Standardized models for cracking due to restraint of imposed strains—The state of the art

Abstract

Crack control throughout the service life of a structure has always been a challenging task for engineers and asset owners, particularly those who are involved with the design and construction of structures with increased durability requirements, such as liquid retaining structures, nuclear containment buildings or structures in direct contact with ground, but also other externally restrained structures. For these reasons, several standardized methods exist throughout the global engineering community which encompass differences between them. This work is a state‐of‐the‐art review of the methods for crack width control due to imposed strains recommended by different regulatory documents from Europe, USA, Australia and Japan, and provide a reasonable degree of guidance with respect to the assumptions, possibilities and restrictions of each method. This work resonates with the scope of the RILEM TC 287‐CCS: Early age and long‐term crack width analysis in RC structures.

Categorization of formulas for calculation of crack width and spacing in reinforced concrete elements

“…Their replacement value is estimated at €28 billion and is growing as new concrete structures are being designed 1,2 . In these structures, loading due to external forces or restrained imposed strains may lead to cracks 3 . Although current studies do not all agree if corrosion increases with increasing crack widths, 4 the impact of cracking on durability performance is indicated by various studies, 5–7 and led to the definition of crack width limits for ingress rates.…”

“…1,2 In these structures, loading due to external forces or restrained imposed strains may lead to cracks. 3 Although current studies do not all agree if corrosion increases with increasing crack widths, 4 the impact of cracking on durability performance is indicated by various studies, [5][6][7] and led to the definition of crack width limits for ingress rates. Cracking can jeopardize the service life of these civil engineering structures, 8 and thus, an accurate description of crack patterns in existing and new concrete structures is essential, considering both the crack width w and spacing between the cracks s r .…”

“…The cracking stages of reinforced and prestressed concrete structures can be divided into the crack formation stage (CS1) and the stabilized cracking stage (CS2), 3 see Figure 3. Following the uncracked behavior, indicated by branch (1), the crack formation stage often applies for cracking due to restrained imposed strains and is characterized by a constant branch (2).…”

Crack monitoring on concrete structures with distributed fiber optic sensors—Toward automated data evaluation and assessment

“…The load bearing contribution of the concrete in-between cracks is called TS. 30 The strains measured with DFOS are influenced by TS. Compensation approaches for concrete strain DFOS 9,31 or reinforcement strain DFOS 3 are available in the literature.…”

The effect of the degree of cracking on the state of stress and cracks width in elements with restrained boundary conditions

“…Most frequently the cracking models recommended in standards specify the cracks maximum width that can occur in a given structural member. The state of the art on the imposed strains induced cracking models recommended in standards were presented by Jędrzejewska et al 23 In the case of end-restrained members only the stage of cracks formation is analyzed rather than the stage of strain increase at a maximum number of cracks. As a result, according to the standardized models the cracks maximum width depends mainly on concrete tensile strength (EN 1992-1-1, 20 EN 1992-3, 6 CIRIA, 9 and CIA Z7 24 ) or indirectly on the stresses in reinforcing steel (FprEN 1992-1-1, 8 AS 3600, 25 AIJ-SRC, 26 ACI 207.2, 27 and ACI 224R-01 28 ).…”