Two Point Loads at One Third Points on a Simple Beam

third point loads
When specifying a beam or joist three things are usually considered;
First,is the beam strong enough that it doesn't fail by the fibers on the bottom being torn apart, a fiber failure.

Second, is the beam stiff enough that there will not be excessive deflection. A bouncy floor, cracked tile or plaster would be examples of this.

Third, is the beam strong enough that its fibers don't slip past one another, bend a magazine and watch the pages slide past one another. This is a horizontal shear failure.

Each Point Load on Beam(pounds)
Span of Beam (inches)
Width of Beam
Depth of Beam
Maximum Allowable Fiberstress in Bending (PSI)
Modulus of Elasticity (million PSI)
Maximum Allowable Horizontal Shear (PSI)
Click Here For Wood Design Values
Fiberstress in Bending Deflection Horizontal shear
Max Moment (ft-lbs) Deflection (inches) Shear (PSI)
Section Modulus Required Max 1/360 (Floor) Section Required
Section Modulus Input Max 1/240 (Roof) Section Input
Section Modulus Pass/Fail Deflection Pass/Fail Shear Pass/Fail

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