Experiments on the seismic performance of hollow-core floor systems in precast concrete buildings

Abstract

This research follows on from recently completed work conducted by Matthews (2004) who investigated the seismic performance of precast concrete frame buildings with precast hollow-core floor slabs and demonstrated major shortcomings in standard construction practice that would lead to very poor seismic performance. Matthews (2004) outlined several areas of future research needs, several of which will be addressed in this research. The super-assemblage constructed by Matthews (2004) was severely damaged during his experiment; however, the precast frames were repaired and reused in this research. New end beams with wider (75mm) seat widths are cast and a simple (pinned) connection between the hollow-core units and the beam adopted. The redeveloped superassemblage is tested in both the longitudinal and transverse directions up to interstorey drifts of ±4.0% and experimental and instrumental observations from the experiment are outlined.

A forensic study is conducted to better understand the observed failure modes. A theoretical pushover curve for predicting the capacity of the super-assemblage is developed using the principles of yield line theory and progressive flange activation. Low cycle fatigue theory is used to show the final failure of such a precast frame is related to the fatigue life of the main beam longitudinal bars. Finally a fragility analysis is used to determine the seismic vulnerability of this class of precast concrete structure. The efficacy of the detailing improvements is clearly demonstrated. There is now at least a 90% confidence interval of satisfactory seismic performance. However, with the old details there is a virtual certainty of extensive irreparable damage and even the possibility of collapse.