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64 TRUSS B

TRUSS B - DelDOT

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64

TRUSS B

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he modern era of bridge technology inthis country was ushered in about1800 when the truss was applied to

longer-span bridges. Until that time, bridgetechnology was limited to stone arches ortimber beam structures. The truss is a tri-angular structure where all members takeeither tension or compression and loadsgenerally come through the vertical mem-bers and are transmitted by the diagonalmembers into the horizontal members andback to the bearings. While the truss wasknown since at least the third century B.C.,what was innovative at the beginning of the19th century was that the basic truss pat-tern was multiplied many times over to spanmuch greater distances than those possible

LEFT: The Market Street bridge over Brandy-wine Creek in Wilmington. The New JerseySteel and Iron Company erected the Prattthru truss bridge in 1887. It served until1928 when it was removed and replaced bythe present steel multi girder bridge (StateBridge NC-575).

with timber beam or king or queen-posttruss bridges of the 18th century.

Truss types and designs vary accordingto the configuration of the members. Thereare three truss types. In the thru truss bridgethe road passes between the truss lines andis carried on the deck and floor system con-nected to the bottom chords at the panelpoints. There is lateral bracing connectingthe top chords of the trusses. This type isgenerally used for spans more than 100’long. A pony truss bridge is the same as athru truss, but it does not have lateral brac-ing between the top chords. This type isgenerally used for shorter spans 45’ to 100’long. In a deck truss bridge the road is abovethe trusses, and the deck system is on thetop chords. There are a variety of truss de-signs, and all have different ways of accom-modating the tensile and compressiveforces. They are frequently named for theengineer that patented the design such asthe Pratt truss patented by Thomas C. Pratt

65

RIDGESMetal truss bridges began appearing

on Delaware highways in numbersafter 1875, and reached their peak

between 1890 and 1910.

T

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in 1844 or the Warren truss patented byJames Warren in 1848.

Wood Truss Bridges

During the late-18th century the needfor bridges of sufficient length for long

waterway crossings stimulated the bur-geoning of bridge engineering. By 1800master carpenters/architects were applyingtruss and arch principles to span greaterlengths, and many of the early, impressivewood truss bridges were built nearby overthe Schuylkill and Delaware rivers inPennsylvania and New Jersey. Nationallyimportant bridges included Timothy Palmer’s1806 arch-truss bridge over the SchuylkillRiver at Philadelphia and Theodore Burr’s1804-05 arch-truss over the Delaware Riverat Trenton. The first documented coveredarch-truss bridge in Delaware was theMarket Street bridge over the BrandywineCreek at Wilmington, built in 1822.

66

Truss Types

Roadway

Thru Truss

Pony Truss

Deck Truss

Roadway

Roadway

Elevation and Isometric Views

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Truss Bridges

A significant innovation in the applica-tion of truss technology to bridge designwas American architect Ithiel Town’s latticetruss design. Patented in 1820, the trusswas constructed of a closely spaced array ofintersecting diagonal members forming aweb between the parallel chords. It waseasy to fabricate and erect, and the simpledesign could be repeated for any desiredlength. The Town lattice truss was im-mensely popular and was used for highwayas well as railroad bridges. Delaware’s twosurviving historic wood truss bridges atAshland (State Bridge NC-118) andWooddale (State Bridge NC-137) are Townlattice trusses. Both were built during themid-19th century, and both were rebuilt inthe late-20th century.

In Delaware, the wood truss bridge wasmost popular in New Castle County whereat least 125 wood truss bridges are known tohave existed during the 19th century. Only

67

Vanished wood truss bridges. The Yorklyn bridge over RedClay Creek (above), a Town lattice truss covered bridgebuilt in 1863 and removed ca. 1929, and an uncovered lat-tice wood thru truss bridge near Wooddale over Red ClayCreek, (left) built ca. 1860, are examples of the dozens ofwood truss bridges known to have existed in Delaware.They were most numerous in northern New Castle County.

