Page 30 - Riem-Vol6_nº3

382 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
Numerical and experimental study of a waffle slab designed to serve as a tennis court floor
Fig. 15 shows the distribution of bending moments obtained using
both numerical models, compared to the estimates of bending mo-
ments derived from the experimental data obtained at location E1.
Both numerical models present a similar shape, indicating maxi-
mum positive bending in the loading area and maximum negative
moment in the solid slab region.
At location E1, the bending moment obtained experimentally using
uncracked section with measured εs close to the values predicted
by the numerical models, indicating a possible beginning of crack-
ing around this section.
Both models indicate a negative moment between the ribs and the
edge beams. The value indicated by the model in FE is, higher.
This difference is probably due to the fact that this model considers
the top slab as a continuous plate, generating greater clamping ef-
fect on the edge beam, when compared with the grid model.
Moreover, the FE model presents peaks of negative moments that are
muchmore pronounced in the solid slab regions. This divergencemay be
associated to the different modeling of the solid slab regions in the soft-
wares. At these locations, unfortunately no experimental data was col-
lected, which could allow for a better assessment of the most adequate
modeling for those connections and the influence of the solid slabs.
5. Conclusions
This study presented a comparative analysis between numerical
and experimental results obtained for a reinforced concrete waf-
fle slab designed to serve as a floor for tennis courts. The results
indicate that, with the two numerical methods used, grid matrix
analysis and finite elements, there are still issues that require fur-
ther studies. The results also show the importance of undertaking
experimental studies with the aim of verifying and adjusting the
numerical models, particularly when new elements are adopted.
The main conclusions are:
1. The results of the numerical analysis of the waffle slab system,
obtained through the grid analogy, represented here by the
TQS software, show that modeling by this method is very effec-
tive, as long as the actual values for the moment of inertia are
used with no reduction in the ribs, slab and beams, and rigid
connections between the structural elements.
2. The finite element model, conceived in the SAP2000 software,
proved to be equally adequate. However, when compared with the
simplicity of an analogy to grids, the FE model proves to be very
laborious, and difficult to use in the daily routine of design firms.
3. The grid analogy results in negative moments both in the slab-
edge beam connection and in the solid slab regions lower than
those indicated by the finite element model. This difference in
results may be related to the different modeling adopted by
each computer program. Therefore, it is important the collection
of experimental data that help define which of the models best
represent this particular aspect of the behavior of a waffle slab.
6. Aknowledgements
The authors would like to thank CNPq (the Brazilian Research Council)
and the companies Projetak - Tavares Eng. Associados S/C Ltda and
Construtora Tedesco for the support they have given to this project.
7. References
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Figure 15 – Moments: SAP, TQS and experimental:
bending moment along line A shown in Fig. 6