ES226 Spring 2018 Lesson 1 – The Big Picture I
“Some countries use the Metric System. Others have been to the Moon.” - Pierce Harger
Lesson 1 – The Big Picture I (DRAFT)
Monday, January 22, 2018
The purpose of this lesson is to teach students the Big Picture:
· We need Statics to tell us the Forces (and Moments) that are acting on members of a structure.
· If the Force (or Moment) that is acting on a member is more than the member can take, that member will FAIL.
· If the member of a structure FAILS, property will be damaged, people may get hurt, and engineers will get sued.
∴ We need Statics
CLASS TUESDAY (TOMORROW): We will be downstairs in Room 117. This is a one-time occurrence that will only happen this week.
Reading
· Read the Syllabus for this course.
Lesson Objectives
1. Know that, for any 2D object that is in Static Equilibrium (i.e., not accelerating), Fx=0, Fy=0, MA=0, where A can be any point in space.
2. Determine the unknown forces acting on a beam in 2D space, using the 3 equations of Static Equilibrium.
3. Determine the internal forces that are acting on the top and bottom members of a trussed girder by taking “a cut” at the position of interest and applying the equations of Static Equilibrium.
4. Define stress.
Homework (Due Wednesday, 5pm)
1.
a. Compute the moment about point A (use counterclockwise positive. Units: ft-lbs)
b. Compute the moment about point B (note: if this is different from previous, something is wrong).
c. State whether or not the beam is in Static Equilibrium.
2. Use Statics to determine the unknown forces FB and FD.
3. Determine the internal horizontal force acting on the top tube at point A in the trussed-girder shown by “taking a cut” and applying Static Equilibrium. GIVEN: The center-to-center distance between the top and bottom tubes is 5”