A Case Study on the Mechnical Properties of a tree "Nattu Illupai"
(mahua-madhuca sp )
S.ThirumalaiKolundu, Scientist SB(Civil)
S.Murali, Scientific Officer (Civil)
Civil Engineering Laboratory, National Test House, Chennai, India
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Introduction
Nattu illupai (Mahua-madhuca sp)is one of the most widely used timber in the filed of
construction of temple car due to its unique properties. Though it is widely used in the
construction of Temple car very limited literature is available on its physical properties, that too
available with respect to another origin from Madhya Pradesh. An attempt is made to establish the
physical properties of illupai received from the south India (Tamil Nadu) region as no data on this
timber is available so far.
As the limiting values on mechanical properties rests with the age, environment & usage of
timber, no limiting value on timber can be given. The Indian Standard specification IS:883:1994 on
"Design of Structural timber in building-code of practice" (fourth revision) and IS:399-1963 on
"Classification of commercial timbers and their zonal distribution" gives a limited idea about the
commercial timbers and it properties. The specification IS:883-1994 gives safe permissible stresses
for the species of timber, recommended moisture content, and requirements of structural timber by
giving grading, suitability in respect of durability and treatability etc
Properties of timber-illupai
The principal characteristics of timber are concerned with respect to its strength durability
and finished appearance. All of these are derived from natural characteristics present in growing
tree, which totally depends upon environment/ climatic conditions, age etc. As far as Temple car is
concerned, a high durability with high strength is expected.
The illupai sample has been tested for the determination of its physical characteristics as per
IS:1708-( Parts 1 to 18 )-1986, Indian standard on "Methods of testing of small clear specimens of
timber"( second revision).
Test for Moisture content ( IS:1708 (1) – 1986)
The strength generally decreases with increase in moisture content. As wood dries, its
strength properties increase in value at the same time an excessive dried-out timber may have a
lower strength. Higher the moisture content of timber might give to the germination and flourishing
of fungal growth or to the attraction of insects. An Indian standard specification in this regard
IS:11215-1991 "Moisture content of timber and timber products"- which determines moisture
content on any timber.
Test for Specific gravity (IS:1708 (2) – 1986)
Density is almost certainly an indication of strength of a timber. The more dense the timber,
the stronger it is. All timber is made up of much the same chemical constituents, but the dense
timber has thicker cell walls, which contribute to the strength of the timber. While it has been said
that strength increases with density , this is not so with increase in moisture content. Generally as
per IS:399-1963 the average weight and range of weights (density) at 12% moisture content is
tested and reported.
Property /Samples 1 2 3 4 5
Moisture content, % 15.40 17.40 19.10 22.40 24.40
Compressive strength
(Perpendicular direction),
kg/sq.cm 195 264 228 250 261
Density kg/cu.m 790 927 982 1089 1031
Specific Gravity 0.790 0.982 0.927 1.089 1.031
Adjusted Specific Gravity 0.684 0.836 0.778 0.875 0.842
Conclusion
These five timbers are collected from various places of Krishnapuram, Perambalur Dist. marked A,
B & C and from Gudiyatam marked as D,E, respectively of Tamil Nadu state. It is observed that,
the Indian standards has data for mahua-madhuca with respect to Madya Pradesh region only. In
addition to, the Forest Research Institute, Dehraudun, does not have any data relating to the species
in this regard.
