tailieunhanh - Simulation and computation of oscillation and stability of hammer pontoon systems

The ambient exciting loads are regarded as deterministic forces and as stochastic ones. In the latter case, the load is given as spectral density function and it is necessary to calculate probability characteristics of system responses. An example is investigated for illustration. | Vietnam Journal of Mechanics, NCST of Vietnam Vol. 22 , 2000 , No 1 (39 ~ 46) SIMULATION AND COMPUTATION OF OSCILLATION AND STABILITY OF HAMMER-PONTOON SYSTEMS NGUYEN CAO MENH, NGUYEN VAN DAC, VU TAN KHIEM, HOANG NGA Insti"tute of Mechanics, 264 Doi Can, Hanoi ABSTRACT. Hammer pontoon systems are usually used for pile-driving of onshore construction. The systems are constantly acted upon by marine wave, wind and current and have to be fixed by moorings. In this paper, on the basis of software ALASKA the system is simulated as dynamics of multi-body systems . Its natural frequencies and mode shapes are computed in order to avoid resonant phenomena by the change of design parameters . The vibration displacement at any point of the system is calculated for estimation of technical stability of the system. The reaction forces at joints between bodies and its inertial forces are obtained for calculation of system strength of material. The ambient exciting loads are regarded as deterministic forces and as stochastic ones. In the latter case, the load is given as spectral density function and it is necessary to calculate probability characteristics of system responses . An example is investigated for illustration. 1. Introduction A Hammer-pontoon system consists of a pontoon, a hydraulic hammer, a hammer-tower creating the direction for motion of the hammer and some equipment for its working such as pile-driving or changing working places (rig. 1). When the hammer-pontoon system is working, it is fixed by moorings and the hammer-tower is in high position, otherwise the hammer-tower is in lower position. The hammer-pontoon system is usually used for foundation pile-driving of onshore construction. The system is always under action of waves, wind and current. On the basis of software ALASKA (Advanced Lagrangfan Solver in Kinetic Analysis) developed by Institute of Mechatronics, TU-Cheriinitz, Germany, the hammer-pontoon system is modeled as dynamics of multi-body system