Wood Truss Bridges

The second MarketStreet covered bridge,built by master builderLewis Wernwag in1839, replaced theearliest documentedarch-truss bridge inDelaware erected in1822 and destroyed bya flood in 1839. Thisview, taken beforeremoval of the bridgein 1887, clearly showsthe wood arch withsuperimposed truss.

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35 wood truss bridgesremained in the countyby 1900, and only tworemained by 1965. Assignificant as were theircontributions to thehistory of bridge tech-nology in Delaware,wood truss bridges werenot without inherentweaknesses that eventu-ally made them defunctas bridge builders de-veloped stronger metalbridge types. They werealso susceptible to fire,from both locomotivesand carelessness, insectdamage, and moisture-related deterioration.

Metal Truss Bridges

The most influential factor in the disap-pearance of wood truss bridges was the

development and acceptance of metal trussbridges. Wood works well in compression,but it cannot accommodate tensile forcesefficiently, especially at the connections.This limitation was resolved by WilliamHowe (1803-1852) who, in 1840, patenteda truss bridge design that used wroughtiron rods for the tension members (verti-cals) and wood for the bulkier compressionmembers and chords. His design with irontension rods heralded the beginning of theswitch from wood to metal truss bridgetechnology.

Cast iron, due to its brittleness, wasused only for compression members. Wroughtiron possesses good tensile qualities, andWilliam Howe, Thomas Pratt, SquireWhipple, and others patented historicallyand technologically important truss designsutilizing these qualities. Their truss designs

68

Ithiel Town of New Haven, Connecticut,submitted this drawing with his patentapplication for a lattice truss bridge in1820.

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Truss Bridges

ushered in an era of unprecedented ad-vancement in metal bridge technology thatwas both a product of and a response to in-dustrial advancement in this country.

It was the railroads and their need forlong spans capable of carrying ever-increas-ing live loads that stimulated the great eraof metal truss bridges after the Civil War.The era also swept in new scientific meth-ods for analyzing and predicting the struc-tural action of bridges. After the war, ad-vances in engineering education accompa-nied new standards and understanding ofmaterials, workmanship, and construction.A generation of college-educated civil engi-neers applied scientific theory and experi-mentation to bridge construction and ener-getically sought out the cooperation ofmanufacturers and builders. They estab-lished the modern approach to bridgebuilding that includes stress analysis, plans,specifications, testing, and inspection.

Nationally and in Delaware, the applica-

tion of metal truss bridges to highway usewas generally not as early, quick, or crucialas with the railroads. Metal truss bridgesbegan appearing on Delaware highways innumbers after 1875, and reached their peakbetween 1890 and 1910. Photo archives atthe Delaware Department of Transportationdocument at least ninety metal truss high-

way bridges in New Castle County prior to1930. Similar archival photos have not sur-vived for Kent and Sussex counties. It isknown that the lower counties had metaltruss bridges but in far fewer numbers thanNew Castle County because of their less de-veloped, rural character.

Over 500 bridge fabricating companies

69

Members of truss bridges, no matter the design, share a common nomenclature.

Stringers

InclinedEnd Post

Top Chord

Floor Beam

LowerPanel Point

BottomChord

Diagonal

UpperPanel Point

Vertical

Abutment

Bearing

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Construction Company of Wilmington,and the Edge Moor Bridge Company, locat-ed north of Wilmington, are the only twoknown Delaware-based metal truss bridgecompanies active in the late-19th century.The Edge Moor Bridge Company is the fab-ricator of Delaware’s oldest surviving truss

70

HoweWood diagonals in compression and metal ver-ticals in tension.

PrattDiagonals in tension, verticals in compression(except for hip verticals adjacent to inclinedend posts).

WarrenSome diagonals carry both compressive andtensile forces.

Common Truss DesignsHeavy lines denote compression members

PinnedConnections

RivetedConnections

operated in the United States from 1840 to1900. They varied from large fabricationand erection companies, often owned bylarge iron and steel manufacturers, market-ing their bridges all across the country, tosmall independent contractors operating with-in a limited geographic region. The Delaware

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Truss Bridges

highway bridges, three nearly identicalWarren pony truss bridges dating from themid 1880s to 1890s (State Bridges NC-66,NC-179A, and NC-424).

