• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.249-258
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• 1999

Dynamic load and static load tests are performed on steel pipe piles and concrete piles at five construction sites in highway to compare the difference of load bearing mechanisms. At each site, one steel pile is instrumented with electric strain gages and dynamic tests are performed on the pile during installation. Damages of strain gages due to the installation are checked and static test is performed upon the same pile after two or seven days as well. It shows that load transfer from side friction to base resistance behaves somewhat differently according to the results of load-settlement analysis obtained from PDA and static load test. Initial elastic stage of load settlement curves of two load tests is almost similar. But after the yielding point, dynamic resistance of pile behaves more stiffer than static resistance, thus, dynamic load test result might overestimate the real pile capacity compared with static result. Analysis of gage readings shows that unit skin friction increases exponentially with depth. The skin friction is mobilized at the 1∼2m above the pile tip and contributes to the considerable side resistance. Comparison of side and base resistances between the measured value and the calculated value by Meyerhof's bearing capacity equation using SPT N value shows that the calculated base resistance is higher than the measured. Therefore, contribution of side resistance to total capacity shouldn't be ignored or underestimated. Finally, based upon the overall test results, a construction control procedure is suggested.

• Steel and Composite Structures
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• 제13권3호
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• pp.295-308
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• 2012

This paper experimentally investigated the buckling capacity of built-up steel columns mainly, Cruciform Columns (CC) and Side-to-Side (SS) columns fabricated from two Universal Beam (UB) sections. A series of nine experimental tests comprised of three UB sections, three CC sections and three SS sections with different lengths were tested to failure to measure the ultimate axial capacity of each column section. The lengths used for each category of columns were 1.8, 2.0, and 2.2 m with slenderness ratios ranging from 39-105. The measured buckling loads of the tested specimens were compared with the predicted ultimate axial capacity using Eurocode 3, AISC LRFD, and BS 5959-1. It was observed that the failure modes of the specimens included flexural buckling, local buckling and flexural-torsional buckling. The results showed that the ultimate axial capacity of the tested cruciform and side-by-side columns were higher than the code predicted design values by up to 20%, with AISC LRFD design values being the least conservative and the Eurocode 3 design values being the most conservative. This study has concluded that cruciform column and side-to-side welded flange columns using universal beam sections are efficient built-up sections that have larger ultimate axial load capacity, larger stiffness with saving in the weight of steel used compared to its equivalent universal beam counterpart.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 추계 학술발표회
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• pp.409-429
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• 2006

In designing rock-socketed drilled shaft, bearing capacity evaluation is very important because the maximum values of base and side resistance are not generally mobilized at the same value of displacement, FHWA and AASHTO code suggest different ultimate bearing capacity formular according to rock type and shaft settlement. In domestic code suggest base resistance and side resistance can be added on condition that after confirming the result of field load test with axial load transfer test. This paper shows that static load test and hi-directional load test result analysis of deep rock-socketed drilled shaft in three different sites. Load-settlement curve, t-z, and q-w curve in rock-socketed part were calculated and compared. t-z curve in weathered and soft rock showed no deflection softening behavior in pretty large strain (about 2-3% of diameter). Ultimate resistance could be the summation of side resistance and base resistance in rock-socketed drilled shaft in domestic sites.

• International Journal of Concrete Structures and Materials
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• 제9권4호
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• pp.401-413
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• 2015

In this study the progressive collapse resisting capacity of a RC beam-column subassemblage with and without strengthening was investigated. Total of five specimens were tested; two unreinforced specimens, the one designed as gravity load-resisting system and the other as seismic load-resisting system, and three specimens reinforced with: (i) bonded strand, (ii) unbonded strand, and (iii) side steel plates with stud bolts. The two-span subassemblages were designed as part of an eight-story RC building. Monotonically increasing load was applied at the middle column of the specimens and the force-displacement relationships were plotted. It was observed that the gravity load-resisting specimen failed by fractures of re-bars in the beams. In the other specimens no failure was observed until the maximum displacement capacity of the actuator was reached. Highest strength was observed in the structure with unbonded strand. The test result of the specimen with side steel plates in beam-column joints showed that the force-displacement curve increased without fracture of re-bars. Based on the test results it was concluded that the progressive collapse resisting capacity of a RC frame could be significantly enhanced using unbonded strands or side plates with stud bolts.

• 한국지반공학회논문집
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• 제23권4호
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• pp.59-68
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• 2007

본 논문에서는 토조에 실시된 모형말뚝 재하실험과 콘관입실험을 통하여, 말뚝형태별 지지력 특성분석과 CPT지지력 상관계수를 평가하였다. 고려된 말뚝의 형태는 일반적인 현장타설말뚝에 적용되는 원통형 말뚝과 테이퍼형 말뚝이 고려되었다. 본 연구는 궁극적으로 강관주 송전탑의 기초구조물 형식개발과 설계기준 수립을 목표로 하고 있으며, 이를 위해 기초형식별 거동과 지반상태의 영향 등을 중점적으로 살펴보았다. 말뚝 토조실험을 통해 나타난 결과에 의하면, 원통형 및 테이퍼형 말뚝의 전체지지력의 차이는 크지 않았으나, 개별 지지력요소의 거동은 말뚝형태별로 상이한 것으로 나타났다. 토조실험결과와 동일한 지반조건에 대해 수행된 CPT결과를 통해 말뚝지지력과 콘지지력의 관계를 나타내는 CPT지지력 상관계수의 변화추이를 도출하였다. CPT상관계수는 원통형 및 테이퍼형 말뚝형태를 비교함으로써 나타내었으며, 선단지지력과 주면마찰력의 요소별 변화추이를 제안하였다.

