Designs on corrugated steel pipe

September 2013 » Features » PROGRESSIVE ENGINEERING
Award-winning projects highlight varied applications.

Earlier this year, the National Corrugated Steel Pipe Association (NCSPA) conducted its first project awards competition to highlight effective, economical, and varied applications of corrugated steel pipe (CSP). NCSPA members – CSP manufacturers – submitted projects for judging in five categories: Department of transportation, Steel structural plate, CSP arch, Detention/retention, and Rehabilitation. Following are summaries of the top project selected in each category.

Department of transportation
According to the National Weather Service, Duluth, Minn., had its wettest two-day period ever when flood-producing storms washed over northeastern Minnesota on June 19-20, 2012, dropping more than 7 inches of rain. Resultant flooding washed out a drainage structure on Minnesota State Highway 210 (MN 210) at the Jay Cook State Park. The original structure was an 8-foot by 6-foot, cast-in-place concrete box. A major washout of this structure in 2006 removed the top to the concrete box and 72-inch by 120-foot reinforced concrete pipe was placed on top of the existing concrete box.

The June 2012 flooding displaced the 72-inch reinforced concrete pipe. Because of the immediate need to get this major roadway back in service, the Minnesota Department of Transportation (MnDOT) designed a replacement structure consisting of a 144-inch by 180 feet of 10 gauge, Aluminized Type 2, 5-inch by 1-inch profile CSP. MnDOT placed an order with TrueNorth Steel on July 11, 2012, and the initial load for this order was ready for delivery July 16. Other design amenities included riprap of the upstream outlet and downstream discharge areas. MnDot also designed concrete headwalls at the upstream and downstream ends of the corrugated steel structure.

MnDOT required that the structural design of the 144-inch structure be analyzed as a bridge because of the large size. Structural calculations were based on American Association of State Highway and Transportation Officials (AASHTO) Standard Specification for Highway Bridges, LRFD Bridge Design Specifications. Design analysis used was HL 93 loading.

The 180-foot structure was placed in four, 45-foot sections. Each section was delivered from the TrueNorth Steel, Fargo, N.D., plant in individual loads on a 48-foot trailer. Reuben Johnson and Son, Superior, Wis., was the contractor for construction of the new drainage structure and connecting headwalls. The contractor started at the outlet end by placing the concrete footing for the headwall. The pipe was connected to the headwall with anchor bolts spaced at 12 inches, center to center, embedded in the concrete headwall and attached to the pipe through predrilled holes in the corrugated steel.

The Minnesota Department of Transportation quickly replaced a washed out drainage structure beneath a state highway with 144-inch-diameter by 180-foot-long, 10 gauge, Aluminized Type 2, 5-inch by 1-inch profile corrugated steel pipe with concrete headwalls.

All construction was completed for the drainage structure and backfilling of the pipe on Aug. 6, 2012. The roadway was paved and open for traffic on Aug. 16.

"RJS Construction has installed many large [CSP] culverts over the years, and this project was one of the more unique challenges we had encountered given the site conditions and schedule, said Steve Picha, RJS project manager. "By using [CSP] pipe on this project, it allowed for the road to be opened quickly in order to restore access to Minnesota Power. Our crews enjoyed the flexibility to maneuver the pipe on a site that did not allow area to store material. The relatively light weight of [CSP] pipe as compared to concrete prevented us from having to bring in a large crane to set the pipe. That alone saved MnDOT considerable amount of time and money."
Information provided by TrueNorth Steel

Steel structural plate
Another phase of the famed Coalfields Expressway started in April 2010, continuing its southwesterly wind through the mountainous coal regions of southern West Virginia into southwestern Virginia. Corridor improvements to mitigate no-passing zones and areas of reduced speeds and to alleviate steep grades required filling a ravine on this $23.4 million, 2.02-mile stretch.

Providing ample drainage along the bottom of that ravine called for sizable pipe buried as much as 165 feet deep. The solution was found in the strengths and sizes available with CSP, in this case steel structural plate (SSP). Under the circumstances, SSP became the only viable option and subsequently was incorporated into the West Virginia Department of Transportation (WVDOT) project specifications.

