• Title, Summary, Keyword: ultimate bearing capacities

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Demand Capacities of Rubber Bear ing for Seismic Isolated Building (고성능 적층고무 면진장치의 요구 성능)

  • Hwang, Kee-Tae;Rim, Jong-Man;Kim, Dong-Won
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.487-494
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    • 2006
  • The ultimate capacities of a rubber bearing are defined by compressive stress, shear strain, and stabilized roster ing force. The experiments were conducted with parameters of shesr elasticity(G) and first shape factor(S1), second shape factor(S2) for rubber bearing. Considering with test results, the ultimate capacities were verified, and furthermore the influence of those parameters were clarified. Using test results stable deformation of rubber bearings for designing was proposed.

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A Study on Design Method of Geogrid Encased Stone Colum for Settlement Reduction in Railroad (철도노반 침하저감을 위한 토목섬유 감쌈 쇄석말뚝 설계방안 고찰)

  • Lee, Dae-Young
    • Journal of the Korean Geosynthetics Society
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    • v.13 no.3
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    • pp.31-38
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    • 2014
  • The geogrid encased stone column (GESC) system, which increases the confinement effect, has been developed to improve the load carrying capacity of stone columns. The resonable design method for calculating the geogrid ring tension force and ultimate bearing capacity that can be applied to the design of GESC is proposed. In order to calculate design procedure for GESC, two ultimate bearing capacities were compared. One is the ultimate bearing capacity measured using data of the field loading test in light railway site and the other is the ultimate bearing capacity using suggested design procedure of GESC. The results indicated that design method of GESC higher ultimate bearing capacities compared with field loading test.

Assessment of Design Criteria for Bearing Capacity of Rock Socketed Drilled Shaft (암반에 근입된 현장타설말뚝의 지지력 산정기준에 대한 평가)

  • 백규호;사공명
    • Journal of the Korean Geotechnical Society
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    • v.19 no.4
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    • pp.95-105
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    • 2003
  • The existing design criteria f3r the estimation of ultimate bearing capacity of drilled shaft socketed into rock masses are mainly obtained from the ultimate pile load capacities, which are determined by inconsistent failure criteria. Therefore, these design criteria generally produce difffrent predictions even for drilled shaft in the same condition. In this paper, the accuracies of the existing design criteria are investigated to develop an optimized design process for drilled shaft socketed into rock masses. Reasonable and consistent ultimate capacities of drilled shafts socked into rock masses, necessary far the check of accuracies of predictions, are determined by applying a specific failure criterion to a total of 11 pile load test results. A comparison between the predicted and the measured load capacities shows that ultimate base load capacities calculated from Zhang and Einstein's equation and NAVFAC are close to the measured values. Rosenberg and Journeaux's equation produces satisfactory prediction f3r ultimate side load capacity.

Repair of flange damage steel-concrete composite girders using CFRP sheets

  • Wang, Lianguang;Hou, Wenyu;Han, Huafeng;Huo, Junhua
    • Structural Engineering and Mechanics
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    • v.55 no.3
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    • pp.511-523
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    • 2015
  • Damaged steel-concrete composite girders can be repaired and retrofitted by epoxy-bonded carbon fiber-reinforced polymer (CFRP) sheets to the critical areas of tension flanges. This paper presents the results of a study on the behavior of damaged steel-concrete composite girders repaired with CFRP sheets under static loading. A total of seven composite girders made of I20A steel sections and 80mm-thick by 900mm-wide concrete slabs were prepared and tested. CFRP sheets and prestressed CFRP sheets were used to repair the specimens. The specimens lost the cross-sectional area of their tension flanges with 30%, 50% and 100%. The results showed that CFRP sheets had no significant effect on the yield loads of strengthened composite girders, but had significant effect on the ultimate loads. The yield loads, elastic stiffness, and ultimate bearing capacities of strengthened composite girders had been changed as a result of prestressed CFRP sheets, the utilization ratio of CFRP sheets could be effectively improved by applying prestress to CFRP sheets. Both the yield loads and ultimate bearing capacities had been changed as a result of steel beam's flange damage level and CFRP sheets could cover the girders' shortage of bearing capacity with 30% and 50% flange damage, respectively.

Evaluation of the Resistance Bias Factors to Develop LRFD for Gravel Compaction Piles (LRFD 설계를 위한 쇄석다짐말뚝공법의 저항편향계수 산정)

  • Han, Yong-Bae;Park, Joon-Mo;Jang, Yeon-Soo
    • Journal of the Korean Geotechnical Society
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    • v.28 no.2
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    • pp.43-55
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    • 2012
  • In this study, the resistance bias factors are calculated to determine the resistance factor of Gravel Compaction Piles which is one of the soft ground improvement methods. In order to calculate resistance bias factors for gravel compaction piles, two ultimate bearing capacities were analyzed. One is the ultimate bearing capacity in 2.54 cm settlement measured using data of the field loading test on 41 piles and the other is the ultimate bearing capacity calculated using the seven equations concerning bulging failure. The results of analysis show that the probability density function of the calculated ultimate bearing capacities has a lognormal distribution. Resistance bias factor and the coefficient of variation for Greenwood equation are 0.91 and 0.38, respectively, and for those of Hughes & Withers are 1.19 and 0.39. The two equations are suitable for calculating resistance factors for LRFD of soil improvement using gravel compaction piles.

