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Learning

Earthquake Design
27 and
Earthquake Tip
Construction

How can Non-structural Elements be protected against Earthquakes?

Non-Structural Elements not anchored adequately to SEs (e.g., a diesel generator
Structural Elements (SEs) in a building have a unit on a floor, and expensive contents of
primary role of resisting the effects of earthquakes museums). Thus, the SEs and the anchors by which
ground shaking, and of protecting life and property of NSEs are secured to SEs should be designed to
building occupants. But, buildings contain many other resist the induced forces corresponding to the
items, such as contents, appendages and services & accelerations developed in these NSEs.
utilities, which are attached to and/or supported by (b) Displacement-sensitive NSEs may bend, compress or
SEs, and affected by earthquake ground shaking; these stretch by large amounts during earthquake
items are called Non-Structural Elements (NSEs). shaking (e.g., glass facades, water and gas pipes
NSEs can be classified into three groups, namely: running between floors of a building, and electric
(a) Contents of buildings: Items required for functionally lines running from a street pole to a building). Also,
enabling the use of spaces, such as (i) furniture and NSEs are significantly affected by the flexibility of
other items, e.g., storage shelves, (ii) facilities and SEs and their deformations. The connection of NSEs
equipment, e.g., refrigerators, multi-level material with SEs should be designed to accommodate
stacks, false ceilings, and (iii) door and window relative displacements generated between support
panels and frames, or ply board or aluminum points on SEs with adequate slack.
partitions; Some NSEs are both displacement and acceleration-
(b) Appendages to buildings: Items projecting out from sensitive, and they have to be designed for both forces
buildings, either horizontally or vertically, such as and relative displacements. For example, false ceilings
chimneys, exterior glass or stone cladding (pasted suspended from floor slabs above, may not only pull
on the building surface as façades), parapets, small out vertically from slabs, but also swing laterally and
water tanks rested on top of buildings, sunshades, knock on walls.

advertisement hoardings and communication
antennas atop buildings;
(c) Services and utilities: Items required for facilitating
essential activities in the buildings, such as water
mains, electricity cables, air-conditioning ducts,
rainwater drain pipes, and elevators. Photos: EERI Annotated Slide Set, 1999
Earthquake Effects on NSEs
During strong earthquake shaking, NSEs can (a) (a)
slide or topple, or (b) move or swing, if they are not

secured well to SEs of the building. These actions can
cause loss to functionality of NSEs and potential
secondary disasters, e.g., spill of chemicals leading to

laboratory fires (Figure 1a). Loss of functionality of an

NSE can be small or substantive depending on its

importance, the function it serves, and its cost. For

instance, if book shelves of a library are not properly
(b)
secured, they can distort (Figure 1b) or topple; the

former may only dislodge books, but the latter can

cause threat to life. If gas pipelines are pulled apart or

electric control panels are toppled (Figure 1c), then

both direct and indirect losses can be significant. With

increasing sophistication in building systems, seismic

performance of NSEs is becoming more important. In
many earthquakes, economic losses due to damages in
NSEs have been very substantial. (c)

Protecting Non-Structural Elements
NSEs can demonstrate either acceleration-sensitive Figure 1: Earthquake performance of non-
or displacement-sensitive behaviour during earthquakes. structural elements – (a) chemical spill in a
laboratory, (b) library book shelves, and (c)
(a) Acceleration-sensitive NSEs may topple or slide, if
water pipelines and electrical control panels.