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RE: termperature range resourse

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And people accuse me of making things over complicated!
The first rule of design is to remove the problem in the first place.

1) Manufacturers of steel roof cladding usually publish maximum runs of
cladding before thermal expansion joints are required. Some
manufacturers roll-form on site so that the cladding is continuous,
achieves the benefits similar to continuously welded railway lines.
{Though I haven't quite figured out how such works.}

2) Pipe lines usually have bearing blocks or hangers that permit the
pipeline to slide. Whilst the pipe itself has some form of expansion
coupling joint, bellows or similar.

3) Bridges are designed with one end on a roller support, not pinned at
both ends, or fixed. The abstract roller support, is physically
constructed with a sliding bearing using PTFE, or some form of
mechanism.

4) Therefore if high temperatures are present such that they are a
concern affecting structural performance, then the preferred design
option is to provide thermal expansion joints, NOT design the structure
to take the additional stresses and strains.

5) If I understand correctly the SR71 Blackbird leaks fuel like a sieve
when its on the ground, only when its in flight does it expand and all
the joints seal.

6) If you really want mechanical data for the materials then MARKS
HANDBOOK FOR MECHANICAL ENGINEERS is a good source.

7) Also the suppliers of the materials that are proposed to be used
should provide mechanical properties appropriate to the intended usage
of their products.

8) Thermal expansion is more a serviceability criteria than a strength
limit state requirement. That is to say what level of
expansion/contraction will make the system cease to be fit-for-function,
or otherwise loose aesthetic appeal? Both are largely subjective
requirements.

9) If dealing with pipelines, then refer to the appropriate codes for
the pipelines concerned. For example Large Oil pipelines through the
permafrost of Canada, are different to the water pipelines in a house. A
residential plumbing code should already explain locations for expansion
joints. Such expansion joints may have multiple purposes. Here in South
Australia for example soils are highly reactive and expand and contract
with variations in moisture content. This soil heave can snap the pipes
at the point where pipe leaves soil and enters the concrete floor slab.

10) Polymers and timber have mechanical properties that are dependent on
moisture content. Water up take makes them more ductile, when they dry
out then they become brittle. Timber structures codes allow for
variations in temperature and humidity. Timber design manuals generally
recommend joints that minimise the stresses/strains resulting from
expansion/contraction due to variations in humidity levels. Therefore
unless temperatures are extreme, then timber framing should be adequate.

11) Here in Australia (Hot place) roof's creak, both timber framing and
steel framing, steel more than timber. The main noise however comes from
the steel roof cladding and this is only significant and annoying when
the installers have failed to install according to manufacturers
instructions. This is principally by using incorrect fasteners.

12) For albedo's (reflection and absorption due to colour), insolation
and other weather and climate factors, refer to books on physical
geography, environmental engineering, meteorology, and air conditioning.
ASHRAE and Carrier design manuals.

13) Find a local mechanical or HVAC engineer.
14) Search the internet for material properties, and climate data.

Regards

Steven CONRAD Harrison
B.Tech(Mfg&Mech), MIIE, gradTIEAust
Adelaide, SA
Australia

METAMORPHS: Beyond Structures
mailto:metamorf(--nospam--at)senet.com.au
http://users.senet.com.au/~metamorf

 
 

-----Original Message-----
From: David Merrick [mailto:MRKGP(--nospam--at)winfirst.com] 
Sent: Saturday, 27 May 2006 1:51 AM
To: SEAINT
Subject: termperature range resourse

Where do I find recommended temperature ranges for structural design
projects that may have significant thermal expansion?

I failed to find a guide in the ASCE7-05 since thermal expansion can be
a load. It would seem reasonable that there should be an agreed standard
of care map reference that contours maximum temperature ranges. Usually
thermal expansion is to be considered for large roofs, roads, long
sidewalks, and long walls. 

Is there a reference on how other properties affect the temperature
ranges? Such as the possible parameters of: Geographic Location, Color,
sun exposure, Thermal Conductivity, Thermal coef. 
of expansion, heat sink

I have a Sacramento Valley, 4" black plastic(HDPE),exposed pipe. I have
started with an assume temperature range of 120 (+-60) degrees F. I
suspect that when it is filled with liquid the temperature will remain
near to what the liquid is. When empty it is more likely to expand in
the sun and reduce with cold nights. Could it be that the maximum
temperature range when exposed to the sun is higher? maybe 180 (+-90)

Load combinations are another mystery. Such as Snow loads and
contraction. Maximum pipe expansion can only occur with a residual
liquid weight, such as 10% of volume. A truss top chord against a hot
roof and outside of the insulation barrier could produce a sag with a
live load on the roof. Heat from fire could have differential expansions
of columns.


-- 
David B. Merrick, Structural Engineer


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