• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.05a
• /
• pp.13-14
• /
• 2016

This study is aimed to analyze temperature history at each section of mat foundation concrete applying double bubble sheets. The results of the study are as follows. Firstly, the results of measuring the temperature history indicate that the lowest external temperature has been recorded at -5.6℃ for the three-day measurement period. For the central section, the result indicates that the lower, center and upper part have all secured the concrete curing temperature of 18℃ or higher. This results are believed to have resulted from excellent heat insulation performance of double bubble sheets. For the edge section between the edge form and the concrete interface, the temperature has been measured, on average, approximately 12℃ lower than the central section. However, all measured sections have indicated the temperature of 5℃ or higher. Meanwhile, an analysis has been conducted through the estimation equation of compressive strength of maturity during the curing period in order to examine the possibility of early frost damage and the aspect of securing strength. It has been confirmed that the compressive strength is higher than 50°D·D, namely, 5MPa, on the 3rd day of the aging process, which allows early frost damage to be avoided.

• Journal of the Korea Institute of Building Construction
• /
• v.4 no.3
• /
• pp.109-116
• /
• 2004

Normally easy task of plat in urban architecture is that using underground full of activities for increase building site efficiency. Especially for using underground space for the parking lot. Also utilize underground is more increase for fulfill requirement in modern society considered with environmental friendly architecture. The primary objective of this study is to apply analyzed formal foundation type for selecting the optimum type of parking lots considered with structural stability, economical efficiency, construction efficiency, construction duration. This study aim to on criteria decided through the questionaries for the selection considered with in the scale of second stories parking lots underground, parking volume is 80 and reinforced concrete structure. The bearing capacity is 6～8m and downward from surface, healthy ground bearing capacity is 40 t/m2. This study comparative analysis and discuss economical efficiency, construction efficiency, construction duration based constructivist stability which applied Single foundation, Mat foundation, Drop Mat foundation. The result of this study is as follows: First, the result of economical efficiency is that on the basis of single foundation, Drop Mat foundation is 1.88, Mat foundation 2.04 as a comparative analysis on the basis of total construction cost included material cost, labor coast and machinery cost. Second, the result of construction efficiency order is single foundation, Drop Mat foundation, Mat foundation as a comparative analysis on the based connected characteristics. Third, the result of construction duration is that on the basis of Mat Foundation, Drop Mat foundation is 1.33, single foundation is 1.87 as a comparative analysis Critical Path. Forth, Each foundational type characteristics order through the matrix method is that overall each formal type of foundation contraries at economical efficiency and construction efficiency, construction duration. Also expect contradiction between engineers and owners due to engineer pursuit construction duration and ewer to begin with economical efficiency. Fifth, The selection of suitable foundation formal type needs that based consider project characteristic and field condition as according to above result of a comparative analysis. As a result, a comparative analysis economical efficiency, construction efficiency, construction duration of Mat foundation, Drop Mat foundation, single foundation with 3Bay reinforced structure underground parking lots on the healthy ground.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10b
• /
• pp.1169-1174
• /
• 2000

Since the cement-water reaction in exothermic by nature, the temperature rise within a large concrete mass. Significant tensile stresses may develop from the volume change associated with the increase and decrease of the temperature with the mass concrete. There thermal stresses will cause temperature-related cracking in mass concrete structure. These typical type of mass concrete include mat foundation, bridge piers, thick wall, box type walls, tunnel linings, etc. Crack control methods can be considered at such stages as designing, selecting the materials, and detailing the construction method. Temperature and analysis was performed by taking into consideration of the cement type and content, boundary and environment conditions including the variations of atmospheric temperature and wind velocity. This is paper, the effect of separate placement of thermal crack control footing was analysed by a three dimensional finite element method. As a result, using this method, thermal crack control can be easily performed for structures such as mat structures.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10b
• /
• pp.1181-1186
• /
• 2000

The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as biers, thick walls, box type walls, mat-slab of nuclear reactor buildings, dams or foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, design change which considers steel bar reinforcement, operation control and so on. In this study, firstly it introduce the thermal cracks control technique by employing low-heat cement concrete, thermal stress analysis considering season. Secondly it shows the application of the cracks control technique like block placement.

• Magazine of the Korea Concrete Institute
• /
• v.13 no.6
• /
• pp.79-88
• /
• 2001

• Magazine of the Korea Concrete Institute
• /
• v.13 no.1
• /
• pp.31-36
• /
• 2001

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2008.11a
• /
• pp.37-41
• /
• 2008

According to the recent rapidly increasing that construction works are gradually Manhattanized mainly the grand scaled residential buildings, the foundation of the building that is related to safety is increasing for building as a grand scaled mat concrete. Because mat concrete can not be simultaneously placing of concrete in a great quantity due to the circumstance at the field, the inequal deformation of the tensile stress that according to the time lag of hydration heat between the upper layer and the lower layer is affecting as a cause that is the possibility of crack occurrence by increasing. Accordingly, this research checked the efficiency of super retard concrete in applying real structures, and we implemented the preparatory experiment to settle up the inequal deformation of the tensile stress substantially that is according to the time lag of placement between the upper layer and the lower layer by controlling the setting time using the super retarding agent. As the result of test, the more target of delay time lengthened, the more fluidity increased and air content indicated a little differences. There was from 2 to 10 hours between the standard curing and the outside curing at the setting time and in case of calculating the rate of mixing at real structure is required that mix promotion, increasing the amount of mixing, by setting up the curing temperature. The super retard concrete showed the result that in compressive strength, early-age strength was smaller than normal concrete whereas it was same or more figures from at the aging 28days because of the super retarding agent.

• International Journal of High-Rise Buildings
• /
• v.5 no.3
• /
• pp.205-211
• /
• 2016

This paper addresses the key technologies for supertall building construction based on the Lotte World Tower project in Korea. First, the mega-mat foundation construction technologies are shown, including ultra-low heat concrete, heat of hydration control programs, and the logistics plan. Then, high strength concrete technologies of 50~80 MPa are introduced and discussed within the context of the highest pumping record in Korea at 514.25 meters. Structural design concepts of gravity load and lateral force resistance systems are introduced, along with surveying systems using GNSS and temporary installation plans of special heavy equipment like tower cranes, hoists, and high pressure concrete pumps. If it is possible to coordinate these key technologies and others, optimizing for the building's design and construction, supertall building construction can be successfully completed.

• Magazine of the Korea Concrete Institute
• /
• v.15 no.6
• /
• pp.85-89
• /
• 2003

• The Journal of the Korea Contents Association
• /
• v.12 no.8
• /
• pp.366-372
• /
• 2012

In most of construction work, especially mat foundation construction, it is very important that accidents be prevented at early aged construction stage. To reduce the risk of accidents, it is necessary to choose the curing method to provide instructions for safety forming work by proper curing of concrete after placing. Therefore, this paper has proposed a designation algorithm of curing method for representing curing type and period by analyzing the transient hydration heat solution, focusing on mat foundation construction. This has been implemented, moreover, using an object oriented programming language to develop structural analysis system taking account crack index. In addition, we present in this paper a safety curing management system developed to assess risk during forming work.