PSI - Issue 64

M. Esmaelian et al. / Procedia Structural Integrity 64 (2024) 2091–2100 M. Esmaelian/ Structural Integrity Procedia 00 (2024) 000 – 000

2095

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3.2. Finite Element Modeling

In all models, all concrete components, including precast segments, loading block, and foundation, were modeled with eight-node linear 3D brick reduced integration elements (C3D8R). All steel reinforcements and Fe-SMA bars were modeled using two-node linear truss elements (T3D2), and the steel jacket in the JH1 model was modeled using shell elements (S4R). 3.2.1. Material Modeling The study utilizes Concrete Damage Plasticity (CDP) to model the inelastic behavior of concrete. The CDP model is defined based on five plasticity parameters and the uniaxial material behavior in tension and compression. The material's behavior under cyclic loading is characterized by implementing damage data in tension and compression. The stress-strain relationships presented by Mander et al. (Mander et al., 1988) are used in this study to model the compressive behavior of unconfined and confined concrete with spirals and steel jackets. In tension, concrete is assumed to have a linear-elastic behavior before reaching peak tensile strength. To avoid convergence issues, the stress-crack opening method is employed in this study to define the post-peak response in tension (Cornelissen et al., 1986). To consider the degradation of stiffness in concrete under cyclic loading, damage data in tension and compression are defined according to (Birtel & Mark, 2006) and (Pavlović et al., 2013) . The steel reinforcement, including longitudinal and transverse bars, ED bars, steel tendons, and steel jackets, are defined using the elastic-perfectly plastic stress-strain material model with isotropic plasticity. Additionally, the material behavior of activated and Fe-SMA under tension-compression reversals was modeled using the combined isotropic/kinematic hardening model. For a detailed description of the modeling approach of Fe-SMA, reader is referred to (Esmaelian et al., 2024). Table 1 provides a summary of the material properties of all the materials used in this study.

Table 1 Properties of the materials

Materials Concrete

Mechanical Property

Value

Compressive strength (MPa) Tensile strength (MPa) Elastic modulus (GPa)

48.7

4.1

32.8 0.2 206 443 0.3 206 303 0.3 151 0.25 439 800 >30

Poisson’s ratio

Elastic modulus (GPa) Yield strength (MPa) Elastic modulus (GPa) Yield strength (MPa) Poisson’s ratio

Longitudinal,Transverse, and ED Bars

Steel Jacket

Poisson’s ratio

Elastic modulus (GPa)

Activated Fe-SMA

Poisson’s ratio

Yield strength (MPa) Ultimate strength (MPa)

Failure strain (%)

3.2.2. Interactions and boundary conditions The interaction between the column segments, comprising of tangential and normal components, was defined using surface-to-surface contact. A friction coefficient of 0.5 was assumed for tangential contact behavior, while hard contact was assumed for the normal component (Dawood et al., 2012). The contact behavior used to simulate the contact between the steel jacket and the bottom segment in JH1 column was similar to that of column joints. The "Embedded Region" constraint in ABAQUS was used to model the embedding of the steel reinforcement in the surrounding concrete. Fe-SMA bars and the tendon were both embedded in concrete at both ends with a similar constraint and left unbonded along the column height. In the column models, the foundation degrees of freedom are completely fixed to simulate the rigid boundary condition. Three loads are defined in the model, the first being the PT force, which is defined using the Predefined Field option in ABAQUS before the first step. In the second step, the gravity load ratio is defined as a surface