Unexpected Seismic Damage vs. SLS Building Code Anomalies

Abstract

The 1992 advent of the Serviceability Limit State (SLS) was for the purpose of eliminating structural and nonstructural damage to buildings subjected to small or moderate SLS Earthquakes (EQs). However, moderate direct structural damage and large indirect losses occurred to many medium-rise concrete-framed buildings as a result of small or moderate EQ ground motions in Christchurch CBD 2010 and in Wellington CBD 2013 and 2016. This is shown to be because of SLS flaws in the New Zealand (NZ) building code, (compared with international codes.) Theses flaws explain most of this unexpected damage. It is important to note that if the SLS flaw was not present in the building code and an Sp factor of 1.0 had been used in the design then a more robust building would have resulted and some of the damaged blamed on incompetent engineering may not have occurred. A cost-benefit study is performed here to measure the benefits of correcting the SLS building code flaw. This is important because the Reserve Bank calculates there is now a 30% increase in New Zealand's projected annualised average loss due to earthquakes. This vulnerability is mostly due to the SLS flaws in the building code, but is also due to deficiencies in engineering building design.