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RE: Allowable Stress Design- Wind Loading

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These days, most codes are based on limit state - In Australia, the 33%
overstress is still applicable in our working stress steel code - but we
have not had a working stress concrete code for many years.  A typical load
combination involving wind load in the concrete, timber or limit states
steel code would be

1.25(DL)+0.4(LL)+1.5(WL) (the LL factor depends on the type of live load)

In principle, allowing an overstress when wind is combined with BOTH dead
and live loads is acceptable given the reduced probability.  The combination
involving only dead and wind loads (no live loads) should not allow the
overstress as the probability of the combination is not reduced.

For foundation design, allowable bearing pressures are often based on a
safety factor against bearing failure of 3-4 - for transient loads such as
wind or earthquake loads it is common to reduce this safety factor to 2-3,
but it does depend on the level to which the assumed earth properties have
been determined.

Dave Meney
Structural Engineer

Yenem Engineering Services

> -----Original Message-----
> From: RoyLevy(--nospam--at) [mailto:RoyLevy(--nospam--at)]
> Sent: Monday, 7 December 1998 11:40 am
> To: seaint(--nospam--at)
> Subject: Allowable Stress Design- Wind Loading
> When wind loading is included, many structural steel
> specifications permit a
> 1/3 increase in the allowable stress, provided that the usual
> allowable stress
> is not exceeded  for the remaining loads when the wind loading is not
> included.  Are there  also corresponding increases  permitted for the
> following ?
> 	a) reinforced concrete structural frames
> 	b) reinforced concrete footings
> 	c) foundations (soil, rock, or piles)
>                            Roy Levy