Effect of Reinforced Concrete Deterioration and Damage on the Seismic Performance of Structures

The response of a system to dynamic excitation depends on the interaction between the forcing function and the system. In practice, change in material properties due to aging, fatigue, or the experience of a hazard are major challenges to the designer. This chapter discusses the effect of material deterioration on the dynamic properties of reinforced concrete structures with consideration to strain compatibility. Aging and loss of steel bond to concrete have significant effects on dynamic response. Aging causes a drop in compressive strength, hence in axial and flexural capacity, altering column interaction diagrams, or beam-column joint strength. The effect of aging in standing structures can be measured through coring and lab tests, but loss of bond is harder to evaluate because its mechanism is interior to structural members. Causes of bond deterioration include poor concrete mix, placement, or protection from chemical agents. However, well-designed mixes and placed materials may lose bond when subjected to an earthquake. Steel bond testing was performed and documented in literature, but there is still a gap in field data. A mathematical model is developed to illustrate the relationship between bond loss and concrete frame stiffness. Field assessment and remedial measures are discussed for structures that are suspected of, or diagnosed with, loss of bond. If the structure is salvageable, such effects call for specialized repairs as a preventive measure against subsequent events. But if loss of bond during an earthquake goes into an irreversible deformation range, the possibility of collapse increases or the structure becomes a candidate for disposal.