Seismic Performance of Precast Hollow-Core Floors: Part 2-Assessment of Existing Buildings

Past research has indicated that precast concrete hollow-core floors in buildings are susceptible to non-ductile failure modes when subjected to earthquake deformations. While this research has led to the development of more robust connection details suitable for hollow-core floors in new buildings, the existing building stock with hollow-core floors in New Zealand is still at risk and needs to be assessed. Damage to buildings containing hollowcore floors in Wellington, New Zealand, during the 2016 Kaikoura Earthquake prompted the need to better understand the behavior of hollow-core floors and enable those with limited drift capacity to be retrofitted or replaced. Based on tests described in a companion paper, models are developed for three potential failure modes: loss of seating (LoS), positive moment failure (PMF), and negative moment failure (NMF). Implementation of these models in the New Zealand Seismic Assessment Guidelines is discussed. Applying the Guidelines to a database of 112 existing buildings with hollowcore floor units in Wellington indicates that the most likely mode of failure is loss of seating.