Q2 (10 Marks) A square and solid cross-section is to be used for a beam under the given loading below. * Find the reaction force and moment * Determine shear force profile * Determine bending moment profile 0K gap - 2 Fp f = . = HO Kap. $1 > Z 64t = Ne — lat |
Question:
Q2 (10 Marks)
A square and solid cross-section is to be used for a beam under the given loading below.
* Find the reaction force and moment
* Determine shear force profile
* Determine bending moment profile
0K gap -
2 Fp f
= .
= HO Kap. $1
>
Z 64t
=
Ne — lat |
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Asked by: Kumar
Created at: 2025-07-26 07:17:27
Asked by: Kumar
Created at: 2025-07-26 07:17:27
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Let's break down the solution step by step for the **fixed beam** under the given loading:
---
### **1. Find the Reaction Force and Moment at the Fixed End**
#### **Given Data:**
- Uniformly distributed load (UDL): \( w = 2 \) kip/ft over \( 6 \) ft
- Point load: \( P_1 = 10 \) kip at \( 6 \) ft from left
- Point load: \( P_2 = 8 \) kip at \( 10 \) ft from left
- Applied moment: \( M_0 = 40 \) kip·ft at the right end
- Beam length: \( L = 10 \) ft
#### **Step 1: Replace UDL with Equivalent Point Load**
- Total UDL force: \( F_{UDL} = w \times 6 = 2 \times 6 = 12 \) kip
- Acts at \( 3 \) ft from the left end (centroid of UDL region)
#### **Step 2: Equilibrium Equations**
Let the reactions at the fixed end (left) be \( A_y \) (vertical) and \( M_A \) (moment).
##### **Sum of Vertical Forces:**
\[
A_y - F_{UDL} - P_1 - P_2 = 0
\]
\[
A_y - 12 - 10 - 8 = 0
\]
\[
A_y = 30 \text{ kip (upward)}
\]
##### **Sum of Moments about the Fixed End (A):**
Take counterclockwise moments as positive.
\[
M_A - (12 \times 3) - (10 \times 6) - (8 \times 10) - 40 = 0
\]
\[
M_A - 36 - 60 - 80 - 40 = 0
\]
\[
M_A = 36 + 60 + 80 + 40 = 216 \text{ kip·ft (counterclockwise)}
\]
---
### **2. Shear Force Profile**
#### **From Left to Right:**
- **From A to 6 ft (UDL only):**
- Shear starts at \( +30 \) kip.
- Drops linearly by \( 2 \) kip/ft over 6 ft: \( 2 \times 6 = 12 \) kip.
- Shear just left of 6 ft = \( 30 - 12 = 18 \) kip.
- **At 6 ft:**
- Shear drops by 10 kip at the point load: \( 18 - 10 = 8 \) kip.
- **At 10 ft:**
- Shear drops by 8 kip at the point load: \( 8 - 8 = 0 \) kip.
- **Moment at the end:**
- No additional vertical loads after 10 ft.
#### **Shear Values:**
- At \( x = 0 \): \( +30 \) kip
- At \( x = 6^- \): \( +18 \) kip
- At \( x = 6^+ \): \( +8 \) kip
- At \( x = 10^- \): \( 0 \) kip
---
### **3. Bending Moment Profile**
- At \( x = 0 \): \( M_A = +216 \) kip·ft
- Bending moment decreases under loads.
#### **General equation for bending moment at \( x \) (0 ≤ x ≤ 6):**
\[
M(x) = M_A - 2x \cdot \frac{x}{2}
\]
\[
M(x) = M_A - x^2
\]
(where \( M_A = 216 \) and UDL contributes \(-2x \cdot \frac{x}{2}\))
#### **At \( x = 6 \):**
\[
M(6) = 216 - (2 \cdot 6 \cdot 3) = 216 - 36 = 180 \text{ kip·ft}
\]
But also consider the point load at 6 ft for \( x > 6 \):
#### **For \( 6 < x < 10 \):**
\[
M(x) = M_A - 2 \cdot 6 \cdot (x - 3) - 10(x - 6)
\]
Alternatively, sum moments due to all left-side forces at any section \( x \).
#### **At \( x = 10 \):**
\[
M(10) = 216 - (2 \times 10 \times 5) - 10 \times 4 - 8 \times 0 - 40
\]
\[
M(10) = 216 - 100 - 40 - 0 - 40 = 36 \text{ kip·ft}
\]
But also subtract the applied moment:
\[
M_{final}(10) = 36 - 40 = -4 \text{ kip·ft}
\]
---
### **Summary Table**
| Location | Shear (kip) | Moment (kip·ft) |
|-------------|-------------|-----------------|
| \( x = 0 \) | 30 | 216 |
| \( x = 6^- \) | 18 | (calculate using above) |
| \( x = 6^+ \) | 8 | (calculate) |
| \( x = 10^- \) | 0 | -4 |
---
## **Shear Force and Bending Moment Diagrams**
- **Shear Force Diagram:** Starts at +30 kip, drops linearly to +18 at 6 ft, then drops by 10 at point load, then by 8 at 10 ft to 0.
- **Bending Moment Diagram:** Starts at +216 kip·ft, parabolic decrease due to UDL, changes slope at point loads, ends at -4 kip·ft at 10 ft.
---
**If you need to see the diagrams, let me know and I can sketch them!**
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