4C-Temp&Stress determines the transient temperature variation over a cross-section by solving the heat equation numerically. A temperature calculation depends on:
- The heat of hydration of the concrete
- The initial temperature of the fresh concrete and the casting rate
- Ambient wind and temperature
- The type of formwork and insulation and the time of stripping
- The use of cooling pipes, heating wires and heating mats.
For prismatic structures (eg. a wall on a base slab), 3-dimensional analyses show that the stress distribution is constant in the central region between the end-zones, assuming that plane sections remain plane. The distribution of normal stresses over a cross-section may be determined by a transient calculation known as the "Compensation Plane Method".
In 4C-Temp&Stress this method is combined with calculation of stresses within the cross-section. The stress-components are connected via the Poisson's ratio. Thus, the full 3-dimensional stress-state is calculated in the central part of a prismatic structure.
In structures with a length/height ratio less than 3-5 the stresses will be overestimated.
The stress calculation depends on:
- Development of the mechanical properties (E-modulus, Poisson's ratio, creep parameters) as a function of maturity
- Thermal deformations
- Autogenous shrinkage
- External loads and support conditions (restraints against free deformations).