• Title/Summary/Keyword: Structural Evaluation Test

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Evaluation of Structural Performance in CFT Truss Girder with the Arch-Shaped Lower Chord (아치형상의 하현재를 갖는 CFT 트러스 거더의 구조성능 평가)

  • Chung, Chul-Hun;Song, Na-Young;Ma, Hyang-Wook;Oh, Hyun-Chul
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.4A
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    • pp.315-327
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    • 2009
  • In this study, the static test of CFT truss girders for different f/L ratios was conducted to determine how the ultimate strength of the CFT truss girder was affected by different f/L ratios. A total of two CFT truss girders were constructed and tested under bending condition. The length of all specimens is 20,000 mm. The CFT truss girder is a tubular truss composed of chord members made of concrete-filled circular tubes. The main parameter analyzed in the experimental study was the f/L ratio. This factor was experimentally investigated to assess their influence on ultimate strength and stiffness. The test results show that CFT truss girder has good elastic-plastic property and ductility. The presence of the f/L ratios in CFT truss girders alters its ultimate strength because of the global stiffness of the CFT truss girders. The ultimate strength of CFT truss girders increases as the f/L ratio increases. If the f/L ratio of the CFT truss girders increases twofold, the ultimate strengths increase by 80%. The CFT truss girders showed that they retained large deformation capacity, even after reaching the ultimate strength. Results of this investigation demonstrated the potential for efficiently using a CFT truss as a bridge girder.

Evaluation of Local Effect Prediction Formulas for RC Slabs Subjected to Impact Loading (충격하중이 작용하는 RC 슬래브의 국부손상 산정식에 대한 고찰)

  • Chung, Chul-Hun;Choi, Hyun;Lee, Jung Whee;Choi, Kang Ryong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.6A
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    • pp.543-560
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    • 2010
  • Safety-related concrete structures in a nuclear power plant must be protected against the impact of flying objects, referred to in the profession as missiles. In practice, the structural verification is usually carried out by means of empirical formulas, which relate the velocity of the impinging missile to the wall thickness needed to prevent scabbing or perforation. The purpose of this study is to reevaluate the predictability of the local effect prediction formulas for the penetration and scabbing depths and perforation thickness. Therefore, available formulas for predicting the penetration depth, scabbing thickness, and perforation thickness of concrete structures impacted by solid missiles are summarized, reviewed, and compared. A series of impact analyses is performed to predict the local effects of the projectile at impact velocities varing from 95 to 215 m/s. The results obtained from the numerical simulations have been compared with tests that were carried out at Kojima to validate numerical modelling. The simulation results show reasonable agreement with the Kojima test results for the overall impact response of the RC slabs. From these results, it seems that the Degen equation give a very good estimate of perforation thickness against a tornado projectile for test data. Finally, the results obtained from the impact analysis have been compared with Degen formula to determine the perforation thickness of the RC slab.

Evaluation of Bonding Performance of Hybrid Materials According to Laser and Plasma Surface Treatment (레이저 및 플라즈마 표면처리에 따른 이종소재 접합특성평가)

  • Minha Shin;Eun Sung Kim;Seong-Jong Kim
    • Composites Research
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    • v.36 no.6
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    • pp.441-447
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    • 2023
  • Recently, as demand for high-strength, lightweight materials has increased, there has been great interest in joining with metals. In the case of mechanical bonding, such as bolting and riveting, chemical bonding using adhesives is attracting attention as stress concentration, cracks, and peeling occur. In this paper, surface treatment was performed to improve the adhesive strength, and the change in adhesive strength was analyzed. For the adhesive strength test were conducted with Carbon Fiber Reinforced Plastic(CFRP), CR340(Steel), and Al6061(Aluminum), and laser and plasma surface treatment were used. After plasma surface treatment, the adhesive strength improved by 7.3% and 39.2% in CFRP-CR340 and CFRP-Al6061, respectively. CR340-Al6061 was improved by 56.2% in laser surface treatment. Surface free energy(SFE) was measured by contact angle after plasma treatment, and it is thought that the adhesion strength was improved by minimizing damage through a chemical reaction mechanism. For laser surface treatment, it is thought that creates a rough bonding surface and improves adhesive strength due to the mechanical interlocking effect. Therefore, surface treatment is effect to improve adhesive strength, and based on this paper, the long-term fatigue test will be conducted to prevent fatigue failure, which is a representative cause of actual structural damage.

