SS (Structural Systems)

Question 1

What is a FORCE? (+ units)

Answer 1

Force is a push/pull exerted on an object. Force has (a) magnitude, (b) direction, and (c) point of application.

Force is measured in units of weight (pounds, kips, Newtons)

Question 2

What is a LOAD?

What is a STRESS?

Answer 2

Load is an EXTERNAL force applied to a body.

Stress is an INTERNAL force that is the resistance of a body to the load.

Question 3

What is the LINE OF ACTION?
What are CONCURRENT FORCES?
What are NON-CONCURRENT FORCES?

Answer 3

Line of action is the line (a) parallel to and (b) in line with the force.

Concurrent forces = when several lines of action pass through a common point.

Nonconcurrent = lines of action do not intersect.

Question 4

What is a FORCE POLYGON?

Answer 4

Order of forces does not matter.
The resultant force points AWAY from the starting point.
The resultant force is concurrent with forces.
The resultant force has magnitude and direction.

Question 5

What is a RESULTANT FORCE?

What is the EQUILIBRANT?

Answer 5

Resultant force = vectorial summation of 2+ forces into a single force (has direction and magnitude

Equilibrant force = equal to magnitude of resultant and has same line of action, but opposite direction (brings the Resultant Force to equilibrium)

Question 6

What is FREE-BODY DIAGRAM?

Answer 6

The internal forces at an imaginary cut through structure (aka turning the section cut into an end point)

Question 7

What is EQUILIBRIUM?

Answer 7

Equilibrium is when an object has no unbalanced force acting upon it (no moving, no rotating)

Sum of horizontal forces = 0
Sum of vertical forces = 0
Sum of moment = 0

Question 8

What is a REACTION?

Answer 8

Reaction is a force acting at supports that hold a beam in equilibrium (solve by taking moments about the ends)

• SUM OF LOADS = SUM OF REACTIONS *

Question 9

What is a MOMENT?

What is a COUPLE?

Answer 9

Moment is the tendency of a force to cause rotation about a given point or axis. Moment does NOT equal actual rotation, only the tendency to rotate.

Couple is 2 forces equal in magnitude but opposite in direction. Moment = 0 (because the tendency to rotate in one direction is balanced by the tendency to rotate in the opposite direction).

Question 10

How to calculate Moment?

Answer 10

M = F x e
Moment = Force x distance from axis of rotation

M = Moment (clockwise) - Moment (counterclockwise)

Question 11

What is TRANSLATION?

What is ROTATION?

Answer 11

Translation is linear displacement motion (up, down, left, right)

Rotation is motion measured angularly as it revolves around a fixed reference point in a radial manner.