ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/296997
38 | ASPIRE , Winter 2013 S TAT E T h e h i s t o r y o f c o n c r e t e b r i d g e s i n Ma s sa chu s et t s i s clo s ely t ie d t o t he histor y of the Massachusetts Department of Transportation (MassDOT). The Massachusetts Highway Commission, the first predecessor of the MassDOT, was established by the state legislature "to improve the public roads" in 1893, during the early era of reinforced concrete bridge construction. Early Days In an article published in the December 1929 Journal of the Boston Society of Civil Engineers, Arthur W. Dean, the chief engineer of Massachusetts Department of Public Works (suc c e s sor t o t he H ig hway Com m i s sion), wrote that Massachusetts "was the pioneer in this country in the use of reinforced concrete for bridges," a distinction that Massachusetts maintains to this day. In those early days, the highway commission experimented with reinforced concrete for a practical reason: it was difficult to obtain good rubble masonr y at a reasonable cost for the construction of culverts and bridges. As stated in its January 1903 Annual Report, in order to save money, the highway commission started to use reinforced concrete because it could be built with less-skilled labor and, as an added bonus "the resulting structure is more pleasing to look at, as well as more enduring." Many of these early bridges were either beam bridges with a reinforced concrete deck or closed spandrel arch bridges. At first, design services were performed by consultant engineers, but by 1904 the highway commission started to design bridges with its own in-house staff. A n early bridge designed and built by the highway commission, and the largest surviving example, is the Sisk Bridge. Built in 1910, it carries Old State Highway over the West Branch of the Westfield River in Chester, Mass., with a skew span of 110 ft and a skew angle of 30 degrees. By the end the twentieth century, the Sisk Bridge was showing its age, with significant freezing and thawing damage of the concrete of the spandrel walls and the outside edges of the arch. However, the rest of the arch was in very good condition. Based on the results of material testing, a structural analysis revealed that it was structurally sound to carry modern truck loads. The bridge was successfully rehabilitated in 2010, which included a slight widening with arch extensions and new spandrel walls while retaining the existing 1910 reinforced concrete arch in the middle. (See ASPIRE™ Summer 2011.) Precast, Prestressed Concrete The introduction of prestressed concrete a fter World War II sig naled a new era in t h e c on s t r u c t ion o f c onc r et e br id ge s i n Massachusetts, and once again, Massachusetts was an early leader in the use of this material. While Massachusetts did not build the first prestressed concrete bridge in the United States, it did recognize the potential of this material for rapid bridge construction. This realization played an important role in 1955 when—over a span of several days in August—two hurricanes, Connie and Diana, r ipp e d a cro s s t he st at e. T he heav y ra i n s a s sociat ed w it h t he s e hur r ica ne s broug ht massive flooding to many waterways in central Ma s sa chu s et t s. Br idge s wer e de st roye d i n domino fashion as debris, swept downstream by the flood waters, piled up against a bridge until it failed, and the resulting wreckage was carried down to repeat the cycle at the next bridge. I n t h e a f t e r m a t h , 2 2 0 M a s s a c hu s e t t s bridges in 80 cities and towns were destroyed. The devastation required a rapid construction m e t h o d t o r e p l a c e t h e f a l l e n b r i d g e s , reconnecting road s and restoring isolated communities. Massachusetts officials turned to precast, prestressed concrete beams to rapidly restore the transportation network. Because many of these bridges spanned less than 40 ft, Massachusetts selected adjacent deck beams (voided slabs) with a membrane and asphalt wearing surface as the structure type. Two standard beam depths were selected: 17-in.- deep beams for spans of 20 to 30 ft and 21-in.- deep beams for spans of 30 to 40 ft. Bridges with spans over 40 ft were individually designed, but many used prestressed concrete deck beams or I-girders. This decision proved to be an excellent one. Not only were the bridges replaced within two years, but many are still in service and carrying modern traffic loads today. A review of the MassDOT– Concrete Bridge Pioneers by Alexander K. Bardow, Massachusetts Department of Transportation A typical early reinforced concrete T-beam bridge built by the Massachusetts Highway Commission. This bridge, erected in 1909, is over Palmer Brook on what became U.S. 20 in the town of Becket. Photo: Massachusetts Department of Transportation Bridge Section Archives. State_Win13.indd 38 12/28/12 11:44 AM