• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.1
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• pp.65-72
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• 2003

The objective of this study is to estimate the frequency characteristics of group walking loads based on the information of measured responses. At first, dynamic properties such as natural frequencies and modes are obtained from input/output relation for building structures by heel drop test. Second, a method to estimate group walking loads by the transfer functions from measured responses to group walking loads is proposed. The method turned out to estimate the group walking loads accurately. Higher modes could be important in estimating the amplitude of group walking loads with the information of single walking load.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.4 s.44
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• pp.19-28
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• 2005

Long span structures with low natural frequencies such as shopping malls, large offices, and assembly rooms may experience signification dynamic responses due to human activities. In many cases, the group activities are common thing in comparison with the single activity. The purpose of this study is to evaluate the responses of building structure subjected to group human loads using mode shapes. For this purpose, equations to estimate the magnitudes ol responses ol structure subjected to group walking loads are derived. And the correlation of loads is verified for identifying the relation of each human load composing of group human loads using two load cells. The method is proposed for evaluating the responses of structure subjected to group loads using mode shapes and correlation function related to each human loads. The effectiveness ol the proposed method is verified analytically using a simple beam and floor and experimentally on a footbridge measuring the structural response induced by group pedestrians for the case of synchronization or not. Results indicate that the amplitudes of group walking loads can be easily estimated if the mode shapes are available, and that the corresponding structural responses can be estimated easily by the simple response measurement using the proposed method.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.37-46
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• 2001

Pile load tests were carried out to investigate the contribution of the pile cap to the carrying capacity of a pile group and load transfer characteristics of piles in the group. A group of 24 piles$(4 \times6 array)$ of 92.5mm diameter steel pipe were installed to the depth of 3m fron the ground surface, the top of weathered rock. A maximum load of 320ton was applied to the pile cap, $1.5\times2.3m$, in contact with the ground surface. At the maximum load of 320ton, the pile cap has carried 22% of the total load. Average ultimate capacity of pile in the pile group was estimated to be 16.4ton, substantially higher than that of single pile, installed at the corner and tested before pile cap construction. For the same magnitude of settlement, the pile in the center carried less load than the pile at the perimeter due to strain superposition effect. Piles in the group showed almost constant contribution(approx. 60%) of side friction to the total capacity for all of the loading stages, while that of single pile decreased from 82% to 65%.

• Journal of the Korean GEO-environmental Society
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• v.20 no.8
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• pp.5-12
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• 2019

A pile group, that consists of several piles connected by a pile cap, is used as the superstructure. The pile supports vertical and horizontal load to design the pile group, but the effect of bearing capacity of the pile cap has not considered. Various researches have been conducted to reflect the effect of bearing capacity of the pile cap in order to reduce the amount of piles in the range of the stability under the vertical load of the superstructure. However, the effect of bearing capacity under the horizontal seismic load has not been studied adequately. Therefore, a shaking table test was carried out with different-sized pile caps that support the superstructure in this study. This test was to verify the influence of the size of the pile cap in the group pile under the horizontal load. The result shows that the size of the pile cap affects to the dynamic behavior of the superstructure and the pile group. Also, the bigger size of the pile group makes the larger constraint effect of ground, and it results that both the ground and the pile moves as a whole.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4863-4868
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• 2012

Static pile load tests were conducted on the two piles which comprised group pile installed in sand and the test results were compared with those obtained from load transfer method. Predicted load bearing capacity of the pile which locates center portion of the group pile was less than that from the load test and the reason is thought to be the densification of the soil due to the installation of the group pile. Predicted pile capacity of the API method, Coyle and Sulaiman method were 77%, 90% of the bearing capacity obtained from the load test, respectively. Comparing ultimate bearing capacities of the pile locating at the edge of the group pile, those predicted by the API method, Coyle and Sulaiman method were 1.1 times, 1.3 times of the bearing capacity obtained from the pile load test, respectively.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.57-64
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• 2012

The lateral behavior characteristics of concrete group pile under the lateral load were examined by the laboratory model tests in this study. Piles were socketed 1D(D : pile diameter) in the concrete block, and model tests were executed on $2{\times}3$ group piles, of which the length were 11D, 15D and 20D. All results of loading tests under each condition was presented by the lateral load-displacement curves, and the displacements in the ground under the lateral loads were measured. As a results of model tests, as the ratio of pile length/diameter(L/D) was decreased, the yielding load and the lateral displacement at that load were increased. The yielding load was evaluated as the load at lateral displacement of 15 mm. The yielding loads at the pile length of 11D, 15D and 20D were 11.7, 6.2kN and 3.4kN. The lateral displacements of pile in the ground under each condition were measured linearly and the failure occurred at the location where the piles were socketed in concrete block.

