Truss Designs & Analysis

Made by Nick Johnson Truss Designs & Analysis Continue

Table of Content Start Lesson How to Teachers Quiz

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The Lessons Design Analysis (statics) (RECOMMENDED TO DO FIRST)

What Is A Truss? • A truss consists of straight members that connect at joints that form a triangular shape.

What Does A Truss Do? • Trusses are engineered to help hold the forces that will be placed on the object. • An example is snow on a roof.

Two Truss Categories All Trusses will fall under these two categories. - Parallel Chord Truss - Pitched Truss

The Categories Pitched Truss Parallel Chord Truss • Characterized for it’s triangular shape • Usually used for roof construction • Will always have a parallel top and bottom chords. • Is often used for bridge design or floor construction.

Parts of a Truss Click Each Part to Learn More Kings Post Top Chord Gusset Truss Web Bottom Chord

Top Chord • An inclined or horizontal member(s) that establishes the top surface member of a truss Top Chord

Bottom Chords • Horizontal or inclined member that establishes the bottom edge of the truss Bottom Chord

Truss Web • Often given to the shorter members that join the top and bottom chords, which form triangular patterns in that truss. Truss Web

King Post • Is used to help support the peak or top of the common truss. King Post

Gussets • Used everywhere the web supports and king post intersect the top and bottom chord as well as at the bearing point Gussets

Types of Trusses Common Truss Flat Truss

Types of Trusses Double Fink Bowstring Truss

Types of Trusses Scissors Dual Pitch

Great Job! • You have just finished one half of the lesson. Go ahead and take a short 5 minute break and come back and finish the other lesson.

Statics Example: FC = 15lb 10in 6in

What You Need to Know The Sign Convention +Y + +X

What You Need to Know Attachments Roller Pin Fx = = Fy Fy

Formulas • ∑Fx = 0, all the forces in the x direction must equal zero. • ∑Fy= 0, all the forces in the y direction must equal zero. • ∑M = 0, all the moments around one point must equal zero.

Solving • Lets go back to the example. FC = 15lb 10in 6in

Free Body Diagram • This is a drawing that shows all the forces that are acting on the model.

Solving • Now transfer the model into a FBD. 3in FC = 15lb 10in FAx 6in FBy FAy

Solving • Find which direction has one unknown. • You can look and see that the x direction has one unknown. Steps: ∑ FX = 0 0 = Fax Fax = 0

Solving • Now lets look at the y direction. • How many unknowns are there? • There are two unknowns so we will have to use moments. 3in FC = 15lb 10in Fax = 0 6in FBy FAy

Solving • So a moment is a force times it’s perpendicular distance to the selected point. • Ex. M= F ∙ d • So you have to pick a point that will cancel a unknown. • So let us pick point A 6in FBy FAy

Solving for the Moment • Steps: ∑MA = 0 0 = Fax (d) + Fay (d) + Fby(d) + Fc (d) 0 = 0(0) + Fay (0) + Fby (6) -15(3) Fby= 7.5lb

Solving For FAy • Now that you found one of the unknowns you can solve for FAy. ∑Fay = 0 0 = Fay + Fby+ Fc 0= Fay + 7.5 – 15 Fay = 7.5lb

Why are these Important? Roof Failure

Why are these Important? Bridge Failure

Congrats! You have now finished the lesson you may now take the quiz or go back to the main menu. Quiz

Question 1 • Support forces from above. • It is used for looks. • They are used to frame a door. 1) What is a Truss used for?

I’m Sorry You answer the question incorrectly. Please go back and try again. Review

What Does A Truss Do? • Trusses are engineered to help hold the forces that will be placed on the object. • An example is snow on a roof. Back To Question

That’s Right You answered the question correct! Next Question

Question 2 2) What can happen if a truss is made wrong? • Roof Failure • Bridge Failure • Nothing will happen • Both A & B

Why Is This Important? • Roof Failure • Bridge Failure • It maximize the amount of strength that can be held. Back To Question