Residual capacity testing of damaged hollow-core precast concrete floors

Abstract

The Kaikoura Earthquake had resulted in extensive damage to precast concrete floor systems in multi-storey buildings in Wellington. Some of the observed damage states, mostly notably those induced in precast concrete hollow-core floors, were inconsistent with the damage observed during past research and led to uncertainty in both the residual gravity load carrying capacity of the floor as well as the behaviour of the floor as seismic deformations are increased. A series of tests are being performed to address these uncertainties with this testing prioritised to examine hollow-core floors containing transverse cracks that have formed vertically through the full depth of floor as well as those containing cracks that have formed diagonally through the webs. A total of eight hollow-core floor specimens were prepared, the detailing of which was varied to encompass construction practices either consistent with typical 1980s construction or construction from this time period considered to be worst case. Testing is conducted with damage induced in the hollow-core floor specimen consistent with a particular targeted damage pattern followed by the application of gravitational and seismic loading to the damaged specimen to gauge the residual capacity of the floor as well as to develop an understanding of the vulnerabilities of various damage states and provide guidance on those damage states that should be addressed during retrofit. The results of the first test are discussed in this paper with this test highlighting the vulnerabilities of hollow-core floors containing a vertical crack through the top half of the floor.