M. A. Lotfollahi Yaghin, K. Farzad and M. Naghipour,
Volume 23, Issue 1 (7-2004)
Abstract
Similar to random sea waves, forces on the offshore structures due to waves are random. These forces can be mainly divided into two components, namely, inline forces and transverse or lift forces. The random nature of lift forces is more complicated than that of inline forces and both should be combined for design purposes. In the present paper, two different approaches have been used to determine time series of lift forces. Along these lines, the determination of lift coefficients is discussed which have then been used to obtain transverse forces and compared with experimental data. The experimental data used in this study were collected at Delft Hydraulics Laboratory on a full-scale rough vertical cylinder.
F. Hosseinlou, A. Mojtahedi , M. A. Lotfollahi,
Volume 36, Issue 1 (9-2017)
Abstract
An important requirement in design is to be able to compare experimental results from prototype structures with predicted results from a corresponding finite element model. In this context, updating the model using measured vibration test can lead to proposing a desired finite element model. Therefore, this paper presents indirect and direct based numerical updating study of a reduced scale four-story spatial frame structure of offshore jacket platforms constructed and tested at the Structural Dynamics and Vibration Laboratory. Besides, the selection procedure for inactive degrees of freedom in the process of reduced model is evalated, with a reasonable criterion, by using sensitivity analysis of system response under base excitation. This performance leads to faster convergence of iterative algorithm and also, eliminates spurious modes. Since the significant problem fundamental to dynamic structural analysis is the amount of time and cost required for computation, the use of these methods will save both in time and cost.
