Burkeville Covered Bridge, Conway Massachusetts
The Burkeville Covered Bridge is one of only five historic-period covered bridges in Massachusetts and one of only a handful in the nation identified with the multiple kingrod variety. It is also the oldest known combination of timber and iron truss in Massachusetts.
Conway is a hilltown on the western edge of the Connecticut Valley in Massachusetts. Rising steeply from the lowlands of the Deerfield River Valley on the east, the town is dominated by the mesomorphic shists which form the bedrock of the town and appear in numerous rock outcrops. The resistance of these rocks, formed in the continental collision 400 million years ago, has provided the town with the natural water power that drove the local economy in the 19th century. The largest and most heavily utilized of these streams was the South River. The river rises in Ashfield, the adjoining town on the west, and runs east through Burkeville and Conway Village before turning north and flowing into the Deerfield River, which forms the northeast border of the town. In its nine-mile course, the river falls over 630 feet.
Although Conway's grazing land may have been used by Deerfield and Shelburne residents for much of the 18th century, the town's earliest non-native permanent settlement did not occur until the end of the French and Indian Wars in 1763. After the Revolution, Conway grew rapidly and by 1790 the town's population of 2,092 was greater than any other town in the Connecticut Valley north of Springfield. Grist and fulling mills were established on the lower reaches of the South River for at least four decades, however, before the water power at Burkeville was tapped.
Burkeville was named for Edmund Burke (c. 1802-1865), who organized the Conway Manufacturing Company in 1837 and built the first woolen mill on the South River, about 450 yards north of the covered bridge. A dam across the South River immediately downstream of the Burkeville Bridge impounded water to supply the Conway Manufacturing Company mill, supplied by a race extending along the north side of Ashfield Road. By 1845, the Burkeville mill alone produced nearly 85% of Franklin County's woolen cloth. Burke's mill was quickly followed by a cotton mill, and in the succeeding decades, both a tool company and cutlery employed Burkeville residents. The first bridge at the covered bridge site is thought to have been constructed in 1850 when Poland Road was rerouted to cross the river closer to the center of the village. One source indicates that it was a covered bridge, and, unlike the present bridge, was supported by a center pier. After the death of Edmund Burke, the Conway Manufacturing Company was sold to Edward Delabarre in 1867, and the millpond was referred to as "Delabarre's Pond," and the covered bridge as "the bridge at Delabarre's Pond."
The torrential rains that hit New England in early October 1869 caused widespread flooding. Many bridges were lifted off their abutments and required replacement. Adelbert Jakeman, commenting in 1935 on the number of covered bridges remaining in the state, wrote that "practically half" of the 26 remaining spans were built in 1870 following the flooding. Town clerk Henry Billings described the havoc caused by the South River in Conway:
(Town Clerk's Records, Book F., p.144)
Although the Burkeville bridge resisted the flood, apparently its center pier and abutments were sufficiently weakened so that the structure required replacement the following year. At the annual town meeting on May 21st, 1870, Philip M. Phillips, whose house stood on the south bank near the bridge, petitioned the town to rebuild the structure. Town Clerk's records that it was "voted-- that the Selectmen be instructed to build a good through bridge at Delabarre's Pond." The town voted to borrow $3,000 to rebuild the bridge, as well as the schoolhouse in Burkeville.
The new bridge was designed as a single-span structure, without a center pier. Construction appears to have begun in August 1870, when the Selectmen's records first report payment for "work on Pond Bridge." All told, nineteen men were paid for work on the Pond Bridge between August and the following May. The total sum paid out for labor on the bridge (and for the schoolhouse also under construction at that time) was $961.83. Nearly 40 percent of this amount ($384.19) was paid to S.P. Sherman for work on the bridge. This amount suggests that Sherman was the principal builder or contractor on the work and may also have been responsible for the design of the bridge.
Sylvanus Persons Sherman (1826-1912) was a native of Worthington. In 1851 he married a Conway woman, Lavinia Trusdel, and moved to Conway soon after. He was a carpenter and builder, and until 1880 his name is frequently on the lists of disbursements of the town highway department. In 1871 he is shown in the County Atlas of that date living on Pleasant (formerly School) Street, not far from the Burkeville Bridge. Sherman moved to Northampton in 1880, where he continued to engage in the building and contracting business for another decade.
