Structural member stability behaviour of steel channels

The analysis of structural members subjected to close-in detonations involves a complicated dynamic scenario. Since the charge is very close to the structural member, the reflected pressure distribution on the member surface is highly non-uniform. In addition, the level of damage to the structural member may be high because of the large magnitude of the load. Due to these phenomena, the response of a structural member to close-in detonation cannot be accurately modelled by relatively simple methods like single-degree of freedom models, and more complicated models are required. Such models need to include numerical simulation of the detonation process, which produces a non-uniform pressure environment, allowing the pressure to reflect and flow around the member section. The local damage and flow around the section are especially of interest in I-shaped, or wide-flange-section members. Herein, the response of such sections is modelled by numerical simulations using a novel technique, which overcomes the difficulty of computation time, and is validated through various calculations. The model is used to perform a parametric study to investigate the response of I-sections subjected to close-in detonations, in terms of local damage and global behaviour, with scaled distances of 0.15–0.29 m/kg1/3 and loading causing flexure about the strong axis. Various aspects that affect the performance are studied, such as: the effect of scaled distance, the addition of welded stiffening plates between the flanges and web, the effect of boundary conditions and the effect of charge shape. Resulting local damage and residual deformations are assessed for the cases studied.

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Toward Structural Health Monitoring of Civil Structures Based on Self-Sensing Concrete Nanocomposites: A Validation in a Reinforced-Concrete Beam

International Journal of Concrete Structures and Materials ◽

10.1186/s40069-020-00451-8 ◽

2021 ◽

Vol 15 (1) ◽

Author(s):

Diego L. Castañeda-Saldarriaga ◽

Joham Alvarez-Montoya ◽

Vladimir Martínez-Tejada ◽

Julián Sierra-Pérez

Keyword(s):

Reinforced Concrete ◽

Damage Detection ◽

Direct Current ◽

Health Monitoring ◽

Electrical Resistance ◽

Concrete Beam ◽

Reinforced Concrete Beam ◽

Structural Member ◽

Rc Beam ◽

Electric Resistance

AbstractSelf-sensing concrete materials, also known as smart concretes, are emerging as a promising technological development for the construction industry, where novel materials with the capability of providing information about the structural integrity while operating as a structural material are required. Despite progress in the field, there are issues related to the integration of these composites in full-scale structural members that need to be addressed before broad practical implementations. This article reports the manufacturing and multipurpose experimental characterization of a cement-based matrix (CBM) composite with carbon nanotube (CNT) inclusions and its integration inside a representative structural member. Methodologies based on current–voltage (I–V) curves, direct current (DC), and biphasic direct current (BDC) were used to study and characterize the electric resistance of the CNT/CBM composite. Their self-sensing behavior was studied using a compression test, while electric resistance measures were taken. To evaluate the damage detection capability, a CNT/CBM parallelepiped was embedded into a reinforced-concrete beam (RC beam) and tested under three-point bending. Principal finding includes the validation of the material’s piezoresistivity behavior and its suitability to be used as strain sensor. Also, test results showed that manufactured composites exhibit an Ohmic response. The embedded CNT/CBM material exhibited a dominant linear proportionality between electrical resistance values, load magnitude, and strain changes into the RC beam. Finally, a change in the global stiffness (associated with a damage occurrence on the beam) was successfully self-sensed using the manufactured sensor by means of the variation in the electrical resistance. These results demonstrate the potential of CNT/CBM composites to be used in real-world structural health monitoring (SHM) applications for damage detection by identifying changes in stiffness of the monitored structural member.

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EXPERIMENTAL DETERMINATION OF THE BUCKLING LOAD OF A STRAIGHT STRUCTURAL MEMBER BY USING DYNAMIC PARAMETERS

Journal of Sound and Vibration ◽

10.1006/jsvi.1995.1047 ◽

1997 ◽

Vol 205 (3) ◽

pp. 257-264 ◽

Cited By ~ 4

Author(s):

C.G. Go ◽

Y.S. Lin ◽

E.H. Khor

Keyword(s):

Experimental Determination ◽

Structural Member ◽

Buckling Load ◽

Dynamic Parameters

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A Note on the Origin of the Triglyph

The Annual of the British School at Athens ◽

10.1017/s0068245400018293 ◽

1951 ◽

Vol 46 ◽

pp. 50-52

Author(s):

R. M. Cook

Keyword(s):

Structural Member ◽

Seventh Century

There are several explanations current about the origin of the triglyph. First, that the frieze of triglyph and metope started from a decorative feature of Mycenaean art and survived—invisibly to us–until eventually Doric architecture emerged. Secondly, that triglyphs are the fossilised remains of barred wooden windows, which early Greeks needed but their successors did not. Thirdly, that triglyphs are the flattened vestiges of an upper row of columns, abandoned by the timid masons of the seventh century. Fourthly, that the triglyph represents the end or a facing of the end of a wooden beam, this though in all ascertainable early instances the beams run from the course above the triglyph. Fifthly, and liable to the same objection, that the metopes were originally the ends of beams and the triglyphs bars between them. To each of these explanations—and probably to any other that has been or can be devised—there are serious objections. But since the treatment and the prominence of the orthodox triglyph give it an appearance of being an important structural member and particularly one of wood, the most popular explanation is the fourth, which derives the triglyph from the wooden beam. If this is accepted, the argument may reasonably be pushed further.

