Boundary Condition Effects on Short Hangers in Suspension Bridges: A Combined Experimental and Numerical Approach

A suspension bridge features a deck suspended beneath cables anchored at both ends and supported by vertical towers, playing a crucial role in enabling long-span crossings. Hanger elements are used to transfer forces from the deck to the main cable, making the accurate identification of hanger capacity essential for predicting potential risks. This capacity is determined by the corresponding forces and tension, typically calculated using standard equations based on cable frequency and length. However, the boundary condition effects differ between long and short cables, and for short cables, these effects must be carefully considered. This paper proposes a novel approach for determining forces in short hangers by combining experimental and numerical methods. The experimental component focuses on identifying the dynamic properties - natural frequencies and mode shapes - while the numerical component involves finite element model updating based on the experimental results. First, the hanger's numerical model is updated using mode shapes to calibrate boundary conditions, followed by calibration of the model by applying forces to match frequencies. The proposed method is validated on a pedestrian suspension bridge case study involving three hangers of varying lengths, confirming the significant influence of boundary conditions on short hangers.