Gemilerde bünyesel titreşimlerin incelenmesi

Özet

Kiriş olarak modellenmiş, büyük güverte açıklığına sahip gemilerde antisimetrik hareketler için titreşim analizi yapılırken eğilme ve burulma titreşim biçimleri bileşik olarak ele alınır Bunun nedeni kayma merkezi ile ağırlık merkezi arasındaki düşey uzaklığın büyük olmasıdır. Ayrıca açık en kesitli kiriş modellemelerinde burulma titreşim analizinde çarpılma etkisi de araştırılmalıdır. Örnek gemi görderi düzeltilmiş ince cidarlı kiriş olarak modellenmiş, böylece dönme ataleti, kesme şekil bozuklukları ve çarpılma terimlerini içine alan model kurulmuş, diğer bazı kiriş modellemelerine (Euler-Bernoulli, Rayleigh, Timoshenko, Düzeltilmiş Timoshenko ve İnce cidarlı) ait hareket denklemleri ile karşılaştırmalar yapılmıştır. Seçilen gemi model kirişine ait doğal frekanslar elde edilmiş ve dalgalı denizdeki tepkisel davranışları incelenmiştir.

Abstract

The examination of the antiymmetic motions of a flexible hull involves the formulation of stuctural dynamic theory defining the motions and distortions, and hydrodynamic theoy that describes the fluid action applied to a ship in waves. The structural dynamic theory is referred to the dry hull analysis and the ship is modeled as a beam with free ends vibrating in a vacuo in the absence of any external force and internal hull damping In the analysis of anti-symmetric vibrations of ships with large deck openings, the bending and torsional vibration behaviours are taken into account simultaneously due to the large vertical distance between the gravity and shear centres. Furthermore, the warping stiffness effect must also be investigated in the analysis of the torsional vibration of any beams with opened sections. In this paper, the ship was modelled as a modified thin walled beam and the model incorporated rotary inertia, bending deformations and warping stiffness. A generalised governing equation was derived to describe the ship motion. This equation can simulate the behaviour of Euler-Bernoulli, Rayleigh, Timoshenko and thin walled beam models through clearly defined parameter adjustments. Natural frequencies, response and behaviour of each selected ship beam models were comprehensively investigated and conclusions were derivedbased models. The cruising speed and heading angle for unit wave amplitude at resonating situation were determined then bending moment, shear force and torsional moment amplitudes were shown in graphics. resonance.