Considerations on computational modeling of concrete structures in fire

Ni, Shuna; Gernay, Thomas

doi:10.1016/j.firesaf.2020.103065

Cited by 15 publications

(13 citation statements)

References 14 publications

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“…The fracture energy to approximate the tension-stiffening effect was taken as 6000 N/m 2 . This value was chosen based on the considerations made by Nia and Gernay [26] to have a more robust numerical simulation. In this respect, the characteristic concrete tensile strength was lowered from 2.5 MPa, typical of a C40/50 concrete strength class, to 1 MPa.…”

Section: Shell Modellingmentioning

confidence: 99%

Fire Behaviour of a Prestressed Thin-Walled Concrete V-Beam

Pedron

Tondini

2021

Fire Technol

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The present work investigates the fire behaviour of a prestressed thin-walled concrete V-beam with variable cross section along its longitudinal axis. In particular, the results obtained from different modelling strategies implemented through analytical computations and Finite Element (FE) thermo-mechanical analyses conducted both with Euler–Bernoulli beam elements and with shell elements were compared. The models were able to properly allow for the prestressing force and its variation with temperature. The mode of failure was analysed both at ambient temperature and at elevated temperature by employing the ISO 834 standard heating curve as well as parametric fire curves so as to investigate the behaviour in the cooling phase. The outcomes showed that the beam model was not capable of accurately predicting the failure mode by largely overestimating the time of collapse. Indeed, the FE analysis with shell elements highlighted that beam behaviour assumptions with sections that remain plane were not satisfied as fire progressed. Furthermore, it also showed that the failure mode was not flexural in the longitudinal direction but due to the failure of the webs in transverse bending that interacted with longitudinal stresses. Finally, the analyses conducted by applying parametric fire curves highlighted possible failure in the cooling phase, which emphasises the need of careful analysis for these types of structural members.

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Section: Shell Modellingmentioning

confidence: 99%

Fire Behaviour of a Prestressed Thin-Walled Concrete V-Beam

Pedron

Tondini

2021

Fire Technol

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“…In addition to the data obtained through strength tests, the authors decided to evaluate the internal structure and how it changes when exposed to high temperatures. In recent years, this topic has been addressed, among others, in the context of fire safety in building structures [32,33]. In this context, it will be particularly important in structures such as road tunnels, for which evacuation conditions can be difficult [34] and for which much higher demands are made on the high temperature resistance of concrete.…”

Section: Introductionmentioning

confidence: 99%

Change of the Structural Properties of High-Performance Concretes Subjected to Thermal Effects

et al. 2022

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The paper refers to studies of the structure of high-performance concrete with polypropylene fibre at different dosages. The authors see a research gap in the study of the effect of adding polypropylene fibre on the parameters of concrete exposed to high temperatures. The study takes into account the thermal effect—groups of samples were heated to 200 °C, 400 °C and 600 °C. The authors carried out basic tests to describe the changes in density, ultrasonic tests, uniaxial compression strength tests and tensile tests by splitting. The positive effect of polypropylene fibres is mainly observed between 20 °C and 200 °C. The melting of polypropylene fibres causes a delay in the development of micro-cracks in the structure of these concretes compared to HPC. Adding polypropylene fibres to the mixtures also increased the speed of ultrasonic wave propagation in the medium. The research was deepened with tomographic imaging. A description of the splitting surface was carried out. The results of tensile by splitting tests clearly show an increase in the relative failure area for unheated concretes in proportion to the number of fibres used. Changes in splitting surfaces under the influence of temperature are graphically illustrated. Furthermore, differences in the samples under the influence of heating at high temperatures are presented. Finally, the porosity development of all sample groups before and after heating at all temperatures is described.

