider both normal and shear stresses for complete analysis. Factor of safety typically 2-3.
Material Properties Steel: E=29,000 ksi, yield=36-50 ksi. Aluminum: E=10,000 ksi, yield=35 ksi. Wood: E varies 1,200-1,800 ksi, allowable stress 1-2 ksi.
Support Conditions Fixed end moment = WL²/2 for point load. Required embedment typically 1.5-2 times cantilever length. Consider torsional effects for eccentric loads.

Design Guidelines

Section Selection

I-beams most efficient for bending. Box sections better for torsion. L/d ratio typically 4-8 for efficiency. Consider lateral-torsional buckling for deep sections.

Deflection Limits

Typical limit L/180 for general use, L/360 for finished areas. Maximum deflection = PL³/3EI for point load. Consider both immediate and long-term deflection.

Connection Design

Moment connections need full penetration welds or multiple bolt rows. Consider prying action in bolted connections. Use stiffeners for heavy loads.

Special Considerations

Account for thermal expansion (±1/8" per 100ft typical). Consider vibration for pedestrian loads. Plan for drainage to prevent water accumulation.

Technical Specifications

Material Properties

Steel: E = 29,000 ksi
Wood: E = 1,600 ksi
Aluminum: E = 10,000 ksi

Typical Applications

Balconies
Overhangs
Sign Supports
Architectural Features

Design Formulas

Point Load

M = P × L

Δ = (P × L³)/(3EI)

Where:

M = Maximum moment
P = Point load
L = Length
E = Elastic modulus
I = Moment of inertia

Uniform Load

M = (w × L²)/2

Δ = (w × L⁴)/(8EI)