• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.196-197
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• 2021

The underground method can be divided into Top-Down, Semi-Top-Down, Up-Up and Down-Up methods according to the construction order of the upper and lower structures. Among them, the Down-Up method proceeds with the construction of the first floor and its lower floors, and when the foundation is completed, the vertical members of the basement are sequentially completed from the foundation and the above-ground floor is constructed. In this paper, the crack reduction method around the open section of the Down-Up method affected by earth pressure was analyzed and divided into design and construction parts.

• 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.

• Journal of the Korea Institute of Building Construction
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• v.1 no.2
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• pp.191-195
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• 2001

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. To minimize the void of reverse placement joint, It is more effect to use the sheath method then direct method in concrete placement.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.6
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• pp.101-109
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• 2019

The purpose of this study is to improve a general Top-Down construction process for superstructure construction period reduction. In a general Top-Down construction sequence, the ground floor slab is set up first. Subsequently, 1st basement level construction including core walls is constructed. Initiation of the ground level superstructure gets waited until then. In this study, removable deck plate installation on the bottom of the core walls of ground level is preceding the concrete casting, therefore, ground level superstructure construction is able to get started earlier. Up to first typical floor concrete casting, total of seventy-two working(calendar) days will be resulted in a reduction from the total construction periods.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.312-331
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• 1991

Top-down Method of basement construction technique has been applied for building of the deep basement car park the close proximity of priceless historic buildings in LONDON. Numerical analysis for the prediction of ground movement of the surrounding buildings was performed in order to compare the field data at the various stages of excavation and support. The predicted results from the elasto-plastic analytical method were compared with the observed data and the agreement is very satisfactory. It may be concluded that the system of diaphragm wall supported by the permanent base slabs (Top-Down Method) was proved to be the most effective technique in terms of reducing any critical damage to the surrounding buildings.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.29-32
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• 2009

Building foundations for Top-Down construction require a special setting, because the foundations have to be placed way before excavation for the substructure of main building, Usually, the foundation goes into the layer of rock and it is often called rock-pier foundation, Currently, a cage of steel reinforcing bars is inserted to the pre-excavated hole in the rock layer, hanging down from the wide flange steel column above. This paper presents a new method for connecting the prefounded column and the steel cage with a coupler for better connection between the two, The use of a circular Concrete Filled Tube (CFT) as a prefounded column makes it possible to have this type of connection. The details of the connection and application to a Top-Down construction site is also included in this paper.

• The Journal of Engineering Geology
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• v.22 no.1
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• pp.39-48
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• 2012

The behaviors of a diaphragm wall and a contiguous pile wall such as CIP(Case-in-place pile) and SCW(Soil-cement wall), applied to the top-down construction method, were analyzed using the SUNEX program, which is widely used to design earth retaining walls. Four types of earth pressures, as described by Rankine (1857), Terzaghi and Peck (1967), Tchbotarioff (1973), and Hong and Yun (1995a), were applied to the analysis program to predict the lateral displacement of walls. The results show that the displacements of an earth retaining walls vary with the applied earth pressure. The predicted lateral displacement based on Hong & Yun's (1995a) earth pressure is similar to the measured displacement. Therefore, the actual lateral displacement of an earth retaining wall, as applied to top-down construction method, can be accurately predicted by using an analysis program considering Hong and Yun's (1995a) earth pressure.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.788-793
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• 2009

Constructing substructures by using Top-Down or Downward method needs an efficient formwork system because of difficulties in supporting concrete slabs from the bottom while excavation is in process. Existing underground formwork systems can be classified by three types: graded ground supported type (Slab On Grade, Beam On Grade), suspension type (Non Supporting Top Down Method), and bracket supported type (Bracket Supported R/C Downward). Each method has its own advantages and limits. Application of a specific formwork system for a given construction site is determined by various conditions and affect construction time and cost. This paper presents a newly developed underground non-supporting formwork system, which combines the advantages of a suspension type and a bracket supported type while it overcomes limits of two types. The developed system has a moving formwork which is supported by suspension cables hanging from the bracket placed at the top of pre-installed substructure columns. Then, the moving formwork is repeatedly lowered down for the next floor below to support concrete slab during curing. The details of this bracket and cable supported system have been investigated for the improvement of easiness in construction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.108-109
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• 2019

Top-down construction is a useful method of utilizing the working space, economic benefits and shorten the construction period. Precision construction of the elevator core is very important for safety of the top-down structure. In this study, the layout system for the field-BIM(Building Information Modeling) was used to precisely construct the elevator core in the basement and the ground. Through the layout system, it was possible to process the construction status, review the design results and construction errors, and confirm whether there is or not within the construction error range for elevator installation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.43-46
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• 2008

In Top-Down construction for underground structures, the placement of slab as a horizontal supporting member against lateral earth pressure is an important process in determining construction time and cost. Usually, a reinforced concrete perimeter girder distributes concentrated lateral loads from earth retaining structures such as Cast-in-place (CIP) piles. By combining the function of the R/C perimeter girder and horizontal slabs, the Opened Slab Method is efficient for reducing construction time by elimination of time-consuming formwork for traditional perimeter girders. The structural performance of the method is also discussed in this paper.