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## Welcome to the official blog of Uncle Ming's Gallery

I have always been among those who believed that the greatest freedom of speech was the greatest safety, because if a man is a fool the best thing to do is to encourage him to advertise the fact by speaking. (我以為讓愚蠢的人自暴其醜, 正是最大之言論自由所以是最安全的主因)

WOODROW WILSON (編輯組譯)

### 從災難說因果規律

Disaster - Chaos or Discipline
-23/8/2011

### 免 責條款 DISCLAIMER

Remarks:

1. Safety Co-efficient: Also know as Safety Factor (SF), There are two distinct uses of the factor of safety: One as a ratio of absolute strength (structural capacity) to actual applied load. This is a measure of the reliability of a particular design. The other use of FoS is a constant value imposed by law, standard, specification, contract or custom to which a structure must conform or exceed.in brief, it is defined as the following:
$\text{Factor of Safety}=\frac{\text{Material Strength}}{\text{Design Load}}$

Source: http://en.wikipedia.org/wiki/Factor_of_safety

References:
http://www.mitcalc.com/doc/help/en/c_safety.htm

2. Preventive Maintenance:

Preventive maintenance (PM) has the following meaning

• The care and servicing by personnel for the purpose of maintaining equipment and facilities in satisfactory operating condition by providing for systematic inspection, detection, and correction of incipient failures either before they occur or before they develop into major defects.
• Maintenance: including tests, measurements, adjustments, and parts replacement, performed specifically to prevent faults from occurring.
Source:
http://en.wikipedia.org/wiki/Preventive_maintenance
http://www.weibull.com/SystemRelWeb/preventive_maintenance.htm
http://www.iapa.ca/pdf/prevent.pdf
http://www.wisegeek.com/what-is-preventive-maintenance.htm

3. cap 123 reg 15: Approval and consent deemed to be given unless refusal notified, BUILDINGS ORDINANCE
Source: http://www.legislation.gov.hk/blis_pdf.nsf/6799165D2FEE3FA94825755E0033E532/439979DE5B92D2C9482575EE003EBFB6?OpenDocument&bt=0

4. CP 2004: 《香港風力效應作業守則 - 2004 年》

Source: http://www.bd.gov.hk/chineseT/documents/code/windcode2004.pdf

5. wind pressure:
The wind pressure can be approximated by: Pressure = ½ x (density of air) x (wind speed)2 x (shape factor)
• The density of air is about 1.25 kg/m3.
• The shape factor (drag coefficient) depends on the shape of the body. It has order of magnitude 1 and is dimension less.
• The wind speed must be expressed in m/s. In that case the pressure has units kg/m/s2, i.e. N/m2.
See this table:
 Bft Wind speed (m/s) Wind pressure (N/m2) Lower limit Upper limit Upper limit 0 0.0 0.2 0.03 1 0.3 1.5 1.4 2 1.6 3.3 6.8 3 3.4 5.4 18 4 5.5 7.9 39 5 8.0 10.7 72 6 10.8 13.8 119 7 13.9 17.1 183 8 17.2 20.7 268 9 20.8 24.4 372 10 24.5 28.4 504 11 28.5 32.5 660 12 32.6 > 660
Since the scale of Beaufort and the wind speed are not related linearly, it is not possible to express the wind pressure as:
Pressure = (constant) x (wind speed in Bft)2.

Source: http://www.knmi.nl/samenw/hydra/faq/press.html

References: