• Journal of the Korea institute for structural maintenance and inspection
• /
• v.4 no.1
• /
• pp.131-138
• /
• 2000

In this study, physical and engineering properties of ordinary portland cement and microcement were investigated to verify reinforcing effect of underpinning of open caisson foundation by using microcement grouting. Laboratory injection tests such as infiltration and injection in case of seepage for the stream bed soil at ${\bigcirc}{\bigcirc}$ Great Bridge in Seoul were carried out. Field injection tests to reinforce open caisson foundation at ${\bigcirc}{\bigcirc}$ Great Bridge were performed and the ability of application by microcement grouting was evaluated. From the test results, physical and engineering properties of microcement are better than those of ordinary portland cement. Also, the ability of infiltration and solidity in case of seepage is better than that of ordinary portland cement. Therefore, it is concluded that microcement is an excellent material to reinforce open caisson foundation of the existing bridge structure under the water and can be used as underpinning material of general foundations.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.03a
• /
• pp.659-662
• /
• 2009

In this paper described are the performance design guidelines of writing the items of foundation structures for designers. To accept the new performance code instead of existing design code in the construction market, performance design focuses on requirements to guidelines of foundation structure.

• Geomechanics and Engineering
• /
• v.24 no.1
• /
• pp.29-42
• /
• 2021

The utilization of buildings can be improved by extending them vertically. However, the added load of the extension might require building foundations to be underpinned; otherwise, the loads on the foundations might exceed their bearing capacity. In this study, a preloading method was presented aiming at transferring partial loads from existing piles to underpinning piles. A pneumatic-type model preloading device was developed and used to carry out centrifuge experiments to evaluate the load-displacement behavior of piles, the pile-soil interaction during preloading, and the additional loading caused by vertical extension. The results showed that the preloading devices effectively transfer load from existing piles to underpinning piles. In the additional loading test of group piles, the load-sharing ratio of a pile increased with its stiffness. The load-sharing ratio of a preloaded micropile was less than that of a non-preloaded micropile as a result of the reduction in axial stiffness caused by preloading before additional loading. Therefore, a slight reduction of the load-sharing capacity of an underpinning pile should be considered if the preloading method is applied. Further, two full scale preloading devices was developed. The devices preload underpinning piles and thereby produce reaction forces on a reaction frame to jack existing piles upward, thus transferring load from the existing piles to the underpinning piles. Specifically, screw-type and hydraulic-jack type devices were developed for the practical application of foundation underpinning during vertical extension, and their operability and load transfer effect verified via full-scale structural experiments.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.4
• /
• pp.149-160
• /
• 2007

Six prototype field tests (five 1/8 and one 1/2 scale tests) have been conducted in order to determine the uplift resistance of deep foundation for transmission line structures. Test sites, located in the city of Eumseng in Choongbuk province, are classified as gneiss. These test results reveal failures not along the foundation-rock interface but either along the damaged surrounding rock mass caused by excavation or along the pre-existing rock joint. Test results also show the uplift resistance which is 20 $\sim$ 30% higher than the current design strength of side friction. In addition to fold tests, four concrete core samples between the liner plate and the surrounding rock mass have been obtained from the existing transmission foundations to study the effect of the liner plate which is installed prior to placing concrete. The compressive strength of these concrete core samples shows 63 $\sim$ 72% of the strength at the time of foundation construction. Side frictional resistance based on such less compacted concrete reaches satisfying uplift design strength.

• Smart Structures and Systems
• /
• v.24 no.4
• /
• pp.525-539
• /
• 2019

In this study, vibration characteristics of a gravity-based caisson-foundation breakwater system are investigated for ambient and geometric parameters such as various waves, sea levels, and foundation conditions. To achieve the objective, following approaches are implemented. Firstly, operational modal analysis methods are selected to identify vibration modes from output-only dynamic responses. Secondly, a finite element model of an existing caisson-foundation breakwater system is established by using a structural analysis program, ANSYS. Thirdly, forced vibration analyses are performed on the caisson-foundation system for two types of external forces such as controlled impacts and wave-induced dynamic pressures. For the ideal impact, the wave force is converted to a triangular impulse function. For the wave flow, the wave pressure acting on the system is obtained from wave field analysis. Fourthly, vibration modes of the caisson-foundation system are identified from the forced vibration responses by combined use of the operational modal analysis methods. Finally, vibration characteristics of the caisson-foundation system are investigated under various waves, sea levels, and foundations. Relative effects of foundation conditions on vibration characteristics are distinguished from that induced by waves and sea levels.

