Problem Set in Mechanics of Deformable Bodies SHEAR & MOMENT DIAGRAMS USING EQUATION METHOD INSTRUCTIONS: Draw the Shear and Moment Diagrams of the following beams. Generate the corresponding Shear and Moment Equations. Problem No. 1 2zkN 7x kN [2m | DJ 4y kN/ B c E xe [2m 4 2m | 4m | 2m |
Question:
Problem Set in Mechanics of Deformable Bodies
SHEAR & MOMENT DIAGRAMS USING EQUATION METHOD
INSTRUCTIONS: Draw the Shear and Moment Diagrams of the following beams.
Generate the corresponding Shear and Moment Equations.
Problem No. 1
2zkN
7x kN [2m |
DJ
4y kN/
B c E xe
[2m 4 2m | 4m | 2m |
This is AI generated Response.
Asked by: Test User 100299
Created at: 2025-05-16 12:42:10
Asked by: Test User 100299
Created at: 2025-05-16 12:42:10
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Let's break down **Problem No. 1** step by step:
### **Given Beam:**
- Supports at A (pin) and F (roller)
- **Loads:**
- Point Load: 7 kN at B (2 m from A)
- Point Load: 2z kN at D (6 m from A, since D is 2 m from C, and C is 4 m from A)
- Distributed Load: 4y kN/m from C to E (length = 4 m)
- **Spans:**
- AB = 2 m
- BC = 2 m
- CD = 2 m
- DE = 2 m
- EF = 2 m
---
## **Step 1: Calculate Reactions at Supports**
Let’s denote:
- Reaction at A: \( R_A \)
- Reaction at F: \( R_F \)
**Sum of vertical forces:**
\[
R_A + R_F = 7 + 2z + (4y \times 4)
\]
\[
R_A + R_F = 7 + 2z + 16y
\]
**Take moments about A:**
\[
\sum M_A = 0
\]
\[
-7 \times 2 - (2z) \times 6 - (4y \times 4) \times (4 + 2) + R_F \times 12 = 0
\]
- 7 kN at 2 m
- 2z kN at 6 m
- 4y kN/m over 4m, acting at 4 + 2 = 6 m from A (center of distributed load at 4 m from C, which starts at 4 m from A, so center is at 4 + 2 = 6 m from A)
**Distributed load:**
- Total load = 4y kN/m × 4 m = 16y kN
- Acts at midpoint of 4 m span from C (so at 4 m + 2 m = 6 m from A)
So, sum of moments about A:
\[
-7 \times 2 - 2z \times 6 - 16y \times 6 + R_F \times 12 = 0
\]
\[
-14 - 12z - 96y + 12R_F = 0
\]
\[
12R_F = 14 + 12z + 96y
\]
\[
R_F = \frac{14 + 12z + 96y}{12}
\]
**Now, sum of vertical forces:**
\[
R_A + R_F = 7 + 2z + 16y
\]
\[
R_A = 7 + 2z + 16y - R_F
\]
\[
R_A = 7 + 2z + 16y - \frac{14 + 12z + 96y}{12}
\]
---
## **Step 2: Shear Force Equations**
Break the beam into sections:
1. **AB:** \( 0 < x < 2 \)
2. **BC:** \( 2 < x < 4 \)
3. **CD:** \( 4 < x < 6 \)
4. **DE:** \( 6 < x < 8 \)
5. **EF:** \( 8 < x < 10 \)
**Write shear equations for each span (using x measured from A):**
### 1. **Section AB (0 < x < 2):**
\[
V(x) = R_A
\]
### 2. **Section BC (2 < x < 4):**
\[
V(x) = R_A - 7
\]
### 3. **Section CD (4 < x < 6):**
\[
V(x) = R_A - 7 - 4y(x-4)
\]
(Distributed load starts at C)
### 4. **Section DE (6 < x < 8):**
\[
V(x) = R_A - 7 - 4y(x-4) - 2z
\]
(Point load at D, 2z kN at x = 6)
### 5. **Section EF (8 < x < 10):**
\[
V(x) = R_A - 7 - 4y(x-4) - 2z
\]
(Distributed load ends at x = 8)
---
## **Step 3: Moment Equations**
Integrate shear equations for moment:
### 1. **Section AB (0 < x < 2):**
\[
M(x) = R_A x
\]
### 2. **Section BC (2 < x < 4):**
\[
