scholarly journals Buckling Resistance of Axially Restrained Chord Members of Grid Structure at Elevated Temperatures

2016 ◽  
Author(s):  
Du Yong ◽  
J.Y. Richard Liew ◽  
Mingxiang Xiong ◽  
Jie Zou ◽  
Zeng Bo
Keyword(s):  
Thermal Expansion ◽  
Critical Temperature ◽  
Cross Section ◽  
Elevated Temperatures ◽  
Slenderness Ratio ◽  
Uniform Temperature ◽  
Grid Structure ◽  
Order Analysis ◽  
Buckling Resistance ◽  
Force Equilibrium

This paper investigates the behavior of large span grid structure exposed to a localized fire. The localized fire may generate hot smoke and thus induce non-uniform temperature distribution in the grid structure. The thermal expansion of the heated members tend to be axially restrained by the adjacent cold members thus inducing additional forces on the critical members of the grid structure. The buckling resistance of axially restrained member at elevated temperature may be obtained based on second order analysis of member with initial lateral imperfection by considering force equilibrium at deformed geometry and cross section resistance being reached. The critical temperature of the member is reached when the axial force reaches its buckling resistance. It is found that the critical temperature of members with initial lateral imperfection was higher than that without such imperfection for chord members with large slenderness ratio and high axial restraint.

scholarly journals Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

2021 ◽  
pp. 000370282199044
Author(s):  
Wubin Weng ◽  
Shen Li ◽  
Marcus Aldén ◽  
Zhongshan Li
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Elevated Temperatures ◽  
Uv Absorption ◽  
Energy Utilization ◽  
Quantitative Detection ◽  
Absorption Cross ◽  
Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

Minimum Mould Exit Shell Thickness of Round Blooms for Peritectic Steel Casting

2011 ◽  
Vol 421 ◽  
pp. 179-183 ◽  
Author(s):  
Li Gen Sun ◽  
Hui Rong Li ◽  
Jia Quan Zhang
Keyword(s):  
Cross Section ◽  
Shell Thickness ◽  
Elevated Temperatures ◽  
Continuous Casting Machine ◽  
Casting Machine ◽  
Mathematic Model ◽  
Cross Point ◽  
Peritectic Steel ◽  
Support Roller ◽  
The Cross

The minimum mould exit shell thickness (MEST) is one of key factors to consider for continuous casting machine design and the strand cooling schemes. Based on the shell strength at elevated temperatures, a concept of shell integral average strength, from its very top surface to the solidus frontier, has been introduced to judge its bulging tendency under ferrostatic pressure. Considering the contribution to the shell stability, a mathematic model for the determination of the minimum MEST has been brought forward. It is shown that, the minimum MEST of the round bloom is decided by not only the cross section and the minimum roller spacing, but also the opening degree of the support roller and the support roller on the side. Taking a round bloom casting of plain carbon steel (grade Q235) as an example, there is the cross point with the curve of the minimum MEST by the minimum roller spacing and the minimum MEST by the fluting include angle of the support roller and the support roller on the side against the cross section, if its own geometry structure cannot hold the ferrostatic pressure, the minimum MEST on the left of the cross point can remain as the determined amount by the minimum roller spacing; but on the right, it is increased with the increasing width of cross section.

scholarly journals Construction of Uniaxial Interaction Diagram for Slender Reinforced Concrete Column Based on Nonlinear Finite Element Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Bedaso Ahmed ◽  
Kefiyalew Zerfu ◽  
Elmer C. Agon
Keyword(s):  
Finite Element Analysis ◽  
Reinforced Concrete ◽  
Slenderness Ratio ◽  
Nonlinear Finite Element ◽  
Concrete Column ◽  
Reinforced Concrete Column ◽  
Element Analysis ◽  
Interaction Diagram ◽  
Order Analysis ◽  
Rc Column

Slender reinforced concrete column may fail in material failure or instability failure. Instability failure is a common problem which cannot be analyzed with first-order analysis. So, second-order analysis is required to analyze instability failure of slender RC column. The main objective of this study was to construct uniaxial interaction diagram for slender reinforced concrete column based on nonlinear finite element analysis (FEA) software. The key parameters which were studied in this study were eccentricity, slenderness ratio, steel ratio, and shape of the column. Concrete damage plasticity (CDP) was utilized in modeling the concrete. Material nonlinearity, geometric nonlinearity, effect of cracking, and tension stiffening effect were included in the modeling. The results reveal that, as slenderness ratio increases, the balanced moment also increases, but the corresponding axial load was decreased. However, increasing the amount of steel reinforcement to the column increases the stability of the column and reduces the effect of slenderness ratio. Also, the capacity of square slender RC column is larger than rectangular slender RC column with equivalent cross section. However, the result is close to each other as slenderness ratio increased. Finally, validation was conducted by taking a benchmark experiment, and it shows that FEA result agrees with the experimental by 85.581%.

scholarly journals Experimental study on the thermal behaviour of fire exposed slim-floor beams

2018 ◽  
Author(s):  
Vicente Albero ◽  
Ana Espinós ◽  
Enrique Serra ◽  
Manuel L. Romero ◽  
Antonio Hospitaler
Keyword(s):  
Cross Section ◽  
Thermal Behaviour ◽  
Thermal Model ◽  
Elevated Temperatures ◽  
Experimental Studies ◽  
Composite Beams ◽  
Technical Equipment ◽  
Design Code ◽  
Special Configuration ◽  
The Cross

