Crack Width Control in RC and Prestressed Members - The Extended Core Method

The extended cross section core method for checking crack width in prestressed and reinforced concrete members subjected to eccentric compression is presented. If the loading force is located in the core of a cross section, checking the crack width is not required. The paper refers to cases in which the force is located outside the core, but within the region of the extended core of a cross section. There are numerous examples of elements that falls under this criterion - reinforced concrete columns and prestressed concrete elements that can be considered as reinforced concrete members subjected to longitudinal compression resulting from prestressing. The assumption was made that the crack width cannot exceed the product of the maximum crack spacing according to the EC2 and the extreme tensile strain of concrete calculated in accordance with the assumption that the plane sections remain plane after the deformation. The eccentricity for which the crack width reaches the limit value is called the extended radius of the cross section's core. Formulas valid for any shape of a cross section as well as formulas and design charts derived for the rectangular and circular cross sections were presented. This method can be applied to check the width of cracks with the conservative results regardless of the amount of reinforcement.