Strength reduction factors for S355 to S500 steel grades under steady-state and transient-state heating

2019 ◽  
Vol 11 (2) ◽  
pp. 137-149
Author(s):  
Francois Hanus ◽  
Nicolas Caillet ◽  
Sylvain Gaillard ◽  
Olivier Vassart
Keyword(s):  
Steady State ◽  
Large Scale ◽  
Elevated Temperatures ◽  
Transient State ◽  
Heating Rates ◽  
Content Type ◽  
State Tests ◽  
Steel Grades ◽  
Scope Of Application ◽  
Reduction Factors

Purpose This paper aims to describe coupon tests performed at elevated temperatures on S355 to S500 steel grades and comparison of test results with previous research studies and current EN 1993-1-2 material laws. The objective is to state if these steel grades satisfy to the current material laws and if the scope of application of these laws could be extended to S500 grades. Design/methodology/approach Two experimental programmes were launched to investigate the behaviour of S460M and S500M steel grades developed for hot-rolled sections. The first research programme was focussed on a comparison between S355 and S460 grades, where the second experimental programme was focussed on the recently developed S500M steel grade. The latter one comprised steady-state tests, transient-state tests and two large-scale beam tests. Findings Results of steady-state and transient-state tests correlate well with the reduction factors defined in EN 1993-1-2, currently limited to S460 grade. On the basis of this study, the scope of EN 1993-1-2 applies to S500 grades. For steady-state tests, the testing procedure (with and without acceleration after Rp0,2) led to noticeable differences. Transient-state tests, which are not standardised up to now, have been performed considering 5 K/min and 10 K/min constant heating rates. The slowest rate leads to lower strengths as creep effects are more significant. However, all the results are in line with EN 1993-1-2 material law. Importance should be given to the reference yield strength of steel at ambient temperature. Originality/value The revision of EN 1993-1-2 is on-going and this piece of work provides a contribution for extending the scope of application of material law of steel under fire conditions.

Thermo-structural analysis of a honeycomb-type volumetric absorber for concentrated solar power applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Masoud Behzad ◽  
Benjamin Herrmann ◽  
Williams R. Calderón-Muñoz ◽  
José M. Cardemil ◽  
Rodrigo Barraza
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Steady State ◽  
Discrete Model ◽  
Continuum Model ◽  
Transient State ◽  
Operating Conditions ◽  
Steady State Condition ◽  
Content Type ◽  
The Continuum

Purpose Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress. Design/methodology/approach The design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events. Findings The steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions. Originality/value Thermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

Bending and flexural-buckling strength of steel members considering strain-rate-effects at elevated temperatures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fuminobu Ozaki ◽  
Takumi Umemura
Keyword(s):  
Strain Rate ◽  
Elevated Temperatures ◽  
Bending Strength ◽  
Transient State ◽  
Bending Test ◽  
Content Type ◽  
Buckling Strength ◽  
Flexural Buckling ◽  
Steel Members ◽  
Collapse Temperature

PurposeIn this study, the bending strength, flexural buckling strength and collapse temperature of small steel specimens with rectangular cross-sections were examined by steady and transient state tests with various heating and deformation rates.Design/methodology/approachThe engineering stress and strain relationships for Japan industrial standard (JIS) SN400 B mild steels at elevated temperatures were obtained by coupon tests under three strain rates. A bending test using a simple supported small beam specimen was conducted to examine the effects of the deformation rates on the centre deflection under steady-state conditions and the heating rates under transient state conditions. Flexural buckling tests using the same cross-section specimen as that used in the bending test were conducted under steady-state and transient-state conditions.FindingsIt was clarified that the bending strength and collapse temperature are evaluated by the full plastic moment using the effective strength when the strain is equal to 0.01 or 0.02 under fast strain rates (0.03 and 0.07 min–1). In contrast, the flexural buckling strength and collapse temperature are approximately evaluated by the buckling strength using the 0.002 offset yield strength under a slow strain rate (0.003 min–1).Originality/valueRegarding both bending and flexural buckling strengths and collapse temperatures of steel members subjected to fire, the relationships among effects of steel strain rate for coupon test results, heating and deformation rates for the heated steel members were minutely investigated by the steady and transient-state tests at elevated temperatures.