• Journal of the Korean GEO-environmental Society
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• v.11 no.3
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• pp.17-22
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• 2010

This paper analyzed the characteristics of p-multiplier and the load distribution of H-pile group installed in weathered soil under horizontal loading. The results of this study conducted in pile arrangement ($2{\times}3$, $3{\times}3$), the pile center to center spacing (2D, 4D, 6D), and soil density (relative density: 40%, 80%) were drawn as follows. As to the average horizontal loading applied to each pile in pile groups, the fewer number of piles was, the larger average horizontal resistance became. As the result of analysis on p-y curves of single piles and pile groups according to the pile distance and the soil density, as the pile spacing was increased from 2D to 6D, the interaction coefficients of pile group showed 0.85~0.94 (piles in the front row), 0.57~0.79 (piles in the middle row), and 0.60~0.71 (piles in the rear row) in the loose ground and showed 0.76~0.82 (piles in the front row), 0.58~0.73 (piles in the middle row), and 0.53~0.70 (piles in the rear row) in the dense ground. As above, the wider pile distance was, the larger interaction coefficient value was shown among piles. In addition, piles in the front row showed bigger interaction coefficients than that of piles in the middle and back row.

• Journal of the Korean Geotechnical Society
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• v.34 no.6
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• pp.5-16
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• 2018

In this study, the large scale laboratory model tests were executed to investigate the lateral resistance characteristics of $2{\times}2$ group pile under lateral loads according to the array method and installation angle of piles. The effect on the behavior of $2{\times}2$ group pile was also investigated through model tests varying the pile diameter and length, distance to pile top from the ground surface, center-to-center (CTC) length and surcharge etc. From these test results, it was found that the lateral resistance of $2{\times}2$ group pile of which piles were constructed slantly in both directions was greater than that of group pile of which piles were constructed vertically. And as a result of parameter tests on the lateral resistance of $2{\times}2$ group pile, it was found that the most important parameter was the pile length. As the embedment depth ratio (L/D) increased to 36.5 from 26.5, the lateral resistance increased 3~4 times or more. But the center-to-center (CTC) length, distance to pile top from the ground surface and surcharge did not affect much on the lateral resistance of group pile.

• Journal of the Korean Geotechnical Society
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• v.34 no.5
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• pp.53-63
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• 2018

Dynamic soil-pile interaction is the main concern in the design of group piles under earthquake loadings. The lateral resistance of the pile group under dynamic loading becomes different from that of a single pile due to the group pile effect. However, this aspect has not yet been properly studied for the pile group under seismic loading condition. Thus, in this study the group pile effect was evaluated by performing a series of dynamic centrifuge tests on $3{\times}3$ group pile in dry loose sand. The multiplier coefficients for ultimate lateral resistance and subgrade reaction modulus were suggested to obtain the p-y curve of the group pile. The suggested coefficients were verified by performing the nonlinear dynamic analyses, which adopted Beam on Nonlinear Winkler Foundation model. The predicted behavior of the pile group showed the reasonable agreement compared with the results of the centrifuge tests under sinusoidal wave and artificial wave.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.27-40
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• 2012

In the design of a piled raft, the axial resistance is offered by the raft and group piles acting on the same supporting ground soils. As a consequence, pile - soil - raft and pile - soil interactions, occurring by stress and displacement duplication with pile and raft loading conditions, act as a key element changing resistances of the raft and group piles. In this study, a series of centrifuge model tests have been performed to compare the axial behavior of group pile and raft with that of a piled raft (having 16 component piles with an array of $4{\times}4$) in sands with different relative densities. The test results revealed that the increase of settlement resistance occurs separately with settlement by group pile - soil interactions. The axial resistance of group piles (at piled raft) increases by group pile - raft (pile cap) interactions and that of raft (at piled raft) decreases by group pile - raft (pile cap) interactions.