Robust finite element model updating of a large-scale benchmark building structure

Matta, E.,De Stefano, A. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.3

Accurate finite element (FE) models are needed in many applications of Civil Engineering such as health monitoring, damage detection, structural control, structural evaluation and assessment. Model accuracy depends on both the model structure (the form of the equations) and the model parameters (the coefficients of the equations), and can be generally improved through that process of experimental reconciliation known as model updating. However, modelling errors, including (i) errors in the model structure and (ii) errors in parameters excluded from adjustment, may bias the solution, leading to an updated model which replicates measurements but lacks physical meaning. In this paper, an application of ambient-vibration-based model updating to a large-scale benchmark prototype of a building structure is reported in which both types of error are met. The error in the model structure, originating from unmodelled secondary structural elements unexpectedly working as resonant appendages, is faced through a reduction of the experimental modal model. The error in the model parameters, due to the inevitable constraints imposed on parameters to avoid ill-conditioning and under-determinacy, is faced through a multi-model parameterization approach consisting in the generation and solution of a multitude of models, each characterized by a different set of updating parameters. Results show that modelling errors may significantly impair updating even in the case of seemingly simple systems and that multi-model reasoning, supported by physical insight, may effectively improve the accuracy and robustness of calibration.

Tensile response of steel/CFRP adhesive bonds for the rehabilitation of civil structures

Matta, F.,Karbhari, Vistasp M.,Vitaliani, Renato Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.5

There is a growing need for the development and implementation of new methods for the rapid and cost-effective rehabilitation of deteriorating steel structural components to offset the drawbacks related to welding and/or bolting in the field. Carbon fiber reinforced polymer (CFRP) composites provide a potential alternative as externally bonded patches for strengthening and repair of metallic structural members for building and bridge systems. This paper describes results of an investigation of tensile and fatigue response of steel/CFRP joints simulating scenarios of strengthening and crack-patching. It is shown that appropriately designed schemes, even when fabricated with levels of inaccuracy as could be expected in the field, can provide significant strain relief and load transfer capability. A simplified elasto-plastic closed form solution for stress analysis is presented, and validated experimentally. It is shown that the bond development length remains constant in the linear range, whereas it increases as the adhesive is deformed plastically. Fatigue resistance is shown to be at least comparable with the requirements for welded cover plates without attendant decreases in stiffness and strength.

Performance of tuned mass dampers against near-field earthquakes

Matta, E. Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.5

Passive tuned mass dampers (TMDs) efficiently suppress vibrations induced by quasi-stationary dynamic inputs, such as winds, sea waves or traffic loads, but may prove of little use against pulse-like excitations, such as near-field (NF) ground motions. The extent of such impairment is however controversial, partly due to the different evaluation criteria adopted within the literature, partly to the limited number of seismic records used in most investigations. In this study, three classical techniques and two new variants for designing a TMD on an SDOF structure are tested under 338 NF records from the PEER NGA database, including 156 records with forward-directivity features. Percentile response reduction spectra are introduced to statistically assess TMD performance, and TMD robustness is verified through Monte Carlo simulations. The methodology is extended to a variety of MDOF bending-type and shear-type frames, and simulated on a case study building structure recently constructed in Central Italy.Results offer an interesting insight into the performance of TMDs against NF earthquakes, ultimately showing that, if properly designed and sufficiently massive, TMDs are effective and robust even in the face of pulse-like ground motions. The two newly proposed design techniques are shown to generally outperform the classical ones.

In vivo Tracking of Mesenchymal Stem Cells Labeled with a Novel Chitosan-coated Superparamagnetic Iron Oxide Nanoparticles using 3.0T MRI

Alavala Matta Reddy,곽병국,심형진,안치영,이효석,서용재,박은섭 대한의학회 2010 Journal of Korean medical science Vol.25 No.2

