ANALYTICAL DESIGN OF OVERLAYS USING FINITE ELEMENT METHOD (SAP'90 PROGRAM )

• Main Author: Sunar Wibowo, Anton
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/2871
• Institution: Institut Teknologi Bandung

ANALYTICAL DESIGN OF OVERLAY USING FINITE ELEMENT METHOD (SAP'90 PROGRAM), Anton, 1996, Program Magister Sistem dan Teknik Jalan Raya, Program Pascasarjana, Instatut Teknologi Bandung. An analytical approach to overlay design requires characterization of the existing pavement layers, primarily in terms of thickness and modulus of elasticity. The modulus of individual pavement layers and the subgrade are obtained by backcalculation, a process that utilizes measurements of pavement surface deflection. Calculated values of surface deflection can be determined by multi-layered linear elastic theory or by the finite element method. The procedure then is to iteratively adjust layer modulus values until there is convergence of measured and calculated deflections. In the investigation described in this thesis, the finite element programme SAP'90 was used to analyse pavement response to traffic load in terms of stress, strain and deflection. Measurements of pavement surface deflection were obtained using a Falling Weight Deflectometer. The first phase of the investigation was to analyse 3 pavement structural systems and to compare stress and strain values calculated by SAP'90 at different depths in the pavements with the output from two other programmes, BISAR and DEFPAV. Surface deflections calculated by SAP'90 and DEFPAV were also compared. Stress and strain values calculated by SAP'90 were in good agreement with BISAR calculations but significant differences were apparent in some cases in the comparison with DEFPAV calculations. Surface deflection profiles given by SAP'90 and DEFPAV were in good agreement, giving a maximum difference of about 11 % at the location of maximum deflection. A programme, MODULI,. was developed for backcalculation of layer modulus. This programme incorporates an optimization technique, utilizing the Nelder and Mead algorithm, to minimize the objective function defined as 1 Ac T Structural response was determined using SAP'90 and modulus values calculated by MODULI are presented for a range in values of maximum surface deflection. A programme OVERCALC was then developed for calculation of overlay thickness using layer modulus values determined from MODULI. The structural response is calculated by SAP'90 and Miner's hypothesis is used to quantify cumulative damage due to traffic load. In the analysis the pavement is modelled as a 4-layer system. Design criteria are tensile strain at the underside of the existing asphalt layer and vertical compressive strain at the surface of the subgrade. Overlay thicknesses determined using the computer programme MODULI and OVERCALC appear to be reasonable