Corrugated SSP is shipped to the site in curved plates and field assembled into its final shape by bolting. SSP can be produced in heavier gauges than that typically used for conventional CSP. Designers called for a 96-inch pipe to handle the expected drainage. At this size and depth, WVDOT specified the maximum plate thickness of 3/8 inch.

Shipments from the plate manufacturer (Lane Enterprises Inc.) began in July 2010, with assembly slated to commence the week of July 19. The 863-foot alignment included 490 plates, altogether weighing more than 250 tons. Directional changes in the alignment were facilitated with structural plate elbows. The ability to incorporate elbows into the alignment eliminated the need for manholes, deep shafts, or other costly alternatives, and at the same time provided structural continuity to the enclosure.

Project specifications required the plate manufacturer to corrugate, punch, and curve 3/8-inch plate, the thickest plate material recognized in AASHTO material specifications. This thickness requires eight 7/8-inch bolts per foot (instead of the usual four 3/4-inch bolts) to provide greater seam strength, resulting in a total of 46,000 bolts for the enclosure.

At 0.38 inch thick with a galvanized coating on each side, the 6-inch by 2-inch corrugated plate is still considered a flexible pipe material that derives its structural integrity from the soil-structure interaction system developed with a structural backfill. Project specifications called for well-graded crushed stone select material. This material provides maximum stability and pipe support for a given density due to the angular interlock particles. Compacted in lifts equally on each side of the pipe to a height of 2 feet above the crown, the composite action mobilizes the full compressive strength of the corrugated steel plate.

Standard plate widths are designated by N, the number of 9.6-inch bolt spaces along the circumferential seam. To obtain the N value, the diameter is divided by three. With N determined, any combination of the five plate widths available (3N, 5N, 6N, 7N, 8N, and 9N) can be used to form the pipe section. The ring of the 96-inch-diameter pipe consisted of six plates, four 5N plates and two 6N plates. The 6N plates were placed at the invert and crown with the 5N plates in the remaining positions.

Directional changes were facilitated with steel structural plate elbows, which eliminated the need for manholes, deep shafts, or other costly alternatives and provided structural continuity to the 96-inch-diameter, 863-foot-long pipe buried as much as 165 feet deep beneath the Coalfields Expressway.

A total of 490 plates were needed for the 863-foot alignment, with standard lengths of 10 and 12 feet to ensure that seams are appropriately staggered. On average, the six-man assembly crew installed around 16 plates per day, longitudinally equating to 30 feet. The assembly began around July 19, 2010, and was substantially complete by the end of August – a good pace considering bolt quantities were doubled, as noted above.
Information provided by Lane Enterprises Inc.

Corrugated steel pipe arch
The Southwestern Illinois College, located in Belleville, Ill., expanded its campus with the addition of a Liberal Arts Complex and was required to develop a parking lot on land across from a drainage ditch that split the property. Just north of campus was the Green Mount Commons retail plaza that was upstream from the university. Winter runoff created a corrosion issue that needed to be addressed in the design of this bridge project. Concentrated road salts and chemical additives for ice and snow melt reduced project life to 20 years in some cases.

Southwestern Illinois College contracted with Hoelscher Engineering to investigate options for a cost-effective "best alternative" for accessing the land with a bridge product that would outlast the project life.

Metal Culverts Inc., Jefferson City, Mo., provided the chosen solution. The culvert solution was an 80-foot run of 8 gauge, polymer-coated, 3-inch by 1-inch (3x1) corrugation, arched pipe measuring 137-inch span by 87-inch rise (114-inch round pipe). Hoelscher Engineering wanted a product that met the state of Illinois specification as well as provided a 100-year service life. The specification called for 8 gauge corrugated metal pipe. Dow Chemical's Trenchcoat product covering 2-ounze galvanized coated steel met the 100-year design life requirement.

An 8 gauge, polymer-coated, 3-inch by 1-inch corrugation, arched pipe measuring 137-inch span by 87-inch rise is expected to provide a 100-year service life in spite of corrosive runoff from an adjacent parking lot.

