Amirkabir Journal of Civil Engineering

Amirkabir Journal of Civil Engineering

Evaluation of Strand Deboning as a Method for Controlling End-Region Damage in Pretensioned Concrete Girders

Document Type : Research Article

Authors
1 Faculty of Civil Engineering, Babol Noshirvani University of Technology
2 Department of Structural and Earthquake Engineering, Faculty of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran
3 Faculty of Civil Engineering,, Babol Noshirvani University of Technology
Abstract
Prestressed concrete is an effective solution for construction of flexural members under significant service loads, which can be pretensioned or posttensioned. In pretensioned concrete members, the transfer of prestressing force relies on direct contact between the prestressing steel and concrete. Modern pretensioned concrete girders employ thin webs and high levels of prestress. The transfer of the large stresses from strands to concrete in such cross sections results in cracking at the ends of the girders and causes concerns about their durability and load-carrying capacity, specially under shear-critical loading. This paper presents a numerical evaluation of pretensioned beams, in which end-region cracking is mitigated by means of strand debonding. Nonlinear, models of prestressed girders are developed to simulate the conditions of the member at the time of transfer and under loading until failure. The model was validated using strains and load-displacement curves obtained from experimental studies on full-scale girders. The structural behavior of the pretensioned girders was investigated using the validated model for debonding of all strands in lengths between 250 and 1000 mm or half of the strands for lengths between 250 and 3000 mm. Results showed that debonding of all strands up to a length of 250 mm or half of strands for up to 1000 mm would control cracking in the end region areas without affecting the load-carrying capacity. Greater debonding lengths cause serious damage to the girder under shear-critical loading and necessitates additional transverse reinforcement at the beginning of the fully bonded zone.
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