• Steel and Composite Structures
• /
• v.18 no.5
• /
• pp.1103-1117
• /
• 2015

It is known that material properties, connection quality and manufacturing methods are among the important factors directly affecting the behavior of steel connections and hence steel structures. The possible performance differences between a fabricated connection and its computer model may cause critical design problems for steel structures. Achieving a reliable design depends, however, on how accurately the material properties and relevant constitutive models are considered to characterize the behavior of structures. Conventionally, the stress and strain fields in structural steel connections are calculated using the finite elements method with assumed material properties and constitutive models. Because the conventional strain gages allow the measurement of deformation only at one point and direction for specific time duration, it is not possible to determine the general characteristics of stress-strain distributions in connections after the laboratory performance tests. In this study, a new method is introduced to measure displacement distribution of simple steel welded connections under tension tests. The method is based on analyzing digital images of connection specimens taken periodically during the laboratory tension test. By using this method, displacement distribution of steel connections can be calculated with an acceptable precision for the tested connections. Calculated displacements based on the digital image correlation method are compared with those calculated using the finite elements method.

• Geomechanics and Engineering
• /
• v.7 no.1
• /
• pp.75-85
• /
• 2014

The application of the mechanized tunnelling has been extended in recent years. There are at present different approaches that are used in the design of segmental tunnel linings supported in mechanized tunnels. Even though segmental lining is utilized for mechanized tunnels, its behaviour is still quite unclear under in situ stress and there is a lack of data regarding the distribution of stresses inside segmental linings. So far no single effective calculation method exists for segmental lining design. The lack of clear solutions makes the use of segmental lining to be more expensive due to the adoption of greater safety factors. Therefore, a particular attention must be given in order to obtain data from monitored tunnels which permits to validate design methods. In this study, strain measurements, which were conducted during the construction of twin tunnels in the Bologna-Florence railway line, have been presented. The behaviour of segmental lining during the excavation and the influence of a new tunnel excavation on an existing tunnel have been shown through the measured data. The data are then compared with the results obtained with Einstein and Schwartz's method and Duddeck and Erdmann's method, which permits to highlight the fact that the two analytical methods underestimate structural forces induced in the segmental lining and then must be used with caution.

• Korean Journal of Microbiology
• /
• v.25 no.1
• /
• pp.17-22
• /
• 1987

For the purpose of securing of strains which can be usefully utilized to study symbiosis between Rhizobium and legume plant, A. tumefaciens T7 was isolated and characterized and then subgroup biovar was determined. A. tumefaciens T7 induced smooth tumor like nopaline type one and did not grow at $37^{\circ}C$ and in the presence of 2% NaCl on yeast extract mannitol medium. The strain was able to grow on the New and Kerr selective media and utilize erythritol but not phenylalanine, tryptophan, and tartarate as a sole carbon source. Negative results were obtained from 3-keto-lactose production and oxidase test. The strain produced alkalifrom malonate and citrate and showed acid litmus milk reaction At least two large plasmids were detected in the cell lysate. According to all of these results, it could be concluded that subdivision of isolated strain was biovar 2.

• 한국가시화정보학회:학술대회논문집
• /
• 2002.11a
• /
• pp.97-99
• /
• 2002

Turbulent premixed flames were a subject of many researches for a number of decades. Especially, Borghi suggested a manificent diagram classifying turbulent combustion reasions and Lipatnikov and Chomiak modified this diagram. But this diagram has difficulties tn defining a flame thickness and velocity and measuring integral length scales In addition, recently experimental techniques are being developed, so we can accurately use PIV diagnostics measuring 2D velocity field instead of LDV and make good use of PLIF techniques for obtaining the flame information. In this study, according to developing techniques, suggest a new diagram replacing the existing Borghi diagram. Simultaneous PIV/OH PLIF measurements are used, which measure a shear strain rate and a location of flames, respectively. The shear strain rate represents turbulence and the OH signal indicates the flame information, but there is no geometric Information which is very important to flame quenching. Hence, to consider the geometric information, calculate fractal dimensions of the OH images. So the diagram suggested in this research has three axes which consist of strain rate, OH signal, and fractal dimension and can classify turbulent premixed flames.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.4
• /
• pp.693-700
• /
• 2002

Recently, the mechanical structures applied to many industrial products, especially in electronic products, appear to be miniaturized and complicated. This trend makes it difficult to analyze the stress distribution of those mechanical structures and generates new challenges for precise measurement of strain. In order to solve this measurement problem many optical measurement techniques have been suggested. Among those, the ESPI(Electronic Speckle Pattern Interferometry) has been considered as one of the most useful tools. But the shortage of recognition and difficulties of measurement have limited its industrial applications in spite of its excellent capabilities. Therefore in this study, not only the verification of the FEA result but the enhancement of industrial application of ESPI was tried by measuring the in-plane displacement of mechanical structure with ESPI, which is difficult to be measured with strain gauge.

