Stress–strain constitutive equations of concrete material at elevated temperatures

Li, Long-yuan; Purkiss, J. A.

doi:10.1016/j.firesaf.2005.06.003

Cited by 170 publications

(94 citation statements)

References 7 publications

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“…This hypothesis is also present on In concrete, transient creep strain develops irrecoverably during first-time heating of concrete under load, compared to concrete loaded at elevated temperature (Anderberg and Thelandersson, 1976). This strain has to be considered in any fire analysis involving concrete in compression (Khoury et al, 1985), (Li and Purkiss, 2005); any stress analysis of heated concrete which ignores transient creep will provide erroneous results (Schrefler et al, 2002). For instance, the effect of not including transient creep strain in a full stress-strain model can be shown to produce erroneous unsafe results for the behavior of columns heated in three sides, thus inducing a thermal moment, in fire (Purkiss, 1996), although the effect may be exacerbated due to the coexistence of thermal and moment gradient.…”

Section: Mechanical Modelsmentioning

confidence: 99%

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Structural behaviour of concrete columns under natural fires

Gernay

Dimia

2013

Engineering Computations

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Structured abstract.Purpose -The paper aims to give an insight into the behavior of reinforced concrete columns during and after the cooling phase of a fire. The study is based on numerical simulations as these tools are frequently used in structural engineering. As the reliability of numerical analysis largely depends on the validity of the constitutive models, the development of a concrete model suitable for natural fire analysis is addressed in the study. Design/methodology/approach -The paper proposes theoretical considerations supported by numerical examples to discuss the capabilities and limitations of different classes of concrete models and eventually to develop a new concrete model that meets the requirements in case of natural fire analysis. Then, the study performs numerical simulations of concrete columns subjected to natural fire using the new concrete model. A parametric analysis allows for determining the main factors that affect the structural behavior in cooling. Findings -Failure of concrete columns during and after the cooling phase of a fire is a possible event. The most critical situations with respect to delayed failure arise for short fires and for columns with low slenderness or massive sections. The concrete model used in the simulations is of prime importance and the use of the Eurocode model would lead to unsafe results. Practical implications -The paper includes implications for the assessment of the fire resistance of concrete elements in a performance-based environment. Originality/value -The paper provides original information about the risk of structural collapse during cooling.

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Section: Mechanical Modelsmentioning

confidence: 99%

“…Basic creep, defined as the strain that develops when only time is changing with all other conditions such as stress and temperature being constant, is generally omitted for the structural calculation of building structures in the fire situation (Li and Purkiss, 2005).…”

Section: Formulation Of the Explicit Transient Creep Eurocode Model Fmentioning

confidence: 99%

Structural behaviour of concrete columns under natural fires

Gernay

Dimia

2013

Engineering Computations

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“…Different parts of deformations are approximated with discrete equations interacting in a new concrete model. This technique is usable to calculate realistically the behaviour of structures (Franssen 2004, Li and Purkiss 2005, Anderberg 2008, especially in the case of restraint and during cooling, which is not possible in EC2. By considering the load history during heating up in several cases an increasing load bearing capacity due to a higher stiffness of concrete may be obtained.…”

Section: Resultsmentioning

confidence: 99%

An Advanced Transient Concrete Model for the Determination of Restraint in Concrete Structures Subjected to Fire

Schneider¹,

Schneider

2009

ACT

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The advanced transient concrete model (ATCM) is an extended model for concrete in compression at elevated temperature that incorporates elastic, plastic and creep strain as a function of temperature and stress history. The ATCM is applied with the material model of the thermal induced strain model. The non-linear model comprises thermal strain, elastic strain, plastic strain and transient temperature strains and load history modelling of restraint concrete structures subjected to fire. The mechanical strain is calculated as a function of elastic strain, plastic strain and thermal induced strain. The thermal induced strain is relative independent compared to dependence of Young's modulus by load history. Actually the term comprises elastic, plastic and (pure) transient creep strains as we will show. A comparison is given between experimental results with cylindrical specimens and calculated results. The equations of the ATCM consider a lot of capabilities, especially for considering the irreversible effects of temperature on some material properties. By considering the load history during heating up, an increasing load bearing capacity due to a higher stiffness of concrete may be obtained. With this model it is possible to apply the thermal-physical behaviour of material laws for calculation of structures under extreme temperature conditions. The effect of load history in highly loaded structures under fire load will be investigated. The theoretical basis is given in this paper.

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“…In this model, the critical temperature represents the experimentally observed temperature threshold of 100°C above which LITS starts developing significantly [8]. Such a bilinear curve was conceived as a simple and effective alternative to the more complex LITS functions available in the literature, valid for applications involving temperatures up to 250°C [20][21][22]. One notable application case is the assessment of nuclear power plants in the case of partial fault of the cooling system [17].…”

Section: Uniaxial Lits Function For Temperatures Up To 500°cmentioning

confidence: 99%

A confinement-dependent load-induced thermal strain constitutive model for concrete subjected to temperatures up to 500 °C

Torelli

Mandal

Gillie

et al. 2018

International Journal of Mechanical Sciences

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T 1 Highlights  LITS development for temperatures up to 500°C is strongly confinement-dependent  A confinement-dependent LITS model for this temperature range is presented  The model is numerically implemented, validated applied to a test case  The behaviour of nuclear vessels is affected by the confinement-dependency of LITS ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T AbstractThis paper proves that, given a Load-Induced Thermal Strain (LITS) curve able to accurately describe the uniaxial LITS development for a specific type of concrete and temperatures up to 500°C, a more accurate prediction of the 3D LITS state is obtained through a confinement-dependent 3D implementation than through the classic confinement-independent approach. In particular, a new model is presented, obtained by extending to 3D a fourth order polynomial LITS derivative function in a way that allows the effects of the stress confinement to be taken into account. For comparison purposes, the same fourth order polynomial LITS derivative function is also implemented in 3D through the classic confinement-independent modelling approach. These constitutive relationships are adopted to model transient experiments performed on concrete subjected to constant uniaxial and biaxial compressive loads. The results show that the confinementdependent modelling approach gives a better prediction of the LITS state developing in the case of biaxial compression than the classic confinement-independent approach. Finally, the validated confinementdependent model is applied to evaluate the LITS-related stress redistribution taking place in a typicalPrestressed Concrete Pressure Vessel (PCPV) subjected to heating to 500°C and cooling back to the normal operating temperature of 50°C. It is found that including the effects of three dimensional LITS behaviour has significant effects on the predicted stress states.

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Stress–strain constitutive equations of concrete material at elevated temperatures

Cited by 170 publications

References 7 publications

Structural behaviour of concrete columns under natural fires

Structural behaviour of concrete columns under natural fires

An Advanced Transient Concrete Model for the Determination of Restraint in Concrete Structures Subjected to Fire

A confinement-dependent load-induced thermal strain constitutive model for concrete subjected to temperatures up to 500 °C

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