• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.6
• /
• pp.182-192
• /
• 2022

Brittle feature is one of the fracture behaviors of structure s and has a great influence on the seismic performance of structure materials. The load velocity acts as one of the main causes of brittle fracture, and in particular, in situations such as earthquakes, a high load velocity acts on buildings. However, most of the seismic performance evaluation of the domestic and external steel connections is conducted through static experiments. Therefore, there is a possibility that brittle fracture due to factors such as degradation of material toughness and reduction of maximum deformation rate due to high load velocity during an earthquake was not sufficiently considered in the existing seismic performance evaluation. This study conducts a static test at a low load velocity according to the existing experimental method and a dynamic test at a high load velocity using a shaking table, respectively. It compares and analyzes the fracture shape and structural performance according to the results of each experiment, and finally analyzes the effect of the load velocity size on the seismic performance of the connection.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.4
• /
• pp.79-88
• /
• 2007

Concrete structures undergo degradation of durability performance and it generally propagates to the structural problems. Recently. a lot of materials for surface protection for concrete are developed, however, performance is not clearly improved due to the difficulties such as repair construction technique and quality of materials for repairing. In this study, liquid inorganic impregnant for concrete structures is developed and durability performance for impregnated concrete specimens is carried out. Furthermore, the performances of the concrete specimens with developed impregnant is also compared with those of the specimens with impregnant conventionally used. Additional CSH gel is formed through the reaction of calcium hydroxide ($Ca(OH)_2$) and impregnant with silicate. As a result of the reaction, impregnated concrete is evaluated to have more denser surface and resistance to deterioration. Finally it is experimentally verified that the concrete specimens with developed impregnant show better durability performance than normal specimens and those with conventional impregnant.

• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.9
• /
• pp.1291-1295
• /
• 2004

Histology and transmission electron microscopy studies were carried out on buffalo muscles that were subjected to repeated freeze-thaw cycles at -10 and $-18^{\circ}C$. In the first freeze thaw cycle ($-10^{\circ}C$) structures of muscle showed slight change and closely resembled to those of normal muscle. There were frequent gaps in the half way across the fibres and some cracks in individual fibre were also noticed in second freeze thaw cycle. In the muscle frozen at $-18^{\circ}C$, more pronounced shrinkage with extensive damage of fibres with tearing was observed. The interfibrillar gaps were wider, shrinkage and tearing of the fibres were more distinct after second freeze-thaw cycle. After the second cycle, the interior portion showed large scale degradation of the ultrastructure. Our studies of buffalo muscle showed that under the proper condition, little structural damage takes place in the meat histology and ultrastructure under repeated freeze-thaw conditions. This study adds continued weight to the evidence that limited freeze-thaw cycles will not deteriorate the quality of meat.

• Environmental Engineering Research
• /
• v.12 no.5
• /
• pp.218-223
• /
• 2007

The hybrid $C/TiO_2$ complexes were prepared by a method involving the penetration of titanium n-butoxide (TNB) solution with porous carbons. The photocatalysts were investigated for their surface textural properties and SEM morphology, structural crystallinity and elemental identification between porous carbon and $TiO_2$, and dye decomposition performance. For all the $C/TiO_2$ complexes prepared by TNB solution methods, the excellent photocatalytic effect for dye degradation should be attributed to the synergitic effects between photo-decomposition of the supported $TiO_2$ and adsorptivity of the porous carbons.

• Computers and Concrete
• /
• v.14 no.6
• /
• pp.635-656
• /
• 2014

A rational estimation of moisture distribution in structural concrete is vital for predicting the possible extent and rate of progression of impending degradation processes. The paper proposes a numerical scheme for analysing the evolution of moisture distribution in concrete subjected to wetting-drying exposure caused by intermittent periods of rainfall. The proposed paradigm is based on the stage wise implementation of non-linear finite element (FE) analysis, with each stage representing a distinct phase of a typical wet-dry cycle. The associated boundary conditions have been constituted to realize the influence of various meteorological elements such as rain, wind, relative humidity and temperature on the exposed concrete surface. The reliability of the developed scheme has been demonstrated through its application for the simulation of experimentally recorded moisture profiles reported in published literature. A sensitivity analysis has also been carried out to study the influence of critical material properties on simulated results. The proposed scheme is vital to the service life modelling of concrete structures in tropical climates which largely remain exposed to the action of alternating rains.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.04a
• /
• pp.31-37
• /
• 2000

