In order for concrete to crack, there has to be a tensile stress present, be it applied or induced. Concrete is actually designed to crack, as it is assumed that the steel reinforcement within it resists all of the tension stress within the element. The sight of cracks does cause concern however, and an understanding of what causes them is important when inspecting new works and/or existing structures.
This Technical Guidance Note describes the causes of cracking in concrete. It does not extend to the numerical analysis of cracked concrete elements as this is beyond the scope of a Level 1 guidance note.