Abstract
This study was carried out to improve the windproof capability of vinyl film clad greenhouses. Generally, vinyl film clad greenhouses are often collapsed due to the strong winds, because they have very light weight structures. In such a case, as it is considered that the pile foundations are subjected to uplift and vibration at the same time, and an investigation on the uplift capacity of pile foundations by only the static load or the ground vibration is considered to possess several problems.
Therefore, this paper discribes the results of an experiment on the decrease of the uplift capacity of short piles under various conditions mainly being the frequency and acceleration of the horizontal vibration and pile length of embedment. The pile used in the pull-out test is a cylindrical concrete pile generally used in greenhouses, and it is subjected to some on uplift load before being vibrated by a vibrator, that is to say ; an uplift load less than the static ultimate uplift capacity (QS). Pile diameter is 43 mm and pile length of the embedment is from 20-40 cm. Pull-out tests were conducted for dry sand of soil placed at either a density of loose and dense.
From these results, the following conclusions were obtained: The dynamic ultimate uplift capacity of pile under horizontal vibration (QD) decreases far larger than in the case of a pile by the static load. The smaller the frequency is, the larger QD decreases. For the same frequency, the larger the acceleration is, the larger QD decreases. The rate of decrease in QD becomes smaller due to the increase in the pile length of the embedment and the unit weight of sand.