The two most common truss designsbuilt in Delaware, and all across the coun-try, were the Pratt and the Warren. Bothdesigns offered simplicity of design andfabrication, made economical by the use ofstandard rolled angle and channel sections,plates, bars, rods, and I beams. Standard-ization of truss design was driven by econ-omy and the trend of engineering sciencetoward greater uniformity and better metal-lurgy. A significant factor in standardizationwas the availability of economical steel fromabout 1890 onward. Steel performs well inboth tension and compression, but it gen-erally has a higher tensile strength thanwrought iron and was thus a superior ma-terial for metal bridges.

The Pratt truss design was patented in1844 by Thomas and Caleb Pratt. The orig-inal design was for a composite timber andiron truss, with the wrought-iron diagonals

71

Vanished metal truss bridges. A ca. 1870 truss bridge over Red Lion Creek, (above right) a ca.1880 bowstring truss bridge at Welsh Tract Baptist Church (above left), and a ca. 1910 Warrentruss bridge at Fleming’s Landing (bottom) are among the variety of metal truss bridge designsdocumented by photo archives at DelDOT. The photos were taken in the 1920s and 1930s as partof the department’s efforts to inventory bridges taken into the state’s highway system from NewCastle County.

Metal Truss Bridges

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Located on the banks of the DelawareRiver north of Wilmington, the Edge

Moor Iron Company was incorporated in1869 as an iron works and rolling mill forthe manufacture of iron rails, rods and barstock, rolled sections and I beams. Under

the direction of President William Sellers, thecompany evolved into a major manufactur-er of iron and steel for bridges, viaductsand roofs. Sellers, the son of an UpperDarby, Pennsylvania, flour miller, was a sig-nificant figure in American industrial histo-ry. In 1853, he and his brother John orga-nized the Sellers Machine Company ofPhiladelphia, one of the first factories in theUnited States to manufacture lathes, plan-ers, and machine tools of many kinds, inlarge numbers, for other machine shops.Sellers was granted over 90 patents for var-ious inventions related to the manufactureof machinery for industrial uses. He wasalso a president of the Franklin Institute.

In 1873, Sellers incorporated the EdgeMoor Bridge Company as an offshoot of theEdge Moor Iron Company. The companybuilt several large river crossing bridges formajor railroads and also supplied most ofthe structural iron for the Brooklyn Bridge.From 1873 to 1900, the Edge Moor BridgeCompany was considered one of the mostcomplete and up-to-date shops in the nation,equipped with Sellers Machine Companyrolling mills and machine tools. By 1900,

72A prefabricated truss being assembled at Edge Moor Iron Works

Edge Moor Iron Company (ca. 1925).The iron works opened in 1869 and abridge fabrication shop was added inthe early 1870s.

Edge Moor Bridge CompanyDelaware’s Premiere Metal Truss Bridge Builder

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Truss Bridges

the company employed approximately 550workers, most of whom lived in the com-pany town of Edgemoor.

In 1900, the Edge Moor Bridge Compa-ny was acquired by the American BridgeCompany, a monopoly formed by J. P.Morgan & Company. Edge Moor was oneof 24 bridge companies folded into the newcorporation, which was intended to domi-nate the metal bridge fabrication industry.William H. Conuel, who succeeded Sellersas president of Edge Moor, was the firsttreasurer of the American Bridge Company.In 1901, American Bridge was itself ac-quired by U.S. Steel Corporation. AmericanBridge continued to operate the Edge Moorworks until 1921, when the plant wasclosed. Its operations were consolidated atmore up-to-date facilities at Trenton, NewJersey, and Ambridge, Pennsylvania. TheEdge Moor Iron Company continued as aseparate organization concentrating on theproduction of steam boilers until its liqui-dation in 1933. The last of its bridge andiron works structures and buildings weredemolished in the 1970s. ■

in tension and the timber verticals in com-pression. The Pratt truss easily adapted in-to an all metal truss, and it was popular be-cause of its simplicity of design, especiallythe use of eye bars and pins to facilitatefield erection. It provided the long-sought-after “stiff truss” that after 1880 came to befabricated with standardized members,made by building up standard shapes likerolled plates, angles, or channels. The Pratttruss design dominated the last quarter ofthe 19th century for both thru and ponytruss bridges.

