• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.691-699
• /
• 2008

In the design of a foundation, settlement of the foundation may exceed allowable design criteria even with a competent bearing stratum. In such a case, a piled-raft foundation system may be adopted using piles as settlement reducing component. In this paper, Disconnected Piled Raft Foundation (DPRF) system, which installs disconnected piles underneath the raft and uses the piles as ground reinforcements, is studied as a cost effective design method against the classical piled-raft foundation system. To this end, large size loading tests were carried out on weathered ground changing area replacement ratio and length of piles. The results indicated that the settlement of the reinforced ground was reduced by 34~87% and the allowable bearing pressure increased by 70% on average from those of the unreinforced original ground, respectively. The correlating formula between the area replacement ratio and the load bearing ratio of piles were derived from the test results and numerical analysis. From the correlation, a design method determining the size and the quantity of the disconnected piles to enhance the bearing capacity of original ground to the desired value was proposed based on one inch settlement criteria.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.1 no.3
• /
• pp.1-10
• /
• 1997

It is recognized that the dynamic of a structure is affected by the characteristics of the soil layer and foundation. However the design codes for the seismic design of structures are partially reflecting the caharcteristics of the soil layers due to the inherent complexity of them and the lack of systematic study results for the foundation-soil system, and leading to unconservative or too conservative results. In this study, the kinematic interaction effects of foundation-soil system was investigated for the seismic analyses of structures estimating the effects of the shear wave velocity, the depth of the soil layer, the embedment of a foundation and pile foundation, and the modified classification criteria of soil layers are proposed for the reasonable seismic analyses of structures considering the characteristics of soil layers and foundations. For the embedded medium or large foundations (including pile foundations), at least 60m soil layer below the foundation should be considered for the seismic analyses of structures to tate into account the kinematic interaction effects of the foundation-soil system, and also the rocking motion of foundation-soil system with or without piles should be included in the seismic analyses of structures.

• Structural Engineering and Mechanics
• /
• v.27 no.2
• /
• pp.199-222
• /
• 2007

Composite laminated structures supported on elastic foundations are being increasingly used in a great variety of engineering applications. Composites exhibit larger dispersion in their material properties compared to the conventional materials due to large number of parameters associated with their manufacturing and fabrication processes. And also the dispersion in elastic foundation stiffness parameter is inherent due to inaccurate modeling and determination of elastic foundation properties in practice. For a better modeling of the material properties and foundation, these are treated as random variables. This paper deals with effects of randomness in material properties and foundation stiffness parameters on the free vibration response of laminated composite plate resting on an elastic foundation. A $C^0$ finite element method has been used for arriving at an eigen value problem. Higher order shear deformation theory has been used to model the displacement field. A mean centered first order perturbation technique has been employed to handle randomness in system properties for obtaining the stochastic characteristic of frequency response. It is observed that small amount of variations in random material properties and foundation stiffness parameters significantly affect the free vibration response of the laminated composite plate. The results have been compared with those available in the literature and an independent Monte Carlo simulation.

• Earthquakes and Structures
• /
• v.3 no.3_4
• /
• pp.549-561
• /
• 2012

Many building foundations are embedded, however it is not easy to compact the backfill around the foundation especially for the deeply embedded ones. The soil condition around the embedded foundation may affect the seismic response of a building due to the weak contact between the soil and the foundation. In this paper, the response accelerations in the short-period range and at the period of 1 second (in the long-period range) for a seismic design spectrum specified in the IBC design code were compared considering perfect and poor backfills to investigate the effect of backfill compaction around the embedded foundation. An in-house finite-element software (P3DASS) which has the capability of horizontal pseudo-3D seismic analysis with linear soil layers was used to perform the seismic analyses of the structure-soil system with an embedded foundation. Seismic analyses were carried out with 7 bedrock earthquake records provided by the Pacific Earthquake Engineering Research Center (PEER), scaling the peak ground accelerations to 0.1 g. The results indicate that the poor backfill is not detrimental to the seismic response of a building, if the foundation is not embedded deeply in the soft soil. However, it is necessary to perform the seismic analysis for the structure-soil system embedded deeply in the soft soil to check the seismic resonance due to the soft soil layer beneath the foundation, and to compact the backfill as well as possible.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1998.10a
• /
• pp.381-388
• /
• 1998

