North Pacific Wheeler's Panel-Lam bridge goes up in hours
By Kurt Glaeseman
It was a race against time. The dilapidated bridge on Oak Run County Road (a vital route into Shasta County's remote forests between Highways 299 and 44) was no longer functional. The woods were dry and fire season was imminent. What could be done --immediately?
Mark Dunton, of Dunton Construction Company in Anderson, and Dick Uran, of North Pacific Wheeler, put their heads together. Some of the original bridge abutments were still solid. Dunton thought a crew of six, plus his Komatsu 220 excavator, could possibly install a 35-foot Panel-Lam span, prefabricated by North Pacific Wheeler, in no more than a few days. Access could not be delayed for much longer than that, and the clock was ticking.
While the crew tore off the old deck, Dunton walked through the plans with Uran. The materials arrived exactly on time, and the crew started with what Dunton called a do-it-by-number installation. "It was like putting together Lincoln Logs, but on a larger scale," he laughs. "My job was to have the right crew and the right tools, and I really appreciated the guidance from the bridge rep."
The span is almost in place: Mark Dutton (dark cap), Mark Dutton, Junior (rope in hands), and Scott Dutton (kneeling).
Demolish & Rebuild
The excavator demolished the old bridge. Dunton used a jib boom to add 15 feet of reach, giving them plenty of stretch to put in the beams. The runners and decking came together smoothly. A series of 12-to-30 inch bolts tied the predrilled pieces together.
"We did do a little additional wood drilling," says Dunton, "and we swabbed in some preservative to protect from insect damage. Then it was just a matter of putting in the bolts and tightening things up."
"The last thing we did was spike down runners for the tire paths, additional wear protection provided by Wheeler. These runners are about 12 inches wide and 2.5 inches thick, so the surface can be monitored for wear and then replaced if necessary."
Dunton adds, "The bottom line is that this was a different job for us and a real joy to install. I'm very satisfied and would like to do more of these bridges. And there was no debris or junk other than the banding straps from shipping. In an incredible 18 hours, the bridge was open and ready for traffic."
Mark Dunton and his father William "Bob" Dunton speak from bridge-building experience. They have installed box culvert bridges, pre-cast concrete decks, poured-in-place concrete bridges, and steel truss bridges. Another Panel-Lam installation was in Trinity County, Calif., at a campground near Rattlesnake Road. This 50-foot span was less critical time-wise, but lots of hunters depended on the bridge during deer season.
"The conditions were a little tight," remembers Mark Dunton, "but everything went smooth. Materials were delivered on time. We used the same 220 Komatsu excavator. Our crew of six had the bridge installed in two days."
North Pacific Wheeler Panel-Lam bridge in Eastern Washington (from David Eids)
Long History of Bridging Gaps
Efficiency, speed, and ease of installation are high priorities for the North Pacific Wheeler Corporation. The employee-owned corporation serves as a large-scale merchant of forest products and services. Started as a small, family-owned business in 1948, it is now headquartered in Portland, Ore., and has around 900 employees in eight business units.
The Wheeler Division, dating back to 1892, has been manufacturing and supplying steel and timber products for more than a century. They do timber retaining walls, timber sound walls, timber recreation bridges, steel recreation bridges, timber culverts, and salt storage buildings. Their Panel-Lam timber slab span bridges have been used for public roads, private driveways, recreation trails, golf course access, temporary bridges, bridge rehabilitation, logging skidder mats, and even covered bridges.
The Wheeler longitudinal timber slab span structures do not have separate beam and deck elements, but instead a solid desk slab. These are well-suited for span lengths of ten to forty feet, but occasionally longer spans are installed. The timber is treated with an oil-borne preservative (Copper Naphthenate) that is unaffected by corrosive action of de-icing chemicals and can withstand repeated freeze-thaw cycles.
The Dowel-Laminated Deck System is designed in accordance with AASHTO standards, so all typical highway load-bearing standards can be applied, including HS20 or HS25. The spans are indeed strong. Numerous members coupled with the use of ductile fasteners create thousands of load paths, so the load sharing ensures that the weakest member does not define the system's strength.
The bridge begins to take shape: Scott Dutton (dark glasses) and Art Meekins (to right with white cap).
Designed for rapid construction, the prefabricated pieces arrive on-site ready for installation. Mark Nicholas, North Pacific Utility and Construction guru, points out that a major advantage of quick and efficient installation is that road closures and detour delays can be reduced.
The prefabricated kit includes individual planks with shop-assembled dowels that comprise the slab span. Dowels are usually positioned in two rows near the top and bottom of the panels and spaced at one foot. Laminates are added two at a time until the desired panel width is achieved. Panels are custom built in the shop for each project. Field installed dome-head spikes fasten the upper and lower splice blocks of adjacent panels.
For bridges requiring an asphalt surface, the individual laminates are allowed to vary in width. When assembled vertically, the bottom surface of the panel is smooth and the top irregular, allowing the bituminous (asphalt) mixture to grip efficiently. North Pacific Wheeler can also offer crane, dragline, laminated, and DURA-BASE mats for special demands.
David Eids, Chief of Engineering and Construction for Walla Walla County in Eastern Washington, is another satisfied customer. He has installed at least three of the North Pacific Wheeler Panel-Lam spans in the rolling hills and wheat fields of the Palouse. He works with a three-man crew and a small crane.
"This application is cheaper and easier than a concrete deck," says Eids, "and we can sometimes use the existing timber abutments, maybe just replacing a 12-inch by 12-inch pile cap. Materials are delivered down gravel roads and everything is easy. The Panel-Lams are great. We put in pre-fab rails and everything looks attractive and solid. The installation plans are simple, pieces are easy to assemble, and we get the bridge strength we want. It's a good, complete package."
Art Meekins is preparing the existing abutment prior to installing a North Pacific Wheeler Panl-Lam Span in Shasta County, California
Remember that bridge on Oak Run Road in Shasta County? Very shortly after installation was complete, fire-fighting machinery and personnel were rolling over it to access a lightning-strike wildfire. Thanks to quick and easy installation, the bridge crew beat the clock, and modern technology saved many acres of valuable timberland. Bridging a critical gap has been made easier with the North Pacific Wheeler Panel-Lam spans.