There are many arbitrary rules for provision of shrinkage strips in concrete floors. I am looking for a rational method for calculating shrinkage strips spacing.
I must assume when your refer to "shrinkage strips" you are refering to control joints. The general rule is 24 to 36 times the thickness of the slab. As an example, if you have a 6-inch thick slab, the maximum control joint spacing would be (6x36)/12 .... 18 feet. Keep the slab sections as nearly square as practicable. If the sections must be rectangular, make sure the ratio of length to width is no more than 1.2:1
Ron,
Whatever you suggested is for sure one of the arbitrary and conservative methods. Assuming there is a 800 feet long parking structure with centre of rigidity located at centre point. The structure may be a flat slab or slab and beam construction. A rule of thumb is to have shrinkage strips every 60 feet c/c to be concreted after 60 days of pouring. This is meant for a reasonable fraction of shrinkage (creep also if prestressed) to take place before structure is tied to rigid vertical elements.
I am looking for calculations to rationalise this and other similar approaches
The relationship I gave you was for unreinforced slabs on grade. For reinforced concrete, those values are not valid. I would suggest you refer to "Properties of Concrete" by A.M. Neville. This text gives a good treatment of shrinkage/creep issues, but the criteria are too diverse and lengthy to get into in this forum.
