*2.1. Testbed Structure*

In order to select a testbed structure with crowdsourcing potential, a link bridge with pedestrian access is implemented. The bridge is a steel frame structure connecting two adjacent buildings in Columbia University Morningside Campus, namely, Mudd and Schapiro Buildings. Mudd Schapiro Link Bridge, shown in Figure 2, is an arch structure with rigid connections spanning approximately 10.5 m. Using the known dimensions of a window and a vision-based scaling procedure, the structural dimensions are approximated without any supplementary documents and design drawings. These dimensions constitute the baseline for the mathematical model, which later on, will be updated with the information from crowdsourced vibration data.

**Figure 2.** Mudd Schapiro Link Bridge.
