Page 66 - ROHANA_Journal_No_11-2019-ok

Research Journal of the University of Ruhuna, Sri Lanka- Rohana 11, 2019

Compressive Strength Parallel to Grain

Table 2 presents the results of the compression parallel to grain test. Figure 10

compares the compressive strength variations of clear and timber jointed species.
The strength reduction of Satin, Mahogani, Jak and Pinus is less than 20%. Jak is

found to be the most suitable species for finger jointing being able to withstand the
compression most. The compressive strength obtained has to be multiplied by 0.571,

modification factor for very short-term loads given in BS 5268-2 to obtain the
corresponding grade compressive stress. Table 2 summarizes the grade stresses of

the specimens when under compression parallel to grain.

Table 2: Compression parallel to grain test results
Compressive strength parallel to Grade stresses
grain
Species Finger Strength Finger
Clear Clear
(N/mm ) jointed reduction (N/mm ) jointed
2
2
2
(N/mm ) % (N/mm )
2
Teak 24.45 18.2 25.54 12.71 11.33
Satin 42.21 36.62 13.24 13.64 12.35
Mahogany 15.62 13.51 13.51 12.01 8.13
Jak 14.93 14.7 1.53 14.94 8.54
Kumbuk 29.53 20.17 31.68 12.59 6.48
Grandis 15.61 13.55 13.22 14.35 7.86
Pine 15.89 15.40 3.04 10.19 8.21

Source: Author compiled

Compressive Strength Perpendicular to Grain

Table 3 presents the results of the compression perpendicular to grain test. Figure 11

compares the compressive strength variations of clear and finger jointed species.

Strength of all finger jointed species except Jak is higher than that of clear timber.
Therefore, finger jointed sections of most timber species can withstand compression

perpendicular to grain better. Based on the modification factor given in BS 5268-2
for very short-term loads, the strength has to be multiplied by 0.571 to obtain the

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