• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.1-8
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• 2005

This paper describes a new objective methodology of seismic building damage assessment which is called Advanced Component Method(ACM). ACM is a major attempt to replace the conventional loss estimation procedure, which is based on subjective measures and the opinions of experts, with one that objectively measures both earthquake intensity and the response ol buildings. First, response of typical buildings is obtained analytically by nonlinear seismic static analysis, push-over analyses. The spectral displacement Is used as a measure of earthquake intensity in order to use Capacity Spectrum Method and the damage functions for each building component, both structural and non-structural, are developed as a function of component deformation. Examples of components Include columns, beams, floors, partitions, glazing, etc. A repair/replacement cost model is developed that maps the physical damage to monetary damage for each component. Finally, building response, component damage functions, and cost model were combined probabilistically, using Wonte Carlo simulation techniques, to develop the final damage functions for each building type. Uncertainties in building response resulting from variability in material properties and load assumptions were incorporated in the Latin Hypercube sampling technique. The paper also presents and compares ACM and conventional building loss estimation based on historical damage data and reported loss data.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.4
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• pp.343-350
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• 2000

In this paper, we propose the Multi-FPNN(Fuzzy Polynomial Neural Networks) model based on FNN and PNN(Polyomial Neural Networks) for optimal system identifacation. Here FNN structure is designed using fuzzy input space divided by each separated input variable, and urilized both in order to get better output performace. Each node of PNN structure based on GMDH(Group Method of Data handing) method uses two types of high-order polynomials such as linearane and quadratic, and the input of that node uses three kinds of multi-variable inputs such as linear and quadratic, and the input of that node and Genetic Algorithms(GAs) to identify both the structure and the prepocessing of parameters of a Multi-FPNN model. Here, HCM clustering method, which is carried out for data preproessing of process system, is utilized to determine the structure method, which is carried out for data preprocessing of process system, is utilized to determance index with a weighting factor is used to according to the divisions of input-output space. A aggregate performance inddex with a wegihting factor is used to achieve a sound balance between approximation and generalization abilities of the model. According to the selection and adjustment of a weighting factor of this aggregate abjective function which it is acailable and effective to design to design and optimal Multi-FPNN model. The study is illustrated with the aid of two representative numerical examples and the aggregate performance index related to the approximation and generalization abilities of the model is evaluated and discussed.

• Composites Research
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• v.34 no.5
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• pp.317-322
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• 2021

When a complex load such as torsion, low-speed impact, or fatigue load is applied, the properties in the thickness direction are weakened through microcracks inside the material due to the nature of the laminated composite material, and delamination occurs. To prevent the interlaminar delamination, various three-dimensional reinforcement methods such as Z-pinning and stitching, and structural health monitoring techniques that detect the microcrack of structures in real time have been continuously studied. In this paper, the single-lap joints with I-fiber stitching process were manufactured by a co-curing method and their strengths and failure detection capability were evaluated. AE and electric resistance method were used for detection of crack and failure signal and electric circuit for signal analysis was manufactured, and failure signal was analyzed during the tensile test of a single-lap joint. From the experiment, the strength of the single lap joint reinforced by I-fiber stitching process was improved by about 44.6% compared to the co-cured single lap joint without reinforcement. In addition, as the single-lap joint reinforced by I-fiber stitching process can detect failure in both the electrical resistance method and the AE method, it has been proven to be an effective structure for failure monitoring as well as strength improvement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.1
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• pp.1-11
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• 2021

In order to reuse existing onshore turbine foundations, it is important to redesign and reinforce the existing foundations according to the upgraded tower diameter and turbine load. In the present study, a slab extension reinforcement method and structure details of an anchorage part were examined in consideration of the reuse of spread footings, which are the most widely used foundation type in onshore wind turbine foundations. Experiments were conducted to evaluate the load resistance performance of a reinforced spread footing according to structure details of an anchorage part. The results showed that (1) the strength of an anchorage part could be increased by more than 30 % by adding reinforcement bars in the anchorage part, (2) pile-sleeves attached to an anchor ring contributed to an increase in rotational stiffness by preventing shear slip behavior between the anchor ring and the concrete, and (3) slab connectors contributed to an increase in the strength and deformation capacity by preventing the separation of new and old concrete slabs.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.841-848
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• 2006

There is a complex variation of stress in PSC anchorage zones and box girder diaphragms because of large concentrated load by prestress. According to the AASHTO LFRD design code, three-dimensional effects due to concentrated jacking loads shall be investigated using three-dimensional analysis procedures or may be approximated by considering separate submodels for two or more planes. In this case, the interaction of the submodels should be considered, and the model loads and results should be consistent. However, box girder diaphragms are 3-dimensional disturbed region which requires a fully three-dimensional model, and two-dimensional models are not satisfactory to model the flow of forces in diaphragms. In this study, the strengths of the prestressed box girder diaphragms are predicted using the 3-dimensional grid strut-tie model approach, which were tested to failure in University of Texas. According to the analysis results, the 3-dimensional strut-tie model approach can be possibly applied to the analysis and design of PSC box girder anchorage zones as a reasonable computer-aided approach with satisfied accuracy.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.26-32
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• 2020

