Abaqus Analysis Ur's Manual
19.6.1 Concrete smeared cracking
Products: Abaqus/Standard Abaqus/CAE
台鉴References
reflect∙ “Material library: overview,” Section 17.1.1
∙ “Inelastic behavior,” Section 19.1.1
∙ *CONCRETE
∙ *TENSION STIFFENING
∙ *SHEAR RETENTION
∙ *FAILURE RATIOS
∙ “Defining concrete smeared cracking” in “Defining plasticity,” Section 12.9.2 of the Abaqus/CAE Ur's Manual
Overview
The smeared crack concrete model in Abaqus/Standard:
右下∙ provides a general capability for modeling concrete in all types of structures, including beams, truss, shells, and solids;
∙ can be ud for plain concrete, even though it is intended primarily for the analysis of reinforced concrete structures;
∙ can be ud with rebar to model concrete reinforcement;
∙ is designed for applications in which the concrete is subjected to esntially monotonic straining at low confining pressures;
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∙ consists of an isotropically hardening yield surface that is active when the stress is dominantly compressive and an independent “crack detection surface” that determines if a point fails by cracking;
∙ us oriented damaged elasticity concepts (smeared cracking) to describe the reversible part of the material's respon after cracking failure;
∙ requires that the linear elastic material model (e “Linear elastic behavior,” Section 18.2.1) be ud to define elastic properties; and
∙ cannot be ud with local orientations (e “Orientations,” Section 2.2.5).
See “Inelastic behavior,” Section 19.1.1, for a discussion of the concrete models available in Abaqus.
Reinforcement
Reinforcement in concrete structures is typically provided by means of rebars, which are one-dimensional strain theory elements (rods) that can be defined singly or embedded in oriented surfaces. Rebars are typically ud with metal plasticity models to describe the behavior of the rebar material and are superpod on a mesh of standard element types ud to model the concrete.
With this modeling approach, the concrete behavior is considered independently of the rebar. Effects associated with the rebar/concrete interface, such as bond slip and dowel action, are modeled approximately by introducing some “tension stiffening” into the concrete modeling to simulate load transfer across cracks through the rebar. Details regarding tension stiffening are provided below.
园林景观设计说明Defining the rebar can be tedious in complex problems, but it is important that this be done accurately since it may cau an analysis to fail due to lack of reinforcement in key regions of a model. See “Defining reinforcement,” Section 2.2.3文章阅读网, for more information regarding rebars.
Cracking
The model is intended as a model of concrete behavior for relatively monotonic loadings under fairly low confining pressures (less than four to five times the magnitude of the largest stress that can be carried by the concrete in uniaxial compression).
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Crack detection
Cracking is assumed to be the most important aspect of the behavior, and reprentation of cracking and of postcracking behavior dominates the modeling. Cracking is assumed to occur when the stress reaches a failure surface that is called the “crack detection surface.” This failure surface is a linear relationship between the equivalent pressure stress, p, and the Mis equivalent deviatoric stress, q, and is illustrated in Figure 19.6.1–5. When a crack has been detected, its orientation is stored for subquent calculations. Subquent cracking at the same point is restricted to being orthogonal to this direction since stress components associated with an open crack are not included in the definition double heart
of the failure surface ud for detecting the additional cracks.
Cracks are irrecoverable: they remain for the rest of the calculation (but may open and clo). No more than three cracks can occur at any point (two in a plane stress ca, one in a uniaxial stress ca). Following crack detection, the crack affects the calculations becau a damaged elasticity model is ud. Oriented, damaged elasticity is discusd in more detail in “An inelastic constitutive model for concrete,” Section 4.5.1 of the Abaqus Theory Manual.
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Smeared cracking
The concrete model is a smeared crack model in the n that it does not track individual “macro” cracks. Constitutive calculations are performed independently at each integration point of the finite element model. The prence of cracks enters into the calculations by the way in which the cracks affect the stress and material stiffness associated with the integration point.
Tension stiffening
The postfailure behavior for direct straining across cracks is modeled with tension stiffening, which allows you to define the strain-softening behavior for cracked concrete. This behavior also allows for the effects of the reinforcement interaction with concrete to be simulated in a simple manner. Tension stiffening is required in the concrete smeared cracking model. You can specify tension stiffening by means of a postfailure stress-strain relation or by applying a fracture energy cracking criterion.
