The correct identification of the load of the bridge is fundamental for the design of each component. The bridge design is iterative in the sense that limb sizes are a function of loads and loads are a function of limb sizes. Therefore, it is necessary to begin by providing members based on previous experience and then adjusting the actual loads and bridge geometry.
The steel bridge is a two-story vertical bridge bridge spanning the Willamette River in Portland, Oregon, United States, opened in 1912. Its lower deck transports rail and bicycle / pedestrian traffic, while the upper deck carries traffic ( on the West Pacific Highway No. 1W, Oregon's former 99W route) and Light Rail (MAX), making the bridge one of the most multimodal in the world. It is the only two-story bridge with independent elevators in the world and the second oldest vertical bridge in North America, after the nearby Hawthorne Bridge. The bridge joins the Rose neighbourhood and the Lloyd district in the east with the Chinatown neighbourhood of the Old City in the west.