COMPUTER AIDED DESIGN OF FLEXIBLE PAVEMENT BASED ON IRC-37, 1984

Abstract

The primary object of the flexible pavement design is to determine composition and the thicknesses of different layers so that the pavement structure is strong enough to resist the action of traffic without any distress. There are several methods in practice for the design of flexible pavements all over the world but highway flexible pavements in India are designed according to IRC-37,1984, (First Revision). The method given in code of practice is manual and thicknesses of different layers are determined by repetitive use of curves drawn for this purpose. The scenario of the computer applications in civil engineering is at drastic veer and it is more true in relation to CADD. The use of CAD has many advantages like easy display, increased accuracy, large storage facilities, quick retrieval and easy modifications to old design. Many softwares related to pavement design are available in international market. These packages being hardware-specific cannot be used on the IBM compatible systems. Also, there are the difficulties in adopting these softwares in India due to different conditions prevailing here. Therefore, the solution lies in indigenous development of packages in a number of modules to be finally integrated. Keeping in view the above aspects, a generalised and user-friendly package for the design of flexible pavement, based on IRC-37,1984, has been developed. In this study, this software package consists of three separate programs viz. IRC37, PLOT and GRAPH. Program IRC37 written in FORTRAN 77 designs the flexible pavement based on IRC-37, 1984 and includes the features of interactive data entry, checking on invalid inputs and warning message for the data exceeding their maximum or minimum limit. When data on axle load spectra on a highway is available, program IRC37 calculates Vehicle Damage Factor (VDF) based on AASHO equivalency factors and also provides more informations about the axle load spectra. This salient feature of program IRC37 is beyond the scope of IRC-37,1984. Programs PLOT and GRAPH utilise PLOT 88 graphics library for drafting purposes. Progam PLOT is used to display or make a hardcopy of the cross-section of the flexible pavement designed by program IRC37, on any of the plotting devices. Program GRAPH is used to display or to make the hardcopy of the histograms for the axle load distribution, proportion of the damaging effects and gross vehicle weight distribution for the traffic data collected on the axle load spectrum on the highway. This software can be run on any of the IBM compatible systems and all currently popular graphics adaptors