Most metal truss bridges built before1895, from light Pratt pony trusses to heav-ier thru truss railroad spans, were assembedin the field (at the site) with pinned con-nections. Better knowledge of the strengthof materials and metallurgy in the 1880scombined with the improvement of fieldpneumatic riveting equipment by 1899leading to the transition from pinned to riv-eted connections. This resulted in a rapidshift from the Pratt to increased use of theWarren truss design by 1905. Patented in1848 by British engineers James Warren and

Willoughby Monzani, the straightforwardtruss is particularly well suited for rigidconnections. It is distinguished by its sim-plicity of design, ease of construction withequal-sized members, and ability of someof the diagonals to act in both tension andcompression. Capacity could be increasedby adding a second set of diagonals (doubleintersection Warren), and it could be stiff-ened by the addition of verticals.

Despite the large number of metal trussbridges that once existed in Delaware, to-day only six remain in service on public

The Washington Street Bridge over Brandy-wine Creek in Wilmington was a deck trussbridge fabricated by the Edge Moor BridgeWorks in 1893. The bridge served until 1921when it was replaced by the present rein-forced concrete open spandrel arch (StateBridge NC-576). Local residents and landdevelopers objected to the truss bridge’snarrow roadway.

73

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21

3

456

7

8

The Locations of Delaware’sHistoric Truss Bridges

1. Brackenville Road over Red Clay CreekState Bridge NC-118Ashland, New Castle County

2. Wooddale Drive over Red Clay CreekState Bridge NC-137Mt. Cuba, New Castle County

3. Wiggins Mill Road over Wiggins Mill Pond*State Bridge NC-424Townsend, New Castle County

4. Breck Lane over Pancake RunState Bridge NC-66Wilmington, New Castle County

5. Rising Sun Lane over Brandywine CreekState Bridge NC-1 A&BWilmington, New Castle County

6. Evanson Road over Mill CreekState Bridge NC-179AHockessin, New Castle County

7. Chambers Rock Rd. over White Clay CreekState Bridge NC-216Thompson, New Castle County

8. Yorklyn Road over Red Clay CreekState Bridge NC-112Yorklyn, New Castle County

roads. Five are riveted Warren pony trussesdated from 1884 to 1929, and the sixth is ariveted Pratt thru truss from 1928. Severaladditional metal truss bridges survive, in-cluding two pin-connected Pratt trusses,but they are located on private properties.

The metal truss bridge type’s decline,like its own rise in prominence, was basedon technological advances of other bridgetypes, particularly steel multi girder and re-inforced concrete spans. Those technolo-gies, introduced in numbers during the firstdecades of the 20th century, proved to bemore economical and required less mainte-nance than metal truss bridges, and bothtechnologies were favored by the newDelaware State Highway Department as itbegan developing the state highway systemstarting in 1916. Additionally, metal trussbridges were the subject of a concentratedbridge replacement program from the1930s through the 1960s. As a result, most

metal truss bridges were removed and re-placed by wider spans.

Brackenville Road overRed Clay Creek

State Bridge NC-118Ashland Covered BridgeAshland, New Castle CountyDesigner/Builder: Unknown

ca. 1850

The Ashland Covered Bridge is a Townlattice truss, composed of oak planks

connected together in a lattice pattern withtapered wood dowels known as trunnels.The bridge measures 52’ long, 14’-6” wide,and carries a single lane of traffic. The trussbridge has plank siding, painted red, and iscovered by a timber frame roof with cedar-shake shingles. The portals are accented bypilasters with flared capitals. The trussbridge is supported on rubble stone abut-

74* Recently replaced

and truss relocatedto Middletown.

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Truss Bridges

ments. The flared stone wingwalls have stoneparapets with concrete coping.

