Problem 1

Problem 2

Problem 3

Problem 4

Problem 5

Problem 1

• A clear initial free body with labelled unknown forces.
• A correct and clear set of equations with units and sign conventions.
• A final free body diagram with correct magnitude, direction, and location of forces.

Problem 2

• Correct reactions.
• A shear diagram with clear sign conventions and labelled key values.
• A moment diagram clear sign conventions, labelled key values, and clear indication of the abrupt change in slope (i.e. kink).

Many people included an answer as shown below; this indicates the kink, but has it in the wrong sense. The slope should be steeper to the right of the point (more negative) since the shear is more negative. The incorrect depiction below shows the slope becoming shallower to the right, which would only happen if the shear became less negative.

Problem 3

• Magnitude
• Direction
• Location

Nearly everyone got the magnitude and direction, but many people had difficulty with location. About a third of the class attempted to solve for the center of gravity of the object, although it is unrelated to the question.

The minimal solution shown below (which includes all the work for the problem) is completely correct.

Problem 4

The key elements of a good answer are:

• The correct shape of the curves.
• Identifying the points of yield and rupture.
• An explanation of reasoning.

Problem 5

Many people said that the purpose of codes is to protect the interests of designers and builders so that they can avoid liability in case something goes wrong with a building; that is akin to saying that the primary purpose of traffic regulations is to protect drivers from liability in case of accidents. It's very far from the truth.

This answer hits the nail on the head, although I accepted answers that hit near the head. Many people said that the term meant that the system of forces are in equilibrium; this is incorrect. Refer to the definitions given in Schodek and the glossary.

For part c), there were several possible answers: e.g. cantilevers, uneven spans, uneven distribution of loads.

For part d), a sufficient answer was "the connection is fixed since the bolts restrain both translation and rotation of the column". People who made other assumptions received at least partial credit when accomanpied by an explanation and sketch of what type of motion the collection allowed.