# Effect of Pre-Damage on the Behavior of Axially and Eccentrically Compressed Concrete Cylinders Confined with PBO-FRCM

## TL;DR

This study examines how pre-damage affects concrete cylinders strengthened with PBO-FRCM under axial and eccentric compression.

## Contribution

The novelty lies in analyzing pre-damaged concrete elements confined with PBO-FRCM, a fire-resistant alternative to FRP composites.

## Key findings

- Pre-damage did not negatively impact the load-bearing capacity of PBO-FRCM confined concrete.
- Digital image correlation identified delamination in PBO mesh overlaps during testing.
- PBO-FRCM confinement improved deformability and ductility even in pre-damaged concrete.

## Abstract

In the case of strengthening building structures, the process usually involves elements that have a certain loading history and are typically subjected to loading during the strengthening process. In scientific research, on the other hand, strengthening is usually applied to elements that are not representative of real structures. This article presents a study of the effect of pre-damage on the behavior of eccentrically compressed concrete cylinders confined with PBO-FRCM (fabric-reinforced cementitious matrix with PBO fibers) composite. Concrete confinement introduces a favorable triaxial stress state, which leads to an increase in the compressive strength of concrete. FRCM systems are an alternative to FRP (fiber-reinforced polymer) composites. Replacing the polymer matrix with a mineral matrix primarily improves the fire resistance of the strengthening system. The elements were made of concrete with a compressive strength of about 40 MPa, which is typical for current reinforced concrete columns. Pre-damage was induced by loading the test elements to 80% of the average compressive strength and then fully unloading. The elements were then strengthened with three layers of PBO-FRCM composite and subjected to axial or eccentric compression with force applied at two different eccentricities. In addition to electric strain gauges, a digital image correlation system was used for measurements, to identify the initiation of PBO mesh overlap delamination. This study analyzed the elements in terms of load-bearing capacity, deformability, ductility, and failure mechanisms. In general, there was no negative effect of pre-damage on the behavior of the tested elements.