The date of construction and builder ofthe Ashland Covered Bridge are undocu-mented in state and county records. Mostlikely, the bridge dates to about 1850, butcould have been built as early as 1840, oras late as 1880. Ithiel Town of New Haven,Connecticut, patented the lattice truss de-sign in 1820, but it was not until about1840 that the truss design gained popular-ity as a common type of highway and rail-road bridge, built from New England toVirginia, and as far west as Ohio. The Town

75

N

Brackenville Road BridgeNC-118

Shar

pless Road

Brac

kenv

illeRoad Barley

Mill Road

Ashl

and

toCl

inton

ville

Scho

olRo

ad

Ashland

82Wilmington

&W

esternRailroad

RedCl

ayC

reek

ABOVE: View of Ashland bridgebefore rehabilitation in 1982.

LEFT: Interior view.

Built in the mid-19th cen-tury, the Ashland CoveredBridge (above) is one ofonly two covered bridgessurviving in Delaware.

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lattice truss, easily erected by local crafts-men, remained popular in some rural local-ities until the 1880s, and only fell frompopularity after the widespread introduc-tion of prefabricated metal truss bridges.

The Ashland Covered Bridge was listedin the National Register of Historic Placesin 1973 as one of only two remaining woodtruss covered bridges in Delaware. DelDOTstrengthened the structure in 1982. Duringrehabilitation, the truss bridge was liftedfrom place, while a new steel multi girdersystem was installed on the stone abut-ments. When the wood truss bridge was setback in place, its timber floorbeams wereremoved, and the truss lines, which had be-

come racked, were realigned with the low-er chords bolted to the fascia of the steelbeams. The steel multi girder system supportsthe deck relieving the trusses of live loads.

Wooddale Drive (Road 263A)over Red Clay Creek

State Bridge NC-137Wooddale Covered BridgeMt. Cuba, New Castle CountyDesigner/Builder: Unknown

ca. 1850

The Wooddale Covered Bridge is a Townlattice truss bridge measuring approx-

imately 53’ long, 16’-wide, and carrying asingle lane of traffic. The bridge is one of onlytwo covered bridges surviving in Delaware,

and is nearly identical to the Ashland CoveredBridge (State Bridge NC-112). The WooddaleCovered Bridge is composed of oak planksforming a lattice pattern joined by wooddowels called trunnels. The truss bridgehas wood plank siding, painted red, and acedar shake shingle covered roof. The cov-ering protects the truss from the weather.The portals are accented by pilasters withflared capitals. The bridge is supported onstone abutments. Wingwalls have stoneparapets with granite capstones.

The builder and date of construction ofthe Wooddale Covered Bridge are undocu-mented. The bridge dates in style to ca.1850, and may have been built to provideimproved access to the Delaware Iron Works,a slitting and rolling mill that occupied the

76

Excerpts from 1982repair drawings forBridge 118.

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Truss Bridges

adjacent property onthe northwest bank ofRed Clay Creek fromabout 1814 to 1891.The earliest documen-tation for the bridgein State Highway De-partment records is adrawing dated 1939,apparently made torecord the bridge short-ly after the July 1938flood had washedout another Town lattice truss, which car-ried Road 261 over Red Clay Creek up-stream of the Wooddale Covered Bridge.

In 1969, the bridge was strengthened bythe addition of two steel beam girders usedto support the wood floorbeams and partial-ly relieve the truss of live loads. Extensionswere made to the stone abutments to providea bearing for the girders. Further strength-ening was required in 1981 when DelDOTreplaced the deck and doubled-up the floor-beams, bolting new timbers to the oldertimbers. The portal and upper lateral brac-ing were raised to increase vertical clearance.

77

The Wooddale Covered Bridge was listed in the NationalRegister of Historic Places in 1973.

These plans, prepared in 1939 by the Delaware State Highway Department, are theearliest known drawing of the Wooddale Covered Bridge.

Wooddale

N

Barley Mill Road

Red Clay Creek

48

Woodale Road BridgeNC-137

Rolli

ngM

illRo

ad

Woodale Road

Lancaster Pike

Wilm

ington&

Western

Railroad

Page 15: TRUSS B - DelDOT

Townsend

N

Wiggins Mill RoadBridgeNC-424

Wiggins Mill Road

Wiggins MillPond

RD. 25

71

NoxontownLake

Moore Road

Delaw

are Roalroad (Conrail)

preparing plans to relocate this bridge to apark in Middletown.

