• Journal of the Korean Geotechnical Society
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• v.23 no.5
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• pp.101-110
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• 2007

In order to investigate the effect of the pile shape on the bearing capacity of non-displacement piles, a series of model pile load tests were performed using a calibration chamber and three model piles with different shape. Results of the model tests showed that the bearing capacity of tapered piles was affected by its taper angle as well as the stress states and relative density of soil. Based on the results of model pile load tests, a new design equation for estimation of the bearing capacity of non-displacement piles was proposed, and it takes into account the effect of the taper angles on the bearing capacity of non-displacement piles.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.81-88
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• 2003

Recently, pile foundations were constructed in rough or soft ground than ground of well condition thus it is important that prediction of ultimate bearing capacity and calculation of proper safety factor applied pile foundation design. This study were performed to dynamic loading tests for the thirty two piles at four different construction sites and selected pile at three site were performed to static loading tests and then compare with measured value and value of static and dynamic loading tests. The load-settlement curve form the dynamic loading tests by CAPWAP was very similar to the results obtained from the static load tests. Based on dynamic and static loading tests, the reliability of pile-driving formula were analyzed and then suggested with proper safety factor for prediction of allowable bearing capacity in this paper.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.198-199
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• 2017

In this paper, the applicability of PHC piles to replace Myanmar local piles were evaluated. In Myanmar, based on the size of the building, foundation design and field applications are carried out using bored pile and square pile. As a result of the analysis, the application of PHC pile is more economical than conventional bored pile or square pile which was applied in the high rise (17-story) and middle story (12-story) buildings. However, in the low - rise (8-story) building, the application of the existing square piles was found to be more economical than PHC pile.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.113-122
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• 2005

Application of Limit State Design in geotechnical engineering has become world-widely popular. While LRFD code in the North America presents geotechnical load and resistance factors, the values of resistance factors proposed by these methods are still unstable with limited application. CPT has been widely used for the pile design and various methods have been proposed to estimate the bearing capacity of piles. In this paper, resistance factors for representative pile design methods based on CPT results are evaluated. Field pile load test and CPT results were collected and analyzed in order to obtain necessary statistical data and resistance factors. Resistance factors of the base, shaft, and total capacity are estimated. From fisrt order second moment (FOSM) analysis, resistance factors of $0.30{\sim}0.55$ are estimated for total load capacity.

• Geomechanics and Engineering
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• v.3 no.1
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• pp.1-16
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• 2011

Piles passing through sloping liquefiable deposits are prone to lateral loading if these deposits liquefy and flow during earthquakes. These lateral loads caused by the relative soil-pile movement will induce bending in the piles and may result in failure of the piles or excessive pile-head displacement. Whilst the weak nature of the flowing liquefied soil would suggest that only small loads would be exerted on the piles, it is known from case histories that piles do fail owing to the influence of laterally spreading soils. It will be shown, based on dynamic centrifuge test data, that dilatant behaviour of soil close to the pile is the major cause of these considerable transient lateral loads which are transferred to the pile. This paper reports the results of geotechnical centrifuge tests in which models of gently sloping liquefiable sand with pile foundations passing through them were subjected to earthquake excitation. The soil close to the pile was instrumented with pore-pressure transducers and contact stress cells in order to monitor the interaction between soil and pile and to track the soil stress state both upslope and downslope of the pile. The presence of instrumentation measuring pore-pressure and lateral stress close to the pile in the research described in this paper gives the opportunity to better study the soil stress state close to the pile and to compare the loads measured as being applied to the piles by the laterally spreading soils with those suggested by the JRA design code. This test data shows that lateral stresses much greater than one might expect from calculations based on the residual strength of liquefied soil may be applied to piles in flowing liquefied slopes owing to the dilative behaviour of the liquefied soil. It is shown at least for the particular geometry studied that the current JRA design code can be un-conservative by a factor of three for these dilation-affected transient lateral loads.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.89-98
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• 2005

Preliminary pile load tests for the design of large diameter drilled shaft were performed on two of reduced scale(D=1370mm) test piles. The maximum loads of 2350 tonf in each direction were applied using bi-directional hydraulic jacks(Osterberg Cell) at toe. Neither of the test piles yielded in terms of skin friction and end bearing. Comparisons of the test results with several methods that estimate pile capacity show that the method of Horvath and Kenney(1979) for skin friction and Zhang and Einstein(1998) for end bearing were most appropriate for the site. The test results were directly applied to pile design in case RQD of skin and toe was larger than that of the test pile. It is desirable, therefore, to consider not only unconfined compression strength but also rock mass properties(i.e. TCR, RQD) for skin friction and end bearing evaluation in the future.

