• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.153-159
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• 2001

Recently, the underground reinforced concrete(RC) box structures have been increasingly built in Korea. In such structures, the heat of hydration may cause serious cracking problems. The RC box structures are classified in this category that needs much attention to control the hydration heat during construction, which causes the restraining effects on the boundaries. The purpose of the present study is to develop the rational construction method to control the thermal cracking problem of the box structures. In this study, the causes and mechanism of thermal cracking according to construction stages in the RC box structures are thoroughly analyzed. The major influencing variables are studied through the finite element analysis which affect the thermal cracking of RC box structures. The research results of the present study can be efficiently used for the control of cracking of box structures during construction stages.

• The Journal of the Korea Contents Association
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• v.14 no.12
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• pp.999-1009
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• 2014

In this paper, $CO_2$ emission and storage amount are evaluated for real RC (Reinforced Concrete) underground structure considering $CO_2$ amount including material manufacturing, moving, and construction, repairing timing stage regarding extended service life. Four mix proportions with mineral admixtures are prepared and $CO_2$ diffusion coefficient are obtained based on a micro modeling. Referred to carbonation durability limit state, $CO_2$ emission and storage amount are evaluated, which shows higher initial $CO_2$ emission is caused due to larger unit content of cement and the storage increases with more rapid carbonation velocity. Furthermore various $CO_2$ concentration is adopted for simulation of $CO_2$ evaluation including measured $CO_2$ concentration (600ppm). With higher concentration of $CO_2$ outside, carbonation velocity increases. In order to reduce $CO_2$ emission through entire service life, reducing initial $CO_2$ emission through mineral admixture like fly ash is more effective than increasing $CO_2$ storage through OPC since $CO_2$ is significantly emitted under manufacturing OPC and $CO_2$ storage in cover concrete of RC structure is not effective considering initial concrete amount in construction.

• International Journal of High-Rise Buildings
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• v.10 no.3
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• pp.211-218
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• 2021

A new type of earthquake resilient reinforced concrete (RC) shear wall structure, installed with replaceable coupling beams and replaceable corner components at the bottom of wall piers, is proposed in this study. At first, the mechanical behavior of replaceable components, such as combined dampers and replaceable corner component, is studied by cyclic loading tests on them. Then, cycling loading tests are conducted on one conventional coupled shear wall and one new type of coupled shear wall with replaceable components. The test results indicate that the damage of the new type of coupled shear wall concentrates on replaceable components and the left parts are well protected. Finally, a case study is introduced. The responses of one conventional frame-tube structure and one new type of structure installed with replaceable components under the wind and the earthquake are compared, which verify that the performance of new type of structure is much better than the conventional structure.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.68-74
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• 2016

This paper presents a new strengthening method of underground box structures against seismic loads for anti-seismic capacity improvement. A threaded steel member with pressure devices(so called 'Pre-flexed member system') is used to improve seismic capacity of the RC box structure. The pre-flexed member system is fixed the corner of opening after chemical anchor was installed by drilling hole on the box structure. The structural performance was evaluated analytically. Two bracing types of strengthening methods were used; conventional bracing method and I-bracing pressure system. For the performance evaluation, seismic analyses were performed on moment and shear resisting structures with and without strength member system. Numerical results confirmed that the proposed pre-flexed member system can enhance the seismic capacity of the underground RC box structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.215-216
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• 2009

Recently, the application of SCC (Self Consolidation Concrete) gets more necessity, in order to solve the problem of quality control, noise, etc. In this study describe the optimum mix proportion and the experience of cast in place of the SCC in main structure of underground RC box.

• Journal of the Korean housing association
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• v.26 no.2
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• pp.103-110
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• 2015

Precast Concrete (PC) construction method can be the one that is suitable for long-life housing due to its merit in respect of maintenance and durability based on crack-free from mass production with indirect construction cost-saving-effect due to shortening construction period comparing to the conventional construction method, but it has the problem that causes the raise of direction construction costs. So, this study analyzed its economic feasibility of PC method whose maintenance and durability are excellent for underground parking lot of apartment house for accomplishing cost-saving long-life housing by applying the various structural system. In evaluation of unit module structural system, two-way PC system requires 10 to 28% more costs for frame work than RC rigid frames, and, one-way PC system 98~112%. Although it varies depending on the method, the costs are similar to RC rigid frame structure, provided a proper method is adopted. Also, Model 11, which was most economical in the evaluation, was applied to an real parking lot and about 2 to 6% of construction costs was reduced than RC rigid frames. This seems to be because, although PC system has a higher production cost, introduction of P.S (prestress) reduces member depth and, therefore, height, as well as the number of members per unit module.

• Computers and Concrete
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• v.27 no.1
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• pp.1-12
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• 2021

This work presents a safety assessment of an underground tunnel subjected to a ballistic missile attack employing the numerical approach. For the impact simulation, a box shaped reinforced concrete (RC) structure with a cross section dimension of 8.0×10.0 m under a soil layer that was attacked by a SCUD missile was modeled using finite element (FE) software LS-DYNA. SCUD missile is one of a series of tactical ballistic missiles developed by Soviet Union during the Cold War, which is adopted for a short-range ballistic missile. The developed FE simulation for the penetration depth of the missile impacting into the soil structure was verified from the well-known formula of the penetration prediction. The soil-structure interaction, the soil type, and the impact missile velocity effects on the penetration depth of the missile into the different soil types were investigated. The safety assessment of the underground tunnel was performed with regard to the different depths of the underground tunnel. For each missile velocity and soil type, a specific depth called the unsafe depth was obtained from the analysis results. The structure beneath the soil beyond this depth remains safe. The unsafe depth was found to be increased with the increasing missile velocity.

• Tunnel and Underground Space
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• v.19 no.1
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• pp.43-51
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• 2009

In order to analyze collapse behavior of structure containing irregular and large displacement, many numerical analyses have been conducted. In this study, using a new method, Applied Element Method (AEM) for collapse analysis of structures, collapse behavior of model RC structures Is simulated. From these simulations results, displacement of X-direction (or horizontal) and displacement of Y-direction (or vertical) is similar to that of mode) RC structures. It is confirmed that collapse behavior of structures using AEN is reliable accurately simulated with that of model RC structures.

• Computers and Concrete
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• v.1 no.1
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• pp.15-30
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• 2004

In this study, a design process for reinforced concrete structures using the nonlinear FEM analysis is developed. Instead of using the nonlinear analysis to evaluate the required performance after design process, the nonlinear analysis is applied before designing the reinforcement arrangement inside the RC structures. An automatic reinforcement generator for computer aided reinforcement agreement is developed for this purpose. Based on a nonlinear FEM program for analyzing the reinforced concrete structure, a smart fictitious material model of steel, is proposed which can self-adjust the reinforcement to the required amount at the cracking location according to the load increment. Using this tool, the reinforcement ratio required at design load level can be decided automatically. In this paper, an example of RC beam with opening is used to verify the proposed process. Finally, a trial design process for a real size underground RC LNG tank is introduced.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.50-51
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• 2013

In case of Korea, it goes frequently that underground parks has been burned. Based on standard temperature time curve(ISO-834), gerber, walls, slab of structures are constructed. However, Standard temperature time Curve is not considered that buildings are affected by vehicle fire. that is why it has the hazard that makes building reinforcement feeble. Based on the result that got from vehicle experiment before, we made four RC slab in this experiment and set the fire severity. according to the loading experiment after heating, we measured the effects that makes reinforcement and shape changes. Furthermore, we examined the safty of the structure by comparing before and after heating.