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Twin Bridges Will Mark First Time PA Uses Precast Concrete Segmental Method

Wed October 05, 2005 - Northeast Edition
Mary Reed



Twin bridges now under construction across the Susquehanna River at Harrisburg, PA, are the first to be built in the Commonwealth using the precast concrete segmental method.

The two spans will replace a 55-year-old bridge owned by the Pennsylvania Turnpike Commission (PTC). Detailed studies carried out as part of the PTC’s long-term program of improvements showed that re-decking the current bridge at this site would be too expensive.

In addition, the job would take up to six years, since work would have to be carried out on one lane at a time, with construction restricted to night hours.

The PTC also was concerned about the possibility that, should bad weather prevent the work lane being re-opened, severe traffic disruption would ensue, particularly bearing in mind that closure of one lane on the existing two-lane span would present safety risks if there were to be an accident or breakdown on the bridge.

Approximately 28,000 vehicles cross the current bridge each day, with l8 percent of them trucks. Although this is considered relatively light usage, PTC studies projected traffic doubling to an average daily total of 55,000 to 60,000 by 2020, meaning a third lane would be needed at that point.

In February 2000, therefore, the PTC decided it was necessary to replace the current bridge, which opened to traffic in November 1950.

Contributing to PTC’s decision to use the precast segmental concrete method were the geometric factors of the project, which are of a nature to which this type of construction is particularly suited.

Another element taken into consideration is the repetitive span lengths of these bridges, which offer the benefit of high productivity, thereby bringing about faster construction. The PTC estimated for this job alone the latter aspect would save approximately $3 million.

Bridges constructed by the precast concrete segmental method were first built 40 years ago in France, from which its use spread across Europe. It arrived in the United States in the late 1970s, where it made its debut when the Florida Key bridges were built.

The Twin Bridges

The Parsons Corporation, headquartered in Pasadena, CA, is providing construction management and inspection services to PTC for this project. The Philadelphia office of their associate company, Parsons Transportation Group of Washington, D.C., is administering the $150-million job, which consists of three interconnected undertakings.

In addition to replacing the Susquehanna bridge, the project will involve:

• Reconstruction/realignment of 1.5 mi. (2.4 km) of approaches;

• Construction of on/off ramps and a bridge at the Harrisburg east interchange.

Notice to proceed on the $52 million job was issued February 2005 to Kinsley Construction Inc. of York, PA. Work began in March 2005 and is on schedule, with a required completion date in November 2008;

• The building of a nine-lane toll plaza, new fare collection office, and addition of a third southbound lane on I-283 at the Harrisburg east interchange. Work will begin on this $15-million job in October 2005;

• Demolition of the existing bridge after construction of its replacements is completed.

Construction of the Susquehanna bridges is a joint venture being handled by G.A. & F.C. Wagman Inc., of York, PA, and Edward Kraemer & Sons Inc., based in Hanover, PA.

The $82.4-million contract was awarded in November 2004, work began the same month, and completion date is May 2007. Funding sources include revenue from an August 2004 increase in turnpike tolls. An official groundbreaking ceremony took place in February 2005.

The two replacement bridges will be constructed north of the current span. Each will provide three traffic lanes and feature 6 ft. (1.8 m) inside and 12 ft. (3.6 m) outside shoulders. At 5,910 ft. (1,800 m) in length (the longest on the turnpike) the twin structures will be built 8 ft. (2.4 m) apart, resting on tulip-shaped piers and standing 90 ft. (27.5 m) above the normal level of the Susquehanna River, although the current bridge is not much above flood height.

“FIGG’s Exton, PA, office was responsible for bridge design, working closely with the PTC to develop a signature structure for this highly-visible mainline bridge.” said W. Jay Rohleder, FIGG project director of the job.

As part of the structures’ aesthetic appeal, the piers’ slenderness is enhanced by vertical rustication. When the piers are cast-in-place, a form liner is used to create the appearance of a band of limestone running the height of the pier.

“This design was developed to reflect the stone pattern on the nearby PTC building,” Rohleder said. “TL-4 compliant barrier rails provide for the necessary crash tested strength, yet allow for as much openness as possible, providing access to views of the river and surrounding area for vehicle passengers enjoyment. Additionally, aesthetic lighting will enhance the structure at night.”

Methodology

Until now Pennsylvania has followed a tradition of building steel bridges, utilizing the output of the many mills that once operated within the Commonwealth. Ironically, these bridges are being built near the Bethlehem Steel Foundry in Steelton, PA.

The precast segmental construction method utilizes sections manufactured on or near the work site. In this instance, concrete box sections will be cast close to the work site at a plant set up in Steelton, from which they will be trucked on flatbed trailers to the river. There they will be linked together in a process, which has been described as resembling building with Lego. Pier sections will be stacked as if making a tower, while segments of the deck will be joined together before being lowered into place by crane onto a steel truss.

As soon as 14 segments have been placed, steel cables will be strung through them and post-tensioned, making the span self-supporting. Each successive span will be similarly constructed, utilizing an Italian self-launching underslung truss. There will be 39 such operations on each bridge.

An attractive aspect of this box-type construction is that inspections of the underside of the decks will be easier and safer to conduct since they will be carried out by passing through the “boxes,” which also allow for easier running through of telephone or Internet cables and public utility lines.

Construction Details

Construction of these bridges calls for:

• 65,900 cu. yds. (50,384 cu m) of concrete;

• More than 1,000 precast concrete segments, weighing approximately 100 tons (91 t) apiece and measuring 57 ft. wide by 8.5 ft. tall by 12 ft. long (17.4 by 2.6 by 3.7 m);

• 8,200 tons (7,439 t) of reinforcing and post-tensioning steel;

• Two stage causeways composed of 143,000 tons (129,727 t) of rock and aggregate.

