Math Problem Statement

The left support is 6 ft from the left. The right support is at the rightmost end. The beam is 18 ft long. There is a concentrated load of 1500 lb that is 8 ft from the left. There is a distributed load of w=200lb/ft spans over 8 ft starting from the leftmost end.

The left support is 6 ft from the left. The right support is at the rightmost end. The beam is 18 ft long. There is a concentrated load of 1500 lb that is 8 ft from the left. There is a distributed load of w=200lb/ft spans over 8 ft starting from the leftmost end.

Solution

To solve this beam problem, we'll perform the following steps:

  1. Determine the support reactions at both the roller (left side) and pinned support (right side).
  2. Create shear force (V) and bending moment (M) diagrams for the beam.

Step 1: Determine Support Reactions

We have:

  • Distributed load (ww) of 200 lb/ft over 8 ft (from 0 to 6 ft).
  • A concentrated load of 1,500 lb located 8 ft from the left end.

Beam dimensions:

  • Distance from the left to the roller support: 6 ft.
  • Total beam length: 18 ft.

Total load from the distributed load:

The distributed load spans 8 ft. So the total load from this is: Fdist=w×L=200lb/ft×8ft=1600lbF_{\text{dist}} = w \times L = 200 \, \text{lb/ft} \times 8 \, \text{ft} = 1600 \, \text{lb} This acts at the centroid of the distributed load, which is at the midpoint of the 8 ft span, i.e., 4 ft from the left end.

Support Reaction Calculation:

We will take moments about the right support (pinned) to find the reaction at the roller support (left):

Let RAR_A be the reaction at the roller (left support), and RBR_B be the reaction at the pinned (right support).

Taking moments about point B (right end support):

ΣMB=0RA×18(1600×4)(1500×8)=0\Sigma M_B = 0 \quad \Rightarrow \quad R_A \times 18 - (1600 \times 4) - (1500 \times 8) = 0 RA×18=6400+12000R_A \times 18 = 6400 + 12000 RA=18400181022.22lbR_A = \frac{18400}{18} \approx 1022.22 \, \text{lb}

Now, use vertical force equilibrium to find RBR_B:

ΣFy=0RA+RB=1600+1500=3100\Sigma F_y = 0 \quad \Rightarrow \quad R_A + R_B = 1600 + 1500 = 3100 RB=3100RA=31001022.22=2077.78lbR_B = 3100 - R_A = 3100 - 1022.22 = 2077.78 \, \text{lb}

Step 2: Shear Force and Bending Moment Diagrams

Shear Force Calculation:

  1. From 0 to 6 ft (Distributed load only): The shear force at xx (distance from left): V(x)=RAw×x=1022.22200×xV(x) = R_A - w \times x = 1022.22 - 200 \times x At x=6ftx = 6 \, \text{ft}, just before the concentrated load: V(6)=1022.22200×6=1022.221200=177.78lbV(6) = 1022.22 - 200 \times 6 = 1022.22 - 1200 = -177.78 \, \text{lb}

  2. From 6 to 8 ft (still under the distributed load): The load remains the same, and the shear will continue decreasing linearly.

  3. At 8 ft (just before the concentrated load): Add the 1500 lb concentrated load: V(8)=V(8)=177.78V(8^-) = V(8) = -177.78 Just after the load: V(8+)=177.781500=1677.78lbV(8^+) = -177.78 - 1500 = -1677.78 \, \text{lb}

Bending Moment Calculation:

We can integrate the shear force diagram to find the bending moment at key points:

  • At x=0x = 0, M(0)=0M(0) = 0.
  • At x=6ftx = 6 \, \text{ft}, calculate the area under the shear force curve to get the moment.

Would you like more detailed calculations for each step, including drawing the shear force and bending moment diagrams?

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Math Problem Analysis

Mathematical Concepts

Statics
Equilibrium
Shear Force
Bending Moment

Formulas

Total load from distributed load = w * L
Moment equation: ΣM = 0
Vertical force equilibrium: ΣFy = 0
Shear force: V(x) = R_A - w * x
Bending moment: M(x) = Integral of shear force

Theorems

Equilibrium of forces and moments

Suitable Grade Level

Undergraduate Civil/Mechanical Engineering