• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.63-70
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• 2009

Failure modes result in fracture or tearing, which may cause deterioration of resistance and reduction of inelastic deformation capacity. The potential failure modes for Special Concentrically Braced Frames (SCBFs) include fracture or tearing of the brace, net section fracture of the brace or gusset plate, fracture of the gusset plate welds, shear fracture of the bolts, block shear, excessive bolt bearing deformation, and buckling of the gusset plate. HSS tubular braces are commonly used in SCBFs, and net section fracture of the tubular brace may also occur through the brace net section at the end of the slot cut into the tube to slip over the gusset plate. This failure mode is categorized as a tension failure mode, and may cause dramatic loss of resistance and brittle behavior. Net section reinforcement is required according to AISC design specifications (AISC 2001). In this paper, the need to reinforce the net section area was discussed. Initially, the results of the net section fracture tests done by the University of California in Berkeley were presented with the modeling of these tests using FE models. To investigate the possibility of net section fracture in an actual frame, the slot end hole model was adapted to the frame FE model, and alternate near-fault histories were applied with tension-dominated cycles, since previous analyses showed that loading history was the most critical factor in net section fracture. The need for this reinforcement (cover plate) and the tension-dominated near-fault history were investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1041-1044
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• 2001

This study was performed to evaluate the effect of non-uniform corrosion distribution on the analysis of concrete cover failure. A series of experiments have been undertaken to measure the corrosion rate of reinforcement according to the concentration of chloride ion so as to suggest a relationship between the reinforcement corrosion rate and chloride ion density. The corrosion induced pressure depending on the density of chloride ion has been derived. And nonlinear analysis assuming nonlinear corrosion distribution for cover cracking was achieved and compared with other experimental results to verify the accuracy of the model. Analysis was also performed for various parameters to compare their effects.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.493-499
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• 1997

Objectives of this study is to investigate the behaviors of the confined concrete columns having different core sizes, lateral reinforcement ratios and spacing ratios by using the 3-dimensional analysis of confined concrete columns. In this paper, analyses are done by 3-D nonlinear finite element analysis considering continuum fracture and plasticity and then analysis results are compared with those of model tests. From the comparison, it is shown that the technique in this paper can be used effectively for the analysis of confined concrete columns.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.649-654
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• 2004

In this paper, the fracture toughness and mechanisms of failure in a random SiC-whisker/$Al_{2}O_3$ ceramic composite were investigated using in situ observations during mode I(opening) loading. $SiC_{w}/Al_{2}O_3$ composite was obtained by hot press sintering of $Al_{2}O_3$ powder and SiC whisker as the matrix and reinforcement, respectively. The whisker and powder were mixed using a turbo mill. The composite was produced at SiC whisker volume fraction of $0.3\%$. Compared with monolithic $Al_{2}O_3$, fracture toughness enhancement was observed in $SiC_{w}/Al_{2}O_3$ composite. This improved fracture toughness was attributed to SiC whisker bridging and crack deflection. $SiC_{w}/Al_{2}O_3$ composite exhibited typically brittle fracture behavior, but a fracture process zone was observed in this composite. This means that the load versus load-line displacement curve of $SiC_{w}/Al_{2}O_3$ composite from a fracture test may involve a small non-linear region near the peak load.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.48-58
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• 2014

In this study, quasi-static according to the displacement-controlled (strain control) method tests on RC columns for seismic reinforcement performance in accordance with the provisions of the seismic design and construction before 1992 design code for highway bridges in korea. Used reinforcement that improves the performance of Inorganic Helical Bar, a kind of alloy steel, circular columns were tested outside the seismic reinforcing. In the experiment, fracture behavior, lateral load-displacement relation, ductility and energy assessment evaluation was performed through tests. The variables in experimental are section force of reinforcement, spiral reinforcement spacing, reinforcement method. Improved seismic performance and effect were confirmed through quasi-static test experiments. The results of study confirmed determination the appropriate size of reinforcement, reinforcement forces, spacing and selection of the type required, furthermore, not only mechanical reinforcement but also substitution of high-strength concrete reinforced with concrete cover improved seismic performance.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.41-48
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• 1998

In this paper, an investigation was performed on the dynamic interlaminar fracture toughness of CFRP(carbon fiber reinforcement plastics) composite laminates. Composite laminates used in this experimentation are CF/EPOXY and CF/PEEK laminated plates. In the experiments, Split Hopkinson's Bar(SHPE) test was applied to dynamic and notched flexure test. The mode Ⅱ fracture toughness of each unidirectional CFRP was estimated by the analyzed deflection of the specimen and J-integral with the measured impulsive load and reactions at the supported points. As an experimental result, the vibration amplitude of CF/PEEK laminates appear more than that of CF/EPOXY laminates for the J-integral and displacement velocity at a measuring point. Also, it is thought that the dynamic fracture toughness of two kind specimens(CFRP/EPOXY and CF/PEEK) with the in crease of displacement velocity becomes a little greater at a measuring point within the range of measurement.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1433-1437
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• 2010

The deep excavation work in Korean downtown is almost excuted near by existing structures and utility lines because of the diminution of available yard for construction. So, it was required more and more that the accurate control of displacement on the earth retaining system for minimizing the popular complaint and the damage from constructional accident. Automatic monitoring system is adopted in fracture zone for real time monitoring. In addition, Face mapping is carried out on the face of fracture zone according to excavation sequence. As the result of automatic monitoring system and face mapping, we was able to take the necessary reinforcement and changing excavation method within suitable time. This paper is informed about a stability case on the deep rock excavation site with fracture zone in urban area by automatic monitoring system.

• Carbon letters
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• v.6 no.1
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• pp.6-14
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• 2005

The study of mechanical properties and fracture behaviour of carbon/carbon composites is significant to its application and development. These are dependent on microstructure and properties of reinforcing fibers and matrix, fiber/matrix interface and porosity/cracks present in the composites. In the present studies high-density carbon/carbon composites have been prepared using PAN and various pitch based carbon fibers as reinforcements and pitch as matrix with repeated densification cycles using high-pressure impregnation and carbonization technique. Scanning electron microscopy has been used to study the fracture behaviour of the highly dense composites and correlated with structure of the composites. The geometry of reinforcement and presence of unfilled voids/cracks was found to influence the path of crack propagation and thereby the strength of composites. The type of stresses (tensile or compressive) accumulated also plays an important role in fracture of composites.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.837-840
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• 2002

An analysis method for rubber toughened PVC is suggested to evaluate critical dynamic strain energy release rates($G_c$) from the Charpy impact energy measurements. An instrumented Charpy impact tester was used to extract ancillary information concerning fracture parameters in addition to total fracture energies and maximum critical loads. The dynamic stress intensity factor $K_{Id}$ was computed for varying amounts of rubber contents from the obtained maximum critical loads and also toughening effects were investigated as well. The fracture surfaces produced under low velocity impact fur PVC/MBS composites were investigated by SEM. The results show that MBS rubber is very effective reinforcement material for toughening PVC.C.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.38-39
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• 2013

In this study, in regard to fiber reinforced mortar mixing steel fiber and 4types of organic fiber, impact test was carried out. Because to predict fracture reduction performance with flexural, tensile strength when types of fiber were different as impact reduction performance of concrete is closely related with toughness such as flexural strength, tensile strength and fracture energy etc. As a result, enhancement of toughness by fiber reinforcement controls the spall of rear. On the other hand in case of steel fiber relatively turned up high toughness in appropriate load compared with organic fiber but in same mixing rate, impact reduction performance by projectile showed low performance due to few number of an individual of mixing.