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Articles by Edwar Yazid
Total Records ( 2 ) for Edwar Yazid
  Edwar Yazid , Setyamartana Parman and Khairul Fuad
  In this paper, dynamic behavior of non-slewing-luffing crane type, namely gantry crane is investigated by introducing the flexibility of crane framework and hoist cable. The dynamic model of such system is obtained by modeling crane framework using finite element method and gantry crane system by using Lagranges equations. The equations of motion constitute nonlinear coupling terms between crane framework and crane system. The coupled dynamic equations are solved numerically using a combinational direct integration technique, namely Newmark-β and fourth-order Runge-Kutta method. Numerical simulations are carried out to obtain the open-loop responses as functions of limited set parameters for quite simple but representative for gantry crane system.
  Edwar Yazid , Mohd. Shahir Liew and Setyamartana Parman
  The purpose of this study is to propose and investigate a new approach for extracting spectral information of motion response of offshore structures. The approach is based on applying Time-varying Autoregressive (TVAR) model. This study is virtually unexplored in offshore engineering field. In the literatures, a number of works have shown that spectral content are extracted using Discrete Fourier Transform (DFT) for the frequency-domain analysis. Here, we outline a practical algorithm for TVAR model which uses Expectation-maximization (EM) algorithm based Kalman smoother. Short time Fourier transformation and Hilbert transformation are used as benchmark. The method is then applied to sampled discrete displacements of a fixed platform as a time series generated from field measurements. All the methods reveal that the spectrum characteristics of sampled platform displacement are time- varying frequency and time- varying gain distribution. The results indicate that TVAR model using KS with EM algorithm is superior to other methods in tackling frequency or amplitude modulation and systems that have low frequency dynamics. It is also found out that the mean frequency derived from the Hilbert transform is lower 8.2%, around 4.8% for short time Fourier transformation and 6.2% for TVAR model than the FFT spectrum.
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