{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

TR7_ENGR111A_2011C_MM (4)

# TR7_ENGR111A_2011C_MM (4) - Calculating Internal Forces in...

This preview shows pages 1–10. Sign up to view the full content.

ENGR 111 Track A 1 Calculating Internal Forces in a Truss using Method of Joints. Zero-force Members. TR-7

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
RAT 05_01 ENGR 111 Track A 2 Page Team Number RAT 02_02 Section Number Date Name Take a NEW clean sheet of paper and write Reminder: Individual work There are two problems on this RAT. Take 3 minutes to solve each of the problems.
RAT 05_01 Estimate the Moment in the problem below. Can the truss below be in static equilibrium? Why or why not? (hint: what are the reaction forces at A and C) ENGR 111 Track A 3 20  lb A B C 30° 60° F = 10 N pivot 1 m

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ENGR 111 Track A 4 Learning Objectives In this module you will learn how to Calculate internal forces in truss members using Method of Joints Draw the free body diagram of the joints in a truss. Develop the equilibrium equations for a joint. Apply the equilibrium equations to find the unknown forces at a joint . Identify whether a member is in tension or compression.
ENGR 111 Track A 5 Trusses: Internal Forces Links in a truss are 2-force members. The force on a truss link is called an axial force . If the force tends to lengthen the member it is called a tensile (tension) force . If the force tends to shorten the member it is called a compressive force . R E V I E W

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ENGR 111 Track A 6 Truss Links are in Equilibrium. Equal and Opposite Forces on the Joint! Link in TENSION : Force points away from the link (force stretches the link) Now think about how this link interacts with the joints: Newtons 3rd law implies forces are equal and opposite Link in COMPRESSION : Force points towards the link (force pushes on the link) Equilibrium implies forces on the link are equal and opposite . R E V I E W
ENGR 111 Track A 7 Trusses: FBDs of Links (Bars) Draw the FBD for each bar. IGNORE GRAVITY. Remember 2-force members. There should be 3 FBDs! If you are unsure whether the bar is in tension or compression, assume tension . We will always assume that the bars are in tension! 20 lb A B C 30° 60° Fab Fab Fac Fac Fbc Fbc R E V I E W

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ENGR 111 Track A 8 Trusses: FBDs of Joints “Exploded view” of the truss ABC. Notice the forces at joints!! 20 lb A B C F AC F AC F BC F BC F AB F AB Ay By Bx F BC F BC F AB F AB F AC F AC
ENGR 111 Track A 9 Internal Forces: Method of Joints How do we find the forces in the links? Three steps: 1. Start with finding the external reaction forces. Work with the truss as a whole: forget about the links for now (links are always in equilibrium!). Draw the FBD of the Truss, write down the equilibrium equations, solve for unknown external reactions. This part we know. 2. New: we need to “explode” the truss. We will work with joints only. Draw the FBD of the Joints: assume that all links are in tension; recall that links (bars) are 2-force members, hence forces act along the bars.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern