Variable depth bridge decks, also known as “sucker decks,” employ a clever design principle to optimize structural performance and aesthetics. By increasing the depth of the continuous multi-span deck at pier supports, these decks effectively absorb sagging moments in the mid-span. This leads to a corresponding increase in hogging moments at the piers, ultimately enabling a significant reduction in mid-span depth due to the diminished sagging moment.
This innovative design principle is particularly advantageous in situations where minimizing headroom is a priority, such as in urban areas with height restrictions or in cases where maintaining clear sightlines is crucial. Additionally, sucker decks offer structural benefits by reducing dead loads compared to voided slabs of equivalent uniform depth, especially for span lengths ranging from 20 to 40 meters.
Beyond their functional advantages, sucker decks also boast aesthetic appeal. The public generally finds the arched forms and curved soffits of these bridges more visually interesting than traditional, uniform deck alignments. This aesthetic quality adds value to the surrounding environment, making sucker decks a popular choice for architects and engineers seeking to create visually striking and efficient bridges.
For further exploration of the sucker deck principle and its applications, readers are encouraged to consult Brian Pritchard’s 1992 work.