• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.438-441
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• 2009

휨강성이 작은 바닥시스템인 플랫 플레이트 구조는 응력조건 뿐만 아니라 사용성조건에 의하여 구조적 성능이 결정될 수 있으며, 특히 과도한 시공 하중의 작용은 시공 중 안전성에 대한 단기적인 손상 뿐만 아니라 사용성에 관련된 장기적인 손상을 발생시킬 수 있다. 이러한 플랫 플레이트의 시공하중은 동바리지지 층 수, 시공주기, 슬래브 콘크리트의 재료적인 강성 뿐만 아니라, 동바리의 강성과 슬래브에 발생하는 균열에 의한 영향에 의하여 결정된다. 본 논문에서는 다양한 설계조건에 대한 해석연구를 통하여, 동바리-슬래브의 강성비 변화 및 콘크리트 균열에 의한 단면강성저하가 슬래브들 간의 하중 분포에 미치는 영향을 분석하고, 이러한 동바리 강성 및 슬래브 균열의 영향을 고려한 시공하중 산정법을 제안한다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.229-232
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• 2008

In rapid cycle construction, RC structure which is not cured fully can be loaded with construction load and this construction load can influence on the safety of construction and cracks on slabs. Therefore, to reduce the term of construction, the safety of construction and prevention of cracks should be assured against construction load. In the previous study, temperature load can significantly influence on the behavior of structure under construction. However, existing construction sequential analysis or design code do not consider temperature load reasonably. In the present study, through construction sequential analysis method using FE analysis, the behavior of structure under construction was analyzed according to temperature changes. According to the results of analysis, as the temperature falls, shoring load drops and the temperature rises, shoring load rises. These variations of shoring load can affect the safety of construction. Moment of slab goes up by fall in temperature. This increase of moment can cause cracks on the slab. Therefore to assure the safety on construction and prevent cracks on slabs, temperature load has to be considered reasonably in construction sequential analysis.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.41-50
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• 2010

Long-term floor deflection caused by excessive construction load became a critical issue for the design of concrete slabs, as a flat plate is becoming popular for tall buildings. To estimate the concrete cracking and deflection of an early age slab, the construction load should be accurately evaluated. The magnitude of construction load acting on a slab is affected by various design parameters. Most of existing methods for estimating construction load addressed only the effects of the construction period per story, material properties of early age concrete, and the number of shored floors. In the present study, in addition to these parameter, the effects of shore stiffness and concrete cracking on construction load were numerically studied. Based on the result, a simplified method for estimating construction load was developed. In the proposed method, the calculation of construction load is divided to two steps: 1)Onset of concrete placement at a top slab. 2)Removal of shoring. At each step, the construction load increment is distributed to the floor slabs according to the ratio of slab stiffness to shore stiffness. The proposed method was compared with existing methods. In a companion paper, the proposed method will be verified by the comparison with the measurements of actual construction loads.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.615-625
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• 2014

Excessive long-term slab deflection caused by construction load is a critical issue for the design of concrete slabs, as long span flat plates become popular for tall buildings. In the present study, the effect of construction load causing early slab cracking on the long-term deflection was theoretically studied. On the basis of the result, a numerical analysis method was developed to predict the long-term deflection of flat plates. In the proposed method, immediate deflection due to slab cracking and long-term effect of creep and shrinkage were considered. To verify the construction load effect, long-term slab deflections were measured in actual flat plate buildings under construction. The results showed that the immediate deflection due to the construction load increased significantly the long-term deflection. The proposed method was used to predict the deflections of the buildings. The results were compared with the measurement results. The predictions agree well with the long-term deflections of flat plate affected by construction load.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.117-120
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• 2008

Recently, according to the increasement of high-rise building construction and domestic situation, requirements of rapid cycle construction are increasing. For more economical and rapid cycle construction, it is required to reduce formwork cost. So formwork have to be stripped as soon as possible. But as fresh concrete is loaded with construction load, it is likely that the structure will have problems with safety and serviceability. To reduce construction cycle economically, safety and serviceability of structure against construction load have to be considered. But as behavior of structure under construction is so complicated, behavior of structure has to be investigated according to construction stage. Therefore, through field instrumentation of apartment, behavior of structure under construction was analyzed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.49-57
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• 2019

Recently, the use of deep deck plate has been increased in various structures, such as underground parking lots, logistics warehouses, because it can reduce construction periods and labor costs. In this study, a newly developed Double Deck (D-deck) plate which can leads to save story heights has been introduced, and experimental tests on a total of five D-deck plates under construction loads have been carried out to investigate their structural performance at construction stage. The loads were applied by sands and concrete to simulate the actual distributed loading conditions, and the vertical deflection of D-Deck and the horizontal deformation of web were measured and analyzed in detail. As a result, it was confirmed that all the D-decks showed very small vertical deflection of less than 5.34 mm under construction loads, which satisfies the maximum deflection limit of L / 180. In addition, the D-Deck plate was found to have a sufficient rigidity to resist construction loads in a stable manner.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.51-58
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• 2010

In a companion paper, a simplified method for the evaluation of the slab construction load was developed. Unlike existing methods, the proposed method includes the effects of shore stiffness and concrete cracking on the construction load. In the present study, construction loads were measured in actual flat-plate slabs. For verification, the measured shore-forces were compared with the predictions by the proposed method and existing methods. Further, the proposed method was applied to a wall-slab structure, and the prediction results were compared with the measurements. The comparison results showed that the proposed method well predicted the construction loads, furthermore it gave better predictions than the existing methods did.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.385-392
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• 2014

Reshoring makes slab deflect and support its own weight. The construction loads on the slabs in lower levels decrease using the reshoring. Simplified analysis proposed by ACI 347.2R-05 showed that if the reshoring is applied, construction loads on slabs and shores, and quantities of forms and shores decreased by 40%, 23%, 40%, and 50%, respectively. Shores' loads were comparatively measured on site. The measured reshore load was half of the load before removing the shores and was also lower than the measured shore load by 35%. To verify the safety of the reshoring, deflections of beams and strains of beam longitudinal bars were also measured. The maximum deflection was only L/5000 and the maximum bar strain was only 3.6% of the yield strain. Consequently, reshoring neither cause problems on the safety nor serviceability. In addition, the beam load was expected from the measured shores' loads and it coincides well with the predicted value by the simplified analysis of ACI 347.2R-05.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.161-162
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• 2009

In this study, the methodology of calculating the construction loads with considering effects of the shoring stiffness and slab cracks is proposed. Comparisons with the proposed method and the existing methods for construction load calculations were performed for measured shoring loads.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.2
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• pp.17-26
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• 2024

In recent times, accidents involving structural elements, formwork, and shore have been persistently occurring during concrete pouring, especially in multi-story reinforced concrete (RC) structures. In previous studies, research on construction load analysis was mainly conducted for cases where the thickness of all slabs is constant. However, when the thickness of some slabs is different, the variation in the stiffness of slab cross-sections can lead to different distributions of construction loads, necessitating further investigation. In this study, the slab thickness was set as a variable, and the analysis of the distribution of construction loads was conducted, taking into account the influence of changes in slab thickness on the concrete stiffness and structure. It was confirmed that not only the concrete material stiffness but also the slab cross-section stiffness should be considered in the estimation of construction loads when the slab thickness changes. As the slab thickness increases, the maximum construction load and maximum damage parameter on the layer with increased thickness significantly increase, and it was observed that a thicker slab results in a higher proportion of construction load.