Seismic Design Philosophy and Codes Questions and Answers

Answer: A

A wall acts as a deep cantilever and attracts a large share of the storey shear, keeping drift small and protecting the frame and its finishes. The price is a stiffer building with a shorter period, which often reads a larger acceleration from the spectrum.

Answer: B

When the two centres coincide, shaking produces translation without twist, and every element takes its intended share of the load. An eccentric layout twists the building about a vertical axis and loads its far corners far more heavily than a plan analysis suggests.

Answer: C

Force follows mass, and mass placed high both lengthens the period and increases the overturning moment on the storeys below. Water tanks and plant rooms at roof level are the usual sources and are worth relocating where the layout allows.

Answer: D

Falling glass, cladding and ceilings account for a large share of injuries and of repair cost in earthquakes that leave the frame standing. Their anchorage is a design requirement in its own right and is checked against the drift the structure is expected to undergo.

Answer: A

Seismic performance depends on details that are easy to omit on site, such as confinement hoops, anchorage lengths and the reinforcement of joints. Post-earthquake surveys in India have repeatedly traced collapses to construction that departed from a sound design rather than to the design itself.

Answer: B

Regularity lets force travel to the foundations without abrupt changes of stiffness or direction, which is what codes reward with the simpler analysis and the fewer penalties. The other three are recognised irregularities, each of which concentrates demand somewhere it is hard to provide for.

Answer: C

The vertical force must travel sideways through the supporting beam before it can continue down, and under reversing seismic load that beam is asked to do something it is poorly suited to. The arrangement is a common cause of distress and is best avoided in a seismic region.

Answer: D

The first two together are the whole basis of the response reduction factor. The third contradicts them: the detailing is what makes the reduction legitimate, and omitting it leaves the structure designed for a force it cannot resist elastically and unable to yield safely.

Answer: A

All three describe the code correctly. The reduced gravity factor recognises that the two effects are unlikely to peak together, and the nine tenths case covers situations in which dead load relieves the seismic effect rather than adding to it.

Answer: B

The ordering reflects how much inelastic deformation each system can sustain, from a fully detailed frame down to walls with no reinforcement at all. A low factor means a large design force, so unreinforced masonry is the most heavily loaded of the three for the same mass and zone.