| Popis: |
An experimental study was undertaken to investigate the impact of mandated link slabs in New Zealand precast hollowcore floor construction on the fire performance of the floors, where the link slabs were required between precast hollowcore floor units and adjacent floor beams due to seismic considerations. A hollowcore floor system, which included the mandated link slab and the supporting beams, was tested at the systems level. The test was undertaken with the furnace conditions according to the ISO 834 and a superimposed load of 5.3kPa. The test was terminated after the insulation criterion, measured on the unexposed surface, was reached at 116 minutes. Of interest was that premature web failure and loss of lower shell of the hollowcore unit adjacent to the link slab was observed only 29 minutes into the test. The preliminary findings from the experimental study are summarised as follows: (1). Hollowcore units could experience considerable thermal gradient across the depth, thus having great web failure potential; (2). Presence of the link slab could significantly exacerbate the sectional distortion of the hollowcore units and horizontal web cracking, leading to increased probabilities of partial collapse of hollowcore units in fires; and (3). Conventional fire rating tests of precast concrete hollowcore floors could overestimate fire resistance ratings. |
