Structural performance of axially loaded FRP-confined rectangular concrete columns as affected by cross-section aspect ratio

Abstract

Wrapping of concrete column using Fiber Reinforced Polymer (FRP) sheets can significantly improve their structural behavior. The aspect ratio of the cross section plays an important role on the efficiency of the applied strengthening technique. This research aimed, experimentally and analytically, to study the effect of aspect ratio on the obtained gain in strength and structural ductility. Also, the effect of both type and configuration of FRP wrapping is discussed. The obtained experimental results showed that the value of the aspect ratio has a significant effect on the gain in strength but it has no obvious influence on the obtained ductility. Moreover, based on the experimental results of 16 specimens concerning the load carrying capacity of FRP-confined specimens, a study to address the applicability of the analytical models (Egyptian code EC, American Concrete Institute ‘ACI’ code) proposed to predict the nominal compressive strength of rectangular columns confined with FRP sheets is presented in this research. Furthermore, this research introduces a modified model to deal with the FRP partial wrapping system. However both the examined models (ACI and EC) haven’t introduced any analytical models to predict the strength of RC columns confined partially with FRP wrapping sheets. The model proposed by ACI code showed an underestimation in predicting the nominal compressive strength, however that proposed by EC showed somewhat an acceptable estimation but inaccurate. Also, the modified expression suggested by the author dealing with columns confined with partially wrapped FRP sheets is examined in this research.