As Sri Lanka is not affected by seismic waves, the main force on stupa is self-weight. Vertical, radial,
hoop, and shear stresses are applied to the dome. The following are the results of the analysis
done by Ranaweera (2001) on Abhayagiriya stupa.
• Vertical compressive stress reaches a maximum of 767kPa at the center of
the base. The average compressive stress at the base is 516kPa.
• Radial stresses and hoop stresses are also compressive throughout the dome
reaching a maximum value of 256 kPa at the center of the base.
Stresses
• The maximum shear stress obtained is 120 kPa at the outer edge of the base.
These stress values are well below the compressive strength of ancient bricks and there is no
tensile force that acts on the structure. Therefore, we can say that the grain heap structure is the
best dome structure when considering dome shapes in Sri Lankan stupas. As a result of that, most
of the largest stupas have been built using grain heap shape. (Ranaweera, 2011)
Ground conditions were highly considered when constructing
stupas. Most of the large stupas were built on the bedrock.
Foundation
In other places, a strong foundation was laid.
“First, the land was dug out to a depth of 6 meters and then,
crushed stones were stamped down by elephants whose feet were bound by leather.
Then, butter clay was spread over the stones and bricks were laid over the clay. Over these, a
rough cement and a network of iron were laid. Finally, a sheet of copper and a sheet of silver were
laid”
This is the Mahawansa description on the construction of Ruvanwelisaya. This shows that the
stupas have a foundation with great strength which is similar to a modern-day reinforced concrete
foundation. This can be defined as a damp proofed construction.
“
Stupas are great
structures in ancient
Sri Lankan culture.
Even though there are no
proper records on
the technical structures
of
these monuments, it is
evident that our ancestors
had a great structural
knowledge that
was developed over a
thousand years.
”
References
1. Geiger, W, 1950, Mahavamsa or the Great Chronicle of Ceylon,
English Translation, Colombo, Ceylon Government Information
Department.
2. Ranaweera, M. P. (2004) ‘Ancient Stupas in Sri Lanka - Largest
Brick Structures in the World’, CHS Newsletter, p. 70.
3. Ranaweera, M. and Abeyruwan, H. (2004) ‘Materials Used in
the Construction, Conservation , and Restoration of Ancient Stupas
in Sri Lanka’, Unknown, (March), pp. 2573–2586.
4. Peiris, K., Jayawardana, C. and Wijesingha, S. (2010) ‘Engineering
Features of Ancient Stupa Structure: A Review Based on Jethavana
Vihara’, Engineer: Journal of the Institution of Engineers,
Sri Lanka, 43(2), p. 59. doi: 10.4038/
engineer. v43i2.6981.
5. Ranaweera, M. P. (2001) ‘Stress
analysis of an ancient stupa in Sri
Lanka in connection with its conservation’,
WIT Transactions on the Built
Environment, 55, pp. 81–90.
Ravindu Daranagama,
Final Year – Department
of Civil Engineering,
Faculty of Engineering,
University of Peradeniya.
GAUGE Magazine
University of Peradeniya
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