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Historic American Engineering Record
Sewickley Bridge
HAER No. PA-53
Spanning the Ohio River in the vicinity of Sewickley Borough
Allegheny County
Pennsylvania
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SEWICKLEY BRIDGE
HAER No. PA-53
(Page 36)
IV. SUBSEQUENT HISTORY
Maintenance and Repairs
Allegheny County was responsible for designing and building the Sewickley Bridge and also, according to the records, was its original owner and completely responsible for all maintenance and repairs until 1961.
During the period from 1911 to 1962, the County maintenance records indicate that some money was spent each year for general repairs. These same records also show the major repair and maintenance work done during these years (Appendix C).
In 1929 the original wood block and sand bed roadway surface was replaced by a 32-inch asphaltic binder course and a 2-inch asphaltic wearing surface. The structure was repainted in 1936, 1946 and 1954. During 1948 major repairs were undertaken which included replacing all of the expansion dams, rebuilding sidewalks, repairing concrete areas on both abutments, encasing
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the pedestal foundations at Bents 3 and 4, replacing the asphalt portions of the roadway surface and repairing and/or reworking both at-grade approach roadways.
In 1950 blast plates were added to the underside of the north anchor span truss over the railroad tracks adjacent to Pier 4. These plates have been since removed but there is no record showing when this work was done.
It is also noted that in 1913 the Pittsburgh Railways Company established regular streetcar service from Pittsburgh to Sewickley via Neville Island, Coraopolis and the Sewickley Bridge.
In 1928 the Pennsylvania Railroad tracks were relocated to the river bank passing under the north anchor span adjacent to Pier 4. Four years later the County reconstructed the north approach roadway of the bridge to intersect with Ohio River Boulevard.
Act 615 of the State Legislature in 1961 divided the bridge maintenance responsibility between Allegheny County
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County and the State. The complete bridge ownership and responsibility for maintenance were transferred from Allegheny County to PennDOT in 1969 by PUC Order No. 94264.
The County records show general maintenance money being spent until May, 1962. The State records show that the state spent money for painting and repairs in 1964, 1965 and 1972 through 1974 (Appendix C).
An in-depth inspection was performed in 1969 for the State. The inspection revealed that the main structural components of the bridge were in fair condition but elements of the approach trusses and main span floor system were deteriorated and overstressed.
The inspection report recommended replacing the sidewalks, sidewalk supports and expansion dams; repairing abutments, piers, floor-system drainage system, main trusses and bridge railings; and complete cleaning and painting of all steel elements of the bridge. As a result of this inspection the bridge was posted
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with a restriction that all trucks be spaced a minimum of 100 feet apart while on the structure.
The painting performed on the structure in 1972 through 1974 had to be discontinued when a section of sidewalk slab collapsed on 30 May 1974. Immediately afterwards the bridge was closed to pedestrian traffic and the concrete sidewalk slabs on both sides of the bridge were removed. This same condition, with exposed steel sidewalk framing, currently exists.
In August, 1975, the bridge was field inspected by engineers from the Federal Highway Administration and from the District and Central Offices of PennDOT. Because of the critical corrosion conditions discovered at the ends of several eyebars and at numerous floorbeam connections, the decision was made in 22 August 1975, to post the bridge for 3 tons maximum load; and on 20 April 1976, the bridge was posted for 10 mph speed limit.
From 2 August 1976 to 1 October 1976, PennDOT performed an in-depth field inspection of the bridge.
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The Department also made a load rating analysis of the structure along with rehabilitation recommendations with estimated costs. As a result of this work the bridge was closed to all traffic on 30 January 1977, with the recommendation that emergency repairs be made that would allow the bridge to be reopened to maximum 3-ton traffic for a limited period of time (1 to 3 years) until a more permanent solution could be completed.(38)
Early in March, 1977, Pennsylvania Governor Shapp ordered the temporary repairs be made and on 20 May 1977 with the repairs completed the span was reopened to traffic with a 3-ton maximum vehicle load limit and a speed restriction of 10 miles per hour.
Changes in Surroundings
Since the completion of the Sewickley Bridge in 1911, there have been many changes in the immediate area of the structure and in the surrounding communities.
