SINGAPORE & THE FEDERATION OF MALAYA
ALLOWABLE WORKING STRESSES FOR MALAYA TIMBERS
By
Timber Research Officer,
The figures herein are allowable working stresses in lb. per square inch and are applicable to good quality timber without serious defects; they may be used whatever the moisture content of the timber.
In those cases where one name, e.g. light red meranti, represents the product of several distinct botanical species, figures are given for the weakest and strongest of the species that have been tested to date.
The weight given in the table is the average for the test material at 15 per cent. moisture content, which is the normal air-dry moisture content for timber inside buildings in Malaya. The allowable working stresses are derived by applying a factor of safety to the average of a large number of tests carried out on small dimensional material in a green condition. This factor of safety is as follows:
In bending
In compression perpendicular to grain In compression along the grain In horizontal shear
Outside
Dry not in Places contact under with Wet cover the soil places
2.75 5.5
6
7
8
1.75
2.25
4
4.5
10
10
10
Horizontal shear refers to the stress set up in beams under bending loads; for localised shear stresses set up by bolts, dowels, and other forms of fastening, the allowable stress may be increased by 40 per cent.
The figure given for the Modulus of Elasticity is the average for the species in 1000 lb. per sq. in. and a factor of safety has not been applied. It is important to note that
Balau (Shorea spp) Strongest
Federation of Malaya
occasional pieces of timber may be deflected 50 per cent more than the calculated deflection using the Modulus of Elasticity obtained from the table. Allowance must also be made for the "creep" that occurs when timber is continuously loaded for long periods; in such cases the Modulus of Elasticity may be only about one-third of that obtained from short time loading.
Test pieces are 6 in. in length along the grain, and 2 in. The load is square in section, with two radial surfaces. applied to one of the radial surfaces through a plate 2 in. wide, placed centrally with the length of the test piece, com- pressing the latter over an area of 2 in. square. Readings of deflection and load are taken simultaneously. The stress computed is the fibre stress at the limit of proportionality, i.e. the point at which the timber will not revert to its former shape when load is released. It is calculated by dividing the load in pounds, over the bearing surface in square inches. The data from tests of compressive strength perpendicular to the grain are of the same order as those obtained from indentation tests used for assessing hardness. High values for resistance to crushing in compression perpendicular to the grain are indicative of woods suitable for use as sleepers, rollers, wedges, bearing blocks, bolted timbers, and other similar purposes.
With the enclosed data the design of wooden structures may be calculated in a similar manner to that of steel struc- tures, but modification of some of the standard design formulae is desirable in some cases. Assistance in the design of wooden structure and further information on the strength, physical properties, durability, seasoning and preservation of Malayan timbers may be obtained from the Timber Research Officer, Forest Department, Kuala Lumpur.
IN COMPRESSION PARALLEL TO GRAIN
Outside Dry not in Places contact In under with Wet cover ground places
IN COMPRESSION PERPENDICULAR TO GRAIN
Dry
Outside not in Places contact In under with Wet cover ground places
1050 810 670 620 480 400
Average Mo- air-dry dulus
IN BENDING
Kind of Timber
Shear weight of along in lb. grain cub. ft.
Elas- ticity
Outside Dry
not in Places contact
In under with Wet cover ground places
185
67
Weakest
165
60
3210 2670
Bitis (Madhuca utilis)
160
72
Chengal (Balanocarpus heimii)
195
59
2630
Giam (Hopea nutans)
195
66
2600
Keruing (Dipterocarpus spp) Strongest
130
61
3000
Weakest
105
49
2170
Damar laut merah (Shorea kunstleri)...
135
57
2750
Resak (Vatica spp) Strongest
180
67
2620
Weakest
135
48
Kempas (Koompassia malaccensis}
145
54
Merawan (Hopea spp) Strongest
Weakest
Merbau (Intsia palembanica)
155
Kapur (Dryobalanops aromatica)
120
Mengkulang (Tarrietia simplicifolia)
115
44
2150
Kulim (Scorodocarpus borneensis)
125
52
1930
White meranti (Shorea spp) Strongest
110
41
2040
Weakest
85
35
Gerutu-gerutu (parashorea lucida) Keladan (Dryobalanops oblongifolia) Dark red meranti (Shorea spp) Strongest
110 43
1920
115
48
1910
3000 2550 2250 2550 2250 1850 2750 2350 2050 2150 1900 1550 3180 2950 2550 2200 2650 2350 1900 2900 2500 2200 2500 2200 1800 2600 2250 1950 2500 2150 1900 1700 1450 1250 2500 2150 1900 2500 2150 1900 2020 1950 1650 1450 2410 2400 2050 1800 135 47 2250
2200 1900 1650 130 43 2180 2150 1850 1600 50 2020 2100 1800 1600 50 2310 2000 1700 1500 1950 1650 1450 1850 1850 1600 1400 1450 1300 1050 1840 1500
1300 1100 1200 1050 1750 1500 1300 1500 1300 1750 1500 1300 1400 1250 1000
1010
790
640
1020
790
650
2400 2150 1750
1110
870
710
1950 1750
1400
500
390
320
1400 1250 1000
300
240
190
2100 1850 1500
580
450
370
2200 1950
1600
950
740
600
1500 1300 1050
410
320
260
1950 1750
1400
520
400
330
1800 1600
1300
460
360
290
1650
1450
1200
420
330
270
1650 1500
1200
530
410
340
1650 1450
1200
350
270
220
1500 1300 1600 1400 1600 1400 1150
1050
360
280 230
370
290
240
330
250
210
850
210
160
130
1050
350
280
230
420
330
270
105
41
2130
Weakest
90
38
1640
Punah (Tetramerista glabra) Mersawa (Anisoptera spp) Strongest
120 49
1860
1700 1450 1250
1350 1200 1400 1200 1050 1050 950 1600 1350 1200 1100 1000
950
320
250
200
750
220
170
140
800
310
240
200
105
38
1650
1450
1250 1100
1150 1050
850
350 270
220
Weakest
95 39
1580
1350
1150
1000
1000 900
750
340
260
210
Light red meranti (Shorea spp)
Strongest
90
31
1650
1400
1200
1050
1050 950
750
210
170
130
Weakest
85
28
1350
1200 1000
900
900
800
650
170
130
110
Yellow meranti (Shorea spp)
85
32
1520 1300 1100
950
1050 950
750
250
190
160
Geromggang (Cratoxylon arborescens) 70
29
1160
950 800
700
650
550
450
160
120
100
SOFTWOOD and HARDWOOD
Seraya Poonah
Kapoh
Merbau
LOGS and PLANKS
Kempas Balau
Jelutong
Keruing
Chenghai
etc.
.
416 BEACH RD., SINGAPORE MILLS; SINGAPORE,
KEMAMAN & MALACCA.
Large stocks available for immediate delivery Samples and quotations gladly submitted on request
CHYE HIN LIMITED.
GENERAL TIMBER MERCHANTS E SAWMILLERS TELE: NOS:-7877 & 7878.
AGENTS IN H. K. THE SINGAPORE SAWMILL LTD., 344 LOCKHART RD.
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