This study aimed to characterize and MRI track the mesenchymal stem cells labeled with chitosan-coated superparamagnetic iron oxide (Chitosan-SPIO). Chitosan-SPIO was synthesized from a mixture of FeCl2 and FeCl3. The human bone marrow derived mesenchymal stem cells (hBM-MSC) were labeled with 50 mg Fe/mL chitosan-SPIO and Resovist. The labeling efficiency was assessed by iron content, Prussian blue staining, electron microscopy and in vitro MR imaging. The labeled cells were also analyzed for cytotoxicity, phenotype and differentiation potential. Electron microscopic observations and Prussian blue staining revealed 100% of cells were labeled with iron particles. MR imaging was able to detect the labeled MSC successfully. Chitosan-SPIO did not show any cytotoxicity up to 200 mg Fe/mL concentration. The labeled stem cells did not exhibit any significant alterations in the surface markers expression or adipo/osteo/chondrogenic differentiation potential when compared to unlabeled control cells. After contralateral injection into rabbit ischemic brain, the iron labeled stem cells were tracked by periodical in vivo MR images. The migration of cells was also confirmed by histological studies. The novel chitosan-SPIO enables to label and track MSC for in vivo MRI without cellular alteration.

Robust finite element model updating of a large-scale benchmark building structure

E. Matta,A. De Stefano 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.3

Accurate finite element (FE) models are needed in many applications of Civil Engineering such as health monitoring, damage detection, structural control, structural evaluation and assessment. Model accuracy depends on both the model structure (the form of the equations) and the model parameters (the coefficients of the equations), and can be generally improved through that process of experimental reconciliation known as model updating. However, modelling errors, including (i) errors in the model structure and (ii) errors in parameters excluded from adjustment, may bias the solution, leading to an updated model which replicates measurements but lacks physical meaning. In this paper, an application of ambient-vibration-based model updating to a large-scale benchmark prototype of a building structure is reported in which both types of error are met. The error in the model structure, originating from unmodelled secondary structural elements unexpectedly working as resonant appendages, is faced through a reduction of the experimental modal model. The error in the model parameters, due to the inevitable constraints imposed on parameters to avoid ill-conditioning and under-determinacy, is faced through a multi-model parameterization approach consisting in the generation and solution of a multitude of models, each characterized by a different set of updating parameters. Results show that modelling errors may significantly impair updating even in the case of seemingly simple systems and that multimodel reasoning, supported by physical insight, may effectively improve the accuracy and robustness of calibration.

Kinetic Property and Phylogenic Relationship of 2-Hydroxymuconic Semialdehyde Dehydrogenase Encoded in tomC Gene of Burkholderia cepacia G4

Alavala Matta Reddy,민경락,Kyoung Lee,임재윤,김치경,김영수 대한약학회 2004 Archives of Pharmacal Research Vol.27 No.5

2-Hydroxymuconic semialdehyde (2-HMS) dehydrogenase catalyzes the conversion of 2-HMS to 4-oxalocrotonate, which is a step in the meta cleavage pathway of aromatic hydrocarbons in bacteria. A tomC gene that encodes 2-HMS dehydrogenase of Burkholderia cepacia G4, a soil bacterium that can grow on toluene, cresol, phenol, or benzene, was overexpressed into E. coli HB101, and its gene product was characterized in this study. 2-HMS dehydrogenase from B. cepacia G4 has a high catalytic efficiency in terms of Vmax/Km towards 2-hydroxy-5-methylmuconic semialdehyde followed by 2-HMS but has a very low efficiency for 5-chloro-2- hydroxymuconic semialdehyde. However, the enzyme did not utilize 2-hydroxy-6-oxo-hepta- 2,4-dienoic acid and 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid as substrates. The molecular weight of 2-HMS dehydrogenase from B. cepacia G4 was predicted to be 52 kDa containing 485 amino acid residues from the nucleotide sequence of the tomC gene, and it exhibited the highest identity of 78% with the amino acid sequence of 2-HMS dehydrogenase that is encoded in the aphC gene of Comamonas testosteroni TA441. 2-HMS dehydrogenase from B. cepacia G4 showed a significant phylogenetic relationship not only with other 2-HMS dehydrogenases, but also with different dehydrogenases from evolutionarily distant organisms.

Performance of tuned mass dampers against near-field earthquakes

E. Matta 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.5

Passive tuned mass dampers (TMDs) efficiently suppress vibrations induced by quasistationary dynamic inputs, such as winds, sea waves or traffic loads, but may prove of little use against pulse-like excitations, such as near-field (NF) ground motions. The extent of such impairment is however controversial, partly due to the different evaluation criteria adopted within the literature, partly to the limited number of seismic records used in most investigations. In this study, three classical techniques and two new variants for designing a TMD on an SDOF structure are tested under 338 NF records from the PEER NGA database, including 156 records with forward-directivity features. Percentile response reduction spectra are introduced to statistically assess TMD performance, and TMD robustness is verified through Monte Carlo simulations. The methodology is extended to a variety of MDOF bending-type and shear-type frames, and simulated on a case study building structure recently constructed in Central Italy. Results offer an interesting insight into the performance of TMDs against NF earthquakes, ultimately showing that, if properly designed and sufficiently massive, TMDs are effective and robust even in the face of pulse-like ground motions. The two newly proposed design techniques are shown to generally outperform the classical ones.

