Applications of fiber optic sensors for structural health monitoring

K. Kesavan,K. Ravisankar,S. Parivallal,P. Sreeshylam 국제구조공학회 2005 Smart Structures and Systems, An International Jou Vol.1 No.4

Large and complex structures are being built now-a-days and, they are required to be functional even under extreme loading and environmental conditions. In order to meet the safety and maintenance demands, there is a need to build sensors integrated structural system, which can sense and provide necessary information about the structural response to complex loading and environment. Sophisticated tools have been developed for the design and construction of civil engineering structures. However, very little has been accomplished in the area of monitoring and rehabilitation. The employment of appropriate sensor is therefore crucial, and efforts must be directed towards non-destructive testing techniques that remain functional throughout the life of the structure. Fiber optic sensors are emerging as a superior non-destructive tool for evaluating the health of civil engineering structures. Flexibility, small in size and corrosion resistance of optical fibers allow them to be directly embedded in concrete structures. The inherent advantages of fiber optic sensors over conventional sensors include high resolution, ability to work in difficult environment, immunity from electromagnetic interference, large band width of signal, low noise and high sensitivity. This paper brings out the potential and current status of technology of fiber optic sensors for civil engineering applications. The importance of employing fiber optic sensors for health monitoring of civil engineering structures has been highlighted. Details of laboratory studies carried out on fiber optic strain sensors to assess their suitability for civil engineering applications are also covered.

Effects of fluorine doping on structural, optical and electrical properties of spray deposited CdO thin films

Kesavan, K.,Kathalingam, A.,Kim, Hyun-Seok,Sundari, A.R. Umayal Academic Press 2016 Superlattices and microstructures Vol.100 No.-

<P><B>Abstract</B></P> <P>Fluorine doped cadmium oxide (CdO:F) thin films were deposited onto glass substrates by spray deposition technique. Fluorine concentration dependent structural, optical and electrical properties of the films are reported. X-ray diffraction study confirms the growth of polycrystalline cubic CdO films. Optical absorption analysis of the films shows increase of optical band gap energy from 2.45 to 2.65 eV for the increase of fluorine concentration. The transparency of the films is found to be ≥ 80% and also it is increased with the fluorine concentration. Hall-Effect measurement of the films shows resistivity change between 2.5 × 10<SUP>−4</SUP> and 4.5 × 10<SUP>−4</SUP> Ω cm and carrier concentration in the range of 4 × 10<SUP>15</SUP> cm<SUP>−3</SUP> to 7 × cm<SUP>−3</SUP> depending on doping concentration. Photoresponse study of the fabricated CdO:F/p-Si heterostructure diode is also studied and reported.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fluorine doped CdO thin film deposited by spray pyrolysis method. </LI> <LI> Fluorine concentration dependent structural, optical and electrical properties studied. </LI> <LI> First time fabrication of heterojunction n-CdO:F/CdO diode and its photoresponse study reported. </LI> </UL> </P>

Modelling of strains in reinforced concrete flexural members using alpha-stable distribution

K. Balaji Rao,M. B. Anoop,K. Kesavan,S. R. Balasubramanian,K. Ravisankar,Nagesh R. Iyer 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.11 No.5

Large fluctuations in surface strain at the level of steel are expected in reinforced concrete flexural members at a given stage of loading due to the emergent structure (emergence of new crack patterns). This has been identified in developing deterministic constitutive models for finite element applications in Ibrahimbegovic et al. (2010). The aim of this paper is to identify a suitable probability distribution for describing the large deviations at far from equilibrium points due to emergent structures, based on phenomenological, thermodynamic and statistical considerations. Motivated by the investigations reported by Prigogine (1978) and Rubi (2008), distributions with heavy tails (namely, alpha-stable distributions) are proposed for modeling the variations in strain in reinforced concrete flexural members to account for the large fluctuations. The applicability of alpha-stable distributions at or in the neighborhood of far from equilibrium points is examined based on the results obtained from carefully planned experimental investigations, on seven reinforced concrete flexural members. It is found that alpha-stable distribution performs better than normal distribution for modeling the observed surface strains in reinforced concrete flexural members at these points.

