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IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 1
J. E. CAMPUZANO | R. DE CASTRO
|
S. ÁVILA
|
G. DOZ
4 Conclusions
It was designed and built a platform for dynamic tests consisted of
a reinforced concrete slab supported by steel beams and columns,
for experimental studies with people walking, dancing and jumping.
Initially were studied various platforms with several geometric fea-
tures, presenting fundamental frequencies below 5 Hz, in order
that the structure is strongly stimulated by loads induced by human
activities, which are characterized by frequencies in a range below
5 Hz. Moreover, was ensured that the second and third frequen-
cies were away from the first one, so as to avoid the phenomenon
of mode coupling.
Once chosen the final geometry, also taking into consideration the
constraints of space at the Structures Laboratory of UNB, began
the numerical analysis to obtain strains and stresses necessary to
design the platform.
The dynamic analysis of the platform was initially characterized
by a modal analysis, which provided the first three natural vibra-
tion modes of the structure and their respective frequencies. It was
noted that the first vibration mode presents a predominance of the
effects of the slab vertical bending. The following two modes are
characterized by lateral bending of steel U-type profiles, which
connect the pillars, due to the low stiffness of the profiles and the
lack of lock between them.
The numerical vibration frequencies associated with these modes
present values between 4.48 and 7.61 Hz Hz. The first value is
close to the frequencies generated by the dynamic loads from peo-
ple practicing physical activities. Therefore, we conclude that these
modes are likely to be stimulated in tests simulating gym exercises.
Following, were also performed the static and transient analyzes
simulating aerobic activities with a group of 16 people. We ob-
tained the static displacements of the slab and the ones caused by
the simulation of a gym class, and the points of the structure with
higher speed and vertical accelerations.
From the static analysis was noted that the moments of project
considered by Borges, [16], are superior to the moments of static
and transient analysis of this work. It is concluded, therefore, that
these meet the requirements for which will be used the dynamic
testing platform.
In the transient analysis were verified large deformations, due to
dynamic loading generated by simulations of people in jumping ac-
tivity during a gym class. It was also observed that from the central
region of the slab results the most requested, with higher speeds
and accelerations, which do not meet the consulted standards.
These accelerations have very high values compared to those re-
quired by the standards due to low stiffness that presents the slab
and the lack of ongoing support, among other factors. It is impor-
tant to make clear that the platform was designed and built with the
aim of presenting excessive vibrations for experimental studies.
The frequencies obtained experimentally showed results near to the
frequencies numerically calculated and, it is believed that the differ-
ences observed are due to the type of support considered in numeri-
cal analysis, crimping, which in practice is not a perfect setting.
5. Acknowledgements
The authors acknowledge the financial support from CAPES and
Professor Yosiaki Nagato for the collaboration throughout the work.
6. References
[01] FAISCA, R.G. Caracterização de cargas dinâmicas
geradas por atividades humanas, Tese de Doutorado-
COPPE/UFRJ, Universidade Federal do Rio de
Janeiro, UFRJ, Rio de Janeiro, Dezembro de 2003.
[02] RAMROTH, WILLIAM G. JR. Planning for Disaster,
How Natural and Manmade Disasters Shape the Built
Environment.
[03] THORNTON, C.H., CUOCO, D.A., VELIVASAKIS,
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(New York), 60 (11), 1990. pp 57-59.
[04] RITCHEY, JHON KENNETH, Application of Magneto-
Rheological Dampers in Tuned Mass Dampers for
Floor Vibration Control, Master of Science, Faculty
of the Virginia Polytechnic Institute and State
University, Blacksburg, Virginia, October 2003.
[05] WEBSTER, A. C. AND VAICAITIS, R. “Application of
Tuned Mass Dampers to Control Vibrations of
Composite Floor Systems.” AISC Engineering
Journal., 3rd Qtr, 1992, pp 116-124.
[06] BATTISTA, R.C., VARELA, W.D., Medidas corretivas
para vibrações de painéis contínuos de lajes de
edifícios, XXX Jornadas Sul-Americanas de
Engenharia Estrutural, Brasil. 2002.
[07] ANSYS, Swanson Analysis Systems,
Version 10.8.0.7, 2007.
[08] BACHMANN, H. Lively footbridges- a real challenge.
International Conference on Design and Dynamic
Behaviour of Footbridges – Footbridges 2002,
Paris, França.
Table 4 – Natural frequencies of the dynamic tests platform and error percentages
regarding the experimental frequencies
Frequency
No
Experimental
Frequencies
Frequencies
Solid65 and
Solid45
Frequencies
Shell63 and
Beam4
Solid65
and
Solid45
Shell63
and
Beam4
f1
4,20 Hz
4,48 Hz
3,83 Hz
6,67%
8,81%
f2
7,23 Hz
7,11 Hz
5,84 Hz
1,66%
19,23%
f3
8,30 Hz
7,61 Hz
6,32 Hz
8,31% 23,86%