Nonlinear Finite Element Analysis of Reinforced Concrete Slab-Column Connections with Headed Stud/Bolt Shear Reinforcement Subjected to Punching Shear
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Date
2022-08-29
Authors
Beaulieu, Patrick Michel
Advisor
Polak, Maria Anna
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
While many experimental tests have been conducted by various researchers on the punching behaviour of
reinforced concrete flat slabs supported on columns with headed stud/bolt shear reinforcement, there are
still many parameters which have not been adequately studied in the laboratory due to cost or time
constraints. As a result much of the current code provisions for designing slab-column connections
against punching shear are based on empirically derived formulations based on tests of partial scale
isolated slab-column specimens. Researchers such as Genikomsou and Polak (2015), Navarro et al
(2018), and Lapi et al (2020) have proven that these experimental tests can be supplemented using
properly calibrated nonlinear finite element analysis (NLFEA) models in the commercial software
ABAQUS.
In this thesis a three-dimensional NLFEA model is calibrated using interior slab-column connection
specimens tested by Adetifa and Polak (2005) in concentric punching and exterior slab-column
connection specimens tested by El-Salakawy et al (1998, 2000) in punching with unbalanced moment.
This calibration uses the concrete damaged plasticity (CDP) model in ABAQUS, and includes discussion
of the main parameters which influence the CDP model and values used in this calibration. The
calibration also includes a study conducted to determine how to effectively model the shear reinforcement
and shear reinforced area based on the “stem-star” method used by Genikomsou and Polak (2016). This
includes a detailed analysis of the modelling of the shear stud star (S3) diameter to ensure enough
rotational capability was provided in the shear reinforced region of the slab without significantly reducing
the predicted capacity of the model. Through this study it was determined that a gap of 6-10mm should be
provided between the column face and the first S3, and that the S3 diameter of subsequent rows of shear
reinforcement had a negligible effect on connection behaviour. Additional effects such as changing the
moment-shear ratio and the effect of adding openings near the column were also considered during
calibration.
These calibrated models are then used to conduct several parametric studies on parameters related to the
shear reinforcement in the specimens. Three parametric studies are presented in this thesis. The first study
investigates the effect of changing the number of shear reinforcement rows and the spacing between
adjacent rows of shear reinforcement. In this study it was determined that the total shear reinforced area
has a larger effect on the connection than the number of reinforcement rows, and that when spaced
between 0.75d and 1.5d no inter-stud punching could occur in any of the models.
The second study investigated the effect of changing the size and number of openings adjacent to the
column, and the change in placement of shear reinforcement which must occur as a result of the opening
changes. This study determined that 90% of the connection capacity was maintained when the opening
width to column width ratio was 0.6 for two openings and 0.33 for four openings. This study also
determined that providing stud rails outside of the openings in a double-cruciform arrangement has no
significant effect on the behaviour of the shear reinforcement when compared to their usual placement.
Finally, the third study investigated the impact of anchorage-controlled shear reinforcement, which was
proposed by Topuzi et al (2017) to increase the ductility of slab-column connections under cyclic loading
without inducing higher lateral stresses in the connection, on the overall capacity of the connections. In
this study it was determined that the inclusion of anchorage-controlled shear reinforcement results in less
than a 10% drop in concentric punching connection capacity for all considered connections, and therefore
could be suitable for inclusion in slab-column connections as proposed by Topuzi et al (2017).
Description
Keywords
Finite Element Analysis, Reinforced Concrete, Punching Shear, Shear Reinforcement, Numerical Modelling, Flat Slabs