Time-dependent numerical modelling of conventional and geopolymer concrete beams serviceability

Controlling deflection in reinforced concrete structures is essential for ensuring serviceability and long-term performance. This study presents a numerical approach to simulate the effects of short-term and long-term service loading on reinforced concrete flexural members, validated against data from experimental investigations conducted at the UNSW Australia including conventional concrete and heat-cured low calcium fly ash geopolymer concrete. The creep coefficient and shrinkage of concrete were calibrated using MATLAB's nonlinear fitting function. AS3600-2018 standard creep and shrinkage models were used for conventional concrete beams. Experimental creep and shrinkage data were used for the geopolymer concrete beam. A three-dimensional finite element analysis (FEA) model was developed in ABAQUS, incorporating creep and shrinkage effects through user subroutines (USDFLD, UEXPAN, and GETVRM) within the concrete damage plasticity (CDP) framework. The model was employed to analyze the short-term deflection after cracking, time-dependent deflection under sustained loading, and long-term stiffness degradation of reinforced concrete beams. The numerical results were successful compared to the experimental results obtained on conventional and geopolymer concrete beams, demonstrating the accuracy and effectiveness of the proposed approach. • A coupled numerical model simulates creep, shrinkage, and concrete damage. • Long-term deflection of concrete beams is predicted with high accuracy. • Model validated against both conventional and geopolymer concrete experiments. • Geopolymer beams show minimal stiffness loss under sustained load. • ABAQUS user subroutine enables time-dependent FEA for structural serviceability.