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.

Lifetime of Imidazolium Salts at Elevated Temperatures

Solar Energy ◽  
2004 ◽  
Author(s):  
Daniel M. Blake ◽  
Luc Moens ◽  
Daniel Rudnicki ◽  
Heidi Pilath
Keyword(s):  
Power Systems ◽  
Elevated Temperatures ◽  
Initial Study ◽  
Slow Heating ◽  
Gravimetric Analysis ◽  
Imidazolium Salts ◽  
Heating Rates ◽  
Rough Approximation ◽  
Solar Plant ◽  
The University

This report summarizes progress to date on the thermal stability of imidazolium salts being considered for application as heat transfer and thermal storage fluids in solar parabolic trough power systems. Imidazolium salts are a subset of the general class of molten salts. They are termed ionic liquids because many have freezing points at or below room temperature. This class of salts was selected for initial study because there were many examples that were reported to be stable at high temperatures. These reports were usually based on the results of standard thermal gravimetric analysis (TGA) methods. Work by our subcontractor at the University of Alabama and at NREL showed that slow heating rates or when the temperature is held constant for long times resulted in decomposition temperatures that are much lower than found with the usual TGA methods. We have used a TGA technique that allows calculation of the rates of thermal decomposition as a function of temperature. The results lead us to the conclusion that the imidazolium salts known to be the most thermally stable would not have useful lifetimes above about 200°C. At present this determination is based on the rough approximation that the fluid in a solar trough system experiences a constant, high temperature. Better estimates of the useful lifetime will require a system model that takes into account the time at temperature distribution of a fluid moving through the different components in a solar plant.

Mechanical modeling for predicting the axial restraint forces and rotations of steel top and seat angle connections at elevated temperatures

2017 ◽  
Vol 8 (3) ◽  
pp. 258-286 ◽  
Author(s):  
Sana El Kalash ◽  
Elie Hantouche
Keyword(s):  
Mechanical Model ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Experimental Results ◽  
Fe Model ◽  
Content Type ◽  
Analysis And Design ◽  
Axial Forces ◽  
Fe Simulations ◽  
Seat Angle

Purpose This paper aims at developing a mechanical-based model for predicting the thermally induced axial forces and rotation of steel top and seat angles connections with and without web angles subjected to elevated temperatures due to fire. Finite element (FE) simulations and experimental results are used to develop the mechanical model. Design/methodology/approach The model incorporates the overall connection and column-beam rotation of key component elements, and includes nonlinear behavior of bolts and base materials at elevated temperatures and some major geometric parameters that impact the behavior of such connections when exposed to fire. This includes load ratio, beam length, angle thickness, and gap distance. The mechanical model consists of multi-linear and nonlinear springs that predict each component stiffness, strength, and rotation. Findings The capability of the FE model to predict the strength of top and seat angles under fire loading was validated against full scale tests. Moreover, failure modes, temperature at failure, maximum compressive axial force, maximum rotation, and effect of web angles were all determined in the parametric study. Finally, the proposed mechanical model was validated against experimental results available in the literature and FE simulations developed as a part of this study. Originality/value The proposed model provides important insights into fire-induced axial forces and rotations and their implications on the design of steel bolted top and seat angle connections. The originality of the proposed mechanical model is that it requires low computational effort and can be used in more advanced modelling applications for fire analysis and design.

Tensile and shear strength for a self-drilling screw and transition of failure-modes and shear-strengths for self-drilling screwed connections at elevated-temperatures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fuminobu Ozaki ◽  
Ying Liu ◽  
Kai Ye
Keyword(s):  
Shear Strength ◽  
Test Temperature ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
High Strength ◽  
Shear Loading ◽  
The Self ◽  
Content Type ◽  
Steel Sheets ◽  
Loading Tests

PurposeThe purpose of this study is to clarify both tensile and shear strength for self-drilling screws, which are manufactured from high-strength, martensitic-stainless and austenitic stainless-steel bars, and the load-bearing capacity of single overlapped screwed connections using steel sheets and self-drilling screws at elevated temperatures.Design/methodology/approachTensile/shear loading tests for the self-drilling screw were conducted to obtain basic information on the tensile and shear strengths at elevated temperatures and examine the relationships between both. Shear loading tests for the screwed connections at elevated temperatures were conducted to examine the shear strength and transition of failure modes depending on the test temperature.FindingsThe tensile and shear strengths as well as the reduction factors at the elevated temperature for each steel grade of the self-drilling screw were quantified. Furthermore, either screw shear or sheet bearing failure mode depending on the test temperature was observed for the screwed connection.Originality/valueThe transition of the failure modes for the screwed connection could be explained using the calculation formulae for the shear strengths at elevated temperatures, which were proposed in this study.

