Simulating Analysis Of Hitting Effect On Piles' Dynamic Test

The vibration source is an important part in piles'dynamic test. However, the research on impulse by hammers lacks emulational computation domestically and overseas. Relevant characteristics and rules of vibration source, which have been verified in practice, are summarized by simulating the process of hammering with the help of an explicit dynamic analyzing program LS-DYNA.Firstly, the computation of the numerical solution of wave-equation using LS-DYNA is analyzed in this paper. The validity and superiority of this program is illustrated through the simulation of the wave propogation along piles. Secondly, the impulse curves in time and frequency domain are compared by changing hammers. Corresponding rules of hitting effect are summarized combining practical data and analytical solution of impulse. Suggestions about the making and using of hammers are put forward, and the fitting functions of impulse curves are also given. Besides the signals in time and frequency domain are compared with each other under the condition of different ratios of hammer to pile. The selection of the testing point and hammers to test different piles, the analysis of signals in frequency domain are also analyzed.The impulse signals in high strain dynamic testing are obtained by installing strain gauges on piles and by installing accelerometers on hammers. The rationality and accuracy of these two methods above are both analyzed in this paper. Furthermore, the focus is the influence of off-center hitting on acceleration and strain in different positions. The advantages and disadvantages of these methods are summed up, and some notices about sensors installation are suggested. Finally the exciting force of the super knockdown hammer for high strain dynamic testing which is designed by Guangdong research institute of building sciences is briefly analyzed.The hitting effect in piles' dynamic test is comprehensively simulated and researched in this paper. The research covers a wide field and is of great significance in both theory and practice.