Page 32 - EQTips_Eng

Learning

16 Earthquake Design
Earthquake Tip and

Construction

How to make Stone Masonry Buildings Earthquake-Resistant?

Behaviour during Past India Earthquakes masonry dwellings. Likewise, a majority of the over
Stone has been used in building construction in 13,800 deaths during 2001 Bhuj (Gujarat) earthquake is
India since ancient times since it is durable and locally attributed to the collapse of this type of construction.
available. There are huge numbers of stone buildings The main patterns of earthquake damage include:
in the country, ranging from rural houses to royal (a) bulging/separation of walls in the horizontal
palaces and temples. In a typical rural stone house, direction into two distinct wythes (Figure 2a), (b)
there are thick stone masonry walls (thickness ranges separation of walls at corners and T-junctions (Figure
from 600 to 1200 mm) built using rounded stones from 2b), (c) separation of poorly constructed roof from
riverbeds bound with mud mortar. These walls are walls, and eventual collapse of roof, and (d)
constructed with stones placed in a random manner, disintegration of walls and eventual collapse of the
and hence do not have the usual layers (or courses) whole dwelling.
seen in brick walls. These uncoursed walls have two
exterior vertical layers (called wythes) of large stones,
filled in between with loose stone rubble and mud
mortar. A typical uncoursed random (UCR) stone
masonry wall is illustrated in Figure 1. In many cases,
these walls support heavy roofs (for example, timber
roof with thick mud overlay).
Vertical gap
Vertically split (a) Separation of a thick wall into two layers
layer of wall
Vertically split layer
of wall

Mud mortar

Outward bulging
of vertical wall
layer
Half-dressed
oblong stones

(b) Separation of unconnected adjacent walls at
junctions

Figure 2: Major concerns in a traditional stone

Figure 1: Schematic of the wall section of a house – deficiencies in walls, roof and in their
traditional stone house – thick walls without connections have been prime causes for failure.
stones that go across split into 2 vertical layers.
Earthquake Resistant Features
Laypersons may consider such stone masonry Low strength stone masonry buildings are weak
buildings robust due to the large wall thickness and against earthquakes, and should be avoided in high
robust appearance of stone construction. But, these seismic zones. The Indian Standard IS:13828-1993
buildings are one of the most deficient building states that inclusion of special earthquake-resistant
systems from earthquake-resistance point of view. The design and construction features may raise the
main deficiencies include excessive wall thickness, earthquake resistance of these buildings and reduce
absence of any connection between the two wythes of the loss of life. However, in spite of the seismic
the wall, and use of round stones (instead of shaped features these buildings may not become totally free
ones). Such dwellings have shown very poor from heavy damage and even collapse in case of a
performance during past earthquakes in India and major earthquake. The contribution of the each of
other countries (e.g., Greece, Iran, Turkey, former these features is difficult to quantify, but qualitatively
Yugoslavia). In the 1993 Killari (Maharashtra) these features have been observed to improve the
earthquake alone, over 8,000 people died, most of performance of stone masonry dwellings during past
them buried under the rubble of traditional stone earthquakes. These features include:
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