| As a global phenomenon of natural disaster,earthquake has brought great impact to the people's lives and property and social economic construction.Our country is located between two largest seismic zone among the world,especially many large coastal ports and terminals along the eastern coast in the earthquake-prone areas.With the rapid growth and development of international shipping industry,the port throughput continues to expand which has brought serious potential security risks to bridge-type grab ship unloader,the main equipment of bulk-cargo in the port terminal accompanied by the total improvement of scale and efficiency.For the moment,the study of bridge-type grab ship unloader is mainly focused on the analysis of the characteristics of structural fatigue and static strength,lacking of comprehensive study on seismic response characteristics and damping type of ship unloader under seismic excitations.In this paper,a bridge-type grab ship unloader is selected as analysis object and the seismic behavior of the ship unloader under the basic seismic intensity of 7 degree are investigated through numerical simulation.Besides,the vibration damping effect of ship unloader under earthquake through the corresponding damping method is studied based on the dynamic characteristics of ship unloader and the vibration and the stress-strain of the ship unloader with damping type are analyzed comprehensively.The detailed researches in this dissertation are summarized as follows:(1)Based on the structural features,working parameters and the material of the structure,a simplified design method for ship unloader metal structure was proposed.By use of the static analysis,the displacement response,stress response and stability of wheel pressure under different working conditions and seismic loads of both longitudinal and transverse are detailed and comparative studied in order to make clear the damage mode and important position of ship unloader under earthquake.(2)On the basis of the court sorts division and structural vibration characteristic,typical seismic wave records and the anti-quaking design reacting spectrum in the proposed project site were chosen and design according to the crane design specification(GB/T 3811-2008),the strength,stress and strain behavior of the ship unloader under seismic loads of both longitudinal and transverse are studied by the response spectrum analysis and the time history analysis.In addition,the test results dynamic response characteristics under equivalent static analysis,seismic response spectrum and time history analysis are compared and analyzed.The research verifies the fact that the ship unloader can satisfy the requirement of seismic fortification intensity and ensure the correctness of the design of steel structure.(3)According to the theory of structural vibration control,combined with the response characteristics of the ship unloader under seismic intensity of the earthquake,the seismic design method for bridge-type grab ship unloader was proposed with the vibration frequency and horizontal stiffness and viscous damping of the shock absorber as the object.Besides,the damping effect of the ship unloader is analyzed by numerical simulation and the vibration and stress tests of the ship unloader after the shock absorber are carried out in the continuous operation.The experimental results show that the method has good effect and reduces the seismic response effectively and the ship unloader has good performance under continuous working condition after shock absorption.This paper systematically studies the dynamic characteristics and seismic performance of the ship unloader under basic seismic intensity of 7 degrees and the damping method of ship unloader was studied on the basis of research and experiment with improving the seismic performance of the structure.The paper has certain reference significance to seismic analysis and vibration reduction of the bridge-type grab ship unloader. |
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