• Structural Engineering and Mechanics
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• v.7 no.6
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• pp.533-550
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• 1999

Optimal design of raft-pile foundations is examined by combining finite element technique and the optimization approach. The piles and soil medium are modeled by three dimensional solid elements while the raft is modelled by shell elements. Drucker-Prager criterion is adopted for the soil medium while the raft and the piles are assumed to be linear elastic. For the optimization process, the approximate semi-analytical method is used for calculating constraint sensitivities and a constraint approximation method which is a combination of the extended Bi-point approximation and Lagrangian polynomial approximation is used for predicting the behaviour of the constraints. The objective function of the problem is the volume of materials of the foundation while the design variables are raft thickness, pile length and pile spacing. The generalized reduced gradient algorithm is chosen for solving the optimization process. It is demonstrated that the method proposed in this study is promising for obtaining optimal design of raft-pile foundations without carrying out a large number of analyses. The results are also compared with those obtained from the previous study in which linear analysis was carried out.

• Geotechnical Engineering
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• v.7 no.3
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• pp.51-64
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• 1991

The reliable estimation of pile bearing capacity is essential for the improvement of the re- liability and the cost-effectiveness of the design. There have been numerous pile bearing capacity prediction methods proposed up to now, however, execpt for the estimation made from the result of the pile loading test, not one method is appropriate for the reliable prediction. Due to the considerable time and expenses required to carry out the pile loading test, the test has seldom been utilized. The development of Simple Pile Loading Test(SPLT) which utilizes the pile skin friction as the required reaction force to cause the pile tip settlement, provides a solution to perform more pile loading tests and consequently a more economical pile design is possible. The separate measurement of skin friction and tip resistance during the course of performing SPLT provides a better understanding of the pile behavior than the result of the conventional pile loading test where only the total resistance is measured. On the other hand, there are some points to be clarified in order to apply the test results of SPLT to practical problem. They are the direction of the applied load to mobilize the skin friction and the use of reduced sized sliding core. In this research, both the SPLT and the conventional pile loading test on 406mm diameter steel pipe pile have been performed. From the result, it would be safe to use the measured SPLT skin friction value directly in the design, since the value is somewhat lower than the value measured in the conventional test. It is further assumed that the tip resistance value of the reduced sized sliding core should properly be analysed by taking the incluonce of scale effect into consideration.

• Journal of the Korean Geotechnical Society
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• v.24 no.7
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• pp.61-73
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• 2008

Piles of a bridge pier are connected with the column through the pile cap (footing). Behavior of the pile foundation can be different according to the connection method between piles and the pile cap. Connection methods between pile heads and the pile cap are divided into two groups : rigid connections and hinge connections. Domestic design code has been specified to use rigid connection method for the highway bridge. In the rigid connection method, maximum bending moment of a pile occurs at the pile head and this helps the pile to prevent the excessive displacement. Rigid methods are also good to improve the seismic performance. However, some specifications prescribe that conservative results through investigations of both the fixed-head condition and the free-head condition should be reflected in the design. This statement may induce an over-estimated design for the bridge which has high-quality structures with casing covered drilled shafts and the PC-house contained pile cap. Because the assumption of free-head conditions (hinge connections) is unreal for the elevated pile cap system with multiple piles of the long span sea-crossing bridges. On the other hand, elastic displacement method to evaluate the pile reactions under the pile cap is not suitable for this type of bridges due to impractical assumptions. So, full modeling techniques which analyze the superstructure and the substructure simultaneously should be performed. Loads and stress state of the large diameter drilled shaft and the pile cap for Incheon Bridge which will be the longest bridge of Korea were investigated through the full modeling for rigid connection conditions.

• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.95-101
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• 2009

As buildings increase in height, lifting plans are becoming increasingly important on construction sites. As a critical piece of load-lifting equipment, the tower crane deserves a well thought-out stability review, since it has a significant impact and is very vulnerable to structural safety disaster. To ensure the structural stability of a tower crane, its lateral support or pile supported foundation designs must include consideration for stability, and pile foundation must be used if site conditions prevent soil from providing the required bearing capacity, or prevent the foundation from being increased to the required extent. Pile supported foundation design requires thorough and systematic review, as more stability parameters need to be considered than with an independent foundation. This paper intends to develop an optimal design algorithm that can minimize associated costs while ensuring the fundamental stability of pile supported foundation design, limiting the scope of research to fixed-type trolley tower cranes using pile supported foundations. The findings herein on pile foundation stability review parameters, process and optimal design are expected to improve the operational efficiency of staff concerned, and reduce the time and efforts required for pile foundation design.