Baxmeyer Construction Inc. of Waterloo, Iowa, was chosen as the excavator for the project. The pipe was installed during the fall of 2011 with the project fully completed in the spring of 2012. This installation was the first known installation of 8-gauge galvanized steel with 3x1 corrugation that was polymer coated with Dow Chemical's Trenchcoat product. Metal Culverts, Inc. subsequently has provided a significant number of bridge and bridge replacements featuring 8-gauge polymer-coated galvanized steel.
Information provided by Metal Culverts Inc.

Federal regulations and prolonged draught in Georgia have forced engineers and specifiers to become creative in storage and reuse of rain water. The University of West Georgia has expanded rapidly during the last several years and has asked design engineers to be resourceful when creating plans for their new developments. The university recently built new student housing with expansive green space and instead of using municipal water sources for irrigation it requested a cistern to store water from the roof drainage system.

Onsite Civil Group designed a three-tank system using 96-inch Aluminized Type 2 CSP. The cost of the CSP system was far below comparable products. There was only one problem – CSP has an allowable leakage rate according to AASHTO specifications, and cisterns are meant to be water tight. The cisterns were manufactured by Southeast Culvert Inc. (SEC), which had to use its expertise in fabrication to accomplish the goal of total water retention.

The tanks were run on long 50-foot sections and bulkheads were welded to each end. The pipe for the tanks was made custom; to achieve the leak-resistant tanks SEC manufactured the pipe with a special gasket run into the lock seam of the pipe – a point of potential leakage. The three tanks were connected using 24-inch flanged pipes with a rubber gasket compressed between the flanges. Each tank had an access manhole riser for inspection.

Once the tanks were complete, they were tested for water tightness at SEC's facilities in Winder, Ga. They passed. The tanks were shipped to the university where they were installed in place and again filled with water to test the installation practice. During a four-day period, the tanks lost less than 1/4 inch from the pump housing and all parties involved were satisfied with the performance. The cisterns will be a long-term positive for the university as it can save money on water for irrigation through stormwater reuse.
Information provided by Southeast Culvert Inc.

A cistern for the University of West Georgia uses a three-tank system comprising 96-inch Aluminized Type 2 corrugated steel pipe with bulkheads welded to each end. Pipe for the tanks was manufactured with a special gasket run into the lock seam of the pipe. The three tanks were connected using 24-inch flanged pipes with a rubber gasket compressed between the flanges.

Only a year after installing a triple, 60-inch-diameter reinforced concrete equalizer pipe under 30 feet of cover at Mitchell Interchange on I-94, just south of Milwaukee, the Wisconsin Department of Transportation (WisDOT) found that the pipe needed to be relined because of structural cracks. After considering its options, WisDOT chose Hel-COR pipe by Contech Engineered Solutions as more economical than two alternative products.

HEL-COR offers a wide range of wall thicknesses, corrugations, diameters, and pipe section lengths to meet any specific job requirements. Durability requirements are addressed by a variety of materials. For this project, WisDOT specified 54-inch-diameter Aluminized Type 2, 5-inch by 1-inch galvanized HEL-COR pipe instead of solid-wall HDPE.

Benefits of HEL-COR pipe include a proven service life that can exceed 100 years with proper specification, sustainability from recycled material, strength, flexibility, versatility, and lightweight material. By using homogenous material, HEL-COR eliminates failures caused by stress cracks, shrinkage cracks, and air voids.

In this project, 10 c internal expanding bands were used with flat gaskets. During install, the pipe was stage grouted in three lifts, and had two grout plugs in each piece of 20-foot pipe length.

WisDOT also chose to further protect the pipe by adding zinc chromate paint to the pipe exterior (a yellow coating on the pipe). The purpose of this extra protection was to protect the aluminized coating from the flowable fill during the curing process.

The Wisconsin Department of Transportation selected 54-inch-diameter, Aluminized Type 2, 5-inch by 1-inch galvanized corrugated steel pipe to line a cracked reinforced concrete pipe under 30 feet of cover at Mitchell Interchange on I-94, just south of Milwaukee. A zinc chromate paint (yellow coating) on the pipe exterior protects the aluminized coating from the flowable fill grout during curing.

The contractor was able to perform this reline project in just seven days without disruption to traffic.
Information provided by Contech Engineered Solutions.

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