Applications of fiber optic sensors for structural health monitoring

Kesavan, K.,Ravisankar, K.,Parivallal, S.,Sreeshylam, P. Techno-Press 2005 Smart Structures and Systems, An International Jou Vol.1 No.4

Large and complex structures are being built now-a-days and, they are required to be functional even under extreme loading and environmental conditions. In order to meet the safety and maintenance demands, there is a need to build sensors integrated structural system, which can sense and provide necessary information about the structural response to complex loading and environment. Sophisticated tools have been developed for the design and construction of civil engineering structures. However, very little has been accomplished in the area of monitoring and rehabilitation. The employment of appropriate sensor is therefore crucial, and efforts must be directed towards non-destructive testing techniques that remain functional throughout the life of the structure. Fiber optic sensors are emerging as a superior non-destructive tool for evaluating the health of civil engineering structures. Flexibility, small in size and corrosion resistance of optical fibers allow them to be directly embedded in concrete structures. The inherent advantages of fiber optic sensors over conventional sensors include high resolution, ability to work in difficult environment, immunity from electromagnetic interference, large band width of signal, low noise and high sensitivity. This paper brings out the potential and current status of technology of fiber optic sensors for civil engineering applications. The importance of employing fiber optic sensors for health monitoring of civil engineering structures has been highlighted. Details of laboratory studies carried out on fiber optic strain sensors to assess their suitability for civil engineering applications are also covered.

Transport, structural and thermal studies on nanocomposite polymer blend electrolytes for Li-ion battery applications

S. Rajendran,K. Kesavan,R. Nithya,M. Ulaganathan 한국물리학회 2012 Current Applied Physics Vol.12 No.3

Nanocomposite polymer electrolytes (NCPEs) composed of poly(vinylidenefluoride-co-hexafluoropropylene)(PVdF-co-HFP) as a host polymer, Poly(vinyl acetate) (PVAc) as an additive, Ethylene Carbonate (EC) as a plasticizer, Lithium Perchlorate as dopant salt and Barium Titanate (BaTiO3) as a filler were prepared for various concentrations of BaTiO3 using solvent casting technique. Thermal stability of the sample having maximum ionic conductivity was found using TG/DTA analysis. Nano composite polymer electrolytes were subjected to ac impedance analysis spectra for acquiring the ionic conductivity values at different temperature. Surface structure of the sample was analysed using scanning electron microscope and the complexations of samples were analysed using X-ray diffraction analysis. It was noted that the polymer electrolyte contains 8 wt. % of BaTiO3 showed maximumionic conductivity than the other ratios of BaTiO3.

Performance evaluation of in-service open web girder steel railway bridge through full scale experimental investigations

Sundaram, B. Arun,Kesavan, K.,Parivallal, S. Techno-Press 2019 Structural monitoring and maintenance Vol.6 No.3

Civil infrastructures, such as bridges and tunnels are most important assets and their failure during service will have significant economic and social impact in any country. Behavior of a bridge can be evaluated only through actual monitoring/measurements of bridge members under the loads of interest. Theoretical analysis alone is not a good predictor of the ability of a bridge. In some cases, theoretical analyses can give less effect than actual since theoretical analyses do not consider the actual condition of the bridge, support conditions, level of corrosion and damage in members and connections etc. Hence actual measurements of bridge response should be considered in making decisions on structural integrity, especially in cases of high value bridges (large spans and major crossings). This paper describes in detail the experimental investigations carried out on an open web type steel railway bridge. Strain gages and displacement transducers were installed at critical locations and responses were measured during passage of locomotives. Stresses were evaluated and extrapolated to maximum design loading. The responses measured from the bridge were within the permissible limits. The methodology adopted shall be used for assessing the structural integrity of the bridge for the design loads.

