The research objective of this Faculty Early Career Development (CAREER) award is to enable civil engineers to design bridges and other critical structures so that the structure will naturally provide signals about its structural state with only a minimum installation of sensors. This will result in a safer and more resilient civil infrastructure as new construction or retrofitting incorporates these designs. This is significant because critical structures have been failing without sufficient warning despite the fact that the cracks in these structures were already being inspected and monitored with the latest modern techniques. The research has the potential to transform the field of structural engineering by detecting damage at the earliest stage. The educational impact of the research will include modifying existing steel and prestressed concrete design courses to introduce damage detection concepts to undergraduate students, developing Honors College research projects, involving high school and undergraduate students into research, and developing mentoring program within female civil engineering students.
In this research, an acoustic based damage detection method will be introduced into the design stage by adding spatially periodic subsystems into structural elements. Existing structures exhibit some localized periodicity such as perforated beams, and equally spaced bolts in steel connections where spacing is based on stress distribution and spacing requirements. The structural periodicity can be tuned to make the design behave as an acoustic metamaterial, which can be able to block, redirect, and strengthen propagating elastic waves released by newly formed crack surfaces in the deployed infrastructure. Local resonance in an acoustic metamaterial medium affects the elastic wave spectrum such that certain wave frequencies cannot propagate to the medium if the frequency falls within these stop bands. Once the periodicity is modified by damage, the elastic wave spectrum will change, and then structural damage can easily be detected as a disturbance of the normal resonant frequencies. Highly narrowband and sensitive micro-mechanical transducers will be tuned to the stop band of the periodic subsystem and positioned strategically such that one sensor will be sufficient to detect the localized damage. The combined response of structural design and periodic behavior will be tested with analytical and numerical models and validated on laboratory scale structural tests.
