Axial compressive strength of slender UHPFRC-filled steel tubes. (15th June 2023)

• Record Type: Journal Article
• Authors: Haidar, Ali; Jawdhari, Akram; Fam, Amir
• Is Part Of: Engineering structures. Volume 285(2023)
• Publication Date: 2023-06-15
• Subjects: UHPFRC -- Concrete-filled tubes -- Columns -- Finite element -- LS DYNA -- Slenderness; Structural engineering -- Periodicals; Structural analysis (Engineering) -- Periodicals; Construction, Technique de la -- Périodiques; Génie parasismique -- Périodiques; Pression du vent -- Périodiques; Earthquake engineering; Structural engineering; Wind-pressure; Periodicals; 624.105
• DOI: 10.1016/j.engstruct.2023.116073
• Languages: English
• ISSNs: 0141-0296

Abstract

Highlights: First study to authors' knowledge on slender UHPFRC-filled steel tube columns. 3D nonlinear FE model developed using LS-DYNA and validated using a large experimental database. Parametric study varying length, diameter-to-thickness ratio, effective length factor and yield strength. Axial strength reduced by 78% when slenderness ratio kL/r increased from 12 to 157. CAN/CSA S16 grossly underestimate strength by 13 to 46% as kL/r increased from 12 to 157. A modification to CAN/CSA S16 is proposed based on multiple regression of parametric study results. Abstract: Ultra-high performance fiber-reinforced concrete (UHPFRC)-filled steel tube (UHPFRC-FST) slender columns have not been studied to date, although ample research exists on this system as short columns. Furthermore, current code provisions (e.g. CAN/CSA S16) were developed for normal strength concrete and are thus potentially inadequate for UHPFRC-FSTs. In this study, a robust three-dimensional nonlinear finite element model was developed and validated using LS-DYNA software to simulate behaviour of slender UHPFRC-FSTs of circular cross-section under concentric axial compressive loads. An extensive parametric study was then performed, varying slenderness ratio ( kL / r ) based on column length ( L ) where r is the radius of gyration, diameter-to-thickness ratio ( D / t ) of the steel tube, effective length factor ( k ), and tube's yield strength ( F y ) . The study showed that axial load-carrying capacity reduced by 78% when slenderness ratio increased from 12 to 157. The column transitions from material failure by diagonal shear plane in concrete, to global buckling at a slenderness ratio of about 80. Axial load-carrying capacity also reduces rapidly with D / t until a ratio of about 45 and then reduces at a much lower rate thereafter. CAN/CSA S16 code provisions grossly underestimate the load-carrying capacity of slender UHPFRC-FSTs by 13 to 46% as slenderness ratio increased from 12 to 157. The underestimation also increased dramatically with diameter-to-thickness ratio, from 8% at D / t = 10 to 40% at D / t = 80, and with effective length factor k, by 15% at k = 0.5 to 48% at k = 2 . 0. A modification to CAN/CSA S16:19 equation is proposed based on multiple regression analysis of the results of the parametric study.