Modal testing and FE model correlation and updating of a long-span prestressed concrete floor

Abstract

There is a lack of information on as-built vibration properties and performance of slender prestressed post-tensioned (PT) concrete floors in buildings. To improve this situation, this paper describes modal testing, finite element (FE) modelling, and model correlation and updating of one such prototype floor. Advanced testing, correlation and updating technologies demonstrated in this paper were successfully transferred from mechanical and aerospace engineering disciplines where they are nowadays used as a standard design tool. Two structural configurations of the full-scale floor were examined: the bare floor in the unclad building, and the same bare floor but in the clad building with services attached underneath. Modal testing showed a considerable increase in stiffness in the latter case. The FE model correlation and updating exercise quantified this contribution and also demonstrated that bending of in situ cast concrete columns supporting the in situ cast concrete floor contributed significantly to the floor bending stiffness and, therefore, should not be modelled as pin-supports. Finally, wide and shallow band-beams, which often feature in PT floors, were shown to have considerable lateral stiffness. This feature has the potential to improve the floor's vibration performance, and was successfully modelled using orthotropic shell elements.