M(x) = R_A x - 7(x-2)
\]
### 3. **Section CD (4 < x < 6):**
\[
M(x) = R_A x - 7(x-2) - 2z(x-6) - 2y(x-4)^2
\]
(The moment due to distributed load is \(-2y(x-4)^2\))
### 4. **Section DE (6 < x < 8):**
\[
M(x) = R_A x - 7(x-2) - 2z(x-6) - 2y(x-4)^2
\]
### 5. **Section EF (8 < x < 10):**
\[
M(x) = R_A x - 7(x-2) - 2z(x-6) - 2y(4)^2
\]
(Distributed load no longer acts beyond E)
---
## **Step 4: Shear and Moment Diagrams**
1. **Plot the shear and moment equations along the length of the beam.**
2. **Indicate discontinuities at points of concentrated loads.**
3. **Show slope changes where distributed loads start and end.**
---
### **Summary Table**
| Section | Shear \( V(x) \) | Moment \( M(x) \) |
|------------|-----------------------------------------------------|--------------------------------------------------------|
| AB (0-2) | \( R_A \) | \( R_A x \) |
| BC (2-4) | \( R_A - 7 \) | \( R_A x - 7(x-2) \) |
| CD (4-6) | \( R_A - 7 - 4y(x-4) \) | \( R_A x - 7(x-2) - 2y(x-4)^2 \) |
| DE (6-8) | \( R_A - 7 - 4y(x-4) - 2z \) | \( R_A x - 7(x-2) - 2z(x-6) - 2y(x-4)^2 \) |
| EF (8-10) | \( R_A - 7 - 4y(4) - 2z \) | \( R_A x - 7(x-2) - 2z(x-6) - 2y(4)^2 \) |
---
### **To Draw the Diagrams:**
- Start from left support and use the equations to plot shear and moment.
- Use calculated reaction values, and substitute x for each segment.
- Indicate jumps and slopes as appropriate.
---
If you provide values for \( y \) and \( z \), I can plug them in and give you the exact diagrams and equations! If you'd like a step-by-step drawing of the diagrams, let me know!
Question:
x=10 y=5 z=9
This is AI generated Response.
Asked by: Test User 100299
Created at: 2025-05-16 12:43:30
Asked by: Test User 100299
Created at: 2025-05-16 12:43:30
Final Answer:
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Given the values:
\[
x = 10\, \text{m}, \quad y = 5\, \text{kN/m}, \quad z = 9\, \text{kN}
\]
Let's proceed step-by-step to compute reactions, shear force, and bending moment, then outline the shear and moment diagrams.
---
### Step 1: Calculate Reactions at Supports
Recall:
\[
R_A + R_F = 7 + 2z + 16 y
\]
\[
R_A + R_F = 7 + 2 \times 9 + 16 \times 5 = 7 + 18 + 80 = 105\, \text{kN}
\]
Moment about A:
\[
12 R_F = 14 + 12z + 96 y
\]
\[
12 R_F = 14 + 12 \times 9 + 96 \times 5 = 14 + 108 + 480 = 602
\]
\[
R_F = \frac{602}{12} \approx 50.17\, \text{kN}
\]
Now, reaction at A:
\[
R_A = 105 - R_F = 105 - 50.17 \approx 54.83\, \text{kN}
\]
---
### **Reactions:**
\[
\boxed{
\begin{aligned}
R_A & \approx 54.83\, \text{kN} \\
R_F & \approx 50.17\, \text{kN}
\end{aligned}
}
\]
---
### Step 2: Shear Force Equations
Using \(x\) from A:
| Section | \(x\) Range | Shear \(V(x)\) |
|---------|--------------|----------------|
| AB | \(0 < x < 2\) | \(V(x) = R_A \approx 54.83\, \text{kN}\) |
| BC | \(2 < x < 4\) | \(V(x) = R_A - 7 \approx 54.83 - 7 = 47.83\, \text{kN}\) |
| CD | \(4 < x < 6\) | \(V(x) = R_A - 7 - 4 y (x - 4) = 54.83 - 7 - 4 \times 5 \times (x - 4)\) <br> Simplify: \(47.83 - 20 (x - 4)\) |
