No_5_July_and_August__1950 — Page 76

Malayan timbers are considerably stronger than British or Scandinavian and a comparative list of the timbers most commonly used is shown below.

fc

The constant "a"

2800 (Morley)

* E

Timber

ƒ

E

Timber

ƒ

E

White deal 900 1,200,000 Spruce

Kapur

900 1,200,000

Meranti

1700 1200

(dark)

Redwood

1000

1,200,000

Balau

Douglas fir 1200 1,500,000

Chengal

2560 2500

Pitch Pine

Oak

1200 1,500,000

Keruing

1200 1,200,000

Meranti

1450 1000

2,310,000 1,640,000

3,210.000 2,630,000 2,170,000 1,350,000

Ewart S. Andrews recommends 2000 so the mean of 2500 has been taken.

=

The safe stress fc is taken as 930 lbs. per square inch with a factor of safety of 7. The ultimate breaking stress per sq. inch = 930 X 7 6510 lbs. (See trade leaflet No. 7). Example 1-To find the safe load for a column 5" X 5′′ X 8'0" high pin jointed both ends.

930

(light)

P

1 X 1

COLUMNS & STRUTS.

(KAPUR)

Pin jointed ends.

2500 (

8X12 2

930

1--1.72

343 lbs. per sq. inch,

1.442

Total load = 343 X 25

=8560 lbs.

The columns and struts shown in Tables are based on the following formula vide Rankine.

p =

p

fc

fc

1 + 1

a

2

()

= Safe load per square inch.

Safe stress per square inch. Least radius of gyration,

Effective length,

а

Constant.

Example 2-The effective length Apply same formula.

=

1⁄2 given height.

930

930

= d

= 646 lbs. per sq. inch,

1+ 1 4X12 2

1÷44

2500 1.442

Total load 646 X 25

-

16,150 lbs.

MODULUS OF

PLASTICITY

IN SENDING

(LBS. PAR

HAME OF

TIMBERS

(INCH LBS)

DRY PLACE UNDER COVER

ALLOWABLE WORKING STRESSES FOR MALAYAN TIMBER (EX. MALAYAN FOREST SERVICE TRADE LEAFLET NO. 7)

SO. IKEN)

OUTSIDE NOT IN

CONTACT WITH THE GROUND

IN COMPRESSIOH PARALLEL (LBS PER So INCH)

ONY PLACE UNDEN COVER

OUTSIDE HOT IN CONTACT WITH

THE GROUND

CHIAR ALONG GRAIN

(LBS. PER SO, IN.)

BALAU

2,670,000

2,750

2,550

2,150

1.900

165

CHANGAL

2,630,000

2,000

2,500

2 500

2,200

195

KERUING

2.170.00D

1.700

1.450

1,400

1. 250

105

KAPUR

1,310,000

2,000

1,700

1.650

1,450

120

МЕЛАНТІ

1.550,000

1.200

1,000

900

800

6 5

X

#

1.725 x 32 425 =

26.12.5 X 6.350 938.25 X 1075.32=

+

170X$250

365

$125-10%

1,4753 X

295

62.125

0237

365

...if it's

ANSWERS

you need...

BORNEO SUMATRA

TRADING CO., (MALAYA) LTD.

INCORPORATED IN THE COLONY OF SINGAPORE

WITH LIMITED LIABILITY)

BUSINESS MACHINES DEPARTMENT

4TH FLOOR. CHAN WING BLDG..

MOUNTBATTEN ROAD

TEL. 4396

KUALA LUMPUR

FRIDEN Fully Automatic Calculators will produce accurate answers to your figure work problems. Discover for your- self, how anyone in your office can operate this modern cal- culator, with less than 15 minutes instruction on your own problems. Just telephone or write and arrange for a demonstration. FRIDEN Calculators are now available to every business. Replace your worn or obsolete equipment with easy-to-operate FRIDEN Fully Automatic Calculators.

FRIDEN CALCULATING MACHINE AGENCY

SINGAPORE

41 ROBINSON ROAD

P. O. BOX 418

TEL. 82275/6/7

EXT 9

PENANG

160 WELD QUAY

PO BOX 312

TEL. 1278

74