KVPT’s Patan Darbar Earthquake Response Campaign - Work to Date - September 2016

Top
Harishankara Temple partial elevation
(l) and Section (r), showing
location of base stones.
Source: E. Sekler 1982 (l),
Bijay Basukala 2015 (r)
Middle
Harishankara Temple northeast
corner base stone after 2015 earthquake.
An overturned corner stone
has been observed on multiple
collapsed tiered temples with outer
timber column arcades. The corner
base stone was not properly tied to
the main structure and dislodged
during the earthquake. Note the
mortise visible on the corner stone.
The column tenon was in this
mortise, and when stone rolled out,
it kicked the corner column base
outward, contributing to collapse of
the structure.
Bottom
Diagram showing minimal intervention
in a typical tiered temple
plinth. This involves a continuous
reinforced concrete ring beam (F)
placed behind the outer plinth/base
stones (D). The ring beam is doweled
(stainless steel rods) into the
backside of the stones to provide
continuity and prevent separation
of the stone base.
A. Timber column, B. Stone
base (ilohan), C. Stone flooring,
D. Plinth stone, E. Foundation,
F. Reinforced concrete ring beam,
G. Inner wall, H. Mud Brick infill
mud mortar between walls
G
H
C
F
E
D
A
B
1. Threshold Base Stone Connections
Description
In the typical tiered temple constructions, the threshold
level, or topmost level of the raised plinth, includes
an outer ring of carved base stone elements. These base
stones are often simply set into place before placing the
superstructure, either brick masonry walls or large timber
columns. The base stones often have mortises to accept
wooden tenons from above, or have small tenons to
act as dowels into the structure above. This connection
is where the load from the outer perimeter columns supporting
the roof comes down into the foundation.
Issues
These base stones are largely just set into place and have
no significant structural connection to the adjacent
stones or to the structure above or below. These connections
seem to have been conceived for compression forces
but not for lateral seismic forces. This lack of direct
connection allows these base stones to shift and move
independently during an earthquake and often results in
corner stones shifting such that corner columns kick out,
accelerating progressive collapse of the building.
Options for Seismic Strengthening
To prevent independent movement or dislodgement of
the base stones, direct structural connections should be
introduced to provide continuity which will help the
structure move as one unit instead of small, independent
pieces. This continuity can be introduced through connecting
each of the stones to adjacent stones via stainless
steel pins, or doweling each of the stones (with a stainless
steel rod) into a homogeneous interior structure such as
a reinforced concrete ring beam.
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