Implementation of New Seismic Hazard Maps into the Building Code Update in Georgia

Session: Alpine-Himalayan Alpide Shallow Earthquakes and the Current and the Future Hazard Assessments
Type: Oral
Date: 4/30/2020
Time: 02:00 PM
Room: 215 + 220
Description: 

A new seismic hazard mapping initiative in Georgia produced a series of national seismic hazard output such as maps, uniform hazard spectra (UHS), hazard curves and deaggregations. The results were integrated into an update of the building code in Georgia through a close interaction with the national building code committee. This is the most major update of the Georgian building code in recent times, as it marks the switch from a Soviet-era code style to the European code system. The hazard assessment was carried out for the reference ground condition to be used in the updated building code, i.e. an average shear wave velocity in the upper 30m (Vs30) of 800 m/s. The UHS, from which engineering design spectra are derived, were produced at various probabilities of exceedance (including 2% in 50 years, 5% in 50 years and 10% in years) or the corresponding return periods (2,475 years, 975 years and 475 years, respectively). The aim was to provide the opportunity for the code committee to make well-informed decisions on the selection of the probability of exceedance for the new code. As an example, US and Canada use ground motions with 2% chance of being exceeded in 50 years for seismic design (i.e. there is a 2% chance that the building will experience a shaking stronger than the design ground motion levels in a 50 year period) and most countries in Europe use 10% chance in 50 years. UHS at each probability level was provided for the following periods of vibration: 0.1s, 0.2s, 0.3s, 0.5s, 1.0s, 2.0s and 4.0s. The goal was to encourage the code update to use the full hazard spectrum rather than derive it from a single or a few spectral acceleration values with the use of formulae to approximate the hazard values in between. The new hazard results and the building code update provide a leading example to a region that lacks contemporary seismic provisions in their building codes.

Presenting Author: Tuna Onur

Authors