Rapid Screening of Buildings for Seismic Retrofit Assessment

1. Rapid Screening of Buildings for Seismic Retrofit Assessment Murat Saatcioglu PhD,P.Eng. Professor and University Research Chair Department of Civil Engineering The University of Ottawa Ottawa, ON

2. Why Seismic Screening? • Seismic retrofitting may be very costly • Before a decision is made, seismic assessment is required. • Before undertaking a detailed seismic assessment, a rapid screening of buildings may be in order. • NRC developed “Manual for Screening of Buildings for Seismic Investigation”

3. Seismic Screening • NRC Screening Manual is dated 1993. It has been revised recently at the request of PWGSC to conform to NBCC 2005 Seismic Hazard • Seismic screening provides a simple tool to a community or authority to easily identify buildings that might pose a risk of life or injury, or severe curtailment of community services in the event of a damaging earthquake

4. Seismic Screening • Seismic screening is conducted by a simple inspection without the cost of a detailed analysis of every building in a given region • Buildings that receive high score and is thus identified to be potentially hazardous require further investigation • NBCC Appendix K recommends that buildings that have seismic resistance of 60% and lower relative to the current code requirement may be retrofitted

5. Seismic Screening • The 60% value is a trigger value and does not indicate that seismically deficient buildings should be retrofitted to have 60% capacity • Once the decision to retrofit is made, it is advisable to improve the building performance up to the current standards expected from new buildings • Cost and performance should be weighed against each other before a decision is made

6. Seismic Screening The following has to be evaluated: • Seismicity(A):The maximum earthquake motion expected for the location of the building (seismic zone). • Soil Conditions(B): Soft soils amplify earthquake motions and damage buildings. • Type of Structure(C): The type of lateral force resisting system (LFRS) is important to assess potential seismic damage.

7. Seismic Screening The following has to be evaluated (Cont’d): • Building Irregularities(D):This applies primarily to weaknesses in configuration like soft storeys and captive columns. • Non-Structural Hazards(F): Non-load-bearing components of the building, such as block partitions, may fall on people or interfere with rescue operation.

8. Seismic Screening The following has to be evaluated (Cont’d): • Design NBC:Buildings designed to recent building codes are less vulnerable than buildings designed to older versions of the code. • Building Importance(E): The consequences of failure are more severe for post-disaster buildings and critical facilities. Also, risk in densely populated buildings is higher.

9. Seismic Screening Form

10. Seismic Priority Index Structural Index (SI) = A*B*C*D*E Non-Structural Index (NSI) = B*E*F Seismic Priority Index (SPI) = SI + NSI • The scores should be used for the purpose of ranking • SI or NSI of 1.0 to 2.0 indicate full compliance with the code. • SPI < 10 indicates low priority • SPI = 10 – 20 indicates medium priority • SPI > 20 indicates high priority • SPI > 30 potentially hazardous

11. Thank You….. Questions or Comments?