Building Management Hawaii February/March - (Page 31)
Ask an Expert
No One Likes to Sag
Few things are more worrisome
than seeing your lanai loll.
By Jon Brandt
Recently I was asked to look at
a building where the owners were
concerned that their lanai were
starting to fall off the building. They
were the typical concrete lanai
that cantilevered off the side of the
building, the kind so common on
buildings here. And the building was
older so they thought it best to call
an engineer since they started seeing
new sagging on the lanai.
The lower level lanai showed
the most damage, and as I looked
higher the damage got less and
less. I also noticed that most of the
sagging lanai had been enclosed,
and the unenclosed lanai showed
no damage. So I started to ask about
the enclosures, but the owners said
that the lanai had been enclosed a
number of years ago and assured me
that they couldn’t be the problem.
Well, actually they were the problem.
www.buildingmanagementhawaii.com
When the lanai were enclosed,
the contractor installed very wide and
stiff aluminum sections to support
the new windows. These supports
started to act like columns connecting
the upper lanai together. As owners
started to use their new enclosed
lanai for storage, the additional weight
caused the lanai to want to sag. This
normally wouldn’t have even been
noticed, but because of the aluminum
sections, the lanai couldn’t sag and
the weight was transferred to the
lower lanai. At a certain point, the
lower lanai couldn’t take the strain
anymore and started to sag a lot and
caused damage to the building. I’ve
seen similar situations, but usually the
aluminum sections are a lot smaller
and they buckle under the weight.
I’m sure the window installer was
proud of his work, thinking the large
aluminum sections would provide a
lasting window system, but it only led
to damaged lanai.
Although the windows had been
installed years ago, concrete can take
years to deflect (or sag). All materials
deflect when additional weight is
placed on them. Sometimes the
weight is small compared to the beam
supporting it so the deflection isn’t
noticeable, but it’s there. And all the
deflection doesn’t happen right away
either. Materials such as steel and
wood have most of their deflection
as soon as the extra weight is placed
on them, but then over time a small
amount of extra deflection occurs.
On the other hand, concrete can
have the majority of deflection occur
over a long period of time with very
little deflection right away. There is
actually a building code requirement
for this. Engineers are to consider the
deflection of the concrete beams after
five years of service. That doesn’t
mean that the deflection is complete at
five years, but shows that it is an issue.
On this project, the owners will
have to rework those windows and
repair the damage, but the concrete
is fine. Sometimes the continued
deflection of concrete does indicate
a bigger problem. If your building
has similar issues be sure to have
it checked by a local licensed
structural engineer.
Jonathan Brandt, S. E.,
is the principal of JPB
Engineering, Inc. and has
engineering licenses in
Hawaii, California and
Guam. He has worked in
both the construction and
engineering fields and
has more than 10 years of
engineering experience.
Visit www.jpbengineering.com.
BMH
February–March 2013
31
http://www.jpbengineering.com
http://www.buildingmanagementhawaii.com
Table of Contents for the Digital Edition of Building Management Hawaii February/March
Top 3 Energy Incentives
On The Grid
Solar: Not A Singular Solution
Saving Money & Art
Payback Projects
Top 10: Turn Energy Into Value
AC: Light-Zapping Clean
Does Your HVAC Talk BACnet?
Editorial: Industry Insights
Association Updates & Industry News
Ask An Expert: No One Likes To Sag
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