• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.117-126
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• 2004

Recently, the top ＆ down method with drilled shafts as a foundation of high rise building is often adopted for the purpose of construction period reduction and construction cost effectiveness. It is common to omit the loading test as a quality assurance on account of the high capacity of drilled shafts for the top ＆ down method. It seems that the capacity of drilled shaft in recent top ＆ down method is beyond that of conventional loading test method. However, the quality assurance for the drilled shaft as foundation of high rise building becomes much more important since the drilled shaft should bear much higher working load. A small scale test pile can be an alternative as a quality assurance for the drilled shaft with hish capacities. Through a case study, this paper gives an idea for solving the limitation of the conventional loading test method for the quality assurance of drilled shaft with high capacities. In particular, this paper analyzed the scale effect for a small drilled shaft installed into bedrock, which could be used for an alternative.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.58-65
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• 2004

Recently, the top & down method with drilled shafts as a foundation of high rise building is often adopted for the purpose of construction period reduction and construction cost effectiveness. It is common to omit the loading test as a Quality assurance on account of the high capacity of drilled shafts for the top & down method. It seems that the capacity of drilled shaft in recent top & down method is beyond that of conventional loading test method.However, the quality assurance for the drilled shaft as foundation of high rise building becomes much more important since the drilled shaft should bear much higher working load. It may be a small scale test pile could be an alternative as a quality assurance for the drilled shaft with high capacities. Through a case study, this paper gives an idea for solving the limitation of the conventional loading test method for the quality assurance of drilled shaft with high capacities. In particular, this paper analyzed the scale effect for a small drilled shaft installed into bedrock, which could be used for an alternative.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.135-139
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• 2008

For deep basement construction of buildings downtown, the usage of Top-Down Method is increasing as much as ever from strong demand. One of the essential elements for the construction by Top Down Method is the pre-founded columns, which are installed in the ground and on which a building is installed. The fact that the pre-founded columns are placed in the ground makes them susceptible to its plumbness; this aspect distinguishes pre-founded columns from general columns. However, there are no criteria for erection tolerance. Therefore, field-measured-data concerning out-of-plumb of pre-founded columns in the construction field should be accumulated and investigated so that criteria and specifications for the erection tolerance of pre-founded columns may be established through the understanding of its aspects. In this paper, we investigate out-of-plumb of pre-founded columns for the construction case and analyze its aspects, and propose considerations for design and construction phase.

• Journal of Korean Association for Spatial Structures
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• v.11 no.2
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• pp.129-138
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• 2011

Construction methods for underground structure are classified as bottom-up, up-up, and top-down methods depending on the procedure of construction related to a superstructure. In top-down construction methods, building's main structure is built from the ground level downwards by sequentially alternating ground excavation and structure construction. In the mean time, the main structure is also used as supporting structure for earth-retaining wall, which results in the increased stability of the earth-retaining wall due to the minimized deformation in adjacent structures and surrounding grounds. In addition, the method makes it easy to secure a field for construction work in the downtown area by using each floor slabs as working spaces. However top-down construction method is often avoided since an excavation under the slab has low efficiency and difficult environment for work, and high cost compared with earth anchor method. This paper proposes a combined construction method where semi-open cut is selected as excavation work, slurry as earth -retaining wall and CWS as top-down construction method. In the case study targeted for an actual construction project, the proposed method is compared with existing top-down construction method in terms of economic feasibility, construction period and work efficiency. The proposed construction method results in increased work efficiency in the transportation of earth and sand, and steel frame erection, better quality management in PHD construction, and reduced construction period.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1107-1112
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• 2000

When top down method is used, it could be a construction method trouble in column joint, between the former concrete and the latter. It could bring a void and weak concrete in column. The purpose of this study is finding a way to prevent concrete void and concrete suitable for top down, through V-metering for top down column and concrete experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.763-768
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• 2001

The purpose of this study is to research a specific material characteristics of top down concrete at column joint and to reduce column joint opening. Based on the established top down study, the experiment to apply an real construction case is performed. When the concrete placed into joint of top down column, raised air bubble is left as opening. This study is examined the incomplete packing reason in the top down column and found to air deflation method. The result of study is below (1) As the method to minimize column opening caused from confined air, it is required that an air exhaust port installation in joint column. (2) From air exhaust port installation, most of air bubble in column part is exhausted. As the concrete placing height is going up, air bubble size is going smaller.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.27-30
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• 2008

For the purpose of developing economical and time-efficient formwork for Top-down construction, a Non-Supporting Form System has been proposed. The system is consisted of two parts: a hanging part to support a steel frame and a section of concrete slab, and the other hanging part to lower the steel frame. In this paper, the proposed system is compared to two existing systems of Non Supporting Top-down Method and Bracket Supported R/C Downward Method. It is expected that this system can be used in Top-down construction with further development.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.179-179
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• 2021

Top-Down construction method is a method of connecting a beam to a column and using a strut to support earth retaining walls. This method has the advantage of reducing the process of underground construction by reducing the work of installation. Recently, there are a lot of cases of damage and defect occurring in H-beam backfill applied to Top-Down construction method and the concrete slab supporting H-beam backfill. For this, appropriate methods were suggested through finite element analysis of the position and installation form of the H-beam backfill.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.13-27
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• 1997

In the modern design technology, a component should be designed to fit into the overall system performance. A design methodology is developed to expedite the mechan- ical design of complex mechanical systems, The relation between the system design and component design is defined by a top-down approach and the results from the system design are utilized in the component design process. As a design example, an automobile exhaust system is selected for the system design and a bellows is chosen for a component design. Design methodology based on the top-down approach consists of five steps; (1) Analysis of service load, (2) Development of a lumped parameter, (3) Completion of the system design, (4) Selection of the component topology, (5) Completion of the component design, A method using a equivalent matrix is developed in order to determine unknown external forces in linear structural analyses. The bellows is also analyzed by the finite element method using a conical frustum shell element. Various experiments are performed to verify the developed theories. The top-down desi- gn approach is demonstrated by a design case using structural and shape optimization technology. Since the method is relatively simple and easy compared to other methods, it can be applied to the general design where system and component designs are involves simultaneously.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.487-492
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• 1999

The purpose of this study to find the mixture of concrete for Top-Down method. Throughout test of elapsed time change and L-type flow, it was proposed basic performance and level of top-down method concrete. When change as to elapsed time is considered, so series of F10 added 10% S.P satisfied slump and demanded flow (60$\pm$5cm), and L-type slump, L-type flow satisfied liquidity, it can be considered basic mixture of designed actual frame later.