Tying the footings of a building together with plinth beams helps seismic performance by
Answer: C
Differential horizontal movement between footings imposes large forces on the columns above, and tying them prevents it. The beams also shorten the effective column length, which is why their effect on column stiffness has to be recognised in the analysis.
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A boundary wall or parapet in a seismic zone needs attention because it
Answer: D
Free-standing masonry has almost no resistance to out-of-plane shaking and has caused many deaths in past earthquakes. Reinforcing it, tying it back or reducing its height are all recognised remedies and cost very little compared with the risk.
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Water tanks placed on the roof of a building affect its seismic behaviour by
Answer: A
Mass high up increases the base shear, the overturning moment and the period all at once, and a full tank is heavy. Placing such loads lower in the building, or accounting for them properly in the model, is the sensible response.
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The first step in the seismic design of a new building is properly
Answer: B
Configuration decisions made at the sketch stage determine how well the building can be made to perform, and no amount of later calculation recovers a poor layout. Analysis and detailing follow once the system and its geometry are settled.
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Which of the following is the least effective way of improving the seismic performance of a building?
Answer: C
Plaster adds mass without useful strength or stiffness, so it makes matters marginally worse rather than better. The other three each address demand, stiffness or ductility, which are the quantities that actually determine how a building behaves.
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