Seismic Design Philosophy and Codes Questions and Answers

Answer: A

Gravity, wind and earthquake are separate cases, and the design must satisfy whichever of them governs each member. Earthquake often governs the lateral system of a heavy building while wind governs a tall light one, so both are checked.

Answer: B

It comprises the full dead load together with a specified fraction of the imposed load, since not all of the imposed load is present or attached when the shaking arrives. Because force follows mass, reducing seismic weight is one of the few measures that lowers demand directly.

Answer: C

Horizontal shaking dominates the design of ordinary buildings, and the code requires it to be considered in each principal direction in turn. Vertical motion exists as well and matters for long spans, cantilevers and isolated structures.

Answer: D

Frames, walls and braces are rarely arranged identically in both directions, so period, force and drift all differ between them. Each direction therefore gets its own analysis, and the code also requires a proportion of the orthogonal effect to be combined in certain cases.

Answer: A

The term describes an objective rather than a promise of immunity, and every code-compliant building is expected to be damaged by shaking near its design level. Buying immunity is possible with isolation and damping but is rarely justified for ordinary construction.

Answer: B

Masonry without reinforcement cracks and sheds panels with almost no capacity to deform, which is why it is assigned the lowest response reduction factor of all. Steel is the most ductile of the four as ordinarily used, and reinforced concrete lies between depending on its detailing.

Answer: C

Confinement hoops hold the core together while it deforms, and longitudinal bars carry the reversing tension that concrete alone cannot. The result is a member that can rotate through large cycles rather than crushing once its elastic limit is passed.

Answer: D

Short periods lie on or near the plateau where the acceleration ordinate is largest, while the corresponding displacement is small. A flexible building makes the opposite trade, which is why drift and separation rather than strength often govern such designs.

Answer: A

Moment is force times lever arm, and the code's parabolic distribution places much of the force high up, so tall buildings develop large base moments. This is what governs the design of foundations to shear walls and the tension in the columns at the perimeter.

Answer: B

Capacity design applies to the foundation as much as to the frame: it should not fail before the intended hinges have formed, because a failed footing cannot be inspected or repaired. Uplift under the reduced dead load combination is often the critical check.