Walnut Lane Memorial Bridge
Coordinates: 40 ° 1 ′ 59 ″ N , 75 ° 11 ′ 16 ″ W.
| Walnut Lane Memorial Bridge | ||
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| use | Road bridge | |
| Crossing of | Monoshone Creek, Lincoln Drive | |
| place | Philadelphia , Pennsylvania , USA | |
| construction | Prestressed concrete girder bridge | |
| width | 19.40 m | |
| Longest span | 49 m | |
| Clear height | ≈ 15 m | |
| start of building | May 1949 | |
| completion | January 1951 | |
| Status | Superstructure replaced (1990) | |
| planner | Gustave Magnel | |
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The Walnut Lane Memorial Bridge is a road bridge in Philadelphia , Pennsylvania that spans Walnut Lane over Monoshone Creek and Lincoln Drive. It stands about one kilometer east of the Walnut Lane Bridge , a concrete arch bridge that runs along the same road over Wissahickon Creek.
Walnut Lane Memorial Bridge (1950)
The original Walnut Lane Memorial Bridge was designed by Gustave Magnel (1889–1955), a Belgian specialist in prestressed concrete and professor at Ghent University , and commissioned by the City of Philadelphia. Construction began in May 1949. The almost completed bridge was inaugurated on November 11, 1950, Armistice Day . After completing the remaining work, the bridge was opened to traffic on February 1, 1951.
It was the first prestressed concrete bridge to be built in the USA. At that time in the USA there were no technical regulations about prestressed concrete, neither standards of the American Concrete Institute nor other regulations. The bridge was therefore largely planned according to Belgian standards. The structure of the bridge was simple and resembled many of the highway bridges that drive traffic over US highways today. It was a yoke bridge with a main opening of 49 m (160 ft ) and two side openings of 22.6 m (74 ft). The two yokes consisted of four square concrete pillars that were connected at the top and bottom by cross beams. Thirteen prefabricated T-shaped prestressed concrete beams were supported on the crossbeams, with only a narrow slot between them. The carriageway girders made of in-situ concrete and its asphalt surface were applied to this beam. The bridge was a total of 19.40 m wide, divided into a 13.41 m wide carriageway and two approximately 3 m wide sidewalks. It had a headroom above Lincoln Drive of about 15 m.
In 1957, cracks were first discovered on the underside of the prestressed concrete beams, which increased and lengthened over the years. In 1969 extensive renovation and sealing work was carried out. However, despite further repair work, the problems could not be finally eliminated. In 1982 a weight limit for traffic was introduced. In 1989 it was decided to replace the superstructure of the bridge.
Walnut Lane Memorial Bridge (1990)
The renovation of the superstructure carried out from 1989 to 1990 left the external appearance of the bridge largely unchanged. Instead of the previous 13, however, only 8 prestressed concrete beams with changed dimensions and correspondingly larger distances were used, which were planned and implemented according to the now existing US standards.
history
prehistory
Walnut Lane and with it the first bridge over Monoshone Creek were opened to traffic in 1876. The bridge had six openings with wrought iron structures and wooden bridge decks. By 1925 it was no longer able to cope with the traffic. In 1929 it was decided to build a new bridge, but the offers received in 1931 for a stone-clad arch bridge exceeded the financial framework. From 1932 the bridge could only be used by pedestrians.
In 1947, another tender for an arch bridge ended with no results because the lowest bid for around $ 1,000,000 was again over budget. Discussions began that the site was suitable for a prestressed concrete bridge and thus for the introduction of this technology to the USA. Initially, a three-span haunched box girder bridge was planned with open tension wires running in the box girders according to the Roebling Company system . However, this design would not have allowed the stress test on a 1: 1 model, which was considered necessary in order to gain the trust of the public as well as the professional world in the new technology.
First prestressed concrete bridge
In this situation, the Preload Company from New York and its licensor Gustave Magnel submitted a first draft for a girder bridge based on the Blaton-Magnel system. It was planned to load a beam as a sample until it failed. The high load values for both the steel and the concrete envisaged in the draft initially presented problems because they were not yet in use in the USA at the time.
In early 1949, the new tender submitted bids for $ 700,000. An even cheaper offer based on the Freyssinet system at $ 652,000 had to be eliminated because it did not meet the specification.
After construction began in May 1949, the abutments and the yokes with the concrete pillars were installed. In September, Preload Co., as a subcontractor for the prestressed concrete beams, concreted the sample beam, which was gradually prestressed in October. On October 25, 1949, the stress test peaked in the presence of three to four hundred engineers from 17 US states and five other countries, to whom Professor Magnel explained the individual steps of the test. The beam was loaded several times with the planned normal load and twice this load, then until cracks appeared and finally with the calculated breaking load, but without the beam actually breaking. It was only when the loads were concentrated in the middle of the beam that it finally failed on October 27, 1949. The success of the test was widely appreciated and recognized.
During the subsequent construction, Magnel made structural and procedural changes in order to solve the problems associated with the high demands on steel and concrete. The construction then proceeded as routine and was finished in January 1951.
Web links
- Charles C. Zollman, Frank Depman, Joseph Nagle, Edward F. Hollander: Building and Rebuilding of Philadelphia's Walnut Lane Memorial Bridge. Part 1: A History of Design, Construction, and Service Life. In: PCI Journal , May / June 1992, pp. 66–82 (PDF; 2.8 MB)
Individual evidence
- ↑ The information in this article is based on the Historic American Engineering Record, HAER PA-125 , unless otherwise stated.
- ↑ Holiday to commemorate the armistice of 1918 to end the First World War
- ↑ Thomas J. D'Arcy, George D. Nasser, SK Ghosh: Building Code Provisions for Precast / Prestressed Concrete: A Brief History. In: PCI Journal , November-December 2003, pp. 116–124 (PDF; 2.1 MB)