Better Roads Staff
By Tina Grady Barbaccia
Bridges that were once inaccessible by traditional methods can now be thoroughly inspected by engineers climbing and rappelling down the structures.When the floodgates of a large dam in Folsom, Calif., unexpectedly failed during a routine opening, the U.S. Bureau of Reclamation and the Army Corps of Engineers (COE) – the dam owners – mobilized quickly to inspect the remaining gates for distress. However, the location of the main structural components – perched on the dam spillway about 250 feet above the base of the dam – was hampering the abilities of engineers to access the critical areas.
The only way to quickly address the problem was to rappel down the structure so climb-trained engineers from COE (from across the United States) and the Office of Structure Maintenance and Investigations at the California Department of Transportation (Caltrans) were brought in. For two weeks after the 1995 incident, Caltrans engineers assisted COE with evaluating the remaining dam gates. “Extensive investigations, evaluations and materials testing were completed with a minimum of expense and effort,” explains Stephen Sahs, senior bridge engineer, emergency response and bridge coordinator/ fracture critical technical access coordinator/seismic specialist, for the Office of Structure Maintenance and Investigation at Caltrans.
The use of climbing techniques – i.e. rope access – for bridge inspection has proven to be a valuable tool for the investigating engineer or technician, Sahs adds. “In some cases, climbing is the only effective means to gain access to certain bridge elements,” he says, adding that the techniques have been proven to be “an economical and effective for a variety of routine and specialized bridge inspections.”
Caltrans bridge engineers have historically used heavy industrial rope and rigging techniques to gain access for bridge inspection. The rigging was done by either Caltrans’ Bay toll bridge paint crew or private contractors following the standards of the construction industry.
Now, rope access techniques are used in California as an alternative means of gaining access to bridges and structures when other conventional methods cannot be used due to inspection equipment limitations and/or when traffic is greatly impacted. More than 50 bridges in Caltrans’ jurisdiction have been identified as structures where climbing is the only means available to perform structural investigations.
“The traditional uses of under bridge inspection trucks, life equipment and rigging are economically and practically limited by bridge size, structure type, traffic demands and support costs,” says Sahs, who authored the paper Climbing Techniques for Bridge Inspection, which was presented at the International Bridge Management Conference. (For a downloadable PDF of the paper, go to http://www.betterroads.com/climbing-techniques-for-bridge-inspection/.)
Sahs says that in some cases, bridges have become damaged by earthquakes and have been identified as possessing fatigue prone or fracture critical details that require thorough tactile investigations. However, he says, the structures aren’t able to safely support the loads of heavy personnel lift equipment. “Gaining access to bridge elements to perform these investigations [with traditional bridge inspection methods is]…difficult and costly,” Sahs points out.
Enter bridge inspection via rope access techniques. To address costs and inaccessibility issues, the Caltrans Office of Structure Materials and Office of Structure Maintenance and Investigations evaluated the use of rock climbing and mountaineering techniques as an alternative means of gaining access for bridge inspection. Caltrans’ districts also have a specialized maintenance rock scaling/climbing program as well for steep slope work.
Thanks to a small research grant, a bridge climbing training course was developed throughthrough a local University of California outdoor recreation group. Subsequently, seven engineers and technicians were initially trained. A comprehensive “Code of Safe Practices,” which established training, procedures and equipment required for bridge inspections, followed. The newly trained team then successfully completed a climb investigation on a large, previously inaccessible arch bridge, Sahs says, proving that the techniques for the “Code of Safe Practices” were “safe, economical and effective.”
Within a year, 20 more bridge maintenance engineers were trained, and a formal program was established to organize, schedule, equip and certify engineers and technicians for bridge climbing. Since the program’s deployment, several other offices within Caltrans and the California Department of Water Resources have since adopted the rope access techniques for specialized structural inspection tasks.
“About 15 years ago, we started [climbing] bridges and created our own program,” Sahs points out. A Caltrans engineer, who was also a mountaineer, adapted climbing to bridges. “We put together our own code of practices,” Sahs explains. Meanwhile, the Society of Professional Rope Access Technicians (SPRAT) was formed, along with its now industry-standard certification process, to create industry-wide standards with enforceable rules. “If you’re certified by [SPRAT], you’re pretty much good to go anywhere,” he says. “It means you’ve passed the tests and can perform at a certain level of rope confidence.”
In 2000, the Occupational Safety and Health Administration (OSHA) adopted the Title 8: General Industry Safety Orders Chapter 4, Subchapter 7, Article 1, Section 3207, And Article 4, Section 3270.1 along with Cal-OSHA. The code has spelled out what constitutes a viable Rope Access program. SPRAT was instrumental in the development of these codes.
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