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“…to achieve more realistic strength predictions compared to those by simplified sectional analysis. ABAQUS ( 2014) is frequently used in simulating the performance of separate structural components, while SAFIR is adopted for building simulations Gernay 2020a, Ni andGernay 2020b). Gao et al (2013), Kodur and Agrawal (2016) and Albrifkani and Wang (2016) proposed their own three-dimensional (3D) FE model in ABAQUS ( 2014) for predicting the thermal and mechanical performance of RC beams during fire exposure.…”

Section: Fe Modelling Approachmentioning

confidence: 99%

“…Instead of modelling individual structural elements, Ni and Gernay (2020a) and Ni and Gernay (2020b) use the software SAFIR to develop a 3D frame model for estimating the behaviour of entire RC building structures at and after a fire event. The model is able to consider effect of 3D restraint condition and continuity on structural responses.…”

Section: Fe Modelling Approachmentioning

confidence: 99%

“…The model is able to consider effect of 3D restraint condition and continuity on structural responses. Despite their intension to capture shear failure modes in the frame model, Ni and Gernay (2020a) only validated the model with test results of deep beams at ambient temperature, but not under fire condition. Therefore, its reliability in modelling shear behaviour of RC components and complete structures at high temperatures has not been verified experimentally.…”

Section: Fe Modelling Approachmentioning

confidence: 99%

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Consistent strut-and-tie modelling of deep and short beams and hollow-core slabs at ambient and elevated temperatures

Fan¹

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Strut-and-tie model (STM) has been widely incorporated in different codes of practice due to its accuracy and consistency in designing Discontinuity-regions.Discontinuity-regions refer to regions where the strain distribution is significantly non-linear and traditional shallow beam theory does not apply. Application of STM to Discontinuity-regions or members comprising entirely of Discontinuity-regions, such as reinforced concrete (RC) deep and short beams, corbels, beam-column joints, etc., under ambient condition has been well verified by different researchers.However, the feasibility of applying STM to deep and short beams subjected to fires or to prestressed precast concrete hollow-core (PCHC) slabs with non-uniform cross-sectional properties and no web reinforcement at ambient temperature have hardly been investigated. Besides, there is a lack of experimental test results of heated short beams with/without axial restraint and fire-exposed deep beams under unequal and/or unsymmetrical loading arrangement. Therefore, experimental data is needed for verification of the proposed STM approaches for deep and short beams at high temperatures. In addition, there are challenges in selecting an optimal STM for RC deep beams with variations in load configurations such as the load magnitude, equality, symmetry and load combinations. Hence, research is needed to develop a direct approach for determining a suitable STM geometry to simplify the analysis procedure for engineers.To bridge the gaps, the present research programme is conducted to:(1) Examine experimentally structural fire behaviour of axially-restrained and unrestrained short beams, with shear-span-to-effective-depth (a/d) ratio ranging from 1.50 to 2.50, followed by the development of a general STM-based approach for simulating the response of short beams subjected to fire.(2) Conduct analytical and experimental studies on RC deep beams under combined effects of load inequality, load asymmetry, and elevated temperatures.(3) Develop and validate a refined and direct STM approach for both symmetricallyand unsymmetrically-loaded deep beams at ambient temperature. Summary viii (4) Establish and verify a STM approach to predict the web-shear capacity of PCHC slabs at ambient temperature.To achieve the research objectives, two series of tests were conducted on seven short beams (Series I in Chapter 3) and six deep beams under elevated temperatures (Series II in Chapter 4). The first series was to investigate experimentally the effects of a/d ratio and thermal-induced axial restraint on structural fire behaviour of short beams, while Series II was for unsymmetrically-loaded RC deep beams at elevated temperatures. The experimental data were utilised to establish proposed STM approaches for assessing the shear resistances and fire durations of deep and short beams when exposed to fires. Based on the experimental and analytical studies, it was found that: (i) The presence of elevated temperatures altered failure model of deep and short beams to a less brittle failure m...

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Considerations on computational modeling of concrete structures in fire

Cited by 15 publications

References 14 publications

Fire Behaviour of a Prestressed Thin-Walled Concrete V-Beam

Fire Behaviour of a Prestressed Thin-Walled Concrete V-Beam

Change of the Structural Properties of High-Performance Concretes Subjected to Thermal Effects

Consistent strut-and-tie modelling of deep and short beams and hollow-core slabs at ambient and elevated temperatures

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