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It would be fair to say the guide sparked a
lot of fairly passionate debate and in some
cases vehement opposition. This was to
be expected; we were changing a guide
that had been in place for nearly five
years and in some cases recommending
over double the requirement.
It was therefore interesting to read
the fantastic article written by Maura
Paternoster in the American Rental
Association (ARA) August 2016 edition
of
Rental Management
. Maura is the
risk manager for the ARA and the article
was an in depth study of how companies
approach weighting and hold down of
tents/marquees in North America.
An interesting observation in the first
section of the article really caught my
eye: “It is only luck that improperly
secured tents and the people and
property around them, survive without
incident, but every time it happens it
reinforces a false sense of confidence and
perpetuates a risky practice borne from
inexperience.”
This is a very powerful statement and my
agreement is total, however I would go
even further. It is human nature to rely on
past experience. No one willingly wants
to do the wrong thing however each time
we get away with something we learn
bad habits. Every time we unknowingly
or wittingly underweight, even if luck
is on our side, we move a step closer to
disaster.
As indicated the article looked at the
various methods for holding a tent/
marquee in place, exploring the accepted
practice and providing reasons why
erectors adopt this practice.
In summary the rule of thumb for them (in
the US) is 10lbs (4.5kg) of weight for each
square foot (0.09m
2
) of fabric. It should
be noted this is for a weekend only. If the
tent/marquee is in place for longer, the
rules change to 15lbs (6.8kg) per square
foot.
This is very interesting and it shows
our Australian guide compares very
favourably. Since the article in the ARA
Revising the weight on our minds
By Tom O'Dowd – National President – Events
The HRIA recently updated the revised weighting guide; this was an update from the
guide's launch in May of last year. The revised guide adds a number of explanatory photos
and a new addition to the tables providing an option for a lower wind speed.
magazine only looked
at a marquee or tent
with all walls open
(no side walls) we can
compare this to our
HRIA guide in the
following study.
For comparison we
have used the LBS
per square foot model
and then converted
the end result to
express the ballast in
kilograms.
USA
10ft x 10ft = 100ft
2
x 10lbs per ft
2
=
1000lbs. This is 450kg
for all four legs.
(10ft x 10ft is
equivalent to a 3m x
3m).
20ft x 20ft = 400ft
2
x 10lbs per ft
2
=
4000lbs. This is
1,812kg for all six legs.
(20ft x 20ft is equivalent to a 6m x 6m).
HRIA
3m x 3m = 9m
2
. Our guide calls for (all
walls open), 90kg per leg x 4 legs = 360kg.
If we have one or more wall open then
the force is multiplied by the factor of the
walls and we call 460kg per leg.
So in the case of a 3m x 3m with three
walls (one wall open) based on the
amount of fabric, looking at it from the
USA perspective:
100ft
2
for the roof = 100ft
2
;
70ft
2
for each wall x 3 = 210ft
2
;
Total - 310ft
2
x 10lbs per ft
2
= 3100lbs.
This converts to 1,404.3kg.
Divide this by four legs and we get 351kg
per leg. Our guide calls up 460kg but is
based on a minimum one week duration
(this is clearly identified in the notes). The
minimum that can be calculated is one
week in accordance with the Temporary
Structures Standard. Adopting the USA
rule of 15lbs per square foot they would
use 4,650lbs or 2,106kg divided by four
legs = 526kg per leg (66kg more than us).
6m x 6m = 36m2 Our guide calls for (all
walls open) 170kg per leg x 6 legs =
1,020kg. If we have one or more wall open
then the force is multiplied by the factor
of the walls and we call 640kg per leg. So
in the case of a 6m x 6m with three walls
on the amount of fabric, looking at it from
the USA perspective:
400ft
2
for the roof = 400ft
2
;
140sq ft each wall x 3 = 420sq ft;
Total – 820ft
2
x 10lbs per square foot =
8,200lbs. This converts to 3,714.6kg.
Divide this by six legs and we get 619kg
per leg our guide calls up 640kg – again
based on a one week duration.
I am sure by now some of you are
thinking the winds in the USA are much
greater than the suburbs of Australia. We
The HRIA recently updated the revised structures weighting guide
46
HIRE AND RENTAL NEWS •
EVENTS in FOCUS
• FEBRUARY 2017
EVENTS in FOCUS