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The Borough of Sewickley itself has generally retained its stature as an affluent residential community with a population of approximately 6,300 persons, the number it has maintained closely since its centennial celebration in 1940.(39) The Sewickley Heights area, originally known for its fine farms, has been transformed into exclusive residential estates.
A number of important events that have changed or influenced the development of Sewickley appear to be those that are closely aligned to the changes in the immediate area of the Sewickley Bridge. The Pittsburgh Railways Company in 1913 established regular service from Pittsburgh to Sewickley following a route through Neville Island and Coraopolis and over the Sewickley Bridge. This new route to Pittsburgh also provided a direct commercial link to the adjacent industrial community of Coraopolis and to the shipyards at Neville Island and Leetsdale.
The Dashield Dam, located approximately one mile downstream from the bridge was completed in 1929.
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This structure raised the pool of the river and caused the elimination of the popular recreational beach areas located on the north shore of the river in the immediate vicinity of the bridge.
The Pennsylvania Railroad track relocation in 1928 permitted the reconstruction in 1932 of a new north approach to the bridge on a much more direct and desirable and eliminated the railroad at-grade crossing that had existed. The improved connections with existing streets and roads also encouraged more vehicular and truck traffic to use the bridge.
The opening in 1952 of the Greater Pittsburgh Airport in Moon Township created a rapid increase in population in the surrounding area and generated increasingly heavy traffic over the bridge.
However, the recent opening in 1977 of the new Glenfield Interchange of the Interstate 79 river crossing at Neville Island, located approximately 3 miles upstream, should somewhat reduce the heavy traffic load on the Sewickley Bridge.
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Physical Condition of Structure
The physical condition of the Sewickley Bridge is so poor that it was necessary to temporarily close the span to all traffic on 30 January 1977, until emergency repairs could be made. These items of emergency repair include the rehabilitating of the eyebar diagonals at four panel points on the suspended span and the eyebar anchorages at Piers 1 and 4, the reinforcing of floorbeam connections at 25 locations on the main truss spans and the reinforcing of 23 pony truss members on the approach spans. The bridge was reopened on 20 May 1977 for restricted usage.
The estimated cost of completely rehabilitating the existing structure is $4,750,000. However, the renovated structure would be restricted to a maximum vehicle load of 5 tons and have a life expectancy of 20 years.
Excessive corrosion with attendant metal losses has occurred in all spans to the majority of the superstructure members and details primarily in the area below the roadway deck. The masonry portions of the
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structure have fared better with the only serious deterioration occurring at the North Abutment and at Anchor Pier 4 where some extensive cracking is visible.
The entire steel superstructure above the apron plates on all spans has been recently painted and presently appears to be in good condition with little or no signs of corrosion. However, close inspections of the individual members indicate some material losses occurred prior to the painting.
The floor system members and connection details below the deck level appear to have suffered the greatest corrosion losses through the years and require the most extensive temporary repairs to keep the bridge open. However, corrosion losses in both the approach and main span truss members are more difficult and expensive to repair, and because of less redundancy in the members, required the imposition of load restrictions. The principle cause of the heavy corrosion appears to be the accumulation and splashing of dirt, debris, deicing chemicals and water at the deck level
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through the open curb and onto the majority of the panel points in the trusses (Dimensioned Drawing 7, Page 125 ) (40)
The most critical problem existing on the main span are as follows:
1. The deterioration of the floorbeam end connections which required the field installation of new reinforcement plates at 25 of the most critical locations (Appendix E, Page 115).
2. The corrosion and/or rusting through of the top and bottom flange angles and lacing on the built-up truss bottom chords (Appendix B, Pages 82 and 83).
3. The accumulation of dirt, debris and water at almost all bottom chord panel points (Appendix B, Page 86).
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4. The necessity for reinforcing four diagonal eyebar truss members due to the severe losses at the ends (Appendix B, Page 85 and Dimensioned Drawing 7, Page 125).
5. The complete deterioration of all sidewalk support brackets and stringers (Appendix E, Page 112).
6. The deterioration of the surfaces and end connections of the majority of all curb stringers and random interior stringers (Appendix B, Page 86).
7. The "freezing up" of the expansion details at the four end anchorages and corrosion of the exposed portion of the hold down eyebars necessitating the addition of emergency hold down rods at all four locations (Dimensioned Drawing 6, Page 124).