Evaluation of the Dynamic Behavior of Inclined Tripod Micropiles Using Dynamic Centrifuge Test (원심모형실험을 이용한 그룹 삼축 마이크로파일의 동적거동 평가)

  • Kim, Yoon-Ah;Kwon, Tae-Hyuk;Kim, Jongkwan;Han, Jin-Tae;Kim, Jae-Hyun;An, Sung-Yul
    • Journal of the Korean Geotechnical Society
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    • v.39 no.12
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    • pp.93-102
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    • 2023
  • Despite recent modifications to building structural standards emphasizing the seismic stability of building foundations, the current design focus remains solely on vertical support, resulting in insufficient consideration of horizontal loads during earthquakes. In this study, we evaluated the dynamic behavior of inclined tripod micropiles (ITMP), which provide additional seismic resistance against horizontal and vertical loads during earthquakes. A comparison of the dynamic characteristics, such as acceleration, displacement, bending moment, and axial force, of ITMP with a 15° installation angle and normal vertical micropiles with a 0° installation angle was performed using dynamic centrifuge model tests. Results show that under moderate seismic loads, the proposed ITMP exhibited lower acceleration responses than the vertical micropiles. However, when subjected to a long-period strong seismic excitation, such as sine (2 Hz), ITMP showed greater responses than the vertical micropiles in terms of acceleration and settlement. These results indicate that the use of ITMP reduces the amplif ication of short-period (high-f requency) contents compared with the use of vertical micropiles. Therefore, ITMP can be used to enhance seismic performance of structures.

Varietal Response to Grain Quality and Palatability of Cooked Rice Influenced by Different Nitrogen Applications (질소 시비조건에 따른 벼 품종의 미질과 식미특성 반응)

  • Kim, Jeong-Il;Choi, Hae-Chun;Kim, Kwang-Ho;Ahn, Jong-Kuk;Park, No-Bong;Park, Dong-Soo;Kim, Chun-Song;Lee, Ji-Yoon;Kim, Jae-Kyu
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.54 no.1
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    • pp.13-23
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    • 2009
  • To intensively analyze and examine the changes in palatability of cooked rice and structural properties of rice grains influenced by increased nitrogen topdressing during the panicle formation and ripening stage, a series of experiments were carried out using three japonica rice cultivars with contrasting rice quality characteristics. The protein content of brown rice increased maximally up to $35{\sim}47%$ of that in standard N6 plot with the increase in nitrogen topdressing fertilizer during 20 days before heading to 10 days after flowering. The high-yielding rice cultivars showing poor palatability of cooked rice revealed larger increase in protein content of rice grains by increased nitrogen topdressing. Under the same nitrogen level of 15 kg per 10a with nitrogen topdressing at 3 kg/10a, high-yielding rice cultivars, Yumehikari and Reihou showed the significant increase in protein content of brown rice when topdressing was applied at 10 days after flowering as compared with when it was applied at 30 days after transplanting. Although the variation in amylose content of milled rice as affected by nitrogen topdressing level was relatively small, it decreased within 1% with the opposite tendency against increased protein content of brown rice by increased nitrogen topdressing. The total score of sensory evaluation was higher in the order of Hinohikari < Yumehikari < Reihou in panel test. It decreased significantly by increased amounts of nitrogen topdressing during 20 days before heading to 10 days after flowering when nitrogen level was higher than 12 kg/10a. The more poor palatable rice cultivar in panel test revealed the larger decreasing in total score of sensory evaluation by higher nitrogen topdressing rates. All sensory evaluation components were largely affected by the change in protein content of brown rice rather than amylose content of milled rice. The influence of protein content to palatability of cooked rice was larger in poor-palatable rice than in high-palatable rice. The protein content decreased drastically from outer layer to inner layer of rice grains, while the amylose content increased on the contrary. The high-palatable rice exhibited higher distribution of protein content on bran layer but lower distribution of protein content on the layer of polished rice as compared with the poor-palatable rice. Especially, the high-palatable rice showed also significantly lower distribution of amylose content on the outer layer of polished rice as compared with the poor-palatable rice.

Development of the Information Delivery System for the Home Nursing Service (가정간호사업 운용을 위한 정보전달체계 개발 I (가정간호 데이터베이스 구축과 뇌졸중 환자의 가정간호 전산개발))