Concrete recycling is becoming mandatory rather selective due to depletion of constructional materials and increase of concrete waste. Studies on recycling concrete are conducted in various point of view for long time. However, standard or guideline of many countries for the application of recycled aggregate concrete(RAC) has restrictions such as low replacement rate of coarse aggregate and no fine aggregate allowed due to inferior material properties of recycled aggregate. This study intends to figure out the feasibility of casting natural aggregate concrete(NAC) and RAC separately in a structural member. In making RAC, replacement rate of coarse aggregate was 50, 100% in RAC and treatment of interface of two concretes is introduced. RAC treatment of recycled aggregate or inclusion of additives was not done as it can increase embodied energy of concrete work. Double-shear test with uniformly distributed loading was adopted to evaluate shear strength at the interface of two concretes. After curing it was hard to distinguish interface of two concretes. Experimental result revealed that specimen with higher replacement rate showed higher shear-to-compressive strength ratio, which is possibly attributed to coarse aggregate size and roughness of sheared section. Further study on the effect of various parameters is required and subsequent research activity is on-going.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.2
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• pp.109-118
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• 2011

The aims of this study were analyze the amount of stress condition when the traction force was applied to the condyle head from the chin area of mandible and amount of distortion condition when intended 0.5 mm distraction distance from surface or one point of dissected midline of mandible. For this study, 3D finite element analysis were performed. The following results were obtained : 1. When traction force of 500 g was applied to the condyle head from the chin area, condylar neck area showed the greatest amount of stress and coronoid process was the least amount of stress area. For the amount of distortion condition, infra dental area showed the greatest. 2. When 0.5 mm of intended surface distortion was applied after dissection of mid-mandible area, base anterior area showed the greatest amount of stress but the least stress area was coronoid process. For the amount of distortion, infra dental, menton area showed the greatest amount. 3. One point distortion was applied after dissection of mid-mandible area, ramus posterior area showed the greatest amount of stress and menton area were the least stress condition. For the amount of distortion, menton area showed the greatest amount of distortion condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.49-55
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• 2017

Most motor cases adopt deep drawing products, which are excellent in waterproof functions, concentricity, right angle, and quality. In addition, the blower motor and seat motor, which are installed in the car interior and do not require waterproof function, adopts a multi-forming manufacturing method. The deep drawing process requires an expensive transfer press that can digest approximately 12 processes, such as drawing, trimming and piercing. On the other hand, products can be produced with low investment because the multi-forming method is composed of one multi-forming machine or one multi-forming machine and one press. The multi-forming machine is a high-priced facility that is mostly imported and a bending / shearing process multi-foaming machine, which was developed by domestic small and medium-sized enterprises, is not enough to reduce the production cost. An integral multi - forming machine is used as a limited working method for thin material and small products. A large product and thick material has a high shear load. A large product and thick material has a high shear load and uses a single crank press. After blanking, the worker manually feeds the material to a multi-forming machine. When the bending operation is performed in the multi-forming machine, it is transferred to the press again to calibrate the dimensions. This variance in work processes has resulted in lower cost competitiveness due to the lower productivity, quality issues, and excessive operator input. The aim of this study was to establish a stable and cost - effective production system through bending / shearing process separation and facility automation.

• Composites Research
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• v.30 no.6
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• pp.356-364
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• 2017

Composite lattice structures are tried to be used in various fields because of its benefit in physical properties. With increase of demand of the composite lattice structure, nondestructive testing technology is also required to certificate the quality of the manufactured structures. Recently, research on the development of the composite lattice structure in Republic of Korea was started and accordingly, fast and accurate non-destructive evaluation technology was needed to finalize the manufacturing process. This paper studied non-destructive testing methods for composite lattice structure using laser ultrasonic propagation imaging systems. Pulse-echo ultrasonic propagation imaging system was able to inspect a rib structure wrapped with a skin structure. To reduce the time of inspection, a band divider, which can get signal in different frequency bands at once, was developed. Its performance was proved in an aluminum sandwich panel. In addition, to increase a quality of results, curvature compensating algorithm was developed. On the other hand, guided wave ultrasonic propagation imaging system was applied to inspect delamination in a rib structure. To increase an area of inspection, multi-source ultrasonic wave propagation image was applied, and defects were successfully highlighted with variable time window amplitude mapping algorithm. These imply that ultrasonic propagation imaging systems provides fast and accurate non-destructive testing results for composite lattice structure in a stage of the manufacturing process.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.381-389
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• 2000

Metal matrix composite(MMCs) have been rapidly becoming one of the strongest candidates for structural materials for high temperature application. It is well recognized that MMCs always experience at least one large cool-down from processing temperature before my significant applied service loading. Due to the large difference in thermal expansion coefficient between the fiber and matrix, large thermal residual stresses generally develop in composites. It was reported from many previous studies that the effects of thermal residual stress on mechanical properties and fracture behavior were much more complex and dramatic than conventional engineering materials. Therefore it is crucial to evaluate the effect of heat treatment which changes the characteristic of distribution of thermal residual stress in MMCs. Single fiber composite(SFC) test based on the balance in a micromechanical model is a quite convenient method to evaluate interfacial shear strength(IFSS) and the failure mode of composite. In this study the effect of heat treatment on IFSS and the microscopic failure mechanism of MMC is investigated by combining acoustic emission(AE) technique with SFC test. The characteristic of AE signal, IFSS and microscopic failure mechanism due to heat treatment condition is discussed.