ALP Response and Stability
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CHAPTER 5 Response and Stability Analysis of Articulated Leg Plateform 5.1 Introduction As discussed in the literature review, stochastic response and stability analysis of Articulated Leg Plateform (ALP) using probability domain technique have not been investigated so far. Although the nonlinear response of ALP to random waves have been studied by various investigators [Datta and Jain (1990), Choi and Lou (1991), Gottlieb et al. (1992), Bar-Avi and Benaroya (1996)] using both time and frequency domain techniques using different mathematical modelings. However, most of the investigators ignored the hydrodynamic damping in their study. ALP has low frequency and size of excitation is also significant. Formulation of the problem in probability domain by modeling ALP as a SDOF system is complicated because of its buoyancy effect and wave induced drag nonlinearity. In the present chapter, ALP is modeled as a SDOF nonlinear oscillator considering the rotation of tower at the base as only degree of freedom. The hydrodynamic loading and the consequent drag induced nonlinearity is expressed in such a way that probability domain technique can be applied. Two ALP problems are analyzed for different significant wave heights to show the effect of various parameters on the response and stability of the system. 5.2 Theory 5.2.1 Assumptions The articulated tower as shown in Fig. 1a is idealized as a rigid column with single degree of freedom as angular rotation at the base hinge. Fig. 2 shows the mathematical model of tower. For the formulation of t he problem, the following assumptions are made
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