Wysard Soares, Rachel (2019-06). Adaptive Control to Reduce the Dynamic Response of Bridges Considering Parametric Changes. Doctoral Dissertation.
Thesis
Parametric variations occur throughout bridges service life as a result of temperature fluctuations, cracking, localized damage and fatigue. Likewise, bridges parameters are difficult to estimate precisely; implemented control schemes may perform unsatisfactorily depending on their sensitivity to parametric changes. Adaptive control may present an alternative to control bridge structures, as adaptive schemes are able to calculate control gains that vary over time based on sensed responses. As a result, adaptive control strategies are able to sustain performance and deal with parametric variations. In this research, adaptive control schemes are developed and implemented to control bridges considering different types of structural configurations. The controllers' ability in mitigating excessive seismic response and sustaining performance, the sensitivity of structural configuration and modeling considerations for control design and implementation on bridge structures are investigated. Initially, an adaptive control approach is developed to control two different highway bridges having as main control algorithm the simple adaptive control strategy. As a preliminary investigation, the control scheme is implemented and designed aiming to mitigate seismic responses of a three-span highway bridge considering realistic implementation and operation conditions. Following the initial investigation, a parametric study is conducted considering a two-span skewed highway bridge in order to assess the robustness of the control approach. Sequentially, adaptive semi-active control schemes are developed to control a cable-stayed bridge having as main control algorithms the simple adaptive control and the neuro-fuzzy control strategies. The bridge is subjected to parametric changes in order to assess the robustness of the control approaches. The effects of multi-support excitation with different angles of incidence are investigated. Lastly, earthquake records matched to the site's design spectra effects are examined. The results indicate the adaptive schemes proposed in this research are a viable alternative to improve robustness to structural control of bridges. The developed adaptive control schemes are suitable to control large bridge structures, as they are able to reduce dynamic responses and offer robustness improvement when compared to nonadaptive schemes.