Study on the residual performance of RC beams exposed to processed temperatures and fire

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sachin Vijaya Kumar ◽  
N. Suresh
Keyword(s):  
Failure Modes ◽  
Elevated Temperatures ◽  
Slow Heating ◽  
Maximum Temperature ◽  
Rc Beams ◽  
Heating Rates ◽  
Fast Heating ◽  
Content Type ◽  
Temperature Increment ◽  
Residual Performance

PurposeThe Reinforced Concrete(RC) elements are known to perform well during exposure to elevated temperatures. Hence, RC elements are widely used to resist the extreme heat developing from accidental fires and other industrial processes. In both of the scenarios, the RC element is exposed to elevated temperatures. However, the primary differences between the fire and processed temperatures are the rate of temperature increase, mode of exposure and exposure durations. In order to determine the effect of two heating modalities, RC beams were exposed to processed temperatures with slow heating rates and fire with fast heating rates.Design/methodology/approachIn the present study, RC beam specimens were exposed to 200 °C, to 800 °C temperature at 200 °C intervals for 2 h' duration by adopting two heating modes; Fire and processed temperatures. An electrical furnace with low-temperature increment and a fire furnace with standard time-temperature increment is adapted to expose the RC elements to elevated temperatures.FindingsIt is observed from test results that, the reduction in load-carrying capacity, first crack load, and thermal crack widths of RC beams exposed to 200 °C, and 600 °C temperature at fire is significantly high from the RC beams exposed to the processed temperature having the same maximum temperature. As the exposure temperature increases to 800 °C, the performance of RC beams at all heating modes becomes approximately equal.Originality/valueIn this work, residual performance, and failure modes of RC beams exposed to elevated temperatures were achieved through two different heating modes are presented.

scholarly journals Effect of Temperature on Material Properties of Carbon Fiber Reinforced Polymer (CFRP) Tendons: Experiments and Model Assessment

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1025 ◽  
Author(s):  
Fei Zhou ◽  
Jiwen Zhang ◽  
Shoutan Song ◽  
Dong Yang ◽  
Chao Wang
Keyword(s):  
Steady State ◽  
Material Properties ◽  
Elevated Temperatures ◽  
Transient State ◽  
Fiber Reinforced Polymer ◽  
Test Results ◽  
Concrete Members ◽  
Frp Composites ◽  
Reinforced Polymer ◽  
State Test

Material properties at elevated temperatures are important factors in the fire safety design and numerical analysis of concrete members strengthened with fiber reinforced polymer (FRP) composites. Most of the previous research mainly focused on tensile strength and elastic modulus in conventional steady state temperature tests. However, the transient state test method is more realistic for strengthening concrete structures. At the same time, the coefficient of thermal expansion of FRP composites is also one of the important factors affecting concrete members at elevated temperatures. This paper presents a detailed experimental investigation on the longitudinal thermal expansion deformation, and the mechanical properties of carbon FRP (CFRP) tendons with 8 mm diameter in the steady state and transient state. The results indicate that longitudinal deformation of CFRP tendons is negative at high temperature; in addition, the transient state test results of CFRP tendons are slightly higher than the steady state test results. The final part of this paper assesses the accuracy of different empirical models. Furthermore, a new equation calculating the properties of CFRP composites at elevated temperatures is presented with the numerical fitting technique, which is in good agreement with the experimental results.

scholarly journals The Temperature Gradient-Forming Device, an Accessory Unit for Normal Light Microscopes To Study the Biology of Hyperthermophilic Microorganisms

2014 ◽  
Vol 80 (15) ◽  
pp. 4764-4770 ◽  
Author(s):  
Maximilian Mora ◽  
Annett Bellack ◽  
Matthias Ugele ◽  
Johann Hopf ◽  
Reinhard Wirth
Keyword(s):  
Temperature Gradient ◽  
Elevated Temperatures ◽  
Strictly Anaerobic ◽  
Heating Rates ◽  
Content Type ◽  
Custom Made ◽  
Temperature Ranges ◽  
Limited Degree ◽  
Normal Light ◽  
First Time

