49529_CovBridgeBroc 10/29/08 9:22 AM Page 1 - T.S. Eliot (1888-1965) Eliot T.S. - Will be to arrive where we started, And know the place for the first time. first the for place the know And started, we where arrive to be Will We shall not cease from exploration, And the end of all our exploring, our all of end the And exploration, from cease not shall We THE BURR TRUSS BURR THE THE QUEENPOST TRUSS QUEENPOST THE Evans. R. June and Evans D. Benjamin by Guide” Complete A Bridges, Covered “Pennsylvania’s book the from comes above information Truss ture. There are more bridges in Pennsylvania using the Burr Truss design than all other truss designs combined. designs truss other all than design Truss Burr the using Pennsylvania in bridges more are There ture. known, used two long arches, resting on the abutments on either end, which typically sandwiched a multiple Kingpost struc- Kingpost multiple a sandwiched typically which end, either on abutments the on resting arches, long two used known, design soon became one of the more frequently used systems in bridge building. The Burr Arch Truss, as the design became design the as Truss, Arch Burr The building. bridge in systems used frequently more the of one became soon design Connecticut. His career began in New York where he built a bridge spanning the Hudson River in 1804. The Burr Truss Burr The 1804. in River Hudson the spanning bridge a built he where York New in began career His Connecticut. is named for one of the earliest and most prominent bridge builders in our country-Theodore Burr from Burr country-Theodore our in builders bridge prominent most and earliest the of one for named is Truss Burr The THE KINGPOST TRUSS KINGPOST THE Frequently, additional diagonal timbers were placed between the corners of the central rectangle. central the of corners the between placed were timbers diagonal additional Frequently, zontal member of that rectangle, however, had to be placed below the horizontal upper chord of the exterior side framework. side exterior the of chord upper horizontal the below placed be to had however, rectangle, that of member zontal - hori upper The timber. Kingpost vertical center the faced originally that triangles two the between placed is which center, the up to 75 feet. The Queenpost truss is really an expansion of the Kingpost design because of an additional rectangular panel in panel rectangular additional an of because design Kingpost the of expansion an really is truss Queenpost The feet. 75 to up system followed the Kingpost in design chronology. It was also used to span long distances, frequently distances, long span to used also was It chronology. design in Kingpost the followed system Truss Queenpost The mately 20 to 30 feet. 30 to 20 mately i- approx of spans short for primarily used is and diagonals two and beam), (vertical Kingpost a stringer, a of consists It above. is the oldest truss design used in bridge construction, initially used under the roadway rather than rather roadway the under used initially construction, bridge in used design truss oldest the is Truss Kingpost The the Susquehanna River Valley River Susquehanna the torted under stress. Each bridge consists of two truss systems, one on each side of the structure. the of side each on one systems, truss two of consists bridge Each stress. under torted Used in Covered Bridges of Bridges Covered in Used The true truss system consists of massive timbers assembled in a triangle – the only two-dimensional figure that cannot be dis- be cannot that figure two-dimensional only the – triangle a in assembled timbers massive of consists system truss true The RS DESIGNS TRUSS A Word About Truss Types Truss About Word A The Engineering of COVERED BRIDGES COVERED BRIDGES of the Susquehanna River Valley As early as 783 B.C., Babylonian records report covered bridges being used to cross the Euphrates River. In more “modern” times, an Italian named Palladios first used the Kingpost truss, the core support element of wooden bridges, in 1570. However, it did not gain popularity in Europe because of the beauty, durability, and strength of stone bridges. Nearly 200 years later, the Kingpost truss was rediscovered as the need for bridges in the New World grew. The popula- tion of the northeastern United States expanded beyond its Susquehanna River Valley Visitors Bureau early tidewater region where streams, rivers, and bays served 81 Hafer Road, Lewisburg, PA 17837 as major transportation routes. As people moved inland, agri- Toll-Free: 800-525-7320 • Phone: 570-524-7234 culture and water-powered industrialization brought a need Website: VisitCentralPA.org • Email: [email protected] for overland transportation, and bridges were built by the score to ford the waterways. For more information about Wooden structures were