  • Park, J.H;Kim, M.J;Hong, K.J;Han, K.J;Park, S.A;Yung, S.N;Lee, I.S;Joh, H.;Bang, K.S
    • Journal of Korean Academic Society of Home Health Care Nursing
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    • v.4
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    • pp.5-22
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    • 1997
  • The purpose of the study was to development an information delivery system for the home nursing service, to demonstrate and to evaluate the efficiency of it. The period of research conduct was from September 1996 to August 31, 1997. At the 1st stage to achieve the purpose, Firstly Assessment tool for the patients with cerebral vascular disease who have the first priority of HNS among the patients with various health problems at home was developed through literature review. Secondly, after identification of patient nursing problem by the home care nurse with the assessment tool, the patient's classification system developed by Park (1988) that was 128 nursing activities under 6 categories was used to identify the home care nurse's activities of the patient with CAV at home. The research team had several workshops with 5 clinical nurse experts to refine it. At last 110 nursing activities under 11 categories for the patients with CVA were derived. At the second stage, algorithms were developed to connect 110 nursing activities with the patient nursing problems identified by assessment tool. The computerizing process of the algorithms is as follows: These algorithms are realized with the computer program by use of the software engineering technique. The development is made by the prototyping method, which is the requirement analysis of the software specifications. The basic features of the usability, compatibility, adaptability and maintainability are taken into consideration. Particular emphasis is given to the efficient construction of the database. To enhance the database efficiency and to establish the structural cohesion, the data field is categorized with the weight of relevance to the particular disease. This approach permits the easy adaptability when numerous diseases are applied in the future. In paralleled with this, the expandability and maintainability is stressed through out the program development, which leads to the modular concept. However since the disease to be applied is increased in number as the project progress and since they are interrelated and coupled each other, the expand ability as well as maintainability should be considered with a big priority. Furthermore, since the system is to be synthesized with other medical systems in the future, these properties are very important. The prototype developed in this project is to be evaluated through the stage of system testing. There are various evaluation metrics such as cohesion, coupling and adaptability so on. But unfortunately, direct measurement of these metrics are very difficult, and accordingly, analytical and quantitative evaluations are almost impossible. Therefore, instead of the analytical evaluation, the experimental evaluation is to be applied through the test run by various users. This system testing will provide the viewpoint analysis of the user's level, and the detail and additional requirement specifications arising from user's real situation will be feedback into the system modeling. Also. the degree of freedom of the input and output will be improved, and the hardware limitation will be investigated. Upon the refining, the prototype system will be used as a design template. and will be used to develop the more extensive system. In detail. the relevant modules will be developed for the various diseases, and the module will be integrated by the macroscopic design process focusing on the inter modularity, generality of the database. and compatibility with other systems. The Home care Evaluation System is comprised of three main modules of : (1) General information on a patient, (2) General health status of a patient, and (3) Cerebrovascular disease patient. The general health status module has five sub modules of physical measurement, vitality, nursing, pharmaceutical description and emotional/cognition ability. The CVA patient module is divided into ten sub modules such as subjective sense, consciousness, memory and language pattern so on. The typical sub modules are described in appendix 3.

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Experimental Evaluation of Bi-directionally Unbonded Prestressed Concrete Panel Impact-Resistance Behavior under Impact Loading (충돌하중을 받는 이방향 비부착 프리스트레스트 콘크리트 패널부재의 충돌저항성능에 대한 실험적 거동 평가)

  • Yi, Na-Hyun;Lee, Sang-Won;Lee, Seung-Jae;Kim, Jang-Ho Jay
    • Journal of the Korea Concrete Institute
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    • v.25 no.5
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    • pp.485-496
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    • 2013
  • In recent years, frequent terror or military attacks by explosion or impact accidents have occurred. Examplary case of these attacks were World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. These attacks of the civil infrastructure have induced numerous casualties and property damage, which raised public concerns and anxiety of potential terrorist attacks. However, a existing design procedure for civil infrastructures do not consider a protective design for extreme loading scenario. Also, the extreme loading researches of prestressed concrete (PSC) member, which widely used for nuclear containment vessel, gas tank, bridges, and tunnel, are insufficient due to experimental limitations of loading characteristics. To protect concrete structures against extreme loading such as explosion and impact with high strain rate, understanding of the effect, characteristic, and propagation mechanism of extreme loadings on structures is needed. Therefore, in this paper, to evaluate the impact resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, impact tests were carried out on $1400mm{\times}1000mm{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PS), prestressed concrete with rebar (PSR, general PSC) specimens. According to test site conditions, impact tests were performed with 14 kN impactor with drop height of 10 m, 5 m, 4 m for preliminary tests and 3.5 m for main tests. Also, in this study, the procedure, layout, and measurement system of impact tests were established. The impact resistance capacity was measured using crack patterns, damage rates, measuring value such as displacement, acceleration, and residual structural strength. The results can be used as basic research references for related research areas, which include protective design and impact numerical simulation under impact loading.

