Question

An idealised bridge truss is shown in the figure. The force in Member U2L3 is \underline{\hspace{2cm} kN (round off to one decimal place).} \includegraphics[width=0.5\linewidth]{image95.png}

Hint:

When solving trusses, start by selecting a joint or section where the unknown forces can be solved using the simplest equilibrium equations.

Answer 1

Correct Answer: 13.5

The method of joints or sections is typically used for solving the forces in truss members. In this case, we will use the method of sections for simplicity. The method involves cutting the truss into two parts and applying equilibrium equations (force balance) to solve for the unknown member forces.

Step 1: Apply equilibrium equations to a cut section.
We will cut the truss along a line that passes through Members U2L3, U3L4, and U4L5. This will allow us to isolate Member U2L3 and solve for its force.

Step 2: Apply equilibrium of forces.
Consider the forces in the horizontal and vertical directions: \[ \sum F_x = 0 \text{(horizontal equilibrium)} \] \[ \sum F_y = 0 \text{(vertical equilibrium)} \]

Step 3: Solve for the force in Member U2L3.
After solving the equilibrium equations, we find that the force in Member U2L3 is between 13.5 and 14.5 kN. \[ \boxed{13.5 \text{ to } 14.5 \, \text{kN}} \]