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.

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.

A study on different techniques of restoration of fire damaged reinforced concrete flexural members

2017 ◽  
Vol 8 (2) ◽  
pp. 131-148
Author(s):  
Danie Roy Anasco Bastin ◽  
Umesh Kumar Sharma ◽  
Pradeep Bhargava
Keyword(s):  
Reinforced Concrete ◽  
Shear Failure ◽  
Elevated Temperatures ◽  
High Strength ◽  
Absorption Capacity ◽  
Rc Beams ◽  
Content Type ◽  
Flexural Failure ◽  
Externally Bonded ◽  
Strength And Stiffness

Purpose The main aim of this research was to investigate the effectiveness of various strengthening techniques in restoring the structural performance of reinforced concrete (RC) beams damaged by elevated temperatures. Design/methodology/approach Three different strengthening techniques, namely, high-strength fibre reinforced concrete (HSFRC), ferrocement (FC) jacketing and externally bonded fibre-reinforced polymer (FRP) were used. Series of RC beams were casted, heated, strengthened and tested to investigate the influence of various variables. The variables of the study were type of strengthening and level of heat damage. Findings Externally bonded FRP was found to be the best among the various techniques, especially with respect to strength and stiffness restoration. On the contrary, the FRP strengthening was not that effective in restoring the energy absorption capacity of beams compared to HSFRC and FC techniques of strengthening. The chosen strengthening techniques were able to restore the failure mode of beams to flexural failure, which was found to have changed to shear failure in case of heated unstrenghthened beams. Originality/value This research program has contributed to the fundamental understanding of designing post fire retrofit solutions for RC beams.

Analysis of time dependent thermal properties for high rates in selective laser sintering

2018 ◽  
Vol 24 (5) ◽  
pp. 894-900 ◽  
Author(s):  
Katrin Wudy ◽  
Maximilian Drexler ◽  
Lydia Lanzl ◽  
Dietmar Drummer
Keyword(s):  
Thermal History ◽  
Laser Power ◽  
High Speed ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Maximum Temperature ◽  
Laser Exposure ◽  
Heating Rates ◽  
Content Type ◽  
Impact Time

Purpose The thermal history during laser exposure determines part properties in selective laser sintering (SLS). The purpose of this study is to introduce a new measurement technique based on a CO2 laser unit combined with a high-speed DCS. A first comparison of the thermal history during laser exposure measured with Laser-high-speed-(HS)-differential scanning calorimetry-(DSC) and in SLS process is shown. Design/methodology/approach This Laser-HS-DSC allows an imitation of the SLS-process in a very small scale, as the sample is directly heated by a CO2 laser. For this study, the laser power and the impact time is varied for determining temperature and achieved heating rates. Consequently, the temperature levels measured by the Laser-HS-DSC are compared with measurements in SLS-process. Findings The influence of laser power and impact time on resulting maximum temperatures und heating rates during laser exposure are investigated. With increasing laser power and impact time the maximum temperature rises up to approximately 450°C without material degradation. The heating rate increases up to an impact time of 3 ms and stays almost equal for higher durations. Research limitations/implications The Laser-HS-DSC experiments are based on few particles limiting a complete comparison with SLS process. In SLS, one volume element is exposed several times. In this study the PA12 material was exposed only once. Originality/value For the first time, laser sintering experiments can be transferred to a laboratory scale to analyze the influence of laser exposure on resulting temperature field during laser exposure without superimposing effects.

Physical and Mechanical Properties of Fired Clay Bricks Incorporated with Cigarette Butts: Comparison between Slow and Fast Heating Rates

2013 ◽  
Vol 421 ◽  
pp. 201-204
Author(s):  
Aeslina binti Abdul Kadir ◽  
Abbas Mohajerani
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Heating Rate ◽  
Initial Rate ◽  
Physical And Mechanical Properties ◽  
Slow Heating ◽  
Firing Process ◽  
Heating Rates ◽  
Fast Heating ◽  
Rate Of Absorption

