Here
are some frequently asked questions regarding engineering
for the THERMOMASS Building System. Click on the links to
the left to read questions and answers for other topics of
interest for the THERMOMASS Building Insulation System.
If you are having
trouble finding all of the answers to your questions about
THERMOMASS, please contact
our technical services department via email or call us
at (800) 232-1748. We can help
you with the choices involved in building with insulated concrete
panels. |
 |
| |
Who engineers the panels? |
|
What is the tensile strength of the composite
material used in the connectors? |
|
What is the strength of one connector? |
|
How much tensile force is a connector subjected
to in a typical panel? |
|
Can the number of connectors be reduced since
there is so much excess capacity? |
|
What is the shear capacity of the connectors? |
|
What is the shear load on a connector in a typical
application? |
|
If the panel is suspended, how much fascia displacement
can be expected? |
|
Can a heavy suspended fascia wythe be supported? |
|
What is an acceptable allowable face displacement? |
|
Does the THERMOMASS Building Insulation System
act compositely? |
|
If the insulation bond is broken, do the connectors
have adequate structural capacity? |
|
Can both wythes be used to resist design loads? |
|
How much movement can be expected due to temperature
change? |
|
Can the connectors take that much movement? |
| |
 |
|
| The connector system spacing is pre-engineered
by CTC. The structural capacity of the panel or structural
wythe thickness should be determined by the project structural
engineer. |
 |
| Back to top |
|
|
| The tensile strength of the connector
composite material is in excess of 827 Mpa (120,000 psi). |
|
| Back to top |
|
|
| A single connector can carry up to 2,500 lbs
of concrete. |
|
| Back to top |
|
|
| A typical connector is subjected to approximately
0.5 kN (110 lbs) of force during the lifting of a panel from
the casting bed. That force can be calculated as follows for
a 75mm (3”) face:
|
|
|
| |
kPa |
lbs/sq ft |
 |
| Face Weight (normal weight concrete) |
1.8 |
37.5 |
| Suction |
1.2 |
25.0 |
|
| Total |
3.0 |
62.5 |
| |
|
|
| Tributary Area for Connector |
0.165 sq m |
1.77 sq ft |
| |
|
|
| Therefore, tensile force per connector |
0.5 kN |
110 lbs |
| |
|
|
| Back to top |
|
|
| Uncertainties in concrete construction
and other factors such as uneven distribution of forces during
initial lifting dictate safety factors of the magnitude that
is present with the system |
|
| Back to top |
|
|
| The shear capacity of each connector is approximately
4kN (910 lbs). |
|
| Back to top |
|
|
The load on a connector with a 75mm (3”)
fascia wythe thickness would be approximately 0.29 kN (66
lbs) calculated as follows:
|
|
|
| |
kPa |
lbs/sq ft |
|
| Face Weight (normal weight concrete) |
1.8 |
37.5 |
| Suction |
N/A |
N/A |
|
| Total |
1.8 |
37.5 |
| |
|
|
| Tributary Area for Connector |
0.165 sq m |
1.77 sq ft |
| |
|
|
| Therefore, tensile force per connector |
0.3 kN |
66.4 lbs |
| |
|
|
| Back to top |
|
|
| A suspended 75 mm (3”) fascia panel
with the concrete/insulation bond completely broken would show
a deflection of the face wythe relative to the rear wythe of
approximately 0.07mm (0.003”) with 50mm (2”) insulation. |
|
| Back to top |
|
|
| In the case where a fascia wythe which exceeds
127mm (5”) is suspended from the interior wythe, or where
the displacement due to super-imposed loads on the face must
be held below 1.27mm (0.05”), longer connectors can be
placed at an angle in certain rows. The angled orientation better
utilizes the tremendous tensile strength of the connector to
reduce displacement of the face wythe. |
|
|
| Design considerations at joints between panels,
at doors, and at windows may make it necessary to restrict the
total face wythe displacement to 1.59mm (0.0625”) relative
to the rear wythe. The project engineers or architects should
determine the actual design parameters. |
|
| Back to top |
|
|
| A strong bond between the concrete and insulation
exists initially. However, the bond can reduce significantly
over time. CTC therefore recommends that panels be designed
as non-composite under service loads. It should be noted, however,
that the connectors and insulation continue to carry shear forces
between the two concrete wythes even after the bond has been
broken. A combination of bending of the connectors and a compression/friction
force system in the insulation resist relative displacement
between the concrete wythes and help to support the weight of
the face wythe. |
|
| Back to top |
|
|
| Yes. The shear capacity of the connectors
far exceeds the weight of the face wythe. |
|
| Back to top |
|
|
| Both wythes, acting independently, can be
used to resist wind loads. Only one wythe should be used to
resist vertical loading (such as roof or floor loading). This
is usually the interior (thicker) wythe but the exterior wythe
can also be used. |
|
| Back to top |
|
|
| The coefficient of thermal expansion for concrete
is 10 x 10-6 mm/mm/°C (5.5 x 10-6 in/in/°F). A 12.19m
(40’) long panel restrained at one end and subjected to
a 56 °C (100 °F) temperature swing can be expected to
expand (or contract) approximately 6.1mm (0.24”). |
|
| Back to top |
|
|
| Tests were performed on connectors in a wall
with 50mm (2”) insulation. The wythes were displaced 11.2mm
(0.44”) for 2,000 cycles with no deterioration of the
connectors or their strength. This represents over 150 years
of exposure in a climate with wide temperature swings. |
|
| Back to top |
| |
What is THERMOMASS?