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8. The twisting and corrosion of the shear transfer details at floorbeam locations 16 and 30 (Figure 7, Page 69).
The structure contains a large number of eyebar tension members made from low carbon steel with forged heads. The eyebar is a design feature which was quite prevalent in highway bridge designs at the turn of the century and until the 1930's.
Eyebar tension members were also used extensively on the three bridges similar to the Sewickley Bridge, as previously described in this report. The same type low carbon steel eyebars were used on the Bellaire Bridge, an almost exact replica of the Sewickley Bridge, while heat-treated steel eyebars with higher working stresses were used on the Ambridge-Aliquippa and Rochester-Monaca Bridges. However, none of the eyebar steels used on any of these bridges are nearly as susceptible to stress corrosion and corrosion fatigue as the heat-treated, high strength steel eyebars used on the Point Pleasant or Silver Bridge, which failed in West Virginia in 1967.
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HAER No. PA-53
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Even though the eyebars on the Sewickley Bridge do not appear to be nearly as fracture-prone as those used on the Silver Bridge, they must still be considered to be the weak links in the overall structural design. Charpy V-notch tests conducted by a testing laboratory on coupons removed from nonload eyebar members on the bridge indicate the steel does not satisfy by a wide margin the current fracture toughness requirements for ASTM A36 steel in the AASHTO Specifications. Until the emergency repairs were made on the bridge, the most critical condition appeared to exist at the low redundant, two eyebar, end anchorages. But because of the severe corrosion and inaccessibility of the eyebar heads at the lower chord panel points of the trusses, critical fatigue cracks could have already developed or could be developing in all of these corroded eyebars. Before these potential failure points can be discovered and monitored, it would be necessary to disassemble and inspect the truss eyebar members intersecting at each suspected lower chord truss joint. This would probably require the dismantling of the entire bridge which would be illogical.
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The logical alternative is the current posted 3-ton live load limitation on the Sewickley Bridge which maintains the eyebar stresses below the critical level. There is also some additional built-in redundancy in these fracture-critical members which are built up from a minimum of four eyebars.
The most critical problems found in the approach spans are the corrosion losses on the bottom chords of the truss members (Appendix B, Page 81), which required the addition of reinforcing plates at 23 random locations. The bearings on the pony truss bents at the south approach are also heavily corroded and the expansion details are "frozen."
The steel bents at the south approach display a general random material loss and rusting through of lacing on all members. The bents on the north approach have had the most recent coating of paint and are in good condition. The concrete bases for all bents are generally sound.
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During the last in-depth inspection of the structure it was also noted that the roadway surface was in a poor and hazardous condition. The wearing surface was generally cracked and separating and in many locations had completely broken down creating potholes, especially throughout the length of the main span. This deteriorated deck condition was remedied under the general emergency repair contract.
The existing wearing surface was completely removed from Bent 1 to Pier 4 and replaced with a specially formulated asphaltic mix to a maximum thickness of 1-1/2 inches. The deck surface replacement had to be done with special equipment weighing not more than 5 tons for stripping and not more than 7 tons for the placing and compacting. Asphalt supply trucks were not permitted on the structure.
The emergency closing and placing of the present load restrictions on the Sewickley Bridge were direct results of the inspection and structural rating analysis work, coupled with the results and conclusions from the laboratory tests made on steel specimens taken
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from the structure. Specific laboratory tests were made to determine the susceptibility of the material to fatigue and brittle fracture. From these tests the following was concluded: That neither the rolled steel section nor steel eyebar materials satisfy the fracture toughness requirements of the current AASHTO Specifications for temperature zone 2; that the most critical condition in the structure appears to be in the low redundant end anchorage eyebars where the heavy corrosion in the linkage eyebar connection and the apparent bending and axial forces that exist in the anchorage eyebar make this steel a prime target for brittle fracture; that truss member M24L22 appears to be a most likely location for fatigue crack growth because of the severe corrosion and the possibility that critical cracks already exist and that a 3-ton load restriction should prevent fatigue crack growth in the riveted truss members.(41)
Cultural, Social and Economic Significance
The Sewickley Bridge has linked the communities of Sewickley and Coraopolis for the past 66 years and
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generally has played a major role in the development of intracommunity ties and services.
