Introduction
This Technical Guidance Note provides an introduction to the assessment of thermal effects on building structures; it does not cover the effects on other types of structures, e.g. bridges or silos.
Thermal effects are just one source of movement in a structure; other sources of movement in buildings include:
- ground conditions
- changes in moisture content
- elastic deformation under load
- side sway due to horizontal loads
- creep due to material properties
- shrinkage due to material properties
- elastic compression due to prestressing.
These effects are outside the scope of this note. However, they can occur simultaneously with thermal effects, and it may be necessary to consider the combined effects of these movements to establish the design actions on the structure or particular elements.
This note sets out how to determine the thermal effects. It is not the change in temperature itself that requires consideration in structural building design; rather it is either:
- the movement caused by the temperature changes that affect the interfaces between members, or
- the restraint to movement that causes strain within a member.
This note will explain how to determine the movement, or restraint to movement, and how it varies depending on a variety of conditions. It will also highlight areas where potential issues can be overlooked.