Research Of Non-destructive Indicating Of Structural Instability Load And Load Identification Method Considered Moment Of Inertia And Additional Water

Working platform for the representatives of the ocean water engineering structures, are mostly complex, bulky and expensive. As the engineering project's needs, their pressure load often work with their depth and increase the weight of the upper structure of growing. Therefore, the possibility of buckling structure instability will also increase. In the early stage of structural design, how to know influence of pressure load on natural frequency and dynamic response of structures, how to forecast its instability load and after the completion of the structure, how to determine the structure of the instability load by non-destructive method for safety monitoring, are the main contents of this thesis.This paper aims to study the relationship between natural frequency of the square and the axial pressure of different vertical beam under axial load. Beginning With the general theory of continuum mechanics and the basic equations of elasticity, by Ritz Method and calculus of variations, the approximate expressions of the relationship between the axial pressure and natural frequency squared of compressed structure under six conditions including the compressed vertical beam with lumped mass attached to upper free end, the compressed vertical beam with platform concerned eccentricity and moment of inertia attached to Uupper free end, the compressed vertical beam with lumped mass attached to upper free end, and with elastic support, the compressed vertical beam with platform concerned eccentricity and moment of inertia attached to upper free end, and with elastic support, the compressed vertical flooding beam with lumped mass attached to upper free end and the compressed vertical flooding beam with platform concerned eccentricity and moment of inertia attached to upper free end have been obtained. Then use Kantorovich-Ritz Hybridization Method to improve the approximate solutions. Lastly, the approximate solutions and finite element solutions or experimental results have been comparatively analyzed and discussed.By comparing, a conclusion can be drawn that there is little difference between the approximate solutions and finite element solutions or experimental results. The precision can also meet the engineering requirements. Thus, an approximate linear relationship can be used to take the place of exact nonlinear relationship in the project. On this basis, by approximate linear relationship, the elastic buckling load of the structures can be identify as long as measured two kinds of natural circular frequency under different axial stress loadings by experiment.