STUDY OF BENDING MOMENT CHARACTERISTICS IN BOX - GIRDER BRIDGES USING FINITE STRIP METHOD

Abstract

The box-girderbridge consists of a top and bottom flange connected by:vertical or inclined webs to form a cellular box-like section. The analysis: .of the box girder is complicated because of distortional charaCteristics of the box-section. However, various method of analysi=s:-are available but the method which is used for the analysis,. is, the'Tinite strip method, because this method gives quite realistic result with less data preparation. q Finite Strip.. method -a hybrid procedure which combines some of the advantages of serieSiution of orthotropic plates with finite elemsmoncept. This ill6thod proves adVantageous over vary versayje,finite element method-f6r the structures having regular geometry„and simple support cOndition. In the method used here, a loworder strip using a cubical polynomial function has been used. Whilst the deflection obtained have been almost always very good, discontinuity of members at strip boundaries exist, this can be removed or minimised by using more number of strips. This can also achieved by using higher order strips and introducing internal nodal line. Since the stiffness matrix and hence the computer time required for the convergence depends upon the no. of non-zero harmonic term taken. Since degrees of freedom at each node are defined, so it is only essential to know appropriate no. of harmonic term required for convergence. At the intermediate vicinity of point load, the stresses and moment obtained by the summation of a fourier series tends to converge very slowly and some time as many as fifty non-zero harmonic have to be taken before a converge solution is arrived at, on the other hand for stresses and moment at a small distance from the point load, hardly any change will be observed after 15 non-zero harmonics. Present work is devoted to the study of the convergence of the transverse bending moment in the box-girder bridges for different type of loadings with respect to the no. of terms and finer discretization. The study is confined to the two cell straight box-girder bridges, simply supported and both inclined and right angle web sections.