J. Marshall Thompson, George Trusdel, and L.F. Eldridge, all in their thirties, also contributed significantly to the construction. Thompson (1839-1924) was paid $104.50, the second-highest amount of any of the builders. In the town records his name is usually associated with a derrick, and it is thought that Marshall may have been a stonemason. Lucien F. Eldridge (1839- ), later a town selectman, was paid $100.00 in two payments; and George Truesdale (1839-1918), who was also Sherman's brother-in-law, was paid $75.00.
No other major repairs to the bridge are documented in the town records until 1939. After the Hurricane and flood of 1938, the structure was sufficiently weakened to cause heavy traffic to be routed around the bridge. At a meeting with the county commissioners, residents petitioned for the repair of the bridge. It had been used for years to bring large quantities of milk and produce from farms in the Poland district of the town. Replacement of the bridge with a concrete span was considered, but rejected after considerable support was expressed for its historic and scenic value. In 1940, under the direction of Leon C. Germain, major repairs were undertaken. These included the replacement of the entire bottom chord on the upstream side of the bridge. The cost of the work, spread over two years, was $2,481. Of this amount, $1,000 was paid by the State, $300 by the county, and the balance by the town.
Approximately twenty years later, additional repairs were necessary to the southwest corner, where three new tie rods were installed, and a section of the bottom chord was replaced. In 1965, a new concrete face was poured on the east pier, matching the west abutment, which had a similar refacing in 1942. Despite extensive repairs to the roof in 1969, however, it had been weakened sufficiently in February 1975 to collapse under a heavy load of snow. Volunteer labor rebuilt the roof the following spring. Despite the repairs to the bridge over time, the integrity of the structure as a whole has not been compromised. The bridge was closed to vehicular traffic in 1980; repaired and reopened in 1982; and closed again in 1985. Existing timbers are reportedly insufficient for an eight-ton load limit. Despite posting, trucks have continued to use the bridge while it was open. The State has closed the bridge until either the bridge is strengthened or heavy vehicles are effectively barred from using the bridge.
The bridge is one of five covered bridges in Massachusetts. The others are the Upper Sheffield Covered Bridge, a Town lattice truss built in 1837-38; the Arthur A. Smith Covered Bridge in Colrain, a hybrid Burr arch-truss built in 1870 and later moved and reconfigured; the Dummerston Bridge at Old Sturbridge Village, an 1874 Town lattice truss moved from Dummerston, Vermont in 1952; and the Gilbertville Covered Bridge, an 1886 Town lattice truss built over the Ware River between the towns of Ware and Hardwick. Franklin County (in which both Conway and Colrain are located) has long retained more covered bridges than any other county in the state. In 1935, of the twenty-six covered bridges which Adelbert Jakeman identified in the state, fifteen were located in Franklin County. (The omission of two Blackstone Valley bridges from Jakeman's list casts some doubt on its completeness). Five of the fifteen were lost the following year to the destructive flooding that affected much of New England, and by 1955 only three historic spans remained. (Greenfield's Pumping Station Road Bridge has since burned and was replaced by a replica in 1972.)
Of the twenty-six bridges reported in 1935, Jakeman reported that "practically half" of the spans "were built in 1870 following the great flood in October, 1869". If this is the case (Jakeman provides few dates in his text), the Burkeville and Colrain bridges are the last of this generation to survive. Today, the two bridges are the second and third oldest of the covered bridges in Massachusetts, and of the two, only the Burkeville example retains its original location.
The Burkeville Covered Bridge is the only example of the multiple kingpost type of truss in the state. At least since the early 20th century, the sub-variety of this type which uses iron tension rods has been described as a "multiple kingrod" truss. A "kingrod" according to J.A.L. Waddell, is "an iron rod used to take the place of a kingpost." In addition to the greater ease of assembly, iron rods allowed a much more certain connection of the tension members to the top and bottom chords. Wood members, fastened with treenails, were more readily broken when subjected to heavy tensile loads than iron rods held in place with nuts and washers. Threaded iron rod also allowed the truss structure to be tightened or otherwise adjusted. However, because the Burkeville bridge combines timber and wrought-iron tie rods, the bridge has sometimes been mistaken for a Howe truss. In consequence, it may be useful to examine briefly the respective roles of the multiple kingpost, kingrod, and Howe trusses in the development of American bridge truss design.