Sewickley is essentially a residential community and supports several small service and specialty businesses. Coraopolis, also a residential community, is the area's commercial and industrial center. Even though the business districts in the two communities have decidedly different characteristics, each community has special attractions which draw customers and employees from both sides of the river.
Sewickley and Coraopolis share a number of human services that appear to have ignored the topographic boundary separation of the river. The communities are both served by one hospital and one two-station ambulance service. Mutual aid fire-fighting pacts exist between the two communities and both belong to the 11-municipalities Quaker Valley School District.(42)
It is therefore very important to note that when the Sewickley Bridge was closed in 1977 it created great disruptions in the economy of the communities
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and hampered the effectiveness of numerous community services. These losses have been reported in two separate studies conducted by local institutions. The one study was included in a report prepared on the bridge crisis in Allegheny County. This report presented the actual effects of the bridge closing on the community with a compilation of data from surveys and interviews with local businessmen and residents of the area. (43) The other report was prepared to identify the number and magnitude of services which would be affected from the permanent closing of the Sewickley Bridge. This study provided an analysis of the effects the service losses might have on the area plus the additional costs that probably would be incurred by each community if it continues to provide to its residents the present level of services, safety welfare and accessibility to services. This second study presented conclusions determined from in-depth personal interviews conducted with municipal and County officials, school superintendents, medical service directors and transportation directors. (44)
Both reports generally concluded that the Sewickley
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Bridge is a critical link in the structure of the communities in the Ohio Valley. To eliminate the Sewickley Bridge means that new costs will be incurred in providing the present level of services and the safety and welfare of the residents and their accessibility to services will be jeopardized.
It is also important to note that the structure serves generally as a major artery for traffic from the airport and from the industries of the surrounding communities. It is anticipated the traffic will greatly increase in the coming years due to the planned expansions at the airport and the future growth of industry, especially at Neville Island.
Structure Replacement
On 22 April 1977, PennDOT District 11-0 received authorization to prepare alternative preliminary designs for a new bridge on the existing Sewickley Bridge alignment.
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HAER No PA-53
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These preliminary designs were to include the utilization of the existing two main river piers and also maintain the basic configuration of the bridge as well as the existing horizontal and vertical navigation clearances under the bridge. The studies were to be made for various roadway widths, including a 7-foot sidewalk located on the upstream side.
In the early phases of the preliminary design studies the steel deck truss, steel deck girder and concrete deck girder bridge schemes were eliminated because they would not be practical. The necessary additional depths required over the piers in each case would require raising the existing 3 percent roadway grade to an undesirable 6 percent or higher in order to maintain the existing vertical clearance under the structure. The additional dead load weight of the concrete girders would also overload the existing river piers.
A steel tied arch type bridge was not seriously studied because of the tangent alignment with no flared ramps and because of the existing conditions which
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are most adaptable to a 3-span continuous main structure. The tied arch and necessary approach structures would also undoubtedly be more expensive than the continuous structures.
The through-truss type of bridge was selected as the logical basis for making the most extensive preliminary design as it is a very economical type of construction, most closely fits the existing pier locations and river clearance requirements and appears to be the most acceptable configuration to the community. The preliminary design summaries include the costs of all the work that would be required for construction of the truss with various roadway widths with a reinforced concrete deck slab. An additional study was made for these trusses using a concrete filled 5-inch deep steel grid decking with 1-inch thick latex overlay.
A cable stayed girder bridge construction was also studied and preliminary designs were done using the same criteria as noted above. Under this scheme the two existing river piers and south end pier would
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be reused while the north end pier would be rebuilt.
The cable stayed girder bridge was designed for bridges with both reinforced concrete and orthotropic plate decks.
The preliminary design study also required additional investigative work which consisted of the following: field surveying and preparation of maps of both approach areas; establishing limits of required new right-of-way; determining what public utilities would be affected; suggesting alternate routes for detouring traffic during construction; taking underwater cores at the existing two river piers; and determining demolition and construction completion schedules. Also included was the investigation of the cost of possibly using a roll-in type construction.
The results of these preliminary studies were compiled into a report submitted on 5 July 1977, to PennDOT for their review. (45) A 32-foot wide roadway has been approved.
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Page created:
18-Feb-2009
Last modified:
18-Feb-2009
HAER Text: Pennsylvania Department of Transportation, February 1978
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