Design and modelling of grouted corrugated duct connections in precast GFRP-reinforced concrete structures

The design of grouted corrugated duct connections (GCDCs) in precast concrete structures requires adequate length of corrugated duct and embedded bar. Both parameters have been extensively studied for conventional steel-reinforced concrete (RC). While equations for corrugated duct length may be adapted to other reinforcement types, bar embedded equations cannot be directly applied to glass-fibre reinforced polymer (GFRP) bars due to their different characters. Nevertheless, studies on GCDCs in GFRP-RC remain limited. To address this gap, this study investigates the behaviour and design of GCDCs in precast GFRP-reinforced concrete and proposes appropriate design equations and procedures. A finite element (FE) model was developed and verified against experimental tests of column-footing assemblies. Several bond models were also evaluated to identify the most appropriate representation of GFRP to grout bond-slip behaviour. The verified FE model was subsequently adopted in a parametric study to examine the effects of bar embedded length, bar diameter, and grout strength. The results highlight the combined influence of these parameters on the column performance, including lateral capacity and bar stress development. The findings demonstrate that the predictive equation for the minimum required embedded length developed for steel bars is not applicable to GFRP bars. Based on the FE results, a refined equation was proposed to estimate the minimum required embedded length of grouted GFRP bars. This equation considers the GFRP bar diameter, grout strength, and bar stress. The refined equation reliably predicts the minimum embedded length required to prevent bar pull-out.