Time-dependent behavior of full-scale precast post-tensioned (PCPT) girders: Experimental and finite element analysis

Abstract

Excessive volumetric changes associated with shrinkage and non-uniform moisture and heat distribution along long-span girders induce unwanted curvatures. This study aims at investigating both short- and long-term measurements of various quantities involving midspan deflections, tendon strains, longitudinal steel bar strains, concrete strains, and thermal changes in precast-post-tensioned (PCPT) girders. A total of 2 PCPT girders were cast in this study with symmetrical structural and geometrical details. Post-tensioning of the first and second girders was performed on the 28th and 120th days of their casting, respectively. Long-term measurement was performed on the first girder. It was observed that all measured parameters increased swiftly during post-tensioning. During the initial 30 days after post-tensioning, a gradual increase in all parameters was observed, whereas all measured parameters exhibited negligible increase beyond that. A Finite Element Model was generated using ATENA to estimate short-term deflections of PCPT girders during post-tensioning. In general, a good agreement between experimental and analytical midspan deflections was observed.

Keywords

• Pre-cast concrete
• Post-tensioned
• Long-term deflection
• Finite element analysis