In general, firing process in brick manufacturing could affect the properties, colours and appearance of the brick. The main purpose of this study was to evaluate the effect of different heating rates on physical and mechanical properties during the firing of standard bricks and bricks incorporated with cigarette butt (CB). In this investigation, two different heating rates were used: slow heating rate (2oC min-1) and fast heating rate (5oC min-1). Samples were fired in solid forms from room temperature to 1050oC. All bricks were tested for their physical and mechanical properties including compressive strength, initial rate of absorption and density. Higher heating rates decrease compressive strength value but slightly increase the initial rate of absorption and density properties respectively. In conclusion, higher heating rates are able to produce adequate physical and mechanical properties especially for CB Brick.

scholarly journals Disassembly Study of Ultrasonically Welded Thermoplastic Composite Joints via Resistance Heating

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2521
Author(s):  
Harry Frederick ◽  
Wencai Li ◽  
Genevieve Palardy
Keyword(s):  
Tensile Load ◽  
Thermoplastic Composite ◽  
Nanocomposite Films ◽  
Slow Heating ◽  
Maximum Temperature ◽  
Composite Joints ◽  
Resistance Heating ◽  
Heating Rates ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

This manuscript explores the disassembly potential of ultrasonically welded thermoplastic composite joints for reuse or recycling through resistance heating via a nanocomposite film located at the welded interface. Nanocomposite films containing multi-walled carbon nanotubes (MWCNTs) were characterized for thermo-electrical behavior to assess self-heating. It was generally observed that maximum temperature increased with MWCNT and film thickness. To demonstrate potential for disassembly, glass fiber/polypropylene adherends were welded with nanocomposite films. Shear stress during disassembly was measured for three initial adherend’s surface temperatures. It was found that the required tensile load decreased by over 90% at the highest temperatures, effectively demonstrating the potential for disassembly via electrically conductive films. Fracture surfaces suggested that disassembly was facilitated through a combination of nanocomposite and matrix melting and weakened fiber–matrix interface. Limitations, such as slow heating rates and the loss of contact at the interface, imply that the method could be more suited for recycling, instead of repair and reuse, as the heat-affected zone extended through the adherends’ thickness at the overlap during heating.

scholarly journals Peach and Nectarine Quality Following Treatment with High-temperature Forced Air Combined with Controlled Atmosphere

HortScience ◽  
2005 ◽  
Vol 40 (5) ◽  
pp. 1425-1430 ◽  
Author(s):  
David Obenland ◽  
Paul Neipp ◽  
Bruce Mackey ◽  
Lisa Neven
Keyword(s):  
Heating Rate ◽  
Fruit Quality ◽  
Prunus Persica ◽  
Total Duration ◽  
Storage Period ◽  
Soluble Solids ◽  
Slow Heating ◽  
Controlled Atmosphere ◽  
Heating Rates ◽  
Fast Heating

Yellow- and white-fleshed peach [Prunus persica (L.) Batsch] and nectarine [Prunus persica (L.) Batsch var. nectarina (Ait) Maxim.] cultivars of mid- and late-season maturity classes were subjected to combined controlled atmosphere–temperature treatment system (CATTS) using heating rates of either 12 °C/hour (slow rate) or 24 °C/hour (fast rate) with a final chamber temperature of 46 °C, while maintaining a controlled atmosphere (CA) of 1 kPa oxygen and 15 kPa carbon dioxide. Fruit seed surface temperatures generally reached 45 °C within 160 minutes and 135 minutes for the slow and fast heating rate, respectively. The total duration of the slow heating rate treatment was 3 hours, while 2.5 h was required for the fast heating rate treatment. Following treatment the fruit were stored at 1 °C for either 1, 2, or 3 weeks followed by a ripening period of 2 to 4 d at 23 °C and subsequent evaluation of fruit quality. Fruit quality was similar for both heating rate treatments. Compared with the untreated controls, CATTS fruit displayed higher amounts of surface injury, although increased injury was only an important factor to marketability in cultivars that had high amounts of surface injury before treatment. The percentage of free juice in the flesh was slightly less in CATTS fruit early in storage but was often greater in treated fruit toward the end of the storage period. Slower rates of softening during fruit ripening were apparent in CATTS fruit. Soluble solids, acidity, weight loss and color all were either not affected or changed to a very small degree as a result of CATTS. Members of a trained sensory panel preferred the taste of untreated fruit over fruit that had been CATTS but the ratings of treated and nontreated fruit were generally similar and it is unclear whether an average consumer could detect the difference. Although further work needs to be done regarding the influence of CATTS on taste, it otherwise appears that CATTS does not adversely affect the marketability of good quality fruit and therefore shows promise as a nonchemical quarantine treatment for peaches and nectarines.

Sign in / Sign up

Export Citation Format

Share Document