Control of cracking
When a statically determinate member is subjected to external applied load of sufficient magnitude to produce cracking, the member stiffness drops and an increase in displacement occurs. As long as the external applied load is sustained, there will be no change in the internal forces. On the other hand, when cracking of a statistically indeterminate structure is due to temperature
variation, volumetric change or settlement of supports, a reduction of stiff¬ ness occurs and the magnitude of the internal forces drops from the values existing before cracking. Cracking in the first and second cases will be referred to as force-induced and displacement-induced cracking and analysis of the two types of cracking will be discussed.