Steel-concrete composite beams embedded in floors (slim-floors) offer various advantages such as the floor thickness reduction or the ease of installation of under-floor technical equipment. However, this typology presents important differences in terms of thermal behaviour, as compared to other composite beams, when exposed to elevated temperatures. These differences are due to their special configuration, being totally contained within the concrete floor depth. Moreover, the current European fire design code for composite steel-concrete structures (EN 1994-1-2) does not provide any simplified thermal model to evaluate the temperature evolution of each slim-floor part during a fire. Additionally, only a few experimental studies can be found which may help understand the thermal behaviour of these composite beams. This paper presents an experimental investigation on the thermal behaviour of slim-floor beams. Electrical radiative panels were used in the test setup to produce the thermal heating. The thermal gap between the lower flange of the steel profile and the bottom steel plate was studied, being found to be one of the most influential elements over the cross-section temperature gradient. The experimental campaign was developed by varying the cross-section configuration in order to evaluate the influence of this parameter over the slim-floor thermal behavior. Finally, the experiments carried out were used to develop and calibrate a finite element thermal model which may help in further research on the thermal behaviour of slim-floor composite beams.

Thermal Expansion of Polyether Ether Ketone Bearing Components

2019 ◽  
Vol 64 (4) ◽  
pp. 1-5 ◽  
Author(s):  
Bryan D. Allison ◽  
Connor M. Vanderwiel
Keyword(s):  
Thermal Expansion ◽  
Elevated Temperatures ◽  
Coefficient Of Thermal Expansion ◽  
Aerospace Applications ◽  
Polyether Ether Ketone ◽  
Molded Parts ◽  
Injection Molded ◽  
Ether Ketone ◽  
Bearing Design ◽  
Strong Candidate

Carbon fiber–reinforced polyether ether ketone (PEEK) is a strong candidate for aerospace bearing cages due to its low density and good mechanical properties. However, there are still concerns regarding its performance at the elevated temperatures seen in aerospace applications. In particular, an accurate measurement of PEEK's coefficient of thermal expansion (CTE) is critical to proper bearing design. In this paper, the CTE of as-manufactured PEEK cages was measured to determine the range of CTE that can be expected for production parts. A range of cage sizes and designs were considered in this study. Components that were manufactured from stock shapes through subtractive methods were studied in addition to components made via injection molding. The CTE of machined PEEK was found to be significantly higher than that of injection-molded PEEK and also varied significantly from part to part. In contrast, the CTE of molded PEEK cages was found to be fairly consistent between parts. Finally, the CTE of PEEK was found to increase above the glass transition temperature of 143 °C, but it was demonstrated that this increase is relatively small for injection-molded parts.

scholarly journals High Strain-Rate Compressive Properties of Carbon/Epoxy Laminated Composites – Effects of loading direction and temperature

2018 ◽  
Vol 183 ◽  
pp. 02011
Author(s):  
Kenji Nakai ◽  
Tsubasa Fukushima ◽  
Takashi Yokoyama ◽  
Kazuo Arakawa
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Slenderness Ratio ◽  
Testing Machine ◽  
Negative Temperature ◽  
Hopkinson Pressure Bar ◽  
Instron Testing Machine

The high strain-rate compressive characteristics of a cross-ply carbon/epoxy laminated composite in the three principal material directions or fibre (1-), in-plane transverse (2-) and throughthickness (3-) directions are investigated on the conventional split Hopkinson pressure bar (SHPB) over a range of temperatures between 20 and 80 °C. A nearly 10 mm thick cross-ply carbon/epoxy composite laminate fabricated using vacuum assisted resin transfer molding (VaRTM) was tested. Cylindrical specimens with a slenderness ratio (= length/diameter) of 0.5 are used in high strain-rate tests, and those with the slenderness ratios of 1.0 and 1.5 are used in low and intermediate strain-rate tests. The uniaxial compressive stress-strain curves up to failure at quasi-static and intermediate strain rates are measured on an Instron testing machine at elevated temperatures. A pair of steel rings is attached to both ends of the cylindrical specimens to prevent premature end crushing in the 1-and 2-direction tests on the Instron testing machine. It is shown that the ultimate compressive strength (or failure stress) exhibits positive strainrate effects and negative temperature ones over a strain-rate range of 10–3 to 103/s and a temperature range of 20 to 80 °C in the three principal material directions.

Static Analysis of Curved Beams with Clamped-Clamped Ends under Thermo Load

2011 ◽  
Vol 117-119 ◽  
pp. 1543-1546
Author(s):  
Xiao Fei Li ◽  
Chun Yi Cui ◽  
De Hai Yu
Keyword(s):  
Thermal Expansion ◽  
Static Analysis ◽  
Cross Section ◽  
Analytical Solutions ◽  
Virtual Work ◽  
Curved Beams ◽  
Curved Bridges ◽  
Internal Forces ◽  
The Cross ◽  
Scientific Base

Based on the principle of thermal expansion and theory of virtual work, a class of equations for in-plane displacements at three freedom direction and internal forces in the cross-section of statically indeterminate curved beams under thermo load are derived explicitly. In the case of infinite limit of radius, these equations coincide with that of the straight beams. Compared with the results of FEM, the analytical solutions by the proposed formulae are accurate. The analytical solutions obtained in this paper would provide a scientific base for further study and design of the curved bridges.

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