High‑performance electric double‑layer capacitor fabricated with nanostructured carbon black‑paint pigment as an electrode

V. Samynaathan,Sangeetha R. Iyer,K. Shree Kesavan,M. S. Michael 한국탄소학회 2021 Carbon Letters Vol.31 No.1

Engineering the microstructure of the carbonaceous materials is a promising strategy to enhance the capacitive performance of supercapacitors. In this work, nanostructured Black Pearl (1500 BP) carbon which is a conductive carbon being commercially used in printing rolls, conductive packaging, conductive paints, etc. is analyzed for its feasibility as an electrode material for Electric Double-Layer Capacitors (EDLCs). To achieve that commercial Black Pearl (BP), carbon is treated with mild acid H3PO4 to remove the impurities and enhance the active sites by regulating the growth of agglomerates and creating micropores in the nano-pigments. Generally, the coalescence of nanoparticles owing to their intrinsic surface energy has tendency to create voids of different sizes that act like meso/micropores facilitating the diffusion of ions. The electrochemical performance of BP carbon before and after chemical activation is investigated in aqueous ( H2SO4, KOH and KCl) and a non-aqueous electrolyte (1 M TEMABF4 in acetonitrile) environment employing different electrochemical techniques such as Cyclic Voltammetry (CV), Galvanostatic charge/discharge (GCD) and Electrochemical Impendence Spectroscopy (EIS). The chemically activated BP carbon delivers the highest specific capacitance of ∼156 F g?1 in an aqueous electrolyte, 6 M KOH. The highest specific power, ~ 15.3 kW kg?1 and specific energy, 14.6 Wh kg?1 are obtained with a symmetric capacitor employing non-aqueous electrolyte because of its high working potential, 2.5 V.

Microbial acclimatization to lipidic-waste facilitates the efficacy of acidogenic fermentation

Saha, Shouvik,Jeon, Byong-Hun,Kurade, Mayur B.,Chatterjee, Pradip K.,Chang, Soon Woong,Markkandan, Kesavan,Salama, El-Sayed,Govindwar, Sanjay P.,Roh, Hyun-Seog Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.358 No.-

<P><B>Abstract</B></P> <P>Lipidic-waste such as fat, oil, and grease (FOG) are promising substrates for achieving higher bioenergy yields. An inadequate presence of an effective microbiome in the anaerobic digesters is the bottleneck for the proper utilization of FOG. Gradual introduction of FOG (0.2%, 1.2%, and 2.4% as volatile solids) in acidogenic fermentation showed a significant improvement in hydrogen yield (72%), compared to the control, after 2.4% FOG loading. Volatile solid (VS) reduction reached up to 65% in high FOG reactors with complete removal of major unsaturated fatty acids. Removal of saturated fatty acids increased to 90%. Improvement in hydrogen productivity (46 mL d<SUP>−1</SUP>) occurred during step-wise loading of 2.4% FOG to the acclimatized microbiome. The metabolic shift toward carboxylic chain elongation produced C4 and C6 fatty acids at concentrations of 1.61 mM and 0.90 mM, respectively in the acidogenic reactors. High-throughput sequencing of 16S rRNA amplicons revealed that the acclimatization process enriched the phylum Firmicutes (90%), followed by Bacteroidetes (12%) and Cloacimonetes (11%). The abundance of these phyla and their respective genera confirmed their preeminent role in hydrolysis, hydrogenogenic acidogenesis, and carboxylic chain elongation to produce hydrogen and C4–C7 fatty acids. Thus, we suggest that the improvement of hydrogen production using a microbiome acclimatized to FOG, and simultaneous production of high value organics (C4–C7 fatty acids), could facilitate the greater efficacy of the acidogenic fermentation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Microbial acclimatization improved lipidic-waste utilization in acidogenic fermentation. </LI> <LI> Firmicutes, Bacteroidetes, and Cloacimonetes were abundant in the acclimatized microbiome. </LI> <LI> Hydrogen productivity enhanced to 46 mL d<SUP>−1</SUP> after acclimatization. </LI> <LI> Hydrogenogenic acidogenesis and carboxylic chain elongation produced C4–C7 fatty acids. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>