The multiple kingpost form of truss is one of the oldest types of truss in use in the world. Palladio illustrated the form as one of four basic bridge trusses in his Treatise on Architecture of 1570. In it, a repeating series of vertical tension members and diagonal compression members transmit the load from the center of the bridge to the abutments. One of the better-known modifications of the form occurred when Theodore Burr (1771-1822) stiffened the truss with the addition of wooden arches, thus making possible greater lengths. Burr patented the combination in 1806, and the bridge was built all over the country as long as wooden truss bridges continued to be built. Modifications to Colrain's Arthur A. Smith Covered Bridge in the 1920s illustrate that the Burr arch-truss continued to be used even into the 20th century.
Although the lattice truss patented by Ithiel Town in 1820 quickly became the most popular type of wooden truss bridge because of the ease with which local builders could erect it, it was the truss patented by Stephen H. Long (1784-1864) in 1830 that was more significant in the history of bridge building. Long's truss was the first in which some measure of mathematical calculations played a part. To the extent that the vertical members were in tension and the principal diagonals were in compression, the Long truss was a variation on the multiple kingpost truss. Long, however, added counters to more accurately reflect the changing load as a vehicle passed over the bridge, thus giving the truss its characteristic appearance as "a series of giant boxed X's". The counters were the "essential feature which distinguished it from a traditional multiple king post truss". The Long truss, built entirely of wood, had an effective popularity of only ten years, replaced, particularly by the railroads, by the Howe truss, developed by Massachusetts millwright William Howe (1803-1852). Today, the term "Howe truss" is a conventional, sometimes loosely applied term for what was essentially a Long truss with iron rods instead of vertical posts. Howe never patented such a truss, however, perhaps because of its similarity to Long's design. (The two trusses he did patent, in July 1840 and 1846, were seldom used.) Two of his earliest bridges, for the Western Railroad (later in Boston and Albany), employed trusses with iron roads and multiple web systems in each panel. The familiar Howe truss with a single diagonal and counter in each panel does not appear to have been employed until his brother-in-law, Amasa Stoner, and D.L. Harris founded their own bridge-building firm in Springfield, Mass in 1841. The simplicity of the form, and the ease with which it could be erected with local materials led to its wide adoption by railroads for the remainder of the century.
Although Stone and Harris quickly adopted iron rods to the Long truss, the multiple kingpost was slower to be so modified, perhaps because of patent restrictions. Howe's patent, for the use of iron rods in any truss as a means of adjusting it, was granted August 3rd, 1840, thus effectively barring all but licensees from its use until 1854. Iron rods do not appear to have been employed in multiple kingpost trusses until the early 1850s. The first example of its use which Carl Condit had identified was one built over the Appomattox River in 1851-53 for the South Side Railroad (later a Norfolk & Western line) in Farmville, Virginia.
Although multiple kingrod through trusses are rare, some railroads, such as the Boston & Maine, continued to build multiple kingrod pony trusses to carry local roads over their tracks. In Massachusetts, the state historic bridge survey conducted by the Department of Public Works, has identified five surviving multiple kingrod pony trusses built by the Boston & Maine between 1892 and 1911.
With this perspective, the Burkeville Bridge, as a multiple kingpost design, can be seen as part of a centuries-long tradition of vernacular bridge construction by local builders. Yet, the use of wrought iron for tension members was a reflection of a technology that was barely thirty years old (and only sixteen years free of license restrictions) when Sherman and his colleagues constructed the bridge. Richard Allen, author of the standard work on covered bridges in the northeast, estimates that the Conway Bridge is "unique" in the northeast and probably represents the state-of-the-art in wooden bridge building as practiced by knowledgeable local builders of the period.
The Burkeville Covered Bridge is a single-span multiple kingrod covered bridge built in 1870-71 over the South River in Burkeville, a former manufacturing village in the town of Conway. Until it was closed to vehicular traffic in 1985, it carried Main Poland Road between State Route 116 and its intersection with Orchard Street.
