Rationale for updating earthquake design forces in modern building codes

Modern seismic design codes aim to prioritize life safety by permitting controlled structural damage during significant earthquakes while preventing catastrophic failures. This philosophy aligns well with regions of low seismic frequency, where major earthquakes occur roughly every 50–100 years. The current approach uses reduction factors (R) to minimize the size of structural members, balancing safety and economic considerations over a building's typical 100-year lifespan. However, this methodology allows for irreparable damage to structures during major seismic events, which is deemed acceptable in areas with low seismic activity.

In high-risk regions, such as Istanbul, where the likelihood of a major earthquake within a short timeframe is considerably high, the economic viability of this approach is questionable. Frequent seismic activity could result in newly constructed buildings being irreparably damaged within a fraction of their intended service life, necessitating demolition and reconstruction. To address these inefficiencies, it is proposed that reduction factors be regionally tailored. Lower R-values in high-risk zones would limit structural damage to repairable levels, enhancing resilience, sustainability, and economic efficiency by extending the usable life of buildings.

Region-specific reduction factors could ensure that seismic design codes accommodate varying risk levels effectively. For example, in areas with low seismic risk, the current R-value may remain suitable. In contrast, high-risk regions would benefit from reduced R-values to mitigate economic and structural losses. Revising reduction factors in this way would align seismic design practices with regional risk profiles, improving the durability and sustainability of urban infrastructure in seismically active areas.