PREPROCESSOR FOR BOX GIRDER BRIDGE ANALYSIS

Abstract

Reinforced and prestressed concrete liok girder construction has been widely used world over for the construction of bridges and flyovers for their structural • efficiency - and pleasing appearance. Because of the Large inherent torsional' rigidity of such sections they are especially'. suitable for bridges curved in both plan and elevation and found to be highly economical for the medium and long spans in comparison to the conventional open girder sections. In the conventional design of box, girders, a. section of the bridge is assumed for the analysis apd.the.section.is checked 'for the maximum stress resultants.to ensure the safety of the design. It is almost impossible to guess-.a cross-section for a given span, width of roadway.and_pAher site conditions which is not only safe but involves the minimum amount of,construction Till nowl the choice of the initial cross-section of a R.C.. box girder has generally been a matter of experience as the enough and adequate guidelines are not available. The purpose of this work is to develop the preprocessor for the 'box girder bridge analysis using finite element method. Using preprocessor it is much easier and less time consuming to choose a box section for the given conditions using repeated trials. This preprocessor computer program *PREBOG* is compatible with an existing analysis program module 'SHELL'. 'PREBOG' is a preprocessor for single cell simply supported box girder bridge. It replaces the work .of preparing a data file which has voluminous data making it errerprone, time consuming and consequently making the repeated trials of the section a difficult task. It asks interactively a number of data, which are as least as possible in number. For better visualisation of the problem at different stages there must be adequate graphics support to present the required data/information in suitable pictorial views. Keeping this in view, program first shows the section we are going to analyse with all its dimensions, then there are provisions for a comprehensive meshed view of the girder, meshed bottom plan, top plan, diaphragms, sections along the span and the side elevation. To test the output of analysis module it draws the deflected shape along the C/L Of girder. Program is written in FORTRAN77 and PLOT88 is used for graphics. Its is compatible with PC386 or PC486. A sample problem is taken and solved using 'PREDOG'. Ori the basis of the time involved and easiness in inputing the data to PRFBOG vs direct input to 'SHELL' we can conclude the usefulness of the PREBOG. It is hoped that the PREPROCESSOR would be useful to the practising engineers in a big way.