| Summary: | Investigation of characteristics of structural elements using vibration
method has been widely applied, especially in predicting internal forces of the
elements by employing several theories that have been developed recently. In a
truss structure, which comprises many elements of angled cross section, an
eccentricity may take place due to the different position between centers of area
of angled cross section and connection, that might violate the existing vibration
theory.
Slender element of single angled steel of L.30.30.3 of 120 cm in length with
10 variations of support type that are pined, clamped and partly clamped were
tested under axial compressive load and applying the vibration method
simultaneously. Stage of loading was carried out at load intervals of 1 kN at
clamped-clamped and 0,5 kN for other type of support combinations. The natural
frequency at each stage of load interval was evaluated by considering beam
vibration theory of flexural, flexural-torsional and elastically constrained ends to
get the characteristics of end rotational stiffness.
The results showed that increasing the axial compressive load led to a
reduction of the natural frequency of the structure. The theory of end rotational
stiffness for pined (�=0) and clamped (�=�) are difficult to occur on the
implementation. Analytical value of the axial compressive force by the data
regression of the frequency for combinations of pined-pined, clamped-clamped
and pined-clamped provide better accuracy than that the preliminary data of the
frequency of the test results. The average relative error was indicated by 0,19%,
8,63% and 0,52% for pined-pined, clamped-clamped and pined-clamped
respectively. Statistically, the analytical value provides the Coefficient of
Variation (COA) of 0,2%, 10,2% and 1% for pined-pined, clamped-clamped and
pined-clamped, which proves the uniformity and the significance of the two sets of
the data.
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