Actions during service 119
In hardened concrete structures, however, temperature gradients also
occur due to the effect of day/night and summer/winter cycles. Deformations
and deflections can be significantly influenced by thermal effects. In cases
where the thermal deformations are fully or partially restrained, thermal stresses will be initiated, possibly resulting in cracking and stiffness
reduction.
Bridges are a typical showcase of the importance of temperature effects
on structures. Due to temperature evolutions of the environment, including
the effect of solar radiation on the bridge deck, a bridge will show significant elongation when the temperature increases or shortening when the temperature drops. The daily and seasonal length variations have to be allowed
for installing adequate bridge bearings and bridge joints. Malfunctioning
of these features can lead to significant stresses and damage. In continuous
girder bridges, temperature variations and thermal gradients, e.g. between
top and bottom faces, will also induce stresses comparable to the effect of
direct loading or the effect of settlements. The stresses due to thermal gradients can be calculated by means of standard design software. However,
an analytical approach enabling the investigation of the effect of temperature change on serviceability of concrete structures is given and illustrated
by ACI Committee 435 (1997).
For industrial buildings, temperature-induced deformations are becoming more and more relevant for sandwich façade panels consisting of an
inner and outer concrete panel separated by a substantial thickness of insulation. In the case of direct solar radiation, very high temperature gradients
can occur over the thickness of the façade panel, leading to highly visible
deformations (outward bending) or to damage (cracking of the concrete or
damage to the dowels connecting the inner and outer panels).
Besides the effect of the thermal gradient, damage to concrete structures
can also be induced by the temperature level itself. Extreme temperatures,
low and high, can have important effects. This is probably well-known in
the case of high temperatures (fire conditions), but also holds for very cold
temperatures (cryogenic conditions). Both situations will be explained in
the following sections.
5.2.5.2 Cryogenic conditions
Cryogenic or very cold temperature conditions can be found in typical
applications such as freeze storage rooms, −10°C to −30°C, and storage
tanks for liquefied gases such as LNG, which are stored at a temperature
below −162°C. Especially in view of rising energy demands after World War
II and after the discovery of natural gas in the North Sea, LNG transport
and storage rapidly grew in the 1970s (The Concrete Society 1981). For
safety reasons, double-walled storage tanks are typically constructed for
liquefied gases such as LNG. The inner or primary tank is usually made of
In hardened concrete structures, however, temperature gradients also
occur due to the effect of day/night and summer/winter cycles. Deformations
and deflections can be significantly influenced by thermal effects. In cases
where the thermal deformations are fully or partially restrained, thermal stresses will be initiated, possibly resulting in cracking and stiffness
reduction.
Bridges are a typical showcase of the importance of temperature effects
on structures. Due to temperature evolutions of the environment, including
the effect of solar radiation on the bridge deck, a bridge will show significant elongation when the temperature increases or shortening when the temperature drops. The daily and seasonal length variations have to be allowed
for installing adequate bridge bearings and bridge joints. Malfunctioning
of these features can lead to significant stresses and damage. In continuous
girder bridges, temperature variations and thermal gradients, e.g. between
top and bottom faces, will also induce stresses comparable to the effect of
direct loading or the effect of settlements. The stresses due to thermal gradients can be calculated by means of standard design software. However,
an analytical approach enabling the investigation of the effect of temperature change on serviceability of concrete structures is given and illustrated
by ACI Committee 435 (1997).
For industrial buildings, temperature-induced deformations are becoming more and more relevant for sandwich façade panels consisting of an
inner and outer concrete panel separated by a substantial thickness of insulation. In the case of direct solar radiation, very high temperature gradients
can occur over the thickness of the façade panel, leading to highly visible
deformations (outward bending) or to damage (cracking of the concrete or
damage to the dowels connecting the inner and outer panels).
Besides the effect of the thermal gradient, damage to concrete structures
can also be induced by the temperature level itself. Extreme temperatures,
low and high, can have important effects. This is probably well-known in
the case of high temperatures (fire conditions), but also holds for very cold
temperatures (cryogenic conditions). Both situations will be explained in
the following sections.
5.2.5.2 Cryogenic conditions
Cryogenic or very cold temperature conditions can be found in typical
applications such as freeze storage rooms, −10°C to −30°C, and storage
tanks for liquefied gases such as LNG, which are stored at a temperature
below −162°C. Especially in view of rising energy demands after World War
II and after the discovery of natural gas in the North Sea, LNG transport
and storage rapidly grew in the 1970s (The Concrete Society 1981). For
safety reasons, double-walled storage tanks are typically constructed for
liquefied gases such as LNG. The inner or primary tank is usually made of