Geologists and engineers of L. Robert Kimball & Associates provided geotechnical services, including on-site inspection. In conjunction with the PTC and Figg Engineering Group, the Ebensburg, PA-based company worked for more than a year on investigatory drilling to establish the type of foundation needed for the project.

This task involved between three and seven employees drilling more than 1,000 samples from shore to shore, as well as under the Susquehanna River itself, utilizing a company-owned CME rig for portions of the job not subcontracted.

The final phase of their work on the project was load testing, carried out by the Osterberg cell method.

According to Kimball Project Manager Ben Gordon, “The O-cell test may seem like a very costly test, but ultimately it should save the Turnpike Commission a great deal of money. When the length of the structure and the number of caissons that will be needed are considered, two O-cell tests are a reasonable cost.”

Savings of more $1 million are possible if the depth of several borings is reduced by even a couple of feet as a result of these tests, he went on.

“While Kimball performed this work on the project in 2001 and 2002, we are currently under contract to provide on-call engineering services during the construction phase,” company Spokesperson Joseph Brett added.

Brayman Construction Corporation of Saxonburg, PA, carried out the drilling of 176 foundation shafts, 100 of which are in the river and thus presented particular challenges due to fluctuating water levels. Of these shafts, 20 are for abutments and the rest for piers. Installed in siltstone and sandstone, the average lengths of their rock sockets ranges from 10 to 15 ft. (3 m to 4.6 m), respectively.

Kinsley Construction Inc., has been building a new roadway embankment, temporary paving and lighting and permanent paving bases as well as drainage, retaining wall, shoring, and extending an existing box culvert.

“The east and west shore abutment fill areas have been turned over to the river bridge contractor, to construct abutments and launch superstructure for the bridge,” said Patrick A. Kinsley, vice president.

“No problems have been encountered. The work remaining includes not only the current on-going activities but also demolition of the existing river bridge, construction of a new mainline bridge on the east shore, and reinforced soil slope. There is also the completion of the east shore interchange reconstruction, which will include new ramps, interchange bridge, and lighting as well as removal of the existing approach roadways and construction of new roadways on both shores.”

Approximately 70 Kinsley employees are working on site, for the most part using equipment from the company’s large fleet, augmented as necessary with rental equipment.

“More than 70 pieces of equipment ranging from a Cat 228 skid steer to a Cat D8R dozer have been used on this job so far,” noted John Marks, equipment division controller of Kinsley Construction. “They include a Caterpillar 963B track loader and a 330CL track excavator, as well as a Cedarapids 10-ft. CR561R paver, a Gradall XL4100 excavator, and a Volvo A35C articulated truck.”

Archaeological Investigation Continues

The PTC conducted digs on both shores of the river as well as on Calver Island, over which the bridge passes. These investigations were required by the National Historic Preservation Act. Last year, equipment and personnel had to be ferried by boat to the island, but the team is now using the construction causeway.

Because the Calver Island dig involved deep excavations, OSHA-required regulatory compliant slopes were unusable as they would have destroyed much of the investigative sites. The PTC, therefore, could not utilize a backhoe for trenching work and so a Geoprobe mounted on a truck carried out soil borings. These samples aided archaeologists to focus their attention on those areas of the island, which were most likely to prove fruitful.

The dig on the eastern side of the river is in an area that had been covered by fill from railroad construction and nearby industrial developments. The site has been dated to between 1000 to 3000 BC (Early Woodland Period). So far archaeologists working there have uncovered evidence of cooking fires and chips from the manufacture of tools as well as spear points, weights for fishing nets, scrapers and drills, an ax, ceramic ware, and a soapstone pendant.

Although nothing of historic importance has been found by the western shore investigations, the eastern shore and island sites are eligible for listing on the National Register of Historic Places because they provide information relating to life in the area before Europeans arrived.

About the Companies

Located in Saxonburg, PA, Brayman Construction Corporation was founded in 1948. It offers civil and marine construction, geotechnical, and demolition services to clients in the eastern United States ranging from power companies and railroads to state departments of transportation and the Army Corps of Engineers.

Past projects include a railway retaining wall in Pittsburgh, PA, and an interchange for the PTC. Company staff working on PennDOT’s State Route 422 Moraine State Park Bridge project included two engineers who had worked 30 years earlier on the original bridge, which also was constructed by Brayman.

Headquartered in Tallahassee, FL, the FIGG Engineering Group is dedicated to bridges, providing engineering, design, and other services to clients in 34 states and in the process earning more than 160 design awards.

Its past projects include Florida’s Sunshine Skyway, the Natchez Trace Parkway Arches in Tennessee, and North Carolina’s Linn Cove Viaduct, all three of which won Presidential Awards.

Based in York, PA, Kinsley Construction Inc. is a second-generation, family-owned business founded in 1963. Originally a concrete services subcontractor, in the 1970s the company moved into general contracting. It has been handling highway work for approximately 20 years. The company provides design/build, general contracting, and construction management services.

Among other things, it offers its clients feasibility studies, site evaluation, excavation, demolition, grading, concrete and utility work, and steel erection and installation.

Kinsley is currently completing a large $58-million contract involving reconstruction of several miles of I-83 in York County, PA, for PennDOT, in addition to several other smaller highway, bridge, and utility projects in Pennsylvania and Maryland.

L. Robert Kimball & Associates, headquartered in Ebensburg, PA, offers clients architectural, civil and environmental engineering, roadway, bridge and airport design, telecommunications and technology consulting, and mapping/GIS services.

The company has four CME drill rigs and provides geotechnical assistance to utility providers, contractors, engineering and architectural firms, and many other entities. It works on approximately 1,500 projects annually through its various divisions. CEG