This paper describes the development of an expert system designed to help engineers select proper foundation types and construction methods for structures under various subsoil conditions. The system includes geographical and geological data in certain areas of Ulsan and a knowledge base for the selection of foundation types. Geological data, such as boring logs, in the areas were collected and arranged to form the subsoil database in the areas concerned Test borings at 30 holes were carried out for reference and confirmation purposes. The use of this system is twofold. It provides the users with a quick view on the geological situations of the areas concerned, and suggests proper foundation types for the specific spot together with some explanations on the selected foundation types and methods.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.2 no.2
• /
• pp.1-12
• /
• 1998

The seismic behaviour of rotating machine-foundation systems subjected to six-component nonstationary earthquake ground accelerations is analyzed. The rotating machine-foundation system is idealized by using discs, rotating shaft, fluid-film journal bearings, pedestals, and space frame foundation. Thus, governing equations of motion for the rotating machine-foundation system are obtained by considering Gyroscopic effect, Coriolis effect, dynamic characteristics of fluid-film journal bearings, and translational and rotational motions of seismic rigid base. The influences due to Gyroscopic effects, Coriolis effects, and rotational motions of seismic base on the overall structural response are demonstrated by a numerical example. The results show that the inclusion of base rotations and Gyroscopic effects contributes significantly to the system response.

• Current Optics and Photonics
• /
• v.1 no.5
• /
• pp.500-504
• /
• 2017

In this paper, we developed a temperature measurement system based on an infrared temperature imaging module for thermal safety verification of a plasma skin treatment device (PSTD). We tested a pilot product of the low-temperature PSTD using the system, and the temperature increase of each plasma torch was well-monitored in real-time. Additionally, through the approximation of the temperature increase of the plasma torches, a certain limitation of the plasma treatment time on skin was established with the International Electrotechnical Commission (IEC) guideline. We determined an appropriate plasma treatment time ($T_{Safe}$ < 24 minutes) using the configured temperature measurement system. We believe that the temperature measurement system has a potential to be employed for testing thermal safety and suitability of various medical devices and industrial instruments.

• Structural Engineering and Mechanics
• /
• v.77 no.6
• /
• pp.753-763
• /
• 2021

Feasibility studies of a reinforced concrete (RC) deep pile foundation system with the compressed air energy storage (CAES) technology were conducted in previous studies. However, those studies showed some technical limitations in its serviceability and durability performances. To overcome such drawbacks of the conventional RC energy pile system, various steel-concrete composite pile foundations are addressed in this study to be utilized as a dual functional system for an energy storage medium and load-resistant foundation. This study conducts finite element analyses to examine the applicability of various composite energy pile foundation systems considering the combined effects of structural loading, soil boundary forces, and internal air pressures induced by the thermos-dynamic cycle of compressed air. On this basis, it was clearly confirmed that the role of inner and outer tubes is essential in terms of reliable storage tank and better constructability of pile, respectively, and the steel tubes in the composite pile foundation can also ensure improved serviceability and durability performances compared to the conventional RC pile system.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2007.09a
• /
• pp.692-700
• /
• 2007

There are several types of foundations for light-weight structures, such as low story buildings, on soft clay deposits. Those foundations, such as piled raft, compensated foundation, mat foundation, floating foundation are commonly used rather then end-bearing piles to get more benefits on the construction and cost savings. In this study, settlement behaviors are computed and compared for several types of foundations on soft clay deposits. Also, theoretical expressions of parameters for piled raft system were provided with co-relations for design purposes. The predictions of settlements of piled rafts foundation are proposed based on the pile dimensions and design loads. From this study, the piled raft foundations is more benefits for reducing the settlement of clay deposits, and it is found that the piled raft system is applicable and effective on thick clay deposits, and that differential settlements of the foundation should be managed by designing the configuration of pile lengths.

• Journal of Ocean Engineering and Technology
• /
• v.18 no.3
• /
• pp.20-25
• /
• 2004

For the structural foundation above the soft clay layer conditions, the design charts are first presented for the evaluation of both bearing capacity and total settlement in the basic raft foundation system. wad settlement relationship curves are used to evaluate the ultimate soil bearing capacity. The total settlement is evaluated by applying various traditional factors into the ultimate bearing capacity. Then, the parametric studies are carried out for the piled-raft foundation system. In the numerical analysis, the elasto-pastic finite element model(Mohr-Coulomb model) is used to present the foundation response and design charts, which enable the determination of the raft size and pile length and spacing.