November_1970 — Page 37

where deliberate attempts were made to cause damage by excessive blasting or by mechanical agitation, even under sustained resonant conditions. Sustain- ed amplitudes of vibration of the order 2500 μ (2.5 mm) were required to pro-

Ομ duce severe cracking of plaster and these are far in excess of the ampli- tudes produced by traffic, factory machinery, compressors, or other com- mon sources of vibration. Door slam- ming or walking about heavily are

주

frequency (Hz)

100

50

30

20

10

Key:

I

II

业

IV

|-|

DIN 4150: 'danger

II

likely to produce greater vibration and shock than will most external sources of vibration.

In building vibration problems there is no evidence that fatigue is significant. For steel beams it can be

Information obtained in recent years has shown that the resistance to shown that there is usually a large fact- or of safety against fatigue failure even when the vibration is such as to be un- pleasant to a person.

velocity of 75mm/sec

velocity of 100mm/s

velocity of 50mm/sec,

NO DAMAGE

POSSIBILITY OF PLASTER CRACKS

(cracks in load-bearing structural units in exceptional cases)

PROBABLE DAMAGE TO LOAD-BEARING STRUCTURAL UNITS

DAMAGE TO LOAD-BEARING UNITS-DESTRUCTION'

E

10

102

102

Fig. 4. Possible damage to buildings

amplitude (u)

16

2

2

10"

fatigue of reinforced and prestressed concrete is also sufficient to ensure that fracture or damage is unlikely to result if the level of vibration can be tolerated personally.

Further reading

1. Vibration in Civil Engineering. B O Skipp (Editor); Butterworth Lon- don 1966

2.

Current Paper Engineering Series 37. Some aspects of structural vibration RJ Steffens. BRS 1966.

3. Library Bibliography No. 199. A

bibliography

vibrations

on

1955-1965. BRS 1966.

4. Library Bibliography No. 217. A bibliography on vibrations in laboratories. BRS 1969.

5. Current Paper 14/70. The problem of vibrations in laboratories. R J Steffens BRS 1970

6. International Series of Monographs in Civil Engineering, Vol. 2. Building on springs. R A Waller. Pergamon Press 1969.

This feature is published by per- mission of the Building Research Sta- tion, Watford, UK. Crown copyright. Part 2 in next month's issue will ex- plain some ways in which nuisance from vibration can be avoided or re- duced to a tolerable level.

Shanks

Curzon Bidet

IN VITREOUS CHINA

62/69 vitreous china bidet fitted

with 1⁄2 in. hot and cold valves to rim and spray, change-over lever, 14 in. pop-up waste.

Available in White or the following colours: SKY BLUE, TURQUOISE, PRIM ROSE, SHELL PINK, SA- VANNAH and SUN KING.

SOLE AGENTS:-

ENGINEERING EQUIPMENT CO., LTD.

532 ALEXANDRA HOUSE, HONG KONG.

TELEPHONE: 237099.

Far East BUILDER, November 1970

33