Bridge Building Requires Knowledge Of Science

In early May this year my entire family converged on Jekyll Island, Ga., home of my in-laws, for a week vacation. On this barrier island, a Georgia State Park, the last mile of a 14-mile bicycle path around the island was being completed.

This required a 200-foot-long boardwalk across a tidal marsh situated too close to the highway to permit a cement sidewalk to be built for the bicycle path.

Early in the week, I stood straddling my road bicycle while watching the workers, some in chest-high waders, attaching cross timbers to double wooden piles, screwing deck planks to the under supports and driving piles with a small, gas-powered pile driver. Boardwalk construction proceeded from two sides of the marsh to meet in the middle just like the first American transcontinental railroad west and east lines met at Promontory Summit, Utah, in 1869.

Only this boardwalk was doomed.

When I returned the next day to watch the boardwalk construction, I was joined by my father-in-law, Darrell, who lived near the start of the boardwalk. Close by, the director of operations for the Jekyll Island Authority, an acquaintance of Darrell, was assessing the boardwalk progress. He explained to us that a miscalculation had been made so the piles at the far end section had been driven too deep, which would create a dip or step in the boardwalk, a dilemma for bicycle riders.

It struck me that building bridges and even boardwalks is a complex undertaking. Highway bridges built from opposite river or ravine banks also have to meet up in the middle. Bridges need to withstand floods, winds and heavy traffic. Complex science is called upon to design and construct bridges and even boardwalks. The job calls for the study of civil engineering. The author and civil engineering professor, David Blockley in his book, “Bridges-The Science and Art of the World’s Most Inspiring Structures” states, “Bridge building is a magnificent example of the practical and everyday use of science.” In my opinion, if a young student studied to become a civil engineer, they could create beautiful, functional bridges which would stand as monuments for further generations as an example of creativity, imagination and knowledge of science.

Revision of the potentially uneven boardwalk was done by splicing a new pile onto the existing short pile then driving the now longer wooden pile to the proper depth, sawing off the excess and finally attaching the decking. As we watched the progress, my father-in-law, a civil engineer by training, related his bridge-building experience to the director of operations and to me. As a career United States Marine in the civil engineering division, the 9th engineer platoon from his Force Support Battalion built a 720-foot-long timber trestle bridge to carry 60-ton tanks over the Song Ba Ren River south of Da Nang, Vietnam, in 1968-69. His bridge replaced a blown up steel girder bridge built by the French.

My own bridge building experience across a shallow, 3-foot-wide brook along the woods in my backyard produced two failures. The first bridge, made with old telephone poles set into the bank of the brook, was designed to support a riding lawn mower. The second bridge, designed for walking, consisted of a 10-foot-long spruce log set into the muddy bank. Both worked fine for several years until a torrential rainstorm overflowed the banks of the brook, sweeping my two bridges downstream. I neglected to consider the environmental action on my bridge in case of flooding.

Today when I use a modern bridge, I will revere the structure created by the civil engineer. Before I left Jekyll Island, I witnessed the completion of the boardwalk decking; it was elegant and level. One week later, after the railings were attached, my father-in-law was invited to christen the new boardwalk by leading a contingent of recreational bicyclists across the structure for the first time.