Hanger replacement influence on seismic response of suspension bridges: Implementation to the Bosphorus Bridge subjected to multi‐support excitation

Abstract

The effects of hanger replacement from inclined to vertical configuration on seismic response of long-span suspension bridges are investigated considering multi-support earthquake excitation. The Bosphorus Bridge is investigated due to its recent comprehensive rehabilitation, mainly involving hanger replacement. The finite-fault stochastic simulation method (FINSIM) is utilized for multi-point earthquake time-history generation. The developed finite element (FE) model both for the inclined and vertical hanger arrangement are verified through the structural health monitoring (SHM) data. Based on the comparative analysis, the tension force of vertical hangers is found to be lower than that of inclined hangers, whereas the tension force of the main and back-stay cables remains the same. The compressive axial force of the deck decreases relatively in the case of the vertical hanger arrangement, whereas the crosssectional forces at the tower base section increase. The approach viaducts are not affected by the vertical hanger arrangement. According to the demand/capacity ratios for damage estimation under the max. earthquake (2475 years return period), structural damage on the tower base section may be expected for both hanger arrangements, while these sections perform well under design scenario earthquake. The expansion joint of the bridge with inclined hangers is also estimated to be damaged; however, this displacement is lower in the case of the vertical hanger arrangement due to the viscous dampers. The findings also reveal that a change in hanger form of a suspension bridge can necessitate other structural retrofit, such as using viscous dampers to limit longitudinal displacements of the deck and retrofitting the bridge towers.

Applications of Computer Vision-Based Structural Monitoring on Long-Span Bridges in Turkey

“…The developed FE model was verified with SHM data and the experimental results presented in reference [39], which were from accelerometers. More details of the 3D FE model of the bridge can be found in the previous work [37].…”

“…It is a gravity-anchored long-span suspension bridge, and only the main span is suspended with hangers and the approach spans are supported at the base with columns of various heights. The original hangers were inclined, and in 2015, they were replaced by vertical hangers [37]. The elevation of the towers has a height of 165 m from sea level to saddle [4].…”

Seismic assessment of bridges through structural health monitoring: a state-of-the-art review

“…Bas et al. ( 2020 ) determined the hanger element replacement effect on the First Bosphorus Bridge’s structural response under a multi-support seismic ground motion. The FE model they adopted was validated using SHM data recorded earlier during the extreme wind event dating back to 2012.…”

“…Based on the results of NDE tests, after the extreme wind event in 2012, KGM decided on a hanger replacement in 2015 due to insufficient bearing capacity. Bas et al (2020) determined the hanger element replacement effect on the First Bosphorus Bridge's structural response under a multi-support seismic ground motion. The FE model they adopted was validated using SHM data recorded earlier during the extreme wind event dating back to 2012.…”