Crack Monitoring during Load Testing of Full-Scale Dapped-End RC Beams with Varying Reinforcement Layouts

Abstract

Reinforced concrete structures from the 1970s and 80s are reaching the end of their service life, with critical zones, such as dapped-end (DE) regions found in Gerber-type bridges, showing increased vulnerability to deterioration. These regions, characterised by geometric discontinuities, are prone to damage due to the combined effects of mechanical loading, consequent cracking, and environmental exposure. As part of a larger research project investigating the interaction between corrosion, sustained loading and mechanical resistance, this study presents the first experimental phase, focused on the short-term mechanical behaviour of full-scale DE beams and, in particular, on the development of the crack patterns. The primary objective of this phase is to establish a reliable mechanical reference for the subsequent long-term experimental campaigns, which will encompass corrosion and creep effects. A combination of traditional and advanced measurement techniques was used during testing, including strain gauges, linear variable differential transducers (LVDT or LT) and crack width monitoring. These tools enabled high-resolution tracking of crack development, strain distribution, and bond-slip behaviour in the critical DE zones. Subsequently, the results from this initial test series are used to validate finite element models for these complex regions.