The Burkeville bridge measures 106'-0.5" between the outer edges of the end posts. The superstructure of the bridge consists of two trusses, 12'-3" in height, supporting the 13'-6" wide roadway and gable roof. Each truss is composed of ten panels, each with a single outward-sloping timber diagonal extending between opposite corners of the panel. There are no counter diagonals. At each of the panel points, a pair of 1-1/4-inch wrought-iron vertical kingrods transmits the load of the deck to the top chord and diagonals. These rods are threaded at either end to take nuts and washers. From top to bottom, each pair of rods passes through an upper lateral strut, the top chord, bottom chord, and floor beam. Three rods at the western end of downstream (south) truss appears to have been replaced by steel rods of the same diameter as the original in the early 1960s.
The bottom chord of each truss is composed of two timbers with a combined cross-section dimension of 13 inches wide by 12 inches deep. The two timbers are bound together with splines and horizontal bolts which pass through the pair at intervals. These splines also serve as spacers to allow air circulation between the timbers. The chord is notched on its upper surface to receive the truss diagonals. Most of the bottom chord on the south (downstream) side appears to be original, though a portion of the western end was replaced in the early 1960s. The bottom chord on the upstream side was completely replaced in 1940 as part of a major repair to the structure. Fir was used instead of pine, according to George Eldridge, who witnessed the repairs, and steel splice plates were bolted to either side of one of the bottom chord members.
An early alteration is evident in the substructure of the bridge, a close examination of which suggests the following construction sequence. Originally the deck was supported by only nine floorbeams, each carried at its ends by the principal paired kingrods. This gave the floor beams a spacing interval of approximately ten feet, coinciding with the panel width of the trusses. At a later date, evidently, to strengthen the bridge for heavier loads, an intermediate set of floor beams was installed, thus halving the spacing of the beams. These new beams are carried by threaded rods from the top of the truss's bottom chord. The main floor beams are paired timbers tied together with threaded rods. The intermediate floor beams are solid timbers and are braced against the main floor beams with diagonal laterals and footblocks.
All floor beams, extending several inches beyond the end of the bottom chord and bridge sheathing, are sheltered from the weather by their own sheathing and a raked top board.
Closely associated with the new floor beams are paired longitudinal tie rods with turnbuckles located beneath the bottom chords. These tie rods, extending between iron faceplates at opposite ends of the bottom chord, form a trussed lower chord in part helping to support the new beams. The tie rods are supported by iron hangers, fastened only to the rods supporting the newer, intermediate floor beams. It is the location of the hangers that suggests that the tie rods are contemporary with the intermediate floor beams.
The bridge deck, receiving the greatest wear from traffic, has probably been replaced frequently during the history of the bridge. The plank deck is carried by several rows of staggered stringers, which in turn are supported by the floor beams. Wood treads have been installed on top of the planks to lessen the wear on the deck.
The main diagonals are the largest solid members in the bridge, with their size decreasing as one approaches the center of the trusses. The four outer (portal) diagonals are 14 inches wide and 10 inches deep. All other diagonals are 12 inches wide with depths of 6 inches (in the two center panels of each truss) 7, or 8 inches.
The top chord of the truss, like the bottom chord, is made up of two beams with a total cross-section of 8.75 by 13 inches. Like the bottom chord, the two members are splined together and cut with notches to take the truss diagonals. It is worthy of note that the top chord of the truss does not extend the full length of the bridge. It reaches only between the penultimate panel points. It thus reflects the action of the truss only and is independent of the sheltering roof and portal structure.
The two trusses are linked across the top by upper lateral struts connecting Opposite panel points. These 7x7-inch members rest on top of the top chords and are fixed to them with the main kingrods. These members play no load-carrying role, only preventing lateral sway. The superstructure is further strengthened with a pattern of lateral cross-bracing, mortised into the crossbeams and bolted together at their intersections.
As noted above, the roof structure is practically independent of the truss. The roof plate is an independent member supported by the end portal posts and the ends of the lateral struts, to which it is bolted. Rafters supported by the plate reach to a ridgeboard and are tied together with collar beams. The roof structure was rebuilt in 1975 after it had collapsed under a heavy load of snow on February 28th, 1975.
The bridge is sheathed with vertical planks extending 10'-0" from the floor, thus leaving an opening about two feet high at the top to admit light and air. The sheathing planks, all circularly sawn, range in width from 5 to 12 inches in width and are nailed to three rows of nailers, which are themselves fastened to the truss. Window openings are cut in the sheathing at irregular intervals, principally on the downstream side. Bridge seats are concealed, and protected from the weather by box enclosures 5'-10" wide and 5'-0" high.
Looking south-southwest (1988)
