Prestress Loss of CFL in a Prestressing Process for Strengthening RC Beams

Xinyan Guo,Xiaohong Zheng,Peiyan Huang,Dong Liu

doi:10.1155/2017/3832468

Abstract

A prestressing system was designed to strengthen reinforced concrete (RC) beams with prestressed carbon fiber laminate (CFL). During different prestressing processes, prestress loss was measured using strain gauges attached on the surface of CFL along the length direction. The prestress loss was 50–68% of the whole prestress loss, which is typically associated with CFL slipping between the grip anchors. Approximately 20–27% of the prestress loss was caused by the elastic shortening of the RC beam. An analytical model using linear-elastic theory was constructed to calculate the prestress loss caused by CFL slipping between the anchors and the elastic shortening of the strengthened beams. The compared results showed that the analytical model of prestress loss can describe the experimental data well. Methods of reducing the prestress loss were also suggested. Compared to other experiments, the prestressing system proposed by this research group was effective because the maximum percentage of prestress loss was 14.9% and the average prestress loss was 12.5%.

Highlights

The application of bonded fiber-reinforced polymer (FRP) to the surfaces of concrete members provides an efficient, lightweight, and noncorrosive alternative to other repair methods
The prestress loss caused by the carbon fiber laminate (CFL) slip was 50–68% of the whole prestress loss, while 20–27% of the whole prestress loss was caused by the elastic shortening of the reinforced concrete (RC) beam
From (5) to (10), the ratio of prestress loss caused by elastic shortening of the RC beam to the prestress on CFL

Summary

Introduction

The application of bonded fiber-reinforced polymer (FRP) to the surfaces of concrete members provides an efficient, lightweight, and noncorrosive alternative to other repair methods. During the process of applying prestress to the plate, sheet, or laminate and bonding the prestressed FRP to an RC member, initial prestress loss was always generated [6, 7]. Diab et al [9] utilized the second prestressing system to investigate rectangular beams bonded to prestressed FRP sheets, including anchored or unanchored FRP sheet ends. Quantrill and Hollaway [3] carried out an experiment on strengthening RC beams using prestressed FRP plates with prestress levels ranging from 21.7% to 46.3% of their strength. An experimental study was carried out to investigate the short- and longterm prestress loss law using the second prestressing system described above and the FRP wrapping arrangement at the ends of FRP.

Experimental Program

Experimental Results and Discussions

Analytical Model of Prestress Loss

Conclusions