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Design Approach, Inspection For Manhole Rehabilitation Technologies
3nd In A 3-Part Series
So what formula should be used? Should it be the formula contained in the ASTM F1216 Appendices that is typically used for pipe liner design? Or should the formula be specific to manholes and incorporate the compressive strength of the material to calculate the buckling load and thereby determine the required wall thickness of the new product? When installed, the new product should be equal to the full loading characteristic provided by the existing manhole. In either event, the formula should be standardized for the industry and require the same criteria for all coating and lining technologies.
To further explore this topic, Underground Construction sought input from a municipal manager, product manufacturer and a consulting engineer for their responses to several questions.
The participants included:
Edward Carpenetti, P.E., P.G., principal civil engineer, Infrastructure Systems Group, Sewer Rehab Unit, Washington State Suburban Sanitary Commission. The commission allows installation of product approved by its Material Evaluation Committee.
Chip Johnson, P.E. director, business development, Sprayroq Inc., manufacturer of structural and corrosion barrier products SprayShield Green 1 and SprayShield Green 2 (elastomeric corrosion barrier products).
Ed Kampbell, P.E. pipeline rehabilitation technologies specialist, Jason Consultants, a consulting engineering company that performs technical reviews and advises clients on alternatives that are appropriate for projects.
What is your definition of full structural rehabilitation, and what is the role of the existing manhole to continue functioning as the structural component after rehabilitation?
Carpenetti: “Full structural rehabilitation is a stand-alone product that does not depend upon the original structure for strength or function. The structural repair should be able to function even if the original structure crumbles.”
Johnson: “The existing manhole essentially acts as a ‘form’ for the installation with partially deteriorated structures handling the forces generated by the hydrostatic head and from the static water table and those fully deteriorated structures requiring that the installed technology will withstand all live and dead loads that are acting on the rehabilitated structure. Any reinforcement from the existing structure offers additional strength in the finished rehab installation, but is not dependent on that.”