ABSTRACTTo date, the behavior of hyperthermophilic microorganisms in their biotope has been studied only to a limited degree; this is especially true for motility. One reason for this lack of knowledge is the requirement for high-temperature microscopy—combined, in most cases, with the need for observations under strictly anaerobic conditions—for such studies. We have developed a custom-made, low-budget device that, for the first time, allows analyses in temperature gradients up to 40°C over a distance of just 2 cm (a biotope-relevant distance) with heating rates up to ∼5°C/s. Our temperature gradient-forming device can convert any upright light microscope into one that works at temperatures as high as 110°C. Data obtained by use of this apparatus show how very well hyperthermophiles are adapted to their biotope: they can react within seconds to elevated temperatures by starting motility—even after 9 months of storage in the cold. Using the temperature gradient-forming device, we determined the temperature ranges for swimming, and the swimming speeds, of 15 selected species of the genusThermococcuswithin a few months, related these findings to the presence of cell surface appendages, and obtained the first evidence for thermotaxis inArchaea.

Behaviour and resistance of cold-formed steel beams with lipped channel sections under fire conditions

2016 ◽  
Vol 7 (4) ◽  
pp. 365-387 ◽  
Author(s):  
Flávio Arrais ◽  
Nuno Lopes ◽  
Paulo Vila Real
Keyword(s):  
Cross Sections ◽  
Elevated Temperatures ◽  
Numerical Results ◽  
Steel Beams ◽  
Finite Element Program ◽  
Content Type ◽  
Current Design ◽  
Element Program ◽  
Steel Grades ◽  
Cold Formed Steel

Purpose Steel beams composed of cold-formed sections are common in buildings because of their lightness and ability to support large spans. However, the instability phenomena associated to these members are not completely understood in fire situation. Thus, the purpose of this study is to analyse the behaviour of beams composed of cold-formed lipped channel sections at elevated temperatures. Design/methodology/approach A numerical analysis is made, applying the finite element program SAFIR, on the behaviour of simply supported cold formed steel beams at elevated temperatures. A parametric study, considering several cross-sections with different slenderness’s values, steel grades and bending diagrams, is presented. The obtained numerical results are compared with the design bending resistances determined from Eurocode 3 Part 1-2 and its French National Annex (FN Annex). Findings The current design expressions revealed to be too conservative when compared with the obtained numerical results. It was possible to observe that the FN Annex is less conservative than the Annex E, the first having a better agreement with the numerical results. Originality/value Following the previous comparisons, new fire design formulae are tested. This new methodology, which introduces minimum changes in the existing formulae, provides safety and accuracy at the same time when compared to the numerical results, considering the occurrence of local, distortional and lateral torsional buckling phenomena in these members at elevated temperatures.

Difference equation−based transient-state and steady-state analysis of flyback converter circuit

2019 ◽  
Vol 38 (1) ◽  
pp. 81-94 ◽  
Author(s):  
Namik Yener ◽  
Ali Bekir Yildiz
Keyword(s):  
Steady State ◽  
Difference Equations ◽  
Transient State ◽  
Switching Converters ◽  
Steady State Analysis ◽  
Content Type ◽  
Flyback Converter ◽  
Switching Circuits ◽  
The Difference ◽  
State Analysis

Purpose This paper aims to present how to use the difference equations for analysis of flyback converter circuit. Design/methodology/approach Switching circuits have variable structural topologies. In every switched-mode, they have different dynamics and different equations. First, the exact equivalent circuit of flyback converter, then, set of difference equations are obtained. The flyback converter has a nonlinear structure; however, the presented technique allows the circuit equations to be linear. The transient-state and steady-state analysis of flyback converter, one of popular switching circuits, are carried out by using difference-equations. Findings The proposed analysis method does not contain any numerical approximation and the results are in the form of exact solution. Another superiority of the method is that the desired instantaneous values can be obtained directly, the simulation does not need to be started from the beginning. Numerical results agree well with the theoretical results of flyback converter. The simulation results obtained by using the proposed method and Matlab-based results are compared. Originality/value This paper contributes a different mathematical background for analysis of switching converters to the literature.

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