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Exposed Bldg Face

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Measuring Height

Building Classification

Unprotected Openings

Size a Radiator

Size a Wood Beam

Size a Steel Beam

Deflection Calculations

TANGENTS

The Area of a Circle

Stonehenge

World Population

Bouncing Ball

The Number One

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Angle of Incidence

Ashrae Window Test

Doors

Exposed Bldg Face

Fire Protection

Fire Walls

Floors

Footings

Foundations

Height Area and Use

Means of Egress

Mezzanines

Roofs

Thermal Massing

Vegetation

Walls

Windows

Ventilation

ENERGY

Solar Energy

Solar PV Panels

Geothermal Energy

Wind Energy

Cost of Energy

RESOURCES

Measuring Height

Building Classification

Unprotected Openings

Size a Radiator

Size a Wood Beam

Size a Steel Beam

Deflection Calculations

TANGENTS

The Area of a Circle

Stonehenge

World Population

Bouncing Ball

The Number One

Here is a chart you can use to calculate the deflection of a beam under specified loading conditions. The information you will need to use this chart is the Linear Load on the beam, the span of the beam, the size of the beam, and the Modulus of Elasticity for the specified material. Typically, in code references you will see deflection limits of L/360 or L/480. Knowing this information, you can solve for an equation to see how much a beam will deflect under different loading conditions.

How do you calculate this?

First, here is the equation

D = 5wL^{4} / 384EI

where

D = Deflection

w = weight per linear foot (or metre)

L= Span

E = Modulus of Elasticity

I = Moment of Inertia

Consider a deflection limit of L/360. The L refers to the span. For instance, a beam spanning 10 feet having a deflection limit of L/360 would equate to 10 ft / 360 which is is 0.0277 ft or convert the feet value to inches to get a more meaningful answer. (10 feet x 12 inches = 120 inches) so 120 / 360 = 0.33 inches or about 3/8". This means that a beam spanning 10 feet with a deflection limit of L/360 can sag a maximum amount of 3/8". When people study this, they sometimes size the beam up in order to decrease the deflection amount.

Knowing the maximum deflection allowed you then have to calculate how much a specific beam will deflect under various loading conditions. Typically, deflection calculations are made with specified loads only, not factored loads.

The chart below is an embedded exce sheet that you can use to calculate different deflection amounts. The chart begins with a linear load value on the beam so you may have to do a few calculations beforehand to come up with this value. Red numbers in the chart are the ones you can change.

Here are some Modulus of Elasticity values for reference

SPF wood No. 2` | 1.4 ksi | |

SPF Select Structural | 1.5 ksi | |

Douglas Fir | 1.6 ksi | |

LVL (Laminated Veneer Lumber) | 1.9 ksi | |

LVL (Laminated Veneer Lumber) | 2.0 ksi | |

Steel | 29.0 ksi | |