The bridge was built in 1884, replacinga bridge of unknown type. The southwestwingwall has a capstone that bears the in-scription, “Rebuilt 1884, J. T. Taylor, L(ower).C(ounty). Com(missioner).”

A bridge of this size could have beenfabricated at Edge Moor’s shops and shippedto the bridge site with a minimal amount ofon-site assembly. It demonstrates the econ-omy of design that contributed to the dom-inance of prefabricated metal truss bridges

78

Wiggins Mill Road bridge as it appears today (above)and as it appeared in 1921 (below). One of the state’sfew surviving late-19th-century prefabricated metaltruss highway bridges, the Warren pony truss bridgeis nearly identical to the Brecks Lane bridge (NC-66)and the Evanson Road bridge (NC-179A). The otherbridges are attributed to the Edge Moor BridgeWorks based on the similarity of construction.

Wiggins Mill Road (Road446) over Wiggins Mill Pond

State Bridge NC-424Townsend, New Castle CountyDesigner/Builder: Edge MoorBridge Works

1884

The Wiggins Mill Road bridge is histor-ically significant as Delaware’s oldest

documented metal truss highway bridge. It isthe work of the state’s most prominent late-19th-century metal truss bridge fabricator,the Edge Moor Bridge Works of Wilmington.The 34’-long, three-panel, riveted, Warrenpony truss bridge has chords, diagonals,and verticals all composed of wrought ironangles. The bridge is supported on stoneabutments and wingwalls topped by stoneparapets. It carries one lane of traffic on a14’-8” wide deck. In 1998, DelDOT was

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Truss Bridges

over earlier traditional bridge types such asstone arches and timber trusses.

Brecks Lane (Road 260) overPancake Run

State Bridge NC-66Wilmington, New Castle CountyDesigner/Builder: Edge Moor Bridge Works

ca. 1890

The Brecks Lane bridge is a rare surviv-ing example of a late-19th-century met-

al truss bridge fabricated by Wilmington’sEdge Moor Bridge Works. The 21’-long, two-panel, riveted, Warren pony truss bridge iscomposed of wrought iron angles for thechords, diagonals and verticals. It carries twolanes of traffic, and measures 20’-8” wide.Early 20th century alterations to the bridgeincluded replacement of the timber deckwith a concrete slab, encasing the floor-

beams and stringers. The slab relieves thetruss bridge of live loads.

DelDOT records do not document thebridge’s date of construction, but based onstyle and comparison to other documentedexamples, it dates to ca. 1890. Two othernearly identical Warren pony truss bridges

in New Castle County are the Wiggins MillRoad bridge (State Bridge NC-424) and theEvanson Road bridge (State Bridge NC-179A). The Brecks Lane bridge is located inthe Henry Clay Village Historic District, ad-jacent to Breck’s Mill that dates to 1814.The bridge is a contributing resource to theNational Register-listed district.

Brecks Lane bridge, a ca. 1890 Warrenpony truss, is typical of the small metaltruss bridges erected along local roadwaysthroughout New Castle County in the late-19th century.

79

Rising Sun Lane BridgeNC-1

Bran

dywine

River

Cancake Run

52

Barley Mill Road

Risin

g Su

n La

neKennett Pike

Brecks Lane

HagleyMuseum

New

Brid

geRo

ad

DuPontExperimental

Station

RockfordPark

141

Brecks Lane BridgeNC-66

Wilmington

N

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Rising Sun Lane (Road 279)over Brandywine Creek

State Bridge NC-1A&BWilmington, New Castle CountyDesigner/Builder: Harrington, Howard &Ash/Standard Engineering & Contracting Co.

1928

The Rising Sun Lane bridge consists ofa 127’-long, riveted, steel Pratt thru truss

span and a 25’-long, stone arch approachspan for an overall length of 193’ includingroadway and fill. The massive ashlar abut-ments and stone arch over a former millrace were built in 1833 when a Burr arch-truss covered bridge was erected. In 1928,the covered bridge was replaced by the pre-sent metal truss bridge. The abutments, whichwere in sound condition, were reused.

