Adaptive modal pushover analysis for efficient buffeting performance evaluation of long-span bridge decks

The long-span bridge decks are susceptible to wind-induced vibrations due to their high flexibility and low damping. Considering the potential material savings by allowing the nonlinearity in structural elements under strong winds, the study is motivated by the recent performance-based wind design methodology to evaluate and understand the inelastic behaviors of long-span bridge decks at multiple buffeting performance levels. While the nonlinear time history analysis can offer very detailed wind structural response information, the required volume of computations is significant due to the long duration of windstorms. Hence, the static nonlinear analyses at multi-level wind hazards (i.e., wind buffeting pushover analysis) are explored in this study to efficiently provide adequate information on wind demands of the bridge deck and its components. To this end, the conventional equivalent static wind loads (ESWLs) for the linear elastic buffeting analysis is extended into the nonlinear inelastic regime, with the consideration of higher structural modes, inelastic behaviors, and multi-location responses. Inspired by the modal pushover analysis procedure for seismic demand evaluation and load-response-correlation method for wind load distribution estimation, the peak displacements at multiple bridge deck locations considering contributions from multiple modes and their coupling effects are first obtained using the pseudo-excitation method, and then the ESWLs are acquired using the displacement influence line. Furthermore, the structural characteristics (e.g., modal properties and displacement influence lines) are updated at each step of the pushover analysis to consider the effects of bridge deck inelastic behaviors on the ESWLs. A long-span truss bridge deck is employed as the case study to demonstrate the high accuracy and efficiency of the developed adaptive modal pushover analysis (AMPA) procedure for buffeting performance evaluation. Based on the inelastic behavior evolution of bridge deck elements with the increase of wind intensity, four buffeting performance levels are identified on the capacity curve. Finally, the sensitivity analysis is conducted to examine the contributions of multiple-mode and inelastic considerations to the wind demands estimated with AMPA.