Math Problem Statement

Find the reactions R1 and R2 for the beam subjected to a triangular distributed load and a concentrated load as shown in the diagram.

Solution

To solve for the reactions R1R_1 and R2R_2 in the beam problem, we must perform static equilibrium analysis. Here's the approach:

Given Data:

  • Triangular distributed load with a maximum of 2kip/ft2 \, \text{kip/ft} over a length of 1010'.
  • Concentrated load of 10kip10 \, \text{kip} applied at 343'4'' (or 3.333.33') from the right support.
  • The beam has two supports: a pin support at R1R_1 and a roller support at R2R_2.

Step 1: Calculate the Total Load of the Triangular Distributed Load

The area of the triangular load gives the total force: Ftriangle=12×base×height=12×10×2kip/ft=10kipF_{\text{triangle}} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 10' \times 2 \, \text{kip/ft} = 10 \, \text{kip} This force acts at the centroid of the triangle, which is located 13\frac{1}{3} of the distance from the left (pin support).

Thus, the location of this force from R1R_1 is: Location of centroid=13×10=3.33 from the left\text{Location of centroid} = \frac{1}{3} \times 10' = 3.33' \text{ from the left}

Step 2: Write the Equilibrium Equations

We will use the three static equilibrium conditions:

  1. Sum of vertical forces: R1+R2=Ftriangle+10kip=10+10=20kipR_1 + R_2 = F_{\text{triangle}} + 10 \, \text{kip} = 10 + 10 = 20 \, \text{kip}

  2. Sum of moments about R1R_1 (to eliminate R1R_1 and solve for R2R_2): Taking counterclockwise moments as positive: Moment at R1:10kip×3.33+10kip×(10+3.33)R2×(10+3.33)=0\text{Moment at } R_1: 10 \, \text{kip} \times 3.33' + 10 \, \text{kip} \times (10' + 3.33') - R_2 \times (10' + 3.33') = 0 Simplifying: 33.3+133.3R2×13.33=033.3 + 133.3 - R_2 \times 13.33 = 0 R2=33.3+133.313.33=12.5kipR_2 = \frac{33.3 + 133.3}{13.33} = 12.5 \, \text{kip}

  3. Sum of forces (to find R1R_1): From the first equilibrium equation: R1+12.5=20R1=7.5kipR_1 + 12.5 = 20 \quad \Rightarrow \quad R_1 = 7.5 \, \text{kip}

Final Reactions:

  • R1=7.5kipR_1 = 7.5 \, \text{kip}
  • R2=12.5kipR_2 = 12.5 \, \text{kip}

Would you like any additional details or further clarification on the solution?


Here are 5 related questions for deeper understanding:

  1. How would the reactions change if the concentrated load were moved closer to the pin support?
  2. What is the significance of the location of the centroid of the triangular load?
  3. How do different types of loads (uniform vs triangular) affect the reaction forces?
  4. How does the pin and roller support system differ from a fixed support system in terms of reaction forces?
  5. What would be the effect of increasing the magnitude of the distributed load?

Tip: Always verify that the sum of moments and forces balances to ensure your calculations are correct.

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Math Problem Analysis

Mathematical Concepts

Statics
Equilibrium of Forces
Moments Calculation

Formulas

F_triangle = (1/2) × base × height
Moment = Force × Distance
Sum of Forces: R1 + R2 = Total Load
Sum of Moments: ∑M = 0

Theorems

Static Equilibrium: Sum of forces and moments must be zero.

Suitable Grade Level

Undergraduate Engineering