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Blackfriars Street Bridge

   

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Bridge Documented: July 12, 2005, August 5, 2006, and July 20, 2012

Primary Photographer(s): Nathan Holth

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Key Facts

	Bridge Name	Facility Carried / Feature Intersected	Location	Structure Type	Construction Date and Builder/Engineer
	Blackfriars Street Bridge	Blackfriars Street Over North Branch Thames River	London: Middlesex County, Ontario	Metal 16 Panel Bowstring Through Truss, Fixed	1875 By Builder/Contractor: Wrought Iron Bridge Company of Canton, Ohio

Technical Facts

Main Span Length	Structure Length	Main Spans
225 Feet (68.58 Meters)	225 Feet (68.58 Meters)	1

View an article about this heritage bridge. 

About This Bridge

This bridge is a through bowstring truss bridge, built in 1875. The bridge was a Wrought Iron Bridge Company bridge, as indicated from this document from a catalogue produced by the bridge company. A plaque in London next to the King Street Bridge credits Isaac Crouse as being the contractor for the bridge. Isaac Crouse apparently purchased the bridge from Wrought Iron Bridge Company, and then erected it himself in London. The bowstring features Keystone columns form the top chord of the bridge. There is extensive v-lacing and lattice on the bridge. A sidewalk is on the south side of the bridge, and appears to be original.

Not only is this bridge London's oldest iron bridge, this was also its first iron bridge when it was built way back in 1875! This is the only surviving iron bowstring known in Ontario, and indeed all of Canada. There are still a small number remaining in the United States, with the longest United States single bowstring span being a bowstring in Mankato, Minnesota, of 190 feet (57.9 meters). The Blackfriars Bridge's span rings in at a considerably larger 225 feet (68.58 meters)! For this reason, Blackfriars Bridge appears to be the longest remaining iron bowstring span in North America and perhaps beyond.

The bridge has undergone numerous repairs, resulting in significant alterations to the original design of the bridge, which has had a detrimental effect on the bridges historic integrity. The most significant alterations include welded plate added to the sides of the Keystone column top chord, which has obscured the trademark Keystone column shape. This document illustrates how the plates are welded on, and what the original Keystone columns would look like as originally created by the iron mill. A number of vertical and diagonal members have had members added and welded to the original members. These added members are also welded to added plate at connection points. A couple added bars of steel run lengthwise through the middle of the truss webs also. Regardless of these alterations, the bridge still manages to be a nationally significant historic structure because it is so rare and old. Additionally, despite the aforementioned alterations, it in contrast retains some original elements that are often lost on old bridges, particularly the original floorbeams. These unique fishbelly style built-up floorbeams have an unusual asymmetrical design that accommodates an extension of the floorbeams beyond the roadway on one side to support the cantilevered sidewalk on the south side of the bridge. Also, the original ornamental lattice railings remain on the sidewalk, albeit with a metal pole welded on above them.

 

Above: View of the bridge in 1967. In this photo, the added piece of steel that runs through the truss in a crooked arch shape is visible. Thus, it is clear that this alteration is older than 1967. Photo Courtesy: City of London.

Overview of Bowstring Truss Bridges

Bowstring truss bridges, sometimes called bowstring truss-arch bridges because they also incorporate design aspects of an arch bridge, are one of the rarest types of bridge, with most date in the 1870s. They were the first type of metal bridge to be used and gain popularity in North America, and could be said to be responsible for the transition from wood to metal as a primary bridge material. Built in this early metal bridge era, bowstring truss bridges often display patented and/or experimental designs developed by the particular builder of each bridge. They rapidly fell out of favor after the 1870s as the simpler pin-connected Pratt truss was developed and embraced, which also brought an end to the broad design experimentation as well. Between their age, lightweight design, and relatively short period in which they were being built, very few bowstring truss bridges survive in North America today. Aside from their historic significance, a bowstring bridge like Blackfriars Bridge also has a great deal of aesthetic value. The bridge's numerous members, which are also often built-up beams with patterns of lattice and v-lacing on them, form a complex geometric art. This large amount of complexity is balanced out by the simple, graceful appearance of the arched top chord. The result is a bridge with incomparable beauty and appeal that is unrivaled by any modern bridge type.

Above: Historical photos of the bridge. Courtesy: City of London 

Suggested Preservation Work

In addition to the substantial repairs made in past years to the superstructure, this bridge has also been maintained through small repair projects that are undertaken on an as-needed basis. For example, in 2006, the bridge was closed for selected repairs to the timber deck. The time may come in the future however when a more extensive project is needed to prepare the bridge for another century of use. At that time, HistoricBridges.org would recommend a comprehensive in-kind restoration. An in-kind restoration would replace beyond-repair parts of the bridge with exact replicas. Failed rivets would be replaced with failed rivets. Any of the cast iron details on the railing or connection points that are failed or missing would also be replicated. It may also be possible to remove some of the more unsightly alterations on the bridge and either leave them off, or replace them with something less noticeable. For example, some of the added welded plate connections are more bulky in appearance than they likely need to be. The decision on whether an alteration could be left off or needed to be replaced with something else would depend on the load limit needs for the bridge, and what purpose the alterations serve. If the alterations were meant to address loss of strength due to deteriorated original material, the restoration of the original material may render the alteration unnecessary. If the alterations were intended to increase the load capacity of the bridge beyond original design capacity, they would need to be substituted with something else, assuming this loading was to be maintained. One idea to consider would be to restore the bridge, but to turn it into a non-motorized crossing and not allow vehicular traffic on the bridge any more. This could decrease the live load requirements, and thus eliminate the need for the alterations.

