Smart Bridge Technology - Government Engineering Journal

Smart BridgeTechnologyWireless sensors provide real-time update of bridge’sstructural conditions.The Massachusetts Port Authority(Massport) has announced that anew structural monitoring systemwill be put in place on theTobin Bridge over the next 18 months.Massport’s board approved a permanenthigh-tech monitoring system, whichwill make the Tobin the state’s firstStrain gauges provide real-time information aboutthe loads and stresses on the Tobin MemorialBridge.Wireless tilt sensors are attached to theTobin Memorial Bridge, providing datathat will be calibrated against actualconditions.“smart bridge.” The Tobin Bridge connectsthe Charlestown section of Bostonwith Chelsea.The monitoring system technologywill allow Massport engineers to betterunderstand the causes of stresses on thebridge. Investing in this innovative technologyenhances—butwill not replace—Massport’s schedule ofinspections, which aredone every two yearsand an in depth inspectionevery four years.The technology willallow theauthority toaddress anyconcernsimmediately.Massport isacting proactivelybecausethe technologyis available andit will buttressM assport’sefforts to maintainthe bridgein good overallcondition.The main structureover the Mystic River isa three-span, cantileveredtruss 1,525 ftin length. Its centerspan is 800 ft and themaximum truss heightis 115 ft. It provides anavigable waterway opening 700 ft wideby 135 ft high. A smaller, simply supportedwarren truss spans the LittleMystic. It reaches a maximum trussheight of 65 ft and is 439 ft long. Itsnavigable waterway opening measures340 ft wide by 100 ft high.The approaches comprise 36 spanson the north and 32 spans on the south.These spans are built-up plate girders ofvariable lengths (average length is 100ft). On the 12-span toll plaza—setPiers in the Mystic River are anchored as deep as 85 ft belowsea level. The tallest measures 339 ft from top to bottom.between the Little and Big Mystic trusses—theroadway widens to 102 ft toaccommodate seven collection lanes.The monitoring system was includedin an amended $21.7-million projectbudget for the Tobin Bridge. Theamendment will fund a contract worthroughly $1 million with Fay, Spofford &Thorndike (www.fstinc.com). The contractcalls for the firm to conduct a finiteelement analysis of forces and strains onthe bridge using a three-dimensionalcomputer engineering model of the28 ■ GOVERNMENT ENGINEERING ■ NOVEMBER-DECEMBER 2008 www.govengr.com

A major link between Boston and northern New England, an estimated 26 million vehicle trips aretaken over the Tobin Bridge annually.entire 2 1/4-mile long bridge.The model will be calibrated againstactual conditions and then wireless sensorswill be attached to areas of thebridge. The sensors’ continuous streamof data will provide important real-timeinformation about stresses and loads onthe bridge, as well as environmentalThe Tobin Memorial Bridgeconditions and corrosion.The computer modeling,calibration, and installationof the sensors should becomplete by 2010.Some 80,000 motoristsuse the Tobin Bridge eachday. Massport has developeda carefully phased maintenanceprogram—includingpainting and redecking—toensure the long-term viabilityof the bridge.Massport operates BostonLogan InternationalAirport, the Port of Boston,Tobin Memorial Bridge,Hanscom Field, andWorcester Regional Airport.Massport is a financiallyself-sustaining publicauthority whose premiertransportation facilities generatemore than $8 billionevery year and enhance andenable economic growth and vitality inNew England. For more information goto www.massport.com.GE■ At 2.25 miles long, the 58-year old cantilever bridgewas built in 1950. The Tobin Memorial Bridge formallyknown as the “Mystic River Bridge” is half a mile longerthan the famous Golden Gate Bridge in San Francisco andis twice as long as the Brooklyn Bridge in New York.■ In 1967, spanning the same Charlestown to Chelseacrossing that was served by the Winnisimet Ferry 400years ago, the Mystic River Bridge, was renamed theMaurice J. Tobin Memorial Bridge after Massachusetts’56th Governor.The Tobin Bridge was built for $27 millionby a specially created public agency with bonding authorityknown as the Mystic River Bridge Authority, an arrangementahead of its time.■ Between 1948 and 1950, 18,000 yards of concreteand 4,500 tons of steel were used in construction. Greatsteel sections of the bridge were pre-fabricated inPennsylvania and shipped to Boston on barges. Some sectionsas large as 45 tons.■ The Tobin Bridge stands 254 ft tall at its highest pointand the lower deck is 135 ft above mean high tide. Thepiers in the Mystic River are anchored as deep as 85 ftbelow sea level, the tallest measuring 339 ft from top tobottom.■ Today, an estimated 26 million vehicle trips are takenover the Tobin Bridge each year, which serves as a majorarterial link between Boston and northern New England.■ The Tobin Bridge provides three travel lanes northboundon its lower level and three lanes southbound onthe upper level. As a convenience to the bridge's roughly80,000 daily vehicle trips, tolls are only collected one way,in the southbound lanes.■ Keeping traffic moving smoothly and safely acrossthe bridge is a vital part of Massport’s strategy for promotingeconomic growth throughout the region.Advertising fees paid by BankNorth and others supplementtoll revenues that are used to improve and maintainthe bridge.■ Recent enhancements include a new toll plaza, overheadelectronic message boards, a fire-suppression system,and a new maintenance garage in nearby Chelsea thatservices and stores the snow plows used to keep thebridge open in winter, as well as other equipment essentialfor the upkeep of the bridge.■ And as part of its state-of-the-art plan for the Tobinof the future, Massport has invested nearly $2 million toequip the bridge with a FastLane electronic toll collectionsystem.www.govengr.com GOVERNMENT ENGINEERING ■ NOVEMBER-DECEMBER 2008 ■ 29