A NUMERICAL INQUIRY INTO THE FLUTTER PHENOMENON IN LONG-SPAN BRIDGES

Abstract

DUE TO THEIR ARCHITECTURAL CHARACTERISTICS AND STRUCTURAL PERFORMANCE, CABLE-STAYED AND SUSPENSION BRIDGES HAVE BECOME AN INCREASINGLY USUAL CHOICE WHERE LONG-SPAN BRIDGES ARE REQUIRED. THIS WORLDWIDE TREND, DATING FROM PAST DECADES, HAS ALSO IN°UENCED BRAZILIAN ENGINEERING PRACTICES IN THE LAST FEW YEARS. SEVERAL SUCH STRUCTURES ARE NOW EITHER BEING DESIGNED OR BUILT IN BRAZIL. ONE OF THE RELEVANT ASPECTS IN THE STRUCTURAL ANALYSIS OF LONGSPAN BRIDGES IS THEIR BEHAVIOR UNDER THE INFLUENCE OF WIND LOADS. PREVIOUS PAPERS PUBLISHED BY THE AUTHORS DEALT WITH THE DETERMINATION OF CRITICAL WIND SPEED CORRESPONDING TO °UTTER INSTABILITY, THROUGH THE USE OF REDUCED MATHEMATICAL MODELS WITH TWO DEGREES OF FREEDOM. THE STRUCTURE WAS ANALYZED THROUGH THE ¯NITE ELEMENTS METHOD AND REDUCTION WAS PERFORMED VIA SUPERPOSITION OF MODES SELECTED TO PERFORM THE BEST DESCRIPTION OF DECK MOVEMENT. CRITICAL WIND SPEED WAS THEN CALCULATED THROUGH THE DETERMINATION OF COMPLEX EIGENVALUES FOR SEVERAL WIND SPEEDS. THE PRESENT STUDY IS MEANT TO GO FURTHER. FLUTTER PHENOMENA IN LONG-SPAN BRIDGES ARE RESEARCHED USING TIME DOMAIN ANALYSIS AND TIME SERIES SPECTRAL ANALYSIS IN ORDER TO DETERMINE VIBRATION CHARACTERISTICS IN THE FREQUENCY DOMAIN. THOSE PROCEDURES ARE USED TO ANALYZE THE NORMANDY BRIDGE.