Math Problem Statement
Find FBD and Reactions
Solution
Let's analyze the image and solve for the reactions at the supports.
Step 1: Identify the elements in the diagram.
- Beam: A simply supported beam with point load and uniformly distributed load (UDL).
- Supports:
- Support A: A pinned support (which can take both vertical and horizontal reactions).
- Support B: A roller support (which can take only vertical reactions).
Step 2: Loadings on the beam.
- Uniformly Distributed Load (UDL): 30 kN/m, acting from A to C over a span of 3.2 m.
- Point Load: 24 kN, applied vertically at point B.
Step 3: Free Body Diagram (FBD)
In the FBD, we can represent the loads and reactions as follows:
- Vertical reaction at A:
- Vertical reaction at B:
- Horizontal reaction at A:
We can ignore the horizontal reaction , as there are no horizontal forces acting on the system.
Step 4: Equilibrium Equations
We will use the static equilibrium conditions:
-
Sum of Forces in the Vertical Direction (ΣF_y = 0): The total load is the sum of the UDL and the point load.
UDL load:
Point load:
Therefore, the total vertical load is: So,
-
Sum of Moments about Point A (ΣM_A = 0): The moment created by each force around point A must sum to zero.
Moment due to UDL: The UDL creates a resultant force of 96 kN acting at the center of its distribution (i.e., 1.6 m from A). Thus, the moment is:
Moment due to point load at B: The point load of 24 kN acts at a distance of 4.0 m from A. The moment is:
Moment due to reaction at B: creates a clockwise moment about A, and its distance from A is 4.0 m:
Using :
-
Sum of Forces in the Vertical Direction (Revisited): Now that we have , we can solve for :
Step 5: Final Reactions
- Reaction at A () = 57.6 kN (upward)
- Reaction at B () = 62.4 kN (upward)
Step 6: Free Body Diagram (FBD)
- UDL of 30 kN/m over 3.2 m acting from A to C.
- Point load of 24 kN acting at B.
- Reaction forces and .
Would you like the detailed drawing of the FBD?
Here are 5 related questions to expand on this topic:
- How would the reaction forces change if the UDL was increased to 40 kN/m?
- What would be the reactions if the point load was moved 0.5 m to the left?
- How does the distance between the supports affect the reaction forces?
- Can you calculate the bending moment at the midpoint between A and B?
- What would happen if the roller support at B was replaced with a pinned support?
Tip: Always double-check your moment calculations by verifying the dimensions and force magnitudes, especially when dealing with distributed loads.
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Math Problem Analysis
Mathematical Concepts
Statics
Equilibrium
Beam Reactions
Formulas
ΣF_y = 0: R_A + R_B = Total Load
ΣM_A = 0: Sum of Moments about A
Moment of UDL = UDL * distance to center
Moment of Point Load = Point Load * distance
Theorems
Equilibrium of Forces and Moments
Suitable Grade Level
Undergraduate Engineering
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