Numerical modelling of the in-plane behaviour of concrete-filled circular steel tubular arches

Numerical modelling approaches are favoured in studying the instability failures of concrete-filled steel tube arches (CFSTAs) due to the complexity and high cost of experimental testing of such structural members. While some of the existing numerical models are able to capture the constitutive behaviour of the materials in CFSTAs accurately, they are computationally expensive to be used for studying the effect of key parameters affecting the CFSTA behaviour. This paper presents a simple yet accurate numerical modelling approach to predict the behaviour of CFSTAs considering in-plane instability failures. Numerical modelling was carried out using open-source finite element (FE) software OpenSees. CFSTAs were modelled using fibre section beam-column elements available in OpenSees. A modified stress-strain model was used to capture the constitutive behaviour of both confined normal and high strength concrete. Bi-axial stress state of steel tube was considered for failure modelling of steel. Proposed FE model for CFSTA was verified using existing experimental results of CFSTAs. Consideration of the bi-axial stress state of the steel tube was shown to increase the accuracy of the predictions. FE results showed that when a CFSTA is failing due to instability, geometric imperfection will significantly influence CFSTA behaviour. Both percentages of steel content and unconfined concrete strength was found to affect the ultimate load of the CFSTAs, but the effect was found to be dependent on the loading conditions. Rise-to-span ratio as well as the shape of the arch was also found to significantly influence the behaviour of CFSTAs, with the parabolic arch shape being found to be the best. (C) 2020 Elsevier Ltd. All rights reserved.