Meso-scale modelling of size effect on pure torsional-shear of RC columns

Meso‐scale modeling of size effect on pure torsional failure of concrete‐filled steel tubular columns

“…The failure process of plain concrete columns exhibits brittle failure characteristics, which is consistent with the experimental phenomenon in literature. 24 However, for CFST columns, due to the strong constraints of the steel tube, the specimens show ductile failure characteristics, which is consistent with the phenomenon of lots of experiments. 10,11 The failure patterns of columns and the equivalent plastic strain of steel tubes with different confinement coefficients are shown in Figure 7.…”

“…The size effect of CFST columns is generated from the following two aspects 21,22,24 : (1) the heterogeneity and mechanical nonlinearity of concrete material; (2) the complex interaction between steel tube and concrete. 11,17 For the first aspect, a mesoscale numerical model that can reveal the heterogeneity of concrete needs to be built, in which concrete is regarded as a three-phase material composed of aggregate, mortar matrix, and the interfacial transition zone (ITZ).…”

“…21,22 Finally, the coarse aggregate volume was set at 35% of the concrete volume. 21,24 Referring to the work of Donza et al, 28 Meddah et al, 29 the mortar matrix can be regarded as a matrix body composed of fine aggregates <5 mm in diameter, microcracks, and pore in the cement paste. The thin coating of coarse aggregate is considered as the ITZ phase, which is a thin layer between the aggregate particles and the mortar matrix.…”

“…21,22 The plastic damage constitutive model applied in the studies 33,34 was used for the constitutive relation of concrete materials. Although the plastic damage is widely applied in the simulation of brittle materials in dynamic load and static load, 24 there are still some limitations, as it cannot accurately describe the mechanical behavior of concrete under the action of a strong constraints. 35 Han et al 17 showed that the plasticity of concrete increased due to the passive constraints of steel tubes.…”

“…At present, the SEL of concrete material has been basically perfected, 25 and the fracture mechanics SEL proposed by Bažant 44 was widely accepted, which applied in many studies. 6,21,31 The SEL for torsion proposed by Bažant 44 was modified by Jin et al, 24 and a new SEL was proposed as…”