Structural Engineering — Quiz 3

Questions in this quiz (10)

1. The truss below is composed of steel members that are $$5\ \mathrm{cm}\times 5\ \mathrm{cm}$$ square with modulus of elasticity of $$200{,}000\ \mathrm{MPa}$$. Ignore the self-weight of the structure and assume compression members are braced against buckling. The magnitude of the horizontal displacement at point $$D$$ due to the applied loads is most nearly:

   • $$1\ \mathrm{mm}$$
   • $$2\ \mathrm{mm}$$
   • $$3\ \mathrm{mm}$$
   • $$4\ \mathrm{mm}$$

2. A cantilever beam with a length of $$10\ \mathrm{ft}$$ carries a concentrated load of $$8\ \mathrm{kips}$$ at its free end. The beam has $$E=29{,}000\ \mathrm{ksi}$$ and $$I=150\ \mathrm{in}^4$$. Determine the deflection at the free end.

   • $$0.07\ \mathrm{in}$$
   • $$0.40\ \mathrm{in}$$
   • $$1.06\ \mathrm{in}$$
   • $$2.12\ \mathrm{in}$$

3. A reinforced concrete beam has width $$b=14\ \mathrm{in}$$, tension steel area $$A_s=4.0\ \mathrm{in}^2$$, steel yield strength $$f_y=60\ \mathrm{ksi}$$, and concrete compressive strength $$f'_c=5\ \mathrm{ksi}$$. Determine the depth of the equivalent rectangular stress block, $$a$$.

   • $$3.43\ \mathrm{in}$$
   • $$3.81\ \mathrm{in}$$
   • $$4.03\ \mathrm{in}$$
   • $$5.65\ \mathrm{in}$$

4. A T-shaped cross-section consists of a bottom flange $$8\ \mathrm{in}$$ wide by $$4\ \mathrm{in}$$ tall and a top stem $$4\ \mathrm{in}$$ wide by $$6\ \mathrm{in}$$ tall centered on the flange. Determine the moment of inertia about the centroidal horizontal axis.

   • $$115\ \mathrm{in}^4$$
   • $$295\ \mathrm{in}^4$$
   • $$458\ \mathrm{in}^4$$
   • $$1000\ \mathrm{in}^4$$

5. A frame with a diagonal brace is subjected to wind load, $$P$$, as shown. The brace consists of $$W10\times 45$$ with $$F_y=50\ \mathrm{ksi}$$, pinned at both ends. The maximum wind force in kips the frame can resist at yield is most nearly:

   • $$675\ \mathrm{kips}$$
   • $$600\ \mathrm{kips}$$
   • $$550\ \mathrm{kips}$$
   • $$0$$

6. A reinforced concrete beam has width $$b=12\ \mathrm{in}$$, effective depth $$d=18\ \mathrm{in}$$, and tension steel area $$A_s=3.5\ \mathrm{in}^2$$. Determine the reinforcement ratio $$\rho$$.

   • $$0.0097$$
   • $$0.0120$$
   • $$0.0162$$
   • $$0.0194$$

7. For the short column shown below with $$f'_c=4000\ \mathrm{psi}$$ and $$f_y=60000\ \mathrm{psi}$$, determine the ultimate axial strength $$\phi P_n$$. Tie reinforcement is used.

   • $$68\ \mathrm{kips}$$
   • $$254\ \mathrm{kips}$$
   • $$501\ \mathrm{kips}$$
   • $$688\ \mathrm{kips}$$

8. The beam below is a W18x71 steel wide flange section. The uniform load includes self-weight. Determine the vertical reaction at support A.

   • $$6.75\ \mathrm{kips}$$
   • $$9.00\ \mathrm{kips}$$
   • $$13.5\ \mathrm{kips}$$
   • $$22.5\ \mathrm{kips}$$

9. From the choices below, determine the lightest wide-flange section that can resist a service dead load of $$125\ \mathrm{kips}$$ and service live load of $$200\ \mathrm{kips}$$ using LRFD.

   • $$W12\times53$$
   • $$W12\times50$$
   • $$W12\times45$$
   • $$W12\times40$$

10. For a three-span continuous beam, which loading pattern produces the maximum positive moment in the middle span?

    • Load all three spans
    • Load only the middle span
    • Load the two end spans only
    • Load the middle span and one end span