Energy-Based Damage Assessment Methodology for Structural Health Monitoring of Modern Reinforced Concrete Bridge Columns

Performance assessment of bridge structures instrumented with structural health monitoring systems requires development of deterministic methodologies producing quantitative information on different damage states. This aim can be achieved through defining engineering limit states that may be expressed by limiting values of quantities such as damage indexes. Displacement-based damage indexes for performance assessment of bridges do not consider the accumulated damage that results from plastic cycling. In more advanced approaches, the parameter that takes into consideration the effect of cyclic loading history and accumulation of damage is the dissipated energy. However, computation of dissipated energy for the purpose of structural health monitoring requires real-time measurement of lateral forces, which is beyond the capability of conventional sensing methodologies. This paper reports on the development of a methodology to evaluate the energy dissipation in reinforced concrete columns with circular cross sections based on the curvatures measured in the plastic hinge area. Integrating the introduced method in a normalized dissipated energy index provides the possibility of detecting and quantifying minor and moderate damage that is barely visible during visual inspection. The scope of the study included the evaluation of the proposed damage assessment method through hybrid simulation tests on $1/10\text{-}$, $1/8\text{-}$, and $1/6\text{-scale}$ hybrid models of a two-span bridge subjected to various amplitudes of near source ground motions of the 1994 Northridge earthquake. Fiber-optic sensors were employed for monitoring the deformation response of the columns in the plastic hinge area.