• Journal of Ocean Engineering and Technology
• /
• v.38 no.2
• /
• pp.74-85
• /
• 2024

Offshore wind turbines are supported by various foundations, each with its considerations in design and construction. Gravity, monopile, and suction bucket foundations encounter geotechnical issues, while jacket and tripod foundations face fatigue problems. Considering this, a gravity foundation based on a steel skirt was developed, and a monopile foundation was analyzed for Pile-Soil Interaction using the p-y curve and 3D finite element method (3D FEM). In addition, for suction bucket foundations, the effects of lateral and vertical loads were analyzed using 3D FEM and centrifuge tests. Fatigue analysis for jacket and tripod foundations was conducted using a hotspot stress approach. Some hybrid foundations and shape optimization techniques that change the shape to complement the problems of each foundation described above were assessed. Hybrid foundations could increase lateral resistance compared to existing foundations because of the combined appendages, and optimization techniques could reduce costs by maximizing the efficiency of the structure or by reducing costs and weight. This paper presents the characteristics and research directions of the foundation through various studies on the foundation. In addition, the optimal design method is presented by explaining the problems of the foundation and suggesting ways to supplement them.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.982-987
• /
• 2002

Recently, as size of building structure becomes larger, mat area of building structure is supported on Inhomogeneous foundation. The equipment machineries in building are mostly on basement story. The slab of the lowest basement story with equipment machineries is considered as plate supported on foundation with concentrated masses. In this paper, vibration analysis of rectangular thin plate is done by use of rectangular finite element with 4 nodes. The solution of this paper are compared with existing solution and natural frequencies of thin plates, with concented mass, on inhomogeneous Pasternak foundation are calculated

• Geotechnical Engineering
• /
• v.9 no.2
• /
• pp.55-64
• /
• 1993

When earth structures such as dykes or embankments are constructed on very soft clay foundation, unexpectedly large deformations of earth structures as well as clay foundation are encountered during and after construction. The final constructed section is composed of a portion of embankment above the existing ground level and that which penetrated into the soft foundation soil. This study is aimed to correctly estimate the shape of earth structures which penetrate some depth into the soft clay foundation. In this study the methods to predict penetration depth and deformation shape of embankment section after dumping of construction material. Model tests were carried out to prove the developed theory and FEM analysis. And when the mat is added, reinforcement effect was markedly noticed.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.12
• /
• pp.5969-5973
• /
• 2012

Introduction: Andhra Pradesh (AP) is one of the largest tobacco producing states in India. About 29% of adults in AP currently use tobacco in some form. Almost 24% of males and 4% of females are smokers. The prevalence of tobacco use in the state is higher than the national average of 15% for male and 2% for female smokers. However, few attempts have been made to understand the current situation of tobacco control resources, activities and strategies in the context of such a high tobacco prevalence state. The present study aimed to identify the gaps in existing tobacco control program and areas where tobacco control efforts can be integrated. Methods: Data were collected using both quantitative and qualitative methods. Semi-structured interviews were undertaken with a total of 95 key officials of state health departments, program managers, and project directors in six districts to understand ongoing tobacco control efforts. To facilitate the interviews, semi-structured guides were developed. Simple descriptive statistical analysis was conducted on the quantitative data using SPSS version 17. Results: The results of the situational analysis suggest that a sufficient health workforce and infrastructure with the potential to integrate tobacco control activities is available in the surveyed districts. However, lack of integration of the tobacco control program intothe tuberculosis control program and the National Rural Health Mission was observed. Information, education and communication activities were lacking at block level health facilities. Conclusions: Our findings indicate that lack of trained health professionals, paucity of dedicated funds, lack of information, education and communication materials and low priority given to tobacco control activities are some of the factors which impede integration of tobacco control into existing health and developmental programmes in the districts of Andhra Pradesh, India.

• Journal of the Korean Geotechnical Society
• /
• v.35 no.3
• /
• pp.17-24
• /
• 2019

The purpose of this study is to understand the characteristics of bearing capacity of shallow foundation on the grounds. We made a comparative study of existing bearing capacity theory, based on the three-dimensional finite element analysis with a variety of conditions such as ground condition, foundation scale and foundation shape. In the finite element analysis, the ultimate bearing capacity showed a gradual convergence in the form of exponential function or logarithm function according to the foundation scale. Although the shear strength increased, the bearing capacity tended not to increase but change linearly. In the results of comparative study of existing bearing capacity theory, bearing capacity ratio ($q_{u(FEA)}/q_{u(theory)}$) of pure sand has the outcome closest to those of the Terzaghi method. Pure clay turned out to be about 0.4~0.6 while normal soil was changed in a range of 0.3~1.3. As shear strength is increased, the results turned out to be less than 1.0. Bearing capacity ratio ($q_u/q_{u(1.0)}$), normalized at 1.0m bearing capacity, was about 35%, 15% and 5% of theoretical formula under the condition of ${\phi}=25^{\circ}$, $30^{\circ}$ and $35^{\circ}$ of pure sand; no scale effect was found with pure clay and the normal soil with lower soil strength level showed less than 10% of the theoretical formula of pure sand. Bearing capacity ratio of each case, in accordance with, the shear strength increase, was largely influenced by the internal friction angle. Shape factor of bearing capacity ratios classified by foundation shapes have different results according to the shapes; the shape factor of circular foundation is 1.50, square foundation is 1.30, rectangular and continuous foundations are 1.1~1.0.