Relation between a Decrease in the Uplift Capacity and Amplitude of Short Piles Subjected to a Horizontal Vibration

Study on the windproof characteristics of a greenhouse

Abstract

In the previous report, the results of a study on the uplift capacity of short piles subjected to various conditions on the frequency and acceleration of horizontal vibration and pile length of embedment were presented.From these experiments, we were able to conclude that the uplift capacity of a pile subjected to horizontal vibrations (Q_D) was much smaller than that without any vibration.The larger the loading weight was, the smaller the frequency, and the larger the acceleration was, the larger Q_D decreased.
We supposed that the matters described above have some close relationship to the horizontal displacement amplitude of a pile.
In this report, so that, we investigated the connection between the decrease in the uplift capacity and amplitude.In these experiments, a pile with a diameter of 43 mm and length of embedment of 20-40 cm, was set into dry sand of two densities: loose and dense.The vibration characteristics for the control had a frequency of between 5-20 Hz with a maximum acceleration of between 50-200cm/s².
From the results of the investigation, the following conclusions could be obtained: The decrease in the uplift capacity of the piles subjected to a horizontal vibration was closely related to the horizontal displacement of the piles.That is to say, the larger the amplitude was, the larger the decrease in the uplift capacity.The reason why the amplitude decreased as time passes was thought to be due to the fact that the sand around the piles became compacted due to the vibration of the piles.