Determination of the Bearing Capacity of Soft and Polluted Silt Soils (연약한 실트지반과 오염된 실트지반의 지지력 결정)

  • Ahn, Jong-Pil;Park, Sang-Bum;Park, Kyung-Ho;Yu, Deok-Chan
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.940-947
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    • 2005
  • In this study, model tests of soft silt soils(ML) and silt soils was polluted with wastewater and waste oil from factories($ML_p$). Distribution of displacement, bearing capacity comparing the test results with existing theoretical expressions and analyzing the test results, the following conclusions were obtained. It was found out that in soft silt soils the relationship of critical surcharge and undrained cohesion is $q_{cr}=4.14C_u$ and polluted silt soils $ML_p$ those are $q_{cr}=1.78C_u$, respectively and the relationship of ultimate capacities $q_{ult}=9.53C_u$ and undrained cohesion in polluted silt soils are $q_{ult}=4.39C_u$. Critical surcharge and ultimate capacity is less in polluted silt soils than in soft silt soils.

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A Study on the Applicability of Bearing Capacity Formulas of Driven Pile by Comparison with the Results of Static Loading Tests (정재하시험 결과를 통한 타입말뚝 지지력 공식의 타당성 분석)

  • Chun, Byung-Sik;Lee, Seung-Beom
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.544-551
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    • 2004
  • Piles are structural elements made of steel, concrete or timber, and utilize as pile foundation which is one of deep foundations. Driven pile among them, which drives pile into the ground, is fast-constructable, less expensive and it supplies much bearing capacity. For these reasons, its demand is steady. In this study, by selecting the cases which reached ultimate failure during in-situ static loading tests, bearing capacities acquired from these tests were compared with those computed by existing theories and formula. As the results of the analysis, ultimate bearing capacity computed by theoretic formula were less or similar to those of test results in most cases, but lower ground water level and more dense layer where end of piles were reached remarkably high bearing capacity in theoretical methods. ${\beta}-method$ and Korean structure foundation design standard were sensitive to ground physical properties. Meyerhof metbod and API code were relatively independent from site condition.

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Fragility curves for the typical multi-span simply supported bridges in northern Pakistan

  • Waseem, Muhammad;Spacone, Enrico
    • Structural Engineering and Mechanics
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    • v.64 no.2
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    • pp.213-223
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    • 2017
  • Bridges are lifeline and integral components of transportation system that are susceptible to seismic actions, their vulnerability assessment is essential for seismic risk assessment and mitigation. The vulnerability assessment of bridges common in Pakistan is very important as it is seismically very active region and the available code for the seismic design of bridges is obsolete. This research presents seismic vulnerability assessment of three real case simply supported multi-span reinforced concrete bridges commonly found in northern Pakistan, having one, two and three bents with circular piers. The vulnerability assessment is carried through the non-linear dynamic time history analyses for the derivation of fragility curves. Finite element based numerical models of the bridges were developed in MIDAS CIVIL (2015) and analyzed through with non-linear dynamic and incremental dynamic analyses, using a suite of bridge-specific natural spectrum compatible ground motion records. Seismic responses of shear key, bearing pad, expansion joint and pier components of each bridges were recorded during analysis and retrieved for performance based analysis. Fragility curves were developed for the bearing pads, shear key, expansion joint and pier of the bridges that first reach ultimate limit state. Dynamic analysis and the derived fragility curves show that ultimate limit state of bearing pads, shear keys and expansion joints of the bridges exceed first, followed by the piers ultimate limit state for all the three bridges. Mean collapse capacities computed for all the components indicated that bearing pads, expansion joints, and shear keys exceed the ultimate limit state at lowest seismic intensities.

The Bearing Capacity Comparison of Drilled Shaft by the Static Load Test and the Suggested Bearing Capacity Formulas (현장타설말뚝의 정재하시험에 의한 지지력과 이론식에 의한 지지력과의 비교)

  • 천병식;김원철;최용규;서덕동
    • Journal of the Korean Geotechnical Society
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    • v.19 no.2
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    • pp.237-246
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    • 2003
  • The driven pile has environmental problems such as vibration and noise. Especially, if the site consists of gravel, cobble and weather rock, the driven pile can not be applied. Therefore, the application of the drilled shafts is increasing in Korea. However, the bearing capacity values by the suggested theoretical formulas are generally considered too conservative. In this paper, static load tests for the rock socketed drilled shaft at Gwangandaero and Suyeong3hogyo are performed and in order to estimate the side friction of the shaft, strain gauges are applied. The bearing capacities from the field test data and the bearing capacity values by the theoretical formula are compared. Even the static load tests didn't reach to the ultimate bearing capacity condition, and all the measured bearing capacity values were higher than those by the theoretical formulas. The field data also showed that the major bearing capacities were not due to end bearings but side friction resistances. Based on the above results, several suggestions are proposed for the drilled shaft design.

Evaluation of Point Bearing Capacity using Field Model Pile Test (현장 축소모형 말뚝 시험을 이용한 선단지지력 예측)

  • Lee, Chang-Ho;Lee, Woo-Jin;Jeong, Hun-Jun;Han, Shin-In
    • Journal of the Korean Geoenvironmental Society
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    • v.6 no.3
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    • pp.47-54
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    • 2005
  • In many practical cases, design methods of pile have been used mainly semi empirical bearing capacity equations. It can be done that confirmation of pile bearing capacities through using of dynamic and static tests during constructing or after constructions. If a prediction of layered point pile bearing capacity could be done through simple tests during field investigation, it could be done that more reliable design of pile than a prediction of using semi empirical equations or static formulations. This paper suggests a method to estimated point bearing capacity during in-situ investigation by using the dynamic rod model pile and verifies the point bearing capacity compare with results of static pile load tests. From test results, the unit ultimate point bearing capacities are relatively similar through a dynamic rod model pile tests and static pile load tests. The unit ultimate point bearing capacity by using N value is shown about 50 % value of measured unit ultimate point bearing capacity from field test result and the prediction of the unit ultimate point bearing capacity by using N value is shown very conservative, illogical and uneconomical pile designs.

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