Numerical Seismic Performance Assessment of Precast Pre-stressed Hollow-core Concrete Floors

Abstract

Precast pre-stressed hollow-core (PPHC) floors have been historically designed and constructed in ways that jeopardize their seismic performance. Particularly, early use of PPHC floors in ductile frames had support connections that were inadequate to accommodate earthquake deformations, making them prone to significant damage, and even collapse, at relatively low drift levels. While improved connection details were developed following past experimental research (Fenwick et al., 2010), concerns regarding the seismic performance of buildings containing PPHC floors have been raised following the 2016 Kaikōura Earthquake. In several cases, damage states observed were inconsistent with the failure modes identified by previous research (Henry et al., 2017), bringing into question the seismic assessment of buildings with PPHC floors, the residual capacity of the floors once damage has been sustained, and the effectiveness of existing retrofit techniques.

To address these concerns, a campaign of detailed nonlinear finite element (FE) analyses is proposed, with the overall purpose of improving the understanding of the likely behavior of PPHC floors during earthquakes and enhancing the ability to define and/or validate broadly applicable procedures for design and assessment. The campaign is organized in three phases corresponding to the following topics to be investigated: web shear strength of the PPHC units, drift capacity of support connections, and post-cracking behavior of PPHC diaphragms. The models developed during each phase will be validated against experimental data and then used to parametrically investigate key aspects of the performance of PPHC floors. Advances in the first phase are presented, for which, constitutive models, based on nonlinear fracture mechanics, have been used to numerically predict the shear strength capacity, evolution of shear stress distributions and crack patterns of PPHC units.