Lessons from Earthquake-affected Structures: The Necessity of Structural Health Monitoring and Instrumentation

Abstract This paper studies two highly earthquake-affected structures in New Zealand, where visual inspection outcomes missed damage, resulting in incorrect and delayed decisions, which cost lives and wasted resources. Specifically: 1) the un-instrumented Canterbury Television (CTV) building; and 2) the instrumented Bank of New Zealand (BNZ) building. This study uses these known outcomes to highlight the importance of reliable structural health monitoring (SHM) methods and SHM instrumentation in earthquake-prone areas, where each damaging earthquake and subsequent further-damaging aftershocks demand continuous monitoring to continuously assess damage and risk to safety. Elastic spectral analyses are carried out for the CTV building using the earthquake acceleration records at a station near the CTV building. For the BNZ building, inter-story drift ratio (IDR) analyses are conducted based on the building's instrumentation data. These simple, low-cost analyses indicate the damage and deterioration in both structures, and thus the importance of sensor networks and SHM instrumentation so quantitative analysis can rapidly examine subjective visual inspection results or better target and augment these inspections. Finally, this study introduces the hysteresis loop analysis (HLA) in the context of the instrumented BNZ building, showing the ability to provide necessary monitoring to assess damage and risk. This paper does not aim to criticize post-earthquake inspections or inspectors. However, it does aim to draw attention to the fact visual inspections are inherently unreliable, and current post-earthquake evaluation policies should be upgraded considering advances in instrumentation technologies and SHM methods. The paper ends discussing how the combined actions of all stakeholders are essential for successful, effective post-earthquake evaluations.