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Stability behaviour of antiretroviral drugs and their combinations. 2: Characterization of interaction products of lamivudine and tenofovir disoproxil fumarate by mass and NMR spectrometry

Journal of Pharmaceutical and Biomedical Analysis ◽

10.1016/j.jpba.2016.03.039 ◽

2016 ◽

Vol 125 ◽

pp. 245-259 ◽

Cited By ~ 13

Author(s):

Moolchand Kurmi ◽

Bhoopendra Singh Kushwah ◽

Archana Sahu ◽

Mallikarjun Narayanam ◽

Saranjit Singh

Keyword(s):

Tenofovir Disoproxil Fumarate ◽

Antiretroviral Drugs ◽

Stability Behaviour ◽

Nmr Spectrometry

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Application of Fly Ash-Based Geopolymer for Structural Member and Repair Materials

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.92.74 ◽

2014 ◽

Vol 92 ◽

pp. 74-83 ◽

Cited By ~ 5

Author(s):

Wanchai Yodsudjai

Keyword(s):

Reinforced Concrete ◽

Fly Ash ◽

Concrete Beam ◽

Setting Time ◽

Reinforced Concrete Beam ◽

Structural Member ◽

Steel Reinforcement ◽

Flexural Behavior ◽

Fundamental Properties ◽

Repair Materials

The applications of using fly ash-based geopolymer as a structural member and a repair materials in reinforced concrete structure was conducted. The optimum mix proportion of fly ash-based geopolymer concrete using for structural beam and fly ash-based geopolymer mortar using for repair material were developed. The flexural behavior of fly ash-based geopolymer reinforced concrete and the durability aspect namely the corrosion of steel reinforcement were investigated using the electrical acceleration. For the repair purpose, the fundamental properties; that is, compressive strength, flexural strength, bonding strength between fly ash-based geopolymer mortar and mortar substrate, setting time and chloride penetration were investigated. Also, the durability of conventional reinforced concrete beam repaired by the fly ash-based geopolymer mortar comparing with the comercial repair mortar was investigated. The behavior of the fly ash-based geopolymer reinforced concrete beam was similar to that of the conventional reinforced concrete beam; however, the corrosion of the steel reinforcement of the fly ash-based geopolymer reinforced concrete beam was higher than that of the conventional reinforced concrete beam. The fundamental properties of the fly ash-based geopolymer mortar were not different from that of the commercial repair materials; however, the durability of the reinforced concrete beam repaired by the fly ash-based geopolymer mortars performed a little lower than that of repaired with the commercial repair motar and also the control reinforced concrete with no repair. As a result, even there will be still a need of improvement there was a good tendency for using the fly ash-based geopolymer as the structural member and the repair materials.

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Effects of finite-rate chemistry and detailed transport on the instability of jet diffusion flames

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.95 ◽

2014 ◽

Vol 745 ◽

pp. 647-681 ◽

Cited By ~ 5

Author(s):

Yee Chee See ◽

Matthias Ihme

Keyword(s):

Transport Properties ◽

Diffusion Flames ◽

Diffusive Transport ◽

Mean Flow ◽

Stability Behaviour ◽

Jet Diffusion Flames ◽

One Step ◽

The Mean ◽

Modelling Assumptions ◽

The Stability

AbstractLocal linear stability analysis has been shown to provide valuable information about the response of jet diffusion flames to flow-field perturbations. However, this analysis commonly relies on several modelling assumptions about the mean flow prescription, the thermo-viscous-diffusive transport properties, and the complexity and representation of the chemical reaction mechanisms. In this work, the effects of these modelling assumptions on the stability behaviour of a jet diffusion flame are systematically investigated. A flamelet formulation is combined with linear stability theory to fully account for the effects of complex transport properties and the detailed reaction chemistry on the perturbation dynamics. The model is applied to a methane–air jet diffusion flame that was experimentally investigated by Füriet al.(Proc. Combust. Inst., vol. 29, 2002, pp. 1653–1661). Detailed simulations are performed to obtain mean flow quantities, about which the stability analysis is performed. Simulation results show that the growth rate of the inviscid instability mode is insensitive to the representation of the transport properties at low frequencies, and exhibits a stronger dependence on the mean flow representation. The effects of the complexity of the reaction chemistry on the stability behaviour are investigated in the context of an adiabatic jet flame configuration. Comparisons with a detailed chemical-kinetics model show that the use of a one-step chemistry representation in combination with a simplified viscous-diffusive transport model can affect the mean flow representation and heat release location, thereby modifying the instability behaviour. This is attributed to the shift in the flame structure predicted by the one-step chemistry model, and is further exacerbated by the representation of the transport properties. A pinch-point analysis is performed to investigate the stability behaviour; it is shown that the shear-layer instability is convectively unstable, while the outer buoyancy-driven instability mode transitions from absolutely to convectively unstable in the nozzle near field, and this transition point is dependent on the Froude number.

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