Fatigue Failure Paths for Offshore Platform Inspection

Karsan, Demir I.; Kumar, Ashok

doi:10.1061/(asce)0733-9445(1990)116:6(1679)

Cited by 20 publications

(3 citation statements)

References 5 publications

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“…It is observed from Fig. 1b that the numerical predictions [7], and it is also noted that anisotropic damage model introduces same profiles of D h and D 1 , where hardening moduli are taken as H t = 25 MPa, H c = 650 MPa. Similarly several biaxial tension tests are performed and failure surface obtained from anisotropic damage model are compared with that of isotropic damage model in Fig.…”

Section: Discussionmentioning

confidence: 55%

“…The performance of both the elasticity based isotropic damage and coupled anisotropic damage models is studied under uniaxial/biaxial load settings. The material constants used are E = 31.7 GPa, ν = 0.21, f ck = 27.6 MPa and f t = 3.48 MPa taken from the experimental data [7]. Initial damage thresholds are computed as κ 0t = f ck /E, κ 0c = 10f t /3E, and model parameters β 1 = 0.85 and β 2 = 0.18 are used in the isotropic damage model.…”

Section: Discussionmentioning

confidence: 99%

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A model for coupled inelastic deformation and anisotropic damage behaviour of concrete

Gafoor

Dinkler

2017

Proc Appl Math and Mech

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The present paper describes a simplified model for isotropic damage developed on continuum damage theory. The model characterizes the distinct behaviour of concrete in tension and compression using a unified equivalent strain, which governs the growth of damage. In reality, concrete exhibits distributed micro-cracking pattern under multi-directional loads. Therefore, the model is extended to incorporate damage induced anisotropy inherently for a reliable representation of damage, and captures the direction of possible damage evolution. Moreover, the model takes the inelastic behaviour of material into account based on the extended version of Lubliner failure criterion. The model is validated with experimental data. Constitutive modellingThe growth and coalescence of microcracks in concrete generally lead to the formation and propagation of macro-cracks and ultimately to fracture. Thus, the deformation behaviour of concrete is influenced. Nowadays, continuum damage models are serving as efficient tools for engineers to understand the deformation behaviour of brittle materials such as concrete, rock, etc. This paper discusses isotropic and anisotropic damage models within the context of continuum damage mechanics. Isotropic damageAccording to continuum damage mechanics, the stress-strain relation for the elasticity behaviour of concrete based on the principle of energy equivalence and adopted damage evolution law [1] are written aswhere, σ and ε are the second-order tensors of Cauchy stress and the strain; C refers the fourth-order elasticity tensor. The constitutive behaviour of the material is influenced by isotropic damage, denoted by a scalar variable D, which usually satisfies the condition (0 ≤ D ≤ 1). The damage evolution law (1b) exhibits exponential softening. The model parameters β 1 and β 2 control the initial rate of damage growth and decay in stress ensuring residual stresses respectively. The growth of damage D is governed by the history deformation parameter κ. There are several alternatives for history parameters which are discussed [1]. But in order to account for both tensile and compressive behaviour of concrete, the damage evolution is considered to be driven by a local measure of equivalent strain eq using a damage loading surface f d due to Lubliner failure criterion [2].Here, I 1 , J 2 , σ max , and H(σ max ) are as defined in [5]. Moreover, D and κ are monotonically increasing parameters. If f d < 0, the material behaves elastically; and when f d = 0, the damage initiates. The damage grows ifḟ d = 0. Thus, the model satisfies Kuhn-Tucker loading/unloading conditions. The initial elastic domain is set by the initial threshold value κ 0 = κ 0t H + κ 0c (1 − H) in tension and compression respectively. Anisotropic damageAlthough the isotropic damage model satisfactorily describes the damage behaviour of concrete as a first approximation, the experimental investigations prove that the internal degradation of the material depending on the direction of loading applied is inherently anisotropic. T...

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Section: Discussionmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 99%

A model for coupled inelastic deformation and anisotropic damage behaviour of concrete

Gafoor

Dinkler

2017

Proc Appl Math and Mech

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“…A technique to identify failure paths was suggested on the basis of the Wirsching's model for nodal fatigue reliability (5). Inspection strategies are suggested on the basis of estimating the fatigue reliability as the platform experiences cyclic loading (3,8,10,12).…”

Section: Introductionmentioning

confidence: 99%

Failure Paths Identification and Damage Tolerance Definition for Marine Platforms in the Bay of Campeche

2000

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Offshore Marine Platforms have been built in the Bay of Campeche since the 60´s. Managers of those facilities have shown a strong interest on keeping the production activities at some of the structures that are close to its lifetime. As a consequence, there is now an important concern about the effect of aging on the structural integrity of these platforms as exposed to environmental loading. A probabilistic approach was developed in order to help to identify the sequence of nodes and level of damage that may be tolerated by the platform before its overall safety is compromised. The referred procedure allows the safety assessment against fatigue and involves the combination of Structural Reliability and Fracture Mechanics concepts. The formulation is applied to the platforms AKAL-N and NOHOCH-B, both located in the Bay of Campeche. Because of the large volume of oil and gas production at risk, a careful and detailed evaluation of these platforms is required. The results show that the structural redundancy degree plays an important role to define the damage level that the platform may tolerate before reaching the minimum limit of the reliability index recommended for its category.

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Applications in Offshore Structures

Skjong¹

1995

Probabilistic Structural Mechanics Handbook

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Fatigue Failure Paths for Offshore Platform Inspection

Cited by 20 publications

References 5 publications

A model for coupled inelastic deformation and anisotropic damage behaviour of concrete

A model for coupled inelastic deformation and anisotropic damage behaviour of concrete

Failure Paths Identification and Damage Tolerance Definition for Marine Platforms in the Bay of Campeche

Applications in Offshore Structures

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