| DE | \(6 < x < 8\) | \(V(x) = V_{CD} - 2z = [47.83 - 20(x - 4)] - 2 \times 9 = 47.83 - 20(x - 4) - 18\) <br> = \(29.83 - 20 (x - 4)\) |
| EF | \(8 < x \leq 10\) | Same as DE, since no additional loads: \(V(x) = 29.83 - 20 (x - 4)\) |
---
### Step 3: Shear Force Values at Key Points
- At \(x=0\): \(V = 54.83\, \text{kN}\)
- At \(x=2\): \(V = 54.83\, \text{kN}\)
- At \(x=4\): \(V = 47.83\, \text{kN}\)
- At \(x=6\): \(V = 47.83 - 20(6-4) = 47.83 - 40 = 7.83\, \text{kN}\)
- At \(x=8\): \(V = 29.83 - 20(8-4) = 29.83 - 80 = -50.17\, \text{kN}\)
- At \(x=10\): \(V = -50.17 - 20(10-8) = -50.17 - 40 = -90.17\, \text{kN}\)
---
### Step 4: Moment Equations
Using the integrated shear:
| Section | \(M(x)\) expression |
|---------|---------------------|
| AB | \(M(x) = R_A x = 54.83 x\) |
| BC | \(M(x) = R_A x - 7(x - 2)\) |
| CD | \(M(x) = R_A x - 7(x - 2) - 2 y (x - 4)^2\) <br> \(= 54.83 x - 7(x-2) - 2 \times 5 (x-4)^2\) <br> \(= 54.83 x - 7x + 14 - 10 (x-4)^2\) <br> \(= (54.83 - 7) x + 14 - 10 (x-4)^2\) <br> \(= 47.83 x + 14 - 10 (x-4)^2\) |
| DE | Same as CD, minus the effect of \(2z\) load, which contributes to moments at \(x \geq 6\):
\[
M(x) = 47.83 x + 14 - 10 (x-4)^2 - 2z (x - 6)
\]
\[
= 47.83 x + 14 - 10 (x-4)^2 - 2 \times 9 (x - 6) = 47.83 x + 14 - 10 (x-4)^2 - 18 (x - 6)
\]
At \(x=8\):
\[
M(8) = 47.83 \times 8 + 14 - 10 \times (8-4)^2 - 18 \times (8 - 6)
\]
Calculate:
\[
47.83 \times 8 = 382.64
\]
\[
(8-4)^2 = 16
\]
So,
\[
M(8) = 382.64 + 14 - 10 \times 16 - 18 \times 2 = 396.64 - 160 - 36 = 200.64\, \text{kNm}
\]
At the free end \(x=10\):
\[
M(10) = 47.83 \times 10 + 14 - 10 \times (10-4)^2 - 18 \times (10 - 6)
\]
\[
= 478.3 + 14 - 10 \times 36 - 18 \times 4 = 492.3 - 360 - 72 = 60.3\, \text{kNm}
\]
---
### **Summary of Key Values:**
| Point | Shear \(V\) (kN) | Moment \(M\) (kNm) |
|--------|------------------|---------------------|
| 0 m | 54.83 | 0 |
| 2 m | 54.83 | \(54.83 \times 2 = 109.66\) |
| 4 m | 47.83 | \(47.83 \times 4 + 14 - 10 \times 0 = 191.32 + 14 = 205.32\) |
| 6 m | 7.83 | \(47.83 \times 6 + 14 - 10 \times 4^2 - 18 \times 0 = 287 - 160 = 127\) |
| 8 m | -50.17 | \(\approx 200.64\) (from above) |
| 10 m | -90.17 | \(\approx 60.3\) |
---
### **Final Notes:**
- **Shear diagram:** starts high (~54.83 kN), decreases linearly, crosses zero somewhere between 6 m and 8 m, then becomes negative.
- **Moment diagram:** parabolic shape due to distributed load, with maximum around mid-span (near 8 m).
---
### **Summary:**
- Reactions: \( R_A \approx 54.83\, \text{kN} \), \( R_F \approx 50.17\, \text{kN} \)
- Shear force varies from about +55 kN at the left to about -90 kN at the right end.
- Bending moment peaks around 200–300 kNm near mid-span, with values depending on exact positions.
---
If you need detailed diagrams, I recommend plotting these equations over the beam length, marking key points and discontinuities. Let me know if you'd like a drawn schematic or further calculations!
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