Review Study on the Durability of FRP-Confined Concrete

Abstract

The use of fiber-reinforced polymer (FRP) composites has recently experienced a steep increase in civil engineering applications because of the high mechanical and low-density properties of such materials. Over the last few decades, concrete columns externally confined with FRP sheets have been widely investigated for their use in structural rehabilitation and the seismic strengthening of civil constructions. There is much scientific literature based on experimental results and analytical or empirical theoretical models. In fact, several numerical models and analytical procedures are able to predict the behavior of FRP-confined structural elements subjected to axial or seismic loads, and researchers worldwide have experimentally studied and analytically calibrated a wide range of significant variables. Nevertheless, there are still few results concerning the durability of FRP-confined concrete exposed to severe environmental conditions, despite being an important issue in design and safety assessment. The objective of this study is to raise awareness about the durability of FRP-confined concrete. To do so, the authors collected and analyzed the results of approximately 760 pure axial compression tests, taken from 17 different experimental studies published in the scientific literature, in order to present a critical comparison between the results of experimental studies and the theoretical models provided by design guidelines and codes. The study was conducted according to the following steps: first, experimental data available in the literature were collected; second, FRP-confined concrete cylinders subjected to axial load were classified according to the different experimental variables investigated (mainly according to the type of environmental agent to which they were exposed); third, experimental results were compared with international provisions for the design and construction of externally bonded FRP systems for strengthening concrete structures. Finally, the strength and limits of the technical codes were analyzed in terms of safety factors, and the formulation of a design equation in the short and long term was critically examined.