A new testing procedure to quantify unfavourable environmental effect on mechanical performance of composite reinforcement system

Abstract

Current technology development ensures a variety of material types for reinforcing and strengthening concrete structures. However, the absence of a uniform testing methodology complicates quantification (and comparison) of the mechanical performance of the composite reinforcements. In addition, the necessity to quantify the long-term degradation of the mechanical resistance intricates the issue. This research employs the equivalent residual stiffness approach to measure structural performance. It adapts a recently developed testing layout and a simplified analytical model to analyse the residual flexural stiffness of standardised laboratory specimens. The developed analytical model explicitly relates the particular moment and curvature values, requiring neither iterative calculations nor the load history. This feature allows the comparative analysis and quantification of the residual stiffness of the repeatedly loaded composite elements with varied reinforcement materials’ layouts. The previous short-term tests identified the efficiency of hybrid systems employing fibre-reinforced polymer (FRP) materials and steel bars. However, the FRP components can be vulnerable to ultraviolet radiation, humidity, freezing-thawing cycles, and elevated temperature. Thus, this study includes 34 composite beams subjected to the service load. After that, the reference specimens were stored in laboratory conditions; the alternative samples, exposed to the open air outside the building, estimated the environmental effect on the stiffness decay. This manuscript reports the partial results of the ongoing test program.