The 1928 Pratt thru truss bridge incor-porates truss details that were standard af-ter 1900. The truss members are all built-up of standard steel sections such as angles,channels, and plates. The bridge is rivetconnected with gusset plates at each panelpoint. A sidewalk with a lattice metal rail-ing is cantilevered from the south side ofthe bridge. In 1979, the original steel

80

ABOVR: The main span of the Rising Sun Lanebridge, (above) erected in 1928, is a riveted steelPratt thru truss, resting on massive granite abutments.

RIGHT: The stone arch (State Bridge NC-1A) at thewestern end of the Rising Sun Lane bridge was builtin 1833 to span a mill race, now unused and filledwith debris.

LEFT: Prior to the present metaltruss bridge, Rising Sun Lanewas carried across theBrandywine Creek by a Burrarch-truss covered bridge, con-structed in 1833. The coveredbridge had three truss lines, andportals for two lanes of traffic,indicative of the steady traffictraveling to and from the millson either side of the stream.

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Truss Bridges

stringers and concrete deck were removed and replacedwith deeper stringers and a composite concrete slabdeck. Rivets have been selectively replaced by high-strength bolts, but otherwise the bridge is unaltered.

A representative example of a standard early 20thcentury Pratt truss bridge, the Rising Sun Lane bridge ishistorically noteworthy in the statewide context as oneof only two surviving pre-1956 thru truss highwaybridges. It is the only thru truss bridge on a public road;the other carries a private road over Brandywine Creeknorth of the Hagley Museum. A historically significantfeature of the Rising Sun Lane bridge is also its 25’-longstone arch, built in 1833, and one of the oldest andlongest stone arch highway spans in Delaware.

Harrington, Howard & Ash, consulting engineersand designers of the truss bridge, were among the mostprolific American bridge engineering firms of the 20thcentury. Founded in 1914 by John L. Harrington, ErnestE. Howard, and Louis R. Ash, the firm was known pri-or to 1940 primarily for its work with movable bridges.In Delaware, Harrington, Howard & Ash designedWilmington’s 1927 South Market Street bascule bridge(State Bridge NC-688) and 1932 North Church Streetbascule bridge (State Bridge NC-577). The RisingSun Lane Bridge was not among the firm’s most note-worthy projects, however, it does document a growingpresence for the firm in Delaware during the late 1920s.After World War II, the firm under its new name,

81

Details from the 1927 drawings for the Rising Sun Lane bridge show thedecorative lattice railings with scroll work.

Page 19: TRUSS B - DelDOT

The 20’-long, two-panel, riveted, Warrenpony truss bridge is composed of wrought-iron angles for the chords, diagonals, andverticals. DelDOT records do not documentits date of construction or builder, but basedon the style of construction and similarityto two other extant bridges in New CastleCounty, the bridge dates to ca. 1890 and islikely the work of the Edge Moor Bridge

82

ABOVE: The Evanson Road bridge is oneof three nearly identical extant late-19th-century Warren truss bridges inDelaware. Metal truss bridges were oncecommon in New Castle County, with over90 documented examples.

BELOW: The Evanson Road bridge as itappeared in 1921.

HockessinOld Lancaste Piker

N

Lancaster Pike

Valle

y Ro

ad

Mill C

reekRoad

EvansonRoad Bridge

NC-179A

Mill Creek

Evanson Road

41

Howard Needles Tammen& Bergendorff, had asignificant influence onDelaware’s transportation history designingthe Delaware Memorial Bridge (1951,1968)and the Delaware Turnpike (1961-1964).

Evanson Road (Road 285)over Mill Creek

State Bridge NC-179AHockessin, New Castle CountyDesigner/Builder: Edge Moor Bridge Works

ca. 1890

The Evanson Road bridge is one of threenearly identical Warren pony truss

bridges surviving in New Castle County.

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Truss Bridges

Works of Wilmington, the fabricator of theother two bridges (State Bridge NC-66 andNC-424).

