NONLINEAR FINITE ELEMENT ANALYSIS OF FULL-SCALE EXTERNAL POST-TENSIONED CONCRETE BOX GIRDER AT JACKING AND SERVICE

Abstract

This paper presents the modelling of a 47-meter of simply supported full-scale external post-tensioned concrete box girder in a bridge using in-house software 3D-NLFEA. The Girder was designed with sections, adequate reinforcements, and the jacking force according to the codes to resist the live load. The objective of this work is to assess the global structural response i.e., the load and deflection capacity under service loading. The detailed response of anchorage and deviator segments concerning their micro-cracking behavior during jacking transfer and service load conditions was also discussed. The constitutive model of materials applied to the modelling covered the hardening and softening of concrete under tension and compression, the nonlinearity of mild steel reinforcement, and prestressing tendons. The first stage was to simulate the self-weight of the girder simultaneously with the application of jacking forces from the tendons. The second stage was to load the girder under three-point bending to replicate the typical wheel axle from vehicles. The load was in the form of displacement-controlled and it was applied at the top midspan. From the results obtained, it was shown that under service limit state conditions, the load-displacement curve of the girder was linear at elastic. Cracks in allowable limit manifested in several parts of anchorage and deviator segments by the end of prestressing sequences. This highlighted the importance of providing crack control reinforcement to alleviate the progression of cracks under jacking service load conditions.