• Journal of Mechanical Science and Technology
• /
• v.17 no.8
• /
• pp.1164-1170
• /
• 2003

The objectives of this work here focus on the differences in responses to multiple cyclic tests of different sections along the length of the same tendon. Tendon specimens were obtained from the hindlimbs of canines and frozen to -70$^{\circ}C$. After thawing, specimens were mounted in the immersion bath at room temperature (22$^{\circ}C$) , preloaded to 0.13 N and then subjected to 3% or 4% of the initial length at a strain rate of 5%/sec. It was found that different sections of the same long tendons had different resistances to deformation. In general, the bone end sections were stiffer and carried greater loads for a given strain than the muscle end sections, and the mid-portions were the least stiff and carried the smallest loads for a given strain. The results of this study offer new information about the mechanical responses of collagenous tissues. We know more about their responses to multiple cyclic extensions and how their responses are different from the positions along the length of the tendon specimen. The nature and causes of these differences in the stiffness are not fully known. However, it is clear that differences in the mechanical response of tendons and other connective tissues are significant to musculoskeletal performance.

• Korean Journal of Food Science and Technology
• /
• v.9 no.1
• /
• pp.1-9
• /
• 1977

A bacterium strain (K-173-10) which was isolated from waste soil of Korea brewing factory, could be grown on acetate as the sole carbon source and accumulated a considerable amount of L-glutamic acid in the medium. This strain was identified as the new species Brevibacterium ammoniagenes. This study was concerned not only with the culture condition for the production of L-glutamic acid and the cell growth, but also with the effects on concentration of various kind of organic substances, growth factors and penicillin. The results obtained were summarized as follow; 1. It was found that the concentrations of acetate and ammonium ions affected the growth of the bacterium as well as its L-glutamate accumulation. The optimum conditions of the composition of grown media for the growth of the bacterium and its glutamic acid production was found to be 40 g/l of total acetate, $100\;{\mu}g/l$ thiamine, $0.5\;{\mu}g/l$ biotin and $1{\sim}2g/l$ corn steep liquor as the growth factors. 2. Organic acid such as succinic acid, malic acid and ${\alpha}-ketoglutaric$ acid inhibited the cell growth as well as its L-glutamic acid production. 3. The penicillin (20 units/ml) stimulated the production of glutamic acid at appropriate incubation period. 4. It was found that this strain could grow in the presence of urea and ammonium acetate but not in other nitrogen sources.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.6 no.4
• /
• pp.342-348
• /
• 2005

In this study, novel strains showing better protein degradation activity were isolated for the production of effective compost from garbages. Well growing bacteria with clear zone on the skim milk agar media were isolated . The strain was identified as Bacillus subtilis PNV-1 through various biochemical tests, Bergy's manual of determinative bacteriology and 165 rDNA partial sequence. The extracellular protease of the strain PNV-1 has its activity at broad pH and the optimal temperature was $50^{\circ}C$. Also, the strain PNV-1 was highly tolerant to high concentration of salt, red/black pepper and mustard.

• Computers and Concrete
• /
• v.11 no.5
• /
• pp.411-440
• /
• 2013

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.

• Advances in concrete construction
• /
• v.1 no.1
• /
• pp.103-119
• /
• 2013

The applicability of limit analysis methods in design and assessment of concrete structures generally requires a certain plastic deformation capacity. The latter is primarily provided by the ductility of the reinforcement, being additionally affected by the bond properties between reinforcing steel and concrete since they provoke strain localization in the reinforcement at cracks. The bond strength of reinforcing bars is not only governed by concrete quality, but also by construction details such as bar ribbing, bar spacing or concrete cover thickness. For new concrete structures, a potentially unfavorable impact on bond strength can easily be anticipated through appropriate code rules on construction details. In existing structures, these requirements may not be necessarily satisfied, consequently requiring additional considerations. This two-part paper investigates in a theoretical study the impacts of the most frequently encountered construction details which may not satisfy design code requirements on bond strength, steel strain localization and plastic deformation capacity of cracked structural concrete. The first part introduces basic considerations on bond, strain localization and plastic deformation capacity as well as the fundamentals of the Tension Chord Model underlying the further investigations. It also analyzes the impacts of the hardening behavior of reinforcing steel and concrete quality. The second part discusses the impacts of construction details (bar ribbing, bar spacing, and concrete cover thickness) and of additional structure-specific features such as bar diameter and crack spacing.