W 8x40 C 8x13.75 Find lx bf

Materials Science And Engineering Properties
1st Edition
ISBN:9781111988609
Author:Charles Gilmore
Publisher:Charles Gilmore
Chapter12: Composite Materials
Section: Chapter Questions
Problem 12.13P
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### Moment of Inertia Calculation for Composite Section

#### Diagram Description:
The diagram represents a composite section consisting of a wide flange beam (W shape) placed over a C-shaped channel.

1. **Wide Flange Beam:**
   - Designation: W 8x40
   - The section is shaped like the letter "H", representing a standard wide-flange beam.

2. **C-Shaped Channel:**
   - Designation: C 8x13.75
   - The C-shaped channel is positioned below the wide flange beam, with its open side facing downward.
   
#### Labels:
- Two important dimensions are labeled:
  - **bf**: This likely represents the width of the flange.
  - **t**: This likely represents the thickness of the web of the section.
  
#### Task:
- The task specified is to find \(I_x\), which is the moment of inertia about the x-axis for the composite section.

### Detailed Explanation:

To calculate the moment of inertia \(I_x\) for the composite section, follow these steps:

1. **Break Down the Section:**
   - Separate the wide flange beam (W 8x40) and the C-shaped channel (C 8x13.75).

2. **Determine Individual Moments of Inertia:**
   - Calculate the moment of inertia for the wide flange beam and the C-shaped channel individually, using standard formulas for these shapes.

3. **Use Parallel Axis Theorem:**
   - For any component that is not centered on the x-axis, use the parallel axis theorem to find its moment of inertia relative to the x-axis of the composite section.

   \[
   I_{x'} = I_x + Ad^2
   \]

   where:
   - \(I_{x'}\) is the moment of inertia about the composite centroidal x-axis.
   - \(I_x\) is the moment of inertia about the component's own centroidal x-axis.
   - \(A\) is the area of the component.
   - \(d\) is the distance from the component's centroid to the composite centroidal x-axis.

4. **Sum of Moments of Inertia:**
   - Sum the moments of inertia (including any adjustments from the parallel axis theorem) to get the total \(I_x\) for the composite section.

By following this method, one can accurately determine the moment of inertia \(I_x\) for
Transcribed Image Text:### Moment of Inertia Calculation for Composite Section #### Diagram Description: The diagram represents a composite section consisting of a wide flange beam (W shape) placed over a C-shaped channel. 1. **Wide Flange Beam:** - Designation: W 8x40 - The section is shaped like the letter "H", representing a standard wide-flange beam. 2. **C-Shaped Channel:** - Designation: C 8x13.75 - The C-shaped channel is positioned below the wide flange beam, with its open side facing downward. #### Labels: - Two important dimensions are labeled: - **bf**: This likely represents the width of the flange. - **t**: This likely represents the thickness of the web of the section. #### Task: - The task specified is to find \(I_x\), which is the moment of inertia about the x-axis for the composite section. ### Detailed Explanation: To calculate the moment of inertia \(I_x\) for the composite section, follow these steps: 1. **Break Down the Section:** - Separate the wide flange beam (W 8x40) and the C-shaped channel (C 8x13.75). 2. **Determine Individual Moments of Inertia:** - Calculate the moment of inertia for the wide flange beam and the C-shaped channel individually, using standard formulas for these shapes. 3. **Use Parallel Axis Theorem:** - For any component that is not centered on the x-axis, use the parallel axis theorem to find its moment of inertia relative to the x-axis of the composite section. \[ I_{x'} = I_x + Ad^2 \] where: - \(I_{x'}\) is the moment of inertia about the composite centroidal x-axis. - \(I_x\) is the moment of inertia about the component's own centroidal x-axis. - \(A\) is the area of the component. - \(d\) is the distance from the component's centroid to the composite centroidal x-axis. 4. **Sum of Moments of Inertia:** - Sum the moments of inertia (including any adjustments from the parallel axis theorem) to get the total \(I_x\) for the composite section. By following this method, one can accurately determine the moment of inertia \(I_x\) for
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ISBN:
9781111988609
Author:
Charles Gilmore
Publisher:
Cengage Learning