Title: New Crack Control Design Provisions in AS 3600-2001

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Publication: CIA

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Date: 2/13/2011

Abstract:
Controlling cracking is a factor that should be carefully considered when designing a concrete structure. If allowed to become excessively wide, cracks can create a poor impression of construction quality, cause durability problems, and may also indicate unacceptably large vertical deflections of floor members. Important new design provisions, included in a new edition of Australian Standard AS 3600 "Concrete Structures", now require calculations to be performed specifically when designing reinforced-concrete beams and slabs for crack control. Apart from improving the quality of buildings with regard to cracking, the new design provisions also allow designers to benefit significantly from the move to high-strength 500 MPa reinforcing steels. This comes about by being able to adjust the allowable stress in the bars under serviceability conditions, depending on their diameter or spacing. By judiciously choosing reinforcement on this basis, it is often possible to utilize the full tensile capacity of the reinforcing steel in beams and slabs, which has important economic implications.