The bridge underwent emergency re-pairs in 1995. The truss lines were cleanedand repainted, and a laminated timber slabdeck was constructed that bears on thestone abutments. The trusses now serve asrailings. Although the bridge has been al-tered, the truss lines are considered signifi-cant due to their rarity and age.

83

Thompson

Hopkins Road

➲N

Chambers RockRoad Bridge

NC-216White Clay Creek

Del

awar

e

Penn

sylv

ania

Chambers Rock Road

Creek

Road

Thompson

StationRoad

Warren pony truss bridges, such as the Thompson’s Station Bridge erected in1928, were a common highway bridge type from the first three decades of the20th century.

Chambers Rock Road (Road329) over White Clay Creek

State Bridge NC-216Thompson’s Station BridgeNewark, New Castle CountyDesigner/Builder: New Castle CountyEngineer’s Office/Belmont Ironworks

1928

The Thompson’s Station Bridge is a 66’-long, Warren with verticals pony truss

bridge that was fabricated in 1928. It hasstandard built-up members composed ofangles, channels and plates. In 1995, DelDOTrehabilitated the structure. The truss lineswere disassembled, and severely rustedmembers, including all of the lower chords,were replaced in-kind. Rivets at the panelpoints were replaced by high-strength bolts.A new laminated timber deck replaced theolder steel grate deck.

New concrete abutments and wingwallswere built and then faced with stone.

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In 1990, DelDOT rehabilitated the bridge.The truss was widened from 20’-wide to30’-wide, and the original floorbeams,stringers, and wood deck were replaced bynew floorbeams supporting a laminatedtimber slab deck. During construction, thetrusses were removed, cleaned and painted,and then replaced. Rivets at the lower pan-el points were replaced by high-strengthbolts. New concrete abutments and wing-walls were constructed.

Although the bridge is altered, it docu-ments a popular early 20th century design.In the 1920s, Warren pony truss bridgeswere the most common type of metal trussbridges on county roads in New CastleCounty. The Yorklyn Road bridge was builtin 1929 by authority of the New Castle

84

Excerpt from the 1928 plans for the Thompson’s Station Bridge.

Yorklyn Road (Road 257)over Red Clay Creek

State Bridge NC-112Yorklyn, New Castle CountyDesigner/Builder: New Castle CountyEngineer’s Office/Belmont Ironworks

1929

Yorklyn Road bridge is a 75’-long, rivet-ed, Warren with verticals pony truss,

fabricated in 1929. The bridge is composedof built-up members of standard steel sec-tions including angles, channels, and plates.A sidewalk with wood deck is cantileveredfrom the east side with an ornamental steelrailing. The bridge is historically significantas a rare surviving example of this oncecommon bridge type in the state.

Although the bridge has been altered, thetruss lines are considered historically signif-icant because they document a once com-mon but now rare bridge type in the state.

Thompson’s Station Bridge was built in1928 by the authority of the Levy Court ofNew Castle County. Plans were prepared bythe County Engineer’s office using a set ofstandard specifications for Warren pony trussbridges prepared by the county engineer.The bridge contractor is undocumented, butthe structural steel was fabricated by theBelmont Ironworks of Philadelphia. Thebridge is one of only two surviving 20th-century examples of the once ubiquitousWarren metal truss bridge type and designin Delaware. The other is the 1929 YorklynRoad Bridge (State Bridge NC-112).

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Truss Bridges

County Levy Court. It was designed by theCounty Engineer’s office, and original plansare on file at DelDOT. The structural steelwas fabricated by the Belmont Ironworksof Philadelphia. The contractor who erect-ed the bridge is not recorded. ■

85

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ABOVE: The 1929 Yorklyn Roadbridge is one of only six trusshighway bridges remaining inpublic service in Delaware.Although once common in thestate, the truss bridge typerapidly vanished from stateroads in the mid-20th century, inpart because truss bridge road-way widths were often too nar-row to be safe for larger andfaster trucks and cars.

LEFT: This plaque detail is fromthe original 1929 drawings forthe Yorklyn Road bridge.