Cracks induced by temperature changes
All structures will be subjected to some form of temperature cycling during their life on a daily and/or seasonal basis. Most concrete structures are relatively stiff and movements caused by temperature changes will be restrained, which may result in cracks forming at right angles to the restraint. Such cracks have a different form to those caused by loading.
For example, in a beam, they will tend to have a uniform width throughout the member, from top to bottom, rather than varying from a maximum width at the tension face and reducing to zero towards the neutral axis. The design process should ensure that sufficient reinforcement is provided to control the crack widths to the specified limits.
Reinforcement will not prevent the formation of cracks but will ensure that they are well distributed.
Appropriate guidance is given in the design Eurocodes Eurocode 2; Part 1-1 covers buildings, Part 2 covers bridges and Part 3 covers Liquid retaining and containing structures. These parts of Eurocode 2 have replaced BS 8110, BS 5400 Part 4 and BS 8007.