preferred for these early U.S. overnight accommodations, bridges for several reasons. The freeze-thaw cycle of the things to do, places to see, and harsh Northeastern climate could overturn stone pavings, much more, please stop by our which were also more expensive to install in comparison to Visitor Info Center, call us, or visit us on the web. the bridges constructed of the readily available supply of lumber of the Northeast forest country. The exposed super- structures of these wooden bridges were vulnerable to rot, however, so covering and roofing them became a practical way to protect them from weather so they would last longer. The Commonwealth of Pennsylvania became a leader in the construction of covered bridges and a resourceful state gov- ernment gave high priority to private and public bridge building. At one time, Pennsylvania had 1,500 covered bridges. Experienced bridge builders were in great demand to build the heavy-duty bridges that were needed throughout the Susquehanna River Valley. There is no doubt that covered bridges played a key role in the economic development of the United States during its early history. We can look with pride at these wooden mon- uments that have weathered time and the elements. They have become part of the rich heritage that is still alive today in Central Pennsylvania thanks to the efforts of concerned citizens and local government leaders who continue to make preserving our covered bridges a priority. Bridges REPRINTED 2008 49529_CovBridgeBroc 10/29/08 9:22 AM Page 1 - T.S. Eliot (1888-1965) Eliot T.S. - Will be to arrive where we started, And know the place for the first time. first the for place the know And started, we where arrive to be Will We shall not cease from exploration, And the end of all our exploring, our all of end the And exploration, from cease not shall We THE BURR TRUSS BURR THE THE QUEENPOST TRUSS QUEENPOST THE Evans. R. June and Evans D. Benjamin by Guide” Complete A Bridges, Covered “Pennsylvania’s book the from comes above information Truss ture. There are more bridges in Pennsylvania using the Burr Truss design than all other truss designs combined. designs truss other all than design Truss Burr the using Pennsylvania in bridges more are There ture. known, used two long arches, resting on the abutments on either end, which typically sandwiched a multiple Kingpost struc- Kingpost multiple a sandwiched typically which end, either on abutments the on resting arches, long two used known, design soon became one of the more frequently used systems in bridge building. The Burr Arch Truss, as the design became design the as Truss, Arch Burr The building. bridge in systems used frequently more the of one became soon design Connecticut. His career began in New York where he built a bridge spanning the Hudson River in 1804. The Burr Truss Burr The 1804. in River Hudson the spanning bridge a built he where York New in began career His Connecticut. is named for one of the earliest and most prominent bridge builders in our country-Theodore Burr from Burr country-Theodore our in builders bridge prominent most and earliest the of one for named is Truss Burr The THE KINGPOST TRUSS KINGPOST THE Frequently, additional diagonal timbers were placed between the corners of the central rectangle. central the of corners the between placed were timbers diagonal additional Frequently, zontal member of that rectangle, however, had to be placed below the horizontal upper chord of the exterior side framework. side exterior the of chord upper horizontal the below placed be to had however, rectangle, that of member zontal - hori upper The timber. Kingpost vertical center the faced originally that triangles two the between placed is which center, the up to 75 feet. The Queenpost truss is really an expansion of the Kingpost design because of an additional rectangular panel in panel rectangular additional an of because design Kingpost the of expansion an really is truss Queenpost The feet. 75 to up system followed the Kingpost in design chronology. It was also used to span long distances, frequently distances, long span to used also was It chronology. design in Kingpost the followed system Truss Queenpost The mately 20 to 30 feet. 30 to 20 mately i- approx of spans short for primarily used is and diagonals two and beam), (vertical Kingpost a stringer, a of consists It above. is the oldest truss design used in bridge construction, initially used under the roadway rather than rather roadway the under used initially construction, bridge in used design truss oldest the is Truss Kingpost The the Susquehanna River Valley River Susquehanna the torted under stress. Each bridge consists of two truss systems, one on each side of the structure. the of side each on one systems, truss two of consists bridge Each stress.