Metal matrix composites(MMCs) are rapidly becoming one of the strongest candidates for structural materials for many high temperature application. Among the high temperature environment, thermal shock is known to cause significant degradation in most MMC system. Therefore, the nondestructive evaluation on thermal shock damage behavior of SiC/A16061 composite has been carried out using ultrasonic surface and SH-waves. For this study, Sic fiber reinforced metal matrix composite specimens fabricated by a squeeze casting technique were thermally cycled in the temperature range 25~$400^{\circ}C$ up to 1000 cycles. Three point bend test was conducted to investigate the effect of thermal shock damage on mechanical properties. The relationship between thermal shock damage behavior and the change of ultrasonic velocity and attenuation were discussed by considering SEM observation of fracture surface.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.04a
• /
• pp.43-46
• /
• 2004

Explosive chemicals have been major soil and groundwater contaminants especially in the nations with active military activities. Of these explosives, 2,4,6-trinitrotoluene (TNT) is the most refractory one due to its structural characteristics. Although its efficient reduction by Fe(0) is well-known, the reduction products - mainly aminotoluenes - still possess toxicities to terrestrial biota, and are resistant to biological degradation. In this study, therefore, abiotic transformation of TNT reduction products via oxidative-coupling reaction was evaluated using Mn oxide which is ubiquitous in natural soils. The transformation efficiency is increased with the number of amino groups. Considering the very efficient reduction rate of TNT by Fe(0), Mn oxide can be successfully used for the removal of TNT reduction products.

• 보존과학연구
• /
• s.26
• /
• pp.5-25
• /
• 2005

A consideration number of investigation have begun to elucidate the essential role biological agents play in the deterioration of stone. What is becoming clear is that many factors affect the durability of stone. Physical, chemical, and biological agentsact in co-association, ranging from synergistic to antagonistic, to deteriorate stone. Biodeterioration has usually been considered to be a degradation process following the initial deterioration effects of inorganic agents, especially objects of cultural value such as pagoda, stature of Buddha etc. These agents were thought to condition stone surfaces for microbial contamination due to structural changes and enrichment of inorganic organic nutrient substrates. This report concentrates on the action of biodeteriogens from bacteria to algae and higher plants. Preventive and remedial methods are surveyed, as are a selection of chemical treatments.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.392-395
• /
• 2004

When a concrete member is damaged by fire accident, it can lose its strength. And the degradation rate of losing its strength affected by many environmental conditions. But there is few research for equation for strength evaluation of fire-damaged concrete. Besides, it is impossible to destruct structural member from the building for the evaluation. So, I will suggest a new equation for strength evaluation of fire-damaged RC beam using non-destructive test. For this purpose, the researchers are exploring the performance of non-destructive testing methods using Ultrasonic test, Schmidt Hammer test and Coring test against fire damaged concrete specimen.

• Journal of Environmental Science International
• /
• v.1 no.2
• /
• pp.69-80
• /
• 1992

Effects of light on leaf senescence of Phseolus vulgaris were investigated by measuring the disassembly of chlorophyll-protein complexes in detached leaves which had been kept in the dark or under light. The loss of chlorophyll accompanied by degradation of chlorophyll- protein complexes. PSI (photosystem I) complex containing LHCI (light harvesting complex of PSI) apoproteins was rapidly decreased after the early stage of dark-induced senescence. RC(reaction center)-Cores was slightly increased until 4 d and slowly decreased thereafter. As disassembly of LHCII trimer progressed after the late stage of senescence, there was a steady increase in the relative amount of SC(small complex)-2 containing LHCII monomer. On the other hand, white and red light adaptation caused the structural stability of chlorophyll-protein complexes during dark-induced senescence. Particularly, red light was more effective in the retardation of LHCII breakdown than white light, whereas white light was slightly effect in protecting the disassembly of PSI complex compared to red light. These results suggest, therefore, that light may be a regulatory factor for stability of chlorophyll-protein complexes in the senescent leaves.