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IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 1
J. E. CAMPUZANO | R. DE CASTRO
|
S. ÁVILA
|
G. DOZ
beams and, the requested negative time was obtained through the
model which considers the beams settings. Therewith, was per-
formed a checking on the useful height of the slab as well as the
dimensioning of the armors. The deflection calculated exceeded
the maximum standard recommended in approximately 10 mm,
considering an acceptable value, since the slab will be used as a
platform for dynamic tests.
3.2.1 Static, modal and transient analysis
With the final dimensions of the chosen platform, were performed static,
modal and transient analysis, considering the model on Figure 3.
For static analysis was considered the actuation of 16 people
spaced 1.5 m, each one with a weight of 800 N. In addition to
this loading, the analysis also considered the own weight of the
structural elements. In Figure 4 we can see the distribution of
point charges.
For modal analysis was considered the own weight obtained from
the physical characteristics listed in Table 2.
In Figure 5 are presented the first three mode shapes corre-
sponding to the first three natural frequencies of the structure, as
well as, the sixth mode shape corresponding to the sixth frame
frequency. For the first natural frequency is clearly noted that this
vibration mode is associated to the effects of vertical bending
of the slab. For the second and third natural frequencies of the
structure, are noted modes with lateral bending of the steel U-
type profiles, that´s due to low rigidity of profiles and lack of lock-
ing between themselves.
The sixth mode shape is characterized by torsion of the slab (ac-
cording to the mode of the slab only) and is shown in Figure 5.
For transient analysis was simulated a gym class with dy-
namic loading acting for 10 seconds with 16 people jump-
ing. The computation time was subdivided into time intervals
of 0,05 s. Was adopted a dynamic excitation frequency of 3.4
Hz, characteristic of the considered aerobic activities (CEB,
Figure 3 – Schematic drawing and general
measures of dynamic testing platform,
mounted at the Structures Laboratory
Figure 4 – Distribution of point charges
(static analysis and transient analysis)
and numbering of matching nodes
Table 2 – Approximated own weight
of the platform of dynamic tests
Material
Own weight
of each part
Steel base
0,447 kN
Steel Pilar type H
2,112 kN
U 4 inch Steel profile
2,595 kN
Steel profile W 200 x 19,3
2,264 kN
Stiffeners
0,045 kN
Shear connectors
0,126 kN
Concrete slab
74,820 kN
Approximate total weight
of the dynamic test platform
82,409 kN