Artemisolide from Artemisia asiatica: Nuclear Factor-κB (NF-κB) Inhibitor Suppressing Prostaglandin E2 and Nitric Oxide Production in Macrophages

Alavala Matta Reddy,Jun-Young Lee,Jee Hee Seo,김병학,Eun Yong Chung,Shi Yong Ryu,김영섭,이종길,민경락,김영수 대한약학회 2006 Archives of Pharmacal Research Vol.29 No.7

Aerial parts of Artemisia asiatica (Compositae) have been traditionally used as an oriental medicine for the treatment of inflammatory and ulcerogenic diseases. In the present study, artemisolide was isolated as a nuclear factor (NF)-κB inhibitor from A. asiatica by activityguided fractionation. Artemisolide inhibited NF-κB transcriptional activity in lipopolysaccharide (LPS)-stimulated macrophages RAW 264.7 with an IC50 value of 5.8 µM. The compound was also effective in blocking NF-κB transcriptional activities elicited by the expression vector encoding the NF-κB p65 or p50 subunits bypassing the inhibitory kB degradation signaling NF- κB activation. The macrophages markedly increased their PGE2 and NO production upon exposure to LPS alone. Artemisolide inhibited LPS-induced PGE2 and NO production with IC50 values of 8.7 µM and 6.4 µM, respectively, but also suppressed LPS-induced synthesis of cyclooxygenase (COX)-2 or inducible NO synthase (iNOS). Taken together, artemisolide is a NF-κB inhibitor that attenuates LPS-induced production of PGE2 or NO via down-regulation of COX-2 or iNOS expression in macrophages RAW 264.7. Therefore, artemisolide could represent and provide the anti-inflammatory principle associated with the traditional medicine, A. asiatica.

Tensile response of steel/CFRP adhesive bonds for the rehabilitation of civil structures

F. Matta,Vistasp M. Karbhari,Renato Vitaliani? 국제구조공학회 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.5

Kinetic Property and Phylogenie Relationship of 2-Hydroxy-muconic Semialdehyde Dehydrogenase Encoded in tomC Gene of Burkholderia cepacia G4

Reddy, Alavala-Matta,Min, Kyung-Rak,Lee, Kyoung,Lim, Jai-Yun,Kim, Chi-Kyung,Kim, Young-Soo The Pharmaceutical Society of Korea 2004 Archives of Pharmacal Research Vol.27 No.5

2-Hydroxymuconic semialdehyde (2-HMS) dehydrogenase catalyzes the conversion of 2-HMS to 4-oxalocrotonate, which is a step in the meta cleavage pathway of aromatic hydrocarbons in bacteria. A tomC gene that encodes 2-HMS dehydrogenase of Burkholderia cepacia G4, a soil bacterium that can grow on toluene, cresol, phenol, or benzene, was overexpressed into E. coli HB 101, and its gene product was characterized in this study. 2-HMS dehydrogenase from B. cepacia G4 has a high catalytic efficiency in terms of V$_{max}$K$_{max}$ towards 2-hydroxy-5-methyl-muconic semialdehyde followed by 2-HMS but has a very low efficiency for 5-chloro-2-hydroxymuconic semialdehyde. However, the enzyme did not utilize 2-hydroxy-6-oxo-hepta 2,4-dienoic acid and 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid as substrates. The molecular weight of 2-HMS dehydrogenase from B. cepacia G4 was predicted to be 52 kDa containing 485 amino acid residues from the nucleotide sequence of the tomC gene, and it exhibited the highest identity of 78% with the amino acid sequence of 2-HMS dehydrogenase that is encoded in the aphC gene of Comamonas testosteroni TA441. 2-HMS dehydrogenase from B. cepacia G4 showed a significant phylogenetic relationship not only with other 2-HMS dehydrogenases, but also with different dehydrogenases from evolutionarily distant organisms.sms.