# Easy Prestressing of FRP for Strengthening RC Beams: Experimental Study with an Analytical Approach

## TL;DR

This paper presents a new manual device to apply prestress to fiber-reinforced polymer (FRP) for strengthening concrete beams, showing improved load capacity and bond performance.

## Contribution

A lightweight, manual prestressing device (EPM) and an analytical model for predicting beam behavior with FRP strengthening are introduced.

## Key findings

- The EPM device successfully applied up to 10% prestressing to FRP, improving beam performance.
- FRP strengthening with anchorage and prestressing increased load capacity by up to 45%.
- The analytical model showed strong agreement with experiments (Pearson correlation >90%).

## Abstract

This study investigates strengthening reinforced concrete (RC) beams using fiber-reinforced polymers (FRPs). Nine samples were cast and strengthened with varying parameters, including the width, number of laminates, use of anchors, and application of prestressing. A novel device—the easy prestressing machine (EPM)—was developed to apply prestress. The EPM is lightweight and operable manually, enabling up to 10% prestressing. All specimens were tested under three-point bending until failure, and load-displacement curves were recorded. An analytical method based on curvature increment and incorporating material nonlinearities is also proposed to estimate the load-displacement response of RC beams with and without FRP strengthening. Both experimental and analytical results are presented and compared. The analytical model strongly agreed with the experimental results, showing Pearson correlation coefficients exceeding 90% for most specimens. According to the experimental findings, applying FRP, particularly when combined with anchorage and prestressing, increased the load-bearing capacity by up to 45%. Anchorage and prestressing effectively mitigate premature debonding, with prestressing showing a more pronounced impact on enhancing bond performance and load capacity. Based on the results, conclusions regarding the analytical model, structural behavior, and optimal strengthening strategies are discussed.