Time-Dependent Reliability for Structures Subjected to Alkali-Aggregate Reaction

This paper discusses the development of a reliability model for the alkali-aggregate reaction (AAR) of mass concrete structures. AAR growth is caused by chemical reaction in concrete between the aggregate and the cements. This creates an unlimited swelling and volumetric expansion of mass concrete, which causes substantial cracking within mass concrete structures. Since constitutive models for AAR growth are not readily available in the literature, the reliability analysis was implemented using a response surface methodology based on finite element analysis. The finite element analysis was calibrated to field measurements for strains and displacements at Chickamauga Lock and Dam. The time-dependent reliability was developed around the "life cycle" methods presented in Patev et al. A Monte Carlo simulation program was developed to determine the reliability and hazard function for the miter gate monolith, Block 47. The reliability results from the simulations show that replacement or repair to the miter gate monoliths at Chickamauga Lock and Dam will be needed in the short term to avoid any potential failure. The applications to other AAR growth problems in a variety of engineering structures are readily adaptable using the methods presented in this paper. Conclusions are drawn and additional finite element and response surface modeling are to be developed for other monoliths at Chickamauga Lock, and rock anchors are to be included into the time-dependent AAR reliability problems as well.