Experimental Performance Evaluation of Steel Mesh as Maintenance and Reinforcement Materials (Steel Mesh Cement Mortar의 보수⋅보강 성능 평가)

  • Kim, Yeon-Sang;Choi, Seung-Jai;Kim, Jang-Ho Jay
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.4
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    • pp.50-58
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    • 2014
  • Due to the cost burden of new construction, the necessity of repair and retrofitting of aged structures is sharply increasing as the domain of repair and retrofitting construction is expanding. Because of the necessity, new technologies for repair and retrofitting are continuously studied in Korea and foreign countries. Steel adhesive method, fiber reinforced plastic (FRP) surface adhesive method, and external prestressing method are used to perform the repair and retrofitting works in Korea. In order to consider a repair method using steel mesh reinforced cement mortar (SMCM), 3-point flexural member test was conducted considering repair area and layer number of SMCM. Five types of specimens including ordinary reinforced concrete (RC) specimen with dimensions of $1400{\times}500{\times}200$ (mm) were cast for testing the deflection measurement, a LVDT was installed at the top center of the specimens. Also, a steel strain gauge and a concrete strain gauge were placed at the center of the specimens. A steel strain gauge was also installed on the shear reinforcement. The 3 point flexural member test results showed that the maximum load of SMCM reinforced specimen was higher than that of basic RC specimen in all of the load-displacement curves. Also, the results showed that, when the whole lower part of the basic RC specimen was reinforced, the maximum load and strain were 1.18 and 1.37 times higher than that of the basic RC specimen, respectively. Each specimen showed a slightly different failure behavior where the difference of the results was caused by the difference in the adhesive level between SMCM and RC. Particularly, in SM-B1 specimen, SMCM spalled off during the experiment. This failure behavior showed that the adhesive performance for RC must be improved in order to utilize SMCM as repair and retrofitting material.

Evaluation of Chloride Diffusion Behavior and Analysis of Probabilistic Service Life in Long Term Aged GGBFS Concrete (장기 재령 GGBFS 콘크리트의 염화물 확산 거동 평가 및 확률론적 염해 내구수명 해석)

  • Yoon, Yong-Sik;Kim, Tae-Hoon;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.3
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    • pp.47-56
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    • 2020
  • In this study, three levels of W/B(Water to Binder) ratio (0.37, 0.42, 0.47) and substitution ratio of GGBFS (Ground Granulated Blast Furnace Slag) rate (0 %, 30 %, 50 %) were considered to perform RCPT (Rapid Chloride Diffusion Test) at the 1,095 aged day. Accelerated chloride diffusion coefficient and passed charge of each concrete mixture were assessed according to Tang's method and ASTM C 1202, and improving behaviors of durability performance with increasing aged days are analyzed based on the test results of previous aged days from the preceding study. As the age of concrete increases, the passed charge and diffusion coefficient have been significantly reduced, and especially the concrete specimens containing GGBFS showed a significantly more reduction than OPC(Ordinary Portland Cement) concrete specimen by latent hydraulic activity. In the case of OPC concrete's results of passed charge, at the 1,095 days, two of them were still in the "Moderate" class. So, if only OPC is used as the binder of concrete, the resistance performance for chloride attack is weak. In this study, the time-parameters (m) were derived based on the results of the accelerated chloride diffusion coefficient, and the deterministic and probabilistic analysis for service life were performed by assuming the design variable as a probability function. For probabilistic service life analysis, durability failure probabilities were calculated using Monte Carlo Simulation (MCS) to evaluate service life. The service life of probabilistic method were lower than that of deterministic method, since the target value of PDF (Probability of Durability Failure) was set very low at 10 %. If the target value of PDF suitable for the purpose of using structure can be set and proper variability can be considered for each design variable, it is believed that more economical durability design can be made.

Performance Evaluation of High Strength Lattice Girder by Structural Analyses and Field Measurements (구조해석과 현장계측에 의한 고강도 격자지보재의 성능 평가)

  • Lee, Jeo-Won;Min, Kyong-Nam;Jeong, Ji-Wook;Roh, Byoung-Kuk;Lee, Sang-Jin;Ahn, Tae-Bong;Kang, Seong-Seung
    • The Journal of Engineering Geology
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    • v.30 no.3
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    • pp.237-251
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    • 2020
  • This study examined structural analysis of supports in tunnel and displacement and underground stress of tunnel by measurement, in order to evaluate the performance of high-strength lattice girders developed as a substitute for H-profiles. According to the three-dimensional nonlinear structural analysis results of the tunnel support, the load and displacement relationship between the H-profiles and the high-strength lattice girders showed almost the same behavior, and the maximum load of the high-strength lattice girders were 1.0 to 1.2 times greater than the H-profiles. By the results of the three-dimensional tunnel cross-section analysis of the supports, the axial force was occurred largely in the lower left and right sides of the tunnel, and showed a similar trend to the field test values. In the results of the measurement of the roof settlement and rod extension, the final displacement of the steel arch rib (H-profile) and high-strength lattice girder section in tunnel was converged to a constant value without significant difference within the first management standard of 23.5 mm. According to the results of underground displacement measurement, the final change amount of the two support sections showed a slight displacement change, but converged to a constant value within the first management standard of 10 mm. By the results of measurement of shotcrete stress and steel arch rib stress, the final change amount of the two support sections showed a slight stress change, but converged to a constant value within the first management standard of 81.1 kg/㎠ and 54.2 tonf.