Calculation method

Requirements for the control of cracking are given in EC2 Section 4.4.2. Crack control is normally achieved by the application of simple detailing rules.

The procedure for the calculation of crack widths is first to calculate the stress and hence the strain in the reinforcement, taking into account the bond properties of the bars and the duration of loading. Next, the average final crack spacing dependent on the type, size and disposition of the reinforcement and the form of strain distribution is established.

The design crack width may then be obtained and compared with the limiting design crack width. In the absence of specific requirements, a limiting crack width of 0.3 mm will generally be satisfactory for reinforced concrete members in buildings with respect to both appearance and durability.

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