Podcast
Questions and Answers
Supports provide what to a structure?
Supports provide what to a structure?
- Expansion and contraction
- Restraints and stability (correct)
- Instability and vibration
- Flexibility and motion
A pin support prevents both horizontal and vertical translation.
A pin support prevents both horizontal and vertical translation.
True (A)
What type of force does a roller support provide?
What type of force does a roller support provide?
vertical
A fixed end support prevents translation and ______.
A fixed end support prevents translation and ______.
Match each support type with the movements it allows:
Match each support type with the movements it allows:
What is the primary purpose of analyzing Free Body Diagrams (FBDs)?
What is the primary purpose of analyzing Free Body Diagrams (FBDs)?
In a Free Body Diagram, internal forces within a sectioned member are always negligible and can be ignored.
In a Free Body Diagram, internal forces within a sectioned member are always negligible and can be ignored.
What condition must be satisfied for a rigid body to be in equilibrium?
What condition must be satisfied for a rigid body to be in equilibrium?
In the equations of equilibrium, ΣΜi represents the sum of all ______ acting on the body.
In the equations of equilibrium, ΣΜi represents the sum of all ______ acting on the body.
In a 2D problem, how many independent equations of equilibrium can be applied to solve for unknowns?
In a 2D problem, how many independent equations of equilibrium can be applied to solve for unknowns?
When solving for reactions in a truss, if a reaction force is calculated as negative, it means the assumed direction was incorrect.
When solving for reactions in a truss, if a reaction force is calculated as negative, it means the assumed direction was incorrect.
What does the abbreviation FBD stand for?
What does the abbreviation FBD stand for?
In structural analysis, supports are used to provide restraints and ______ to the structure.
In structural analysis, supports are used to provide restraints and ______ to the structure.
Which type of support prevents both translation and rotation?
Which type of support prevents both translation and rotation?
ΣΜc=0 is one of the equations of equilibrium.
ΣΜc=0 is one of the equations of equilibrium.
Flashcards
What do supports provide?
What do supports provide?
Supports provide resistance and stability to structures, developing reactions against translations and rotations from applied forces.
What movements does a 'pin' prevent?
What movements does a 'pin' prevent?
A pin support prevents horizontal and vertical translation, but allows rotation.
What movements does a 'roller' prevent?
What movements does a 'roller' prevent?
A roller support prevents vertical translation, but allows horizontal translation and rotation.
What movements does a 'fixed end' prevent?
What movements does a 'fixed end' prevent?
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What movements does a 'hinge' allow?
What movements does a 'hinge' allow?
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What's included in a Free Body Diagram?
What's included in a Free Body Diagram?
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What are the equations for equilibrium?
What are the equations for equilibrium?
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Study Notes
- The lecture discusses support types, connections, and free body diagrams for rigid bodies.
- It reviews equations of equilibrium and provides guidance for problem-solving.
Support Types and Connections
- Supports restrain movement and provide stability.
- Supports develop reactions that prevent translations and rotations.
- Reactions include moment reactions and force reactions.
- Pin Support: Prevents horizontal and vertical translation, allows rotation.
- The reaction forces are a single linear force of unknown direction or a horizontal force and a vertical force.
- Roller Support: Prevents vertical translation, but allows horizontal translation and rotation.
- The reaction is a single linear force (either upward or downward).
- Rocker Support: Functions similarly to a roller support.
- Elastomeric Pad Support: Acts like a roller support.
- Link Support: Prevents translation in the direction of the link, allows translation perpendicular to the link and rotation.
- The reaction is a single linear force in the direction of the link.
- Fixed End Support: Prevents horizontal and vertical translation, and rotation.
- The reactions are horizontal and vertical components of a linear resultant, and a moment.
- Hinge Support: Prevents relative displacement of member ends, allows both rotation, and horizontal and vertical displacement.
- The reactions are equal and oppositely directed horizontal and vertical forces.
Free Body Diagrams (FBD) of Rigid Bodies (2D)
- FBDs for rigid bodies include concurrent and non-concurrent coplanar forces.
- FBDs include:
- Externally applied forces and moments.
- Weight of the rigid body (mostly negligible unless noted).
- Reaction forces and Moment reactions (from constraints).
- Forces developed within a sectioned member.
- Equilibrium is satisfied by: ΣFx=0, ΣFy=0, ΣΜi=0
Problem Solving and Equations of Equilibrium
- Equations of equilibrium in a 2-dimensional problem
- ΣFx=0
- ΣFy=0
- ΣΜi=0
- Example Problem: Find the reactions for Truss 1.
- Step 1: Draw a free body diagram.
- Step 2: Set equations of equilibrium and solve for unknowns.
- Given: 5k forces at various points on the truss, 2'-6" and 5'-0" dimensions, 30'-0" total length (6 equal spaces).
- Calculations:
- ΣFx = 0 = 5 k + Rx, therefore Rx = -5 k (opposite to assumed).
- ΣΜB = 0 = -55 + 515 + 510 + 55 –R'y*30, therefore R'y= (125 k-ft)/30 =4.17 k.
- ∑Fy = 0 = -5 -5 -5 + R'y + Ry therefore Ry= 15 -4.17 = 10.83 k.
Assignments
- Problem 2: Solve problem 2.36 on page 84, always draw a free body diagram (FBD).
- Homework 6: Do problems 2.37 and 2.38 on pages 84 and 85, always draw FBDs.
- Upcoming Quiz: Lectures L1 through L6 and all related material.
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Description
Explanation of support types and connections for rigid bodies, including pin, roller, and link supports. Covers reaction forces and their role in preventing translation and rotation. Includes free body diagrams and equations of equilibrium.
