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Sci Tech
Quake resistant design, construction
Simple plan shape buildings do well during quakes.
BEHAVIOUR OF a building during earthquakes depends critically on its shape, size and geometry, in addition to how the quake forces are carried to the ground.
Hence, during the planning stage, architects and structural engineers must ensure that unfavourable features are avoided and a good building configuration is chosen.
The importance of configuration of a building was aptly summarised by Late Henry Degenkolb, a noted earthquake engineer of U. S., as: "If we have a poor configuration to start with, all that the engineer can do is to provide a band-aid — improve a basically poor solution as best as he can. Conversely, if we start off with a good configuration and reasonable framing system, even a poor engineer cannot harm its ultimate performance much."
Architectural features
Desire to create aesthetic and functionally efficient structure drives architects to conceive wonderful and imaginative structures.
Choice of shape and structure has significant bearing on the performance of the building during very strong earthquakes. The wide range of structural damages observed during past earthquakes across the world is educative in identifying structural configurations that are desirable versus those which must be avoided.
Size of buildings
In tall buildings with large height-to-base size ratio, horizontal movement of floors during ground shaking is large. In short long buildings, damaging effects during quakes are many. In buildings with large plan area like warehouses, the horizontal seismic forces can be excessive to be carried by columns and walls.
In buildings with simple geometry in plan have performed well during strong earthquakes. Buildings with re-entrant corners, like those U, V, H and + shaped in plan, have sustained significant damage.
Many times, the bad effects of these interior corners in the plan of buildings are avoided by making the buildings in two parts.
For example, an L-shaped plan can be broken up into two rectangular plan shapes using a separation joint at the junction.
Often, the plan is simple, but the columns/walls are not equally distributed. Buildings with such features tend to twist during earthquake shaking. Sponsored by Buildings Materials & Technology Promotion Council, India.
C.V.R.Murthy
IIT,Kanpur
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