Long story short, the technology exists to take this bridge and bring it back to nearly the exact appearance it had when erected in 1875, and to do so while maintaining the majority of original material on the bridge. To see what a bowstring bridge of this design looked like without alterations on it, see this unaltered bridge in Iowa.. Also below is a photo showing the Blackfriars Street Bridge in its earlier years before alteration. Presumably the photo was taken before 1900 because a metal truss seen in the distance in the above 1900 photo is not visible in the photo below. Photo Courtesy: Ivey Family London Room, London Public Library, London, Ontario, Canada

 

Information and Findings From Canada's Historic Places Description of Historic Place The Blackfriars Bridge, a reinforced wrought-iron bowstring bridge, was constructed in 1875. It spans the North Branch of the Thames River, on Blackfriars Street, in the City of London. The property was designated by the City of London in 1992 for its heritage value under Part IV of the Ontario Heritage Act (By-law L.S.P.-3140-106). The Blackfriars Bridge has also been listed on the Ontario Heritage Bridge list, a list of provincially significant bridges, maintained by the Ministry of Culture. Heritage Value The Blackfriars Bridge is a landmark, in the City of London, and has been a source of inspiration to local artists, writers, photographers, and historians for many years. The gentle curve of Ridout Street onto the east side entrance of the bridge augments the experimental qualities inherent in the structure, including its narrow width, the texture of the wooden deck and the streamlined elegance of its bowed profile. These characteristics and the steep, well-treed riverbanks and parkland create a rural feel in this downtown location. Formerly the principle link between the City of London and its hinterland, the Blackfriars Bridge was the first iron bridge, in London, to span the Thames River. Constructed, in 1875, under the supervision of local contractor Issac Crouse, it replaced the last of several wooden bridges that had spanned the river, at this location, since 1826. None of these bridges could withstand the severe spring flooding. By 1889, all wooden bridges, in London, were replaced with iron structures and only the Blackfriars Bridge remains. TThe Blackfriars Bridge is a fine example of bowstring construction and one of the few such bridges still standing, in Canada. It was designed and fabricated to an American prototype that was first patented by the Wrought Iron Bridge Company of Ohio, in 1870. Wrought iron was chosen because of its excellent qualities of strength, malleability and resistance to corrosion. A low parabolic chord tops the bridge and gives it a sense of floating above the river, as it extends over the Thames River, for an unsupported 212 feet. Other distinctive features of this style of bridge construction include; the pin connections, the timber decking and the lattice girders. Due to a relatively low volume of traffic, Blackfriars Bridge has survived. It is the oldest wrought-iron bridge in North America still used for vehicular traffic. It is recognized as a significant example of early engineering technology. Sources: City of London By-law (L.S.P.-3140-106); Research article by Harvey Revington and Eila Milne, 2005. Character-Defining Elements ChCharacter defining elements that contribute to the heritage value of the Blackfriars Bridge include its: - prominent location spanning the Thames River providing a gateway between the downtown and former West London areas, of the City of London - orientation to Ridout Street - gentle curve that augments the bridge's narrow width, texture of the wooden deck and streamlined elegance of its bowed profiler - reinforced bowstring bridge construction, based on an 1870 prototype by the Wrought Iron Bridge Company - wrought-iron construction including the low parabolic chord that tops the bridge - unsupported length of 212 feet - pin connections and lattice girders - timber deck beams HeHeritage Designation and Type: Yes, Municipal Heritage Designation (Part IV)

Photos and Videos: Blackfriars Street Bridge

Available Photo Galleries and Videos

Click on a thumbnail or gallery name below to visit that particular photo gallery. If videos are available, click on a video name to view and/or download that particular video.

 

	Structure Overview Original / Full Size Photos	A collection of overview photos that show the bridge as a whole and general areas of the bridge. For the best visual immersion and full detail, or for use as a desktop background, this gallery presents the photos for this bridge in the original digital camera resolution.
	Structure Details Original / Full Size Photos	A collection of detail photos that document the parts, construction, and condition of the bridge. For the best visual immersion and full detail, or for use as a desktop background, this gallery presents the photos for this bridge in the original digital camera resolution.
	Structure Overview Mobile Optimized Gallery	A collection of overview photos that show the bridge as a whole and general areas of the bridge. View the photos for this bridge in a reduced size which is useful for mobile/smartphone users, modem (dial-up) users, or those who do not wish to wait for the longer download times of the full-size photos. Alternatively, view this photo gallery using a popup slideshow viewer (great for mobile users) by clicking the link below. Browse Gallery With Popup Viewer
	Structure Details Mobile Optimized Gallery	A collection of detail photos that document the parts, construction, and condition of the bridge. View the photos for this bridge in a reduced size which is useful for mobile/smartphone users, modem (dial-up) users, or those who do not wish to wait for the longer download times of the full-size photos. Alternatively, view this photo gallery using a popup slideshow viewer (great for mobile users) by clicking the link below. Browse Gallery With Popup Viewer

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