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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 2
T.E.T. BUTTIGNOL |
L.C ALMEIDA
Comparison between numerical and experimental models demonstrat-
ed a good approximation. A fragile collapse by concrete crushing and
pile cap concrete splitting occurred in all numerical models analyzed.
Prismatic struts were developed in all models. Added to this, ten-
sile stresses, which are responsible for concrete splitting, were ob-
served across the struts.
Stress flow within the pile caps was divided equally in two halves
on the inferior column cross-section and was propagated up to the
piles superior surfaces, where stress concentration occurred on
the pile’s cross-section area, close to the column.
Figure 12 – Tensile stresses [MPa] at the bottom of pile cap: (a) model 4; (b) model 5 (ATENA)
(a)
(b)
Table 9 – Ultimate load of numerical models
and Delalibera [1] experimental specimen
Model
Load (kN)
Delalibera [1]
1820
Model 1
1900
Model 2
1980
Model 3
1775
Model 4
2075
Model 5
1825
Figure 13 – Reinforcement bars stresses - (a) model 1; (b) model 2; (c) model 3; (d) model 5 (ATENA)
(a)
(b)
(c)
(d)
First cracks appeared in the inferior nodal zones and propagated in
direction to the superior nodal zone. Intensive cracks were devel-
oped with a rupture plane formation along the struts.
Principal tie stresses were not constant along the reinforcing bars.
An abrupt reduction in ties stresses was observed in the inferior
nodal zones due to favorable compressive struts action.
At the border of the ties steel bars stresses were very low or null,
which proves the non-necessity of hooks anchorage.
Splitting reinforcing bars contributed to pile cap’s ultimate load ca-
pacity increase and to crack control and reduction.
Steel bars adherence was not a relevant factor and did not influ-
ence in the pile cap’s resistance. In all models ties steel bars did
not slip until pile cap’s ruin.
6. Acknowledgements
To FEC-UNICAMP for the provision of the necessary tools to de-
velop this work. And to CAPES for its support to the first author’s
participation in the 52º Brazilian Concrete Congress which resulted
in an article publication and presentation which originated this paper.
7. References
[01] DELALIBERA, R. G. Numerical and experimental