압출가설거더의 휨모멘트 최소화를 위한 압출노즈의 개선된 설계기법 연구

Abstract

ABSTRACT

A Study on Improved Design Techniques for the Launching Nose Minimizing the Bending Moments of Launching Girder by

Joung Sun Lee Doctor of Philosophy in Civil Engineering Graduated School, Hanyang University August 2013

Dissertation Supervisor, Professor Dong-Ho Choi

In the application of incremental launching method, it is the most important how the launching girders and nose can be designed economically. However, in practice, the noses have been designed with about 60~70% of the maximum span length of girder and approximately 10% of girder weight based on the experience. Because of no rational design method, the sections of girders are unnecessarily big and time is wasted for the analysis of construction stage. The nose-deck interaction system is related with the relative ratios of length and flexural stiffness of nose to girder as a geometric and mechanical property. The loadings significantly influencing the nose-deck system are the relative nose weight and the relative diaphragm weight to girder as mechanical loadings and the temperature gradients and the misplacement of launching bearings as non- mechanical loadings. These loads except the nose weight have not been included not to make the model complicate excessively in Rosignoli Model (1998); however, in practical applications, it need to account these loadings. Using the theorem of three moments, this thesis develops the improved theoretical model of the nose-girder systems to make it more realistic, which is composed by four dimensionless parameters, such as the relative flexural stiffness, the relative nose length, the relative nose weight, and the relative diaphragm weight. Through intensive parametric studies of the theoretical model and surface fittings for the design equations, this thesis proposes the techniques of designing launching nose for minimizing launching girder bending moment. As the diaphragm weight acts on the connection of nose and girder, the maximum negative bending moment occurs not at the end point but somewhere near the middle of the second phase of launching. Therefore, the negative bending moment at the ending point of the first phase of launching should be same as the maximum negative bending moment during the second phase of launching to minimize the negative bending moment of girder during launching. According to the improved theoretical model, the maximum positive bending moment at the first span occur at the launching nose, the nose-girder joint section, and the launching girder in order as launching not like always on the girder (Rosignoli, 1998). The results of positive bending moment could be used for the design of the launching nose. Not only the negative moment but also the maximum positive moment and reaction of girder are minimized under the condition of minimizing negative bending moment. The launching bending moments and reactions are efficiently controlled by installing the launching nose designed by improved design method. Finally, applying only the improved design method is enough to design the girder by the incremental launching method to be safe and economical. So it can be eliminated the complicated calculations of the launching girders.