Effects Of Vibration Duration Research Articles

An investigation of the contribution of vibration duration on subjective response to horizontal building vibration

As an evaluation method for evaluating the habitability to building vibration, the ISO 2031 series of international standards defines the VDV for transient vibration, in which the vibration duration is considered by time integration. The evaluation method for non-stationary-like vibrations in the guidelines for the evaluation of habitability to building vibration of the Architectural Institute of Japan (AIJ) also specifies a method to consider the effect of vibration duration on the evaluation. In this paper, laboratory experiments using an electrodynamic shaker were conducted to investigate the relationship between the subjective response regarding occupant habitability and the horizontal vibration of buildings caused by external vibration sources such as road traffic and railways. Binomial logistic regression analysis was used to quantify the effects of acceleration magnitude and vibration duration on the exposure-response relationship. The comparison of models with different proportions of occurrence (cutoff values) of subjective responses showed different effects of acceleration magnitude and vibration duration.

PENGARUH LAMA WAKTU PENGGETARAN ULTRASONIC BATH TERHADAP SIFAT MEKANIK DAN MORFOLOGI PATAHAN BIOKOMPOSIT PATI TAPIOKA/SERAT RAMI (BOEHMERIA NIVEA)

This study reported about mechanical properties and fracture surface of ramie fiber reinforced tapioca starch based biocomposites. The amount of fibers in matrix was kept constant at 10% from dry weight starch basis. Fabrication of biocomposites was solution casting. The effect of vibration duration from ultrasonic bath was 0, 15, 30, and 45 min. This treatment was applied to biocomposites while gelatinized. Tensile test was carried out to determine the mechanical properties of biocomposites. Fracture surface of biocomposites after tensile test was observed by using scanning electron microscopy (SEM). The result shows that, tensile strength increased when vibration time was added. The maximum tensile strength was obtained at 45 min vibration time with 2,84 MPa. This phenomenon was supported by SEM observation which indicate compact structure.
 Keywords: Tapioca starch, ramie fiber, biocomposites, mechanical properties, SEM

Factors affecting perception thresholds of vertical whole-body vibration in recumbent subjects: Gender and age of subjects, and vibration duration

Some factors that may affect human perception thresholds of the vertical whole-body vibrations were investigated in two laboratory experiments with recumbent subjects. In the first experiment, the effects of gender and age of subjects on perception were investigated with three groups of 12 subjects, i.e., young males, young females and old males. For continuous sinusoidal vibrations at 2, 4, 8, 16, 31.5 and 63 Hz, there were no significant differences in the perception thresholds between male and female subjects, while the thresholds of young subjects tended to be significantly lower than the thresholds of old subjects. In the second experiment, the effect of vibration duration was investigated by using sinusoidal vibrations, at the same frequencies as above, modulated by the Hanning windows with different lengths (i.e., 0.5, 1.0, 2.0 and 4.0 s) for 12 subjects. It was found that the peak acceleration at the threshold tended to decrease with increasing duration of vibration. The perception thresholds were also evaluated by the running root-mean-square (rms) acceleration and the fourth power acceleration method defined in the current standards. The differences in the threshold of the transient vibrations for different durations were less with the fourth power acceleration method. Additionally, the effect of the integration time on the threshold was investigated for the running rms acceleration and the fourth power acceleration. It was found that the integration time that yielded less differences in the threshold of vibrations for different durations depended on the frequency of vibration.