DYNAMIC PROPERTIES OF A CABLE-STAYED BRIDGE WITH SEISMIC ISOLATION SYSTEM

Abstract

The modal response of the bridge over the Napo River was studied. This bridge spans a total length of approximately 740 meters across its various spans, with a cable-stayed section of 590 meters that constitutes the main focus of the vibration mode analysis. The structural response was assessed considering the inclusion of seismic isolators and energy dissipators, which modify the overall behavior of the structure. A three-dimensional model was developed using structural analysis software, and the primary results were verified through a manual procedure. Based on data derived from the corresponding construction drawings, the structural model of the bridge was assembled, including both superstructure and substructure components represented by abutments, piers, pylons, girders, deck slab, bearing devices, stay cables, and all relevant live and dead loads. The bridge features two vehicular lanes, two bicycle lanes, two safety barriers and handrails, and pedestrian walkways on each side of the deck. For the modal analysis, the effective mass considered the full dead load plus 25% of the live load. The properties of each component of the seismic isolation system were defined in detail, and the fundamental periods of vibration, mode shapes, and participating masses were determined using the specified methods. Finally, after characterizing the seismic demand based on code requirements, a static seismic analysis was conducted in the structure's most flexible direction, yielding response parameters such as displacement profile, acceleration, and lateral seismic forces.