Methodologies for the Seismic Design of Liquid Retaining Structures and the Seismic Retrofit of a Case Study Wwtp


Abstract eng:
Water retaining structures form a large portion of the public infrastructure portfolio and provide a variety of functions including irrigation, power generation, water control, flood control and the treatment of water/waste water. Water retaining tanks can consist of steel plates, stainless steel plates or reinforced concrete walls. Water and Waste water treatment plants (WWWTP) are of particular importance. The dependence of the local public on continuous functioning of WWWTP makes structural damage and their downtime following major earthquakes, a public safety and a health concern. Reinforced concrete tanks are typically designed to remain elastic which would limit cracking and nonlinear deformations, and hence, water leakage. Therefore, in the seismic design of tanks, nonlinear deformations cannot be relied upon to sustain the seismic energy. Consequently, tanks must be designed for the total elastic seismic load without the use of force modification factors. The opportunity for energy dissipation in these structures, through other pathways could be an economical way to design for seismic events, while fulfilling the facilities mandate to remain operational. Limited guidance is provided to the Canadian engineering community with respect to the seismic design and analysis of WWWTP facilities, especially in the case of liquid retaining structures. These facilities normally utilize concrete tanks for process and storage of liquids. The concrete tanks may be stand-alone structures or incorporated into related building structures. Present Canadian standards do not provide explicit design methods or procedures for non-building structures such as these tanks. This paper investigates the available Canadian Engineering Standards and compares them to the leading design codes in order to identify an industry accepted standard of analysis. The ACI 350.3-06 analysis methodology is adapted for a Canadian application and is applied in a case study. The case study consists of the seismic retrofitting of large aeration tanks located on the second storey of an existing secondary clarifier designed and constructed in the 1970’s. A dynamic analysis is performed considering the vibrational modes of the contained liquid while considering different fixity assumptions at the foundation. Energy dissipation is evaluated at the foundation level considering the effects of soil damping and base slab averaging.

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Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 3487.:
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