FEASIBLE CONTROL STRATEGIES IN THE PROTECTION OF LONG SPAN BRIDGES AGAINST EXTERNAL DYNAMIC LOADS

Two numerical models of long-span bridges, namely a suspension and a cable-stayed one, are herein developed in a commercial finite element code, starting from original data, and used to simulate the structural response under wind excitation and seismic excitation. Passive and semi-active control strategies have been proposed and implemented on the bridge structural models for mitigating the induced dynamic effects. Such control schemes have been designed and proven effective on the suspension bridge for wind action, on the cable-stayed bridge for the seismic action. In light of this introduction, this paper is intended to collect the research group recent advances in the mitigation of unwanted vibrations on different long-span bridges typologies aiming to underlining general observations and strategies useful for their protection. The attention has been initially given to seismic and wind excitation, characterized to high intensities and low probability of occurrence. The control performance in such conditions is typically related on the reduction of instantaneous structural variables, as accelerations, displacements, internal forces. However, by changing the input characteristics in terms of intensity and statistic, wind actions described by low intensity and high probability of occurrence has been addressed also on the suspension bridge model, by evaluating the effectiveness of the proposed control strategies in the mitigation of indirect effects such as fatigue damage in the steel frame deck.