• 전기학회논문지
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• 제64권6호
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• pp.852-856
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• 2015

Demand side management (DSM) program has been frequently used for reducing the system peak load because it gives utilities and independent system operator (ISO) a convenient way to control and change amount of electric usage of end-use customer. Planning and operating methods are needed to efficiently manage a DSM program. This paper presents a planning method for DSM program. A planning method for DSM program should include an electric load forecasting, because this is the most important factor in determining how much to reduce electric load. In this paper, load forecasting with the temperature stochastic modeling and the sensitivity to temperature of the electric load is used for improving load forecasting accuracy. The proposed planning method can also estimate the required day, hour and total capacity of DSM program using Monte-Carlo simulation. The results of case studies are presented to show the effectiveness of the proposed planning method.

• Geomechanics and Engineering
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• 제6권5호
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• pp.469-485
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• 2014

A series of bearing capacity tests was conducted with eccentrically loaded model surface and shallow strip footings resting close to a slope to investigate behavior of such footings (ultimate loads, failure surfaces, load-displacement curves, rotation of footing, etc.). Ultimate loads of footing close to slope decreased with increasing eccentricity for both surface and shallow footings. Failure surfaces were not symmetrical, primary failure surfaces occurred on the eccentricity side (the slope side) and secondary failure surfaces occurred on the other side. Lengths of failure surfaces decreased with increasing eccentricity. Footings always rotated towards eccentricity side a few degrees. For eccentrically loaded footing, decrease in ultimate load with increasing eccentricity is roughly in agreement with Customary Analysis.

• Advances in Computational Design
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• 제4권3호
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• pp.251-272
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• 2019

This study performed lateral load testing on seventeen wood wall frames in two sections. Section one included eight tests studying structural foam sheathing of shear walls subjected to monotonic loads following the ASTM E564 test method. In this section, the wood frame was sheathed with four different types of structural foam sheathing on one side and gypsum wallboard (GWB) on the opposite side of the wall frame, with Simpson HDQ8 hold down anchors at the terminal studs. Section two included nine tests studying wall constructed with oriented strand board (OSB) only on one side of the wall frame subjected to gradually applied monotonic loads. Three of the OSB walls were tied to the baseplate with Simpson LSTA 9 tie on each stud. From the test results for Section one; the monotonic tests showed an 11 to 27 percent reduction in capacity from the published design values and for Section two; doubling baseplates, reducing anchor bolt spacing, using bearing plate washers and LSTA 9 ties effectively improved the OSB wall capacity. In comparison of sections one and two, it is expected the walls with structural foam sheathing without hold downs and GWB have a lower wall capacity as hold down and GWB improved the capacity.

• 한국지반공학회논문집
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• 제19권4호
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• pp.95-105
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• 2003

암반에 근입된 현장타설말뚝의 지지력 산정을 위하여 제안된 기존의 설계기준과 경험식들의 대부분은 재하시험의 결과에 일관되지 않은 파괴기준을 적용해서 얻어진 극한지지력에 근거해서 얻어졌다. 그 결과 이들산정식들은 동일한 조건에 설치된 말뚝에 대해서도 서로 다른 예측치를 제공하게 된다. 본 연구에서는 암반에 근입된 현장타설말뚝의 지지력을 합리적으로 산정할 수 있는 최적의 지지력산정식을 결정하기 위하여 기존의 지지력산정식들에 대하여 정확도를 조사하였다. 이를 위해서 11개의 재하시험 결과에 동일한 파괴기준을 적용함으로써 말뚝의 극한선단지지력과 극한주면마찰력을 결정하였으며, 이들은 기존 산정식으로부터 계산된 예측치의 정확도 조사에 이용되었다. 예측치와 측정치를 비교한 결과 Zhang과 Einstein의 제안식과 NAVFAC의 설계기준에 의해 계산된 극한선단지지력이 실측치에 가장 근접한 것으로 나타났다. 그리고 극한주면마찰력의 경우에는 Rosenberg와 Journeaux의 제안식이 만족스러운 예측치를 제공하였다.

• Computers and Concrete
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• 제24권2호
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• pp.159-172
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• 2019

This paper presents an investigation into the flexural behavior of reinforced concrete (RC) beams retrofitted by ultra-high performance fiber-reinforced concrete (UHPFRC) layers. The experimental study has been conducted in two parts. In the first part, four methods of retrofitting with UHPFRC layers in both the up and down sides of the beams have been proposed and their efficiency in the bonding of the normal concrete and ultra-high performance fiber-reinforced concrete has been discussed. The results showed that using the grooving method and the pre-casted UHPFRC layers in comparison with the sandblasting method and the cast-in-place UHPFRC layers leads to increase the load carrying capacity and the energy absorption capacity and causes high bond strength between two concretes. In the second part of the experimental study, the tests have been conducted on the beams with single UHPFRC layer in the down side and in the up side, using the effective retrofitting method chosen from the first part. The results are compared with those of non-retrofitted beam and the results of the first part of experimental study. The results showed that the retrofitted beam with two UHPFRC layers in the up and down sides has the highest energy absorption and load carrying capacity. A finite element analysis was applied to prediction the flexural behavior of the composite beams. A good agreement was achieved between the finite element and experimental results. Finally, a parametric study was carried out on full-scale retrofitted beams. The results indicated that in all retrofitted beams with UHPFRC in single and two sides, increasing of the UHPFRC layer thickness causes the load carrying capacity to be increased. Also, increases of the normal concrete compressive strength improved the cracking load of the beams.