Asma köprü kulelerinin dinamik davranışında kütle sönümleyici kullanmanın faydalarının sismik performansla değerlendirilmesi

This thesis intends to investigate the effects of utilizing tuned mass dampers in mitigating the dynamic response of suspension bridge towers subjected to seismic actions. For this purpose Izmit Bay Suspension Bridge tower, which is located in Izmit Bay, is chosen as the case study bridge. Main span length of the bridge is 1550 meters and the two side spans are 550 meters each. Dynamic response of the Izmit Bay Bridge Tower structure is investigated considering two models: (1) with mass damper and (2) without mass damper to be able to estimate the impact of utilization of mass damper on the seismic response. For this purpose, member-based detailed three-dimensional simplified models of the tower are developed in CSI SAP2000 analysis software. Exact tower cross section is created in the analysis software, and for each section of Izmit Bay Bridge tower is reflected to the model with considering as-built geometry of erected tower. Additionally, loads acting on the tower that are coming from the deck and the cable are applied to the model. Also tuned mass damper (TMD) dynamic characteristics are defined according to actual masses of the existing dampers of the Izmit Bay Bridge Tower. At present, active mass dampers are built in the towers. These dampers are setup for mitigating wind and traffic induced vibrations. The existing active dampers are configured to shut down during seismic events. In this thesis, the hypothetical case of utilizing tuned mass dampers for mitigating the seismic vibrations of the towers is investigated. TMD's dynamic characteristic are estimated regarding the Eigen values obtained from the modal analysis result. Eigen vectors are used to evaluate and understand the modal behavior of each joint of the tower. Twelve ground motions records are applied with direct time integration history using Newmark's constant average method considering the geometrical nonlinearities. Failure cases are investigated for tower by approximately considering the full-scale bridge effects, accordingly limit state case is defined. Upon obtaining the results of time history analysis, seismic fragility curves are derived comparing the stress demand with the strength capacity at the critical joint sections of the tower. Finally, fragility curves of two models are compared. As it is expected, failure probability is lower for the model with the tuned mass damper compared to that for the model without damper. In addition, time history analysis results are compared to each model in order to review the effect of mass dampers.