Minnesota's bridges — past, present and future
This scene of the Hennepin Avenue Steel Arch Bridge under construction adorns the cover of Denis Gardner’s new book chronicling the bridges of Minnesota.
Denis P. Gardner will read from and sign “Wood, Concrete, Stone, and Steel: Minnesota’s Historic Bridges” on Thursday, May 22, 7 p.m., at the Mill City Museum, 704 S. Second St. Call 612-341-7555 for information.
Denis P. Gardner was readying his new book, Wood, Concrete, Stone, and Steel: Minnesota’s Historic Bridges, for publication last year when a bridge he hadn’t included suddenly became history.
Bridges, which might have seemed an esoteric topic to many people on July 31, 2007, were on everyone’s mind by the next day. Gardner and his publisher, the University of Minnesota Press, decided they couldn’t leave out an event as significant as the collapse of the I-35W bridge, so the author quickly added some thoughts on it to the book’s introduction.
“What should we do about our aging bridges?” he asked. Rather than replacing them all, Gardner advocates replacing “the system that has allowed much of our bridge infrastructure to deteriorate to the point where so much needs replacing.”
Wood, Concrete, Stone, and Steel, published by the University of Minnesota Press, is replete with evidence — crisp photos and well-placed facts — to support the idea that the state’s historic bridges are worth preserving. The title gives away Gardner’s novel way of organizing the book — he traces the evolution of bridges’ design and construction by the materials people used to build them, first with wood and stone, then iron and steel, and now concrete. A two-page guide to bridge trusses at the beginning of the book is a handy reference, since many of the designs were used with several of the materials that form the book’s main sections.
Although some contain hinges, gears and other devices to help them flex, bridges appear to be static to the average onlooker’s eye. That is also, of course, how they appear in the many photographs that generously illustrate the book.
However, the dynamic image on the cover— a shot of the old Hennepin Avenue Steel Arch Bridge under construction alongside the stone-tower suspension bridge it replaced —makes you feel like you’re part of the crowd passing in the foreground. The scene is a great emblem of how it is people that make bridges come alive. That little-seen image, first used on a marker along the St. Anthony Falls Heritage Trail in the 1990s, is re-enacted daily on the Tenth Avenue Bridge, as crowds gather along the edge of one bridge to watch construction of another — the new I-35W crossing.
The bridges of Bridgeland
The gorge that the Mississippi River cuts through Bridgeland is the setting for many of the most dramatic spans Gardner discusses and shows in Wood, Concrete, Stone, and Steel. He notes that the terrain practically dictated that engineers use of “deck truss” — the box-shaped supports evident on several local spans made of metal, including Bridge 9, the now-pedestrian crossing between the university’s east and west bank campuses, and the Short Line Bridge just downstream from Franklin Avenue.
But engineers can be artists too, and they showed it in designs such as the castle-like
second Hennepin Avenue bridge and the Stone Arch Bridge, shown on page 30 under construction with a wood framework in place to hold up the stone arches. It’s surprising to learn the Stone Arch Bridge is the only existing stone arch bridge to cross the Mississippi. Another one once existed just upriver, between the East Bank and Nicollet Island. Old timers say it took much more TNT than expected to blow it up during the urban renewal period of the early 1970s.
The Third Avenue and Franklin bridges demonstrated the artistry concrete is capable of, with their wide arches and thin ribs. Gardner reserves his highest praise for the concrete arch that leaps above the road on St. Paul’s Robert Street Bridge.
A year ago, this book might have been of greatest interest to bridge aficionados and historians. Now, with the twisted remains of the I-35W bridge splayed out along Bohemian Flats Park on the West Bank and a new bridge rising from the river in its place, everyone’s a bridge fan. Gardner’s book comes along at the perfect time to capture that burgeoning interest.
last revised: May 24, 2008