1 Technical Advisor, Engineering – Bruce Power, 123 Front Street (W) Toronto M5J 2M2, Canada, dara@mcmaster.ca
2 Martini, Mascarin and George Chair in Masonry Design, Department of Civil Engineering, McMaster University, Hamilton ON, Canada, L8S 4L7, eldak@mcmaster.ca
3 Assistant Professor, Department of Civil Engineering, McMaster University, Hamilton, ON L8S 4L7, Canada, konstant@mcmaster.ca
ABSTRACT
Seismic qualification of existing masonry walls in Nuclear Power Plants (NPPs) has been challenging due to perceived masonry vulnerability to the lateral forces caused by a seismic event. Due to some of the recent earthquakes exceeding the design basis, beyond design basis evaluation of NPPs is required by the regulators all across the world including Canada. The existing masonry construction is required to be evaluated for its seismic interaction with the seismically qualified systems and components. In some of the probabilistic risk assessment studies, the unreinforced masonry (URM) has been found to be one of the dominant contributors to the reactor core damage frequency.
The Design Basis Earthquake (DBE) spectrum recommended by CSA N289.3 is similar to the NBK spectrum (by Newmark, Blume and Kapoor) based on various California earthquake records and hence is referred to as the west coast spectrum. Recent research indicates that the hazard at rock sites on the east coast of North America is better represented by a spectrum having lower spectral accelerations than the west coast spectrum at the low frequency range and higher spectral accelerations than the west coast spectrum over the high frequency range up to 100 Hz. Such a spectrum is known as the East North American (ENA) spectrum. Masonry walls in NPPs in Eastern Canada that are designed for the west coast spectrum are required to be evaluated for the ENA spectrum. This paper focuses on the beyond design basis evaluation of typical masonry wall configurations that can be found in Canadian NPPs and attempts to find their seismic margin over and above the design or evaluation basis.
KEYWORDS: concrete block masonry, nuclear power plants, seismic response, beyond design basis seismic evaluation
395.pdf
