Guidelines for Determining the Capacity of D-Regions with Premature Concrete Deterioration of ASR/DEF (0-5997-P1)

When a bridge engineer encounters a design or analysis problem concerning a bridge substructure, that structure will commonly have a mixture of member types, some slender and some squat. A structure may shows signs of damage and deterioration from the effects of alkali-silica reaction (ASR), delayed ettringite formation (DEF), or other deterioration mechanisms. These guidelines present the capacity of D-regions without and with premature concrete deterioration, in particular ASR and DEF effects. In many cases either beam theory or strut-and-tie methods should suffice in assessing the strength and safety of bridge substructures with or without ASR/DEF effects. However, as a supplementary analysis tool the Compatibility Strut-and-Tie Model approach can be used to augment the design process by accurately assessing the force-deformation response and nonlinear failure modes of deep beams with small span-to-depth ratios or D-regions. The computational truss modeling technique developed has the following highlights:

• Incorporates a method for apportioning the interaction of different truss and arch shear-resisting mechanisms.
• Incorporates the contribution of both flexural steel and concrete in compression chord members transformed from conventional stress block methods, which in turn defines nodal coordinates.
• Incorporates a direct method of modeling the softened constitutive relations of cracked reinforced concrete struts, which does not require an iterative process to obtain convergence.
• Enables modeling of the effects of ASR/DEF in the analysis.
• Accurately simulates the global force-deformation response of the structure without and with ASR/DEF damage.
• Enables "seeing" the nonlinear mechanism that progressively develops in the structure and precisely pinpoints the failure point and mechanism.