• Computers and Concrete
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• v.31 no.1
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• pp.23-32
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• 2023

Reinforced concrete flat slab (RCFS) with columns is a standard gravity floor system for tall buildings in North America. Typically, RCFS-column connections are designed to resist gravity loads, and their contribution to resisting seismic forces is ignored. However, past experimental research has shown that RCFS-column connections have some strength and ductility, which may not be ignored. Advanced numerical models have been developed in the past to determine the nonlinear cyclic behavior of RCFS-column connections. However, these models are either too complicated for nonlinear dynamic analysis of an entire building or not developed to model the behavior of modern RCFS-column connections. This paper proposes a new nonlinear model suitable for modern RCFS-column connections. The numerical model is verified using experimental data of specimens with various material and reinforcement properties. A 40-story RC shear wall building was designed and analyzed to investigate the influence of RCFS on the global response of tall concrete buildings. The seismic responses of the building with and without the RCFS were modelled and compared. The results show that the modelling of RCFS has a significant impact on the inter-story drifts and force demands on both the seismic force-resisting and gravity elements.

• Journal of Korean Society of Steel Construction
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• v.23 no.1
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• pp.125-135
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• 2011

To obtain a lower story height with a long span and better fire resistance, a new composite floor system using GFRP (glass-fiber-reinforced plastics) was proposed. This floor system consists of asymmetric steel with a web opening, a hollow core ball, concrete, and GFRP. To evaluate the flexural performance of the new composite floor system, an experiment was conducted. The test parameters were the presence of GFRP, the void ratio in relation to the hollow core balls, and the web opening. The test results showed that the resistance and stiffness of the specimen with GFRP were 10% higher than those of the reference specimen, and that fully composite action was accomplished up to the yielding point. After the attainment of the yield strength, the ductility of the specimen was reduced due to the stress concentration around the web openings. The slip between the concrete and steel beam, however, was small. Thus, in the design of the proposed new floor systems, it is desirable that the calculated resistance be reduced by 15%, for safety.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.31-39
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• 1997

This paper is on the vibration control of access floor on the frames of reinforced structure. In this study, the horizontal anti-vibration system using precise spring damper was developed and modeling and vibration analysis of the RC structure was performed for the control of horizontal vibration coused by machinery and worker's moving. Experiment was done in three cases, no damper at the RC structures, dampers connecting pedestal to pedestal and pedestal to the structure, for the investigation of the effect of the system on disigned RC structure. For each experiment, the occeleration responses on slab and access floor after giving impact wave and external vibration were measured. It was shown that the magnitude of resonance response of the system with dampers are smaller than without damper and the resonance peak also partly moved to low-frequency range. Furthermore. It was shown that the acceleration components of the system with domoers decreased greatly in high-frequency range and the system was very much effective especially for external vibration. In order to verify the anti-vibration effect of the developed system, the vibration analysis was also done for the system by using the finite element modelling. The analysis results was in good agreement with experimental results. Thus, It is concluded that this study is useful for the design of precise anti-vibration system and micro-vibration control of concrete structures.

• Journal of the Korea Institute of Building Construction
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• v.11 no.5
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• pp.501-514
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• 2011

Recently, there have been many cases in which the difficulty of repair and replacement of principal elements in the bearing wall structure for apartment buildings, which is a major part of apartment buildings in Korea, has led to the reconstruction of buildings rather than their remodeling. To address this problem, the Korea government now allows a floor area ratio of up to 20 %, and has relaxed the building height limits to encourage the use of a rahmen structure instead of a bearing wall structure. However, since reinforced concrete rahmen structures have many problems, including higher floor height and greater construction cost, a great deal of research into rahmen composite precast concrete structures have been conducted. Green Frame, one of the developed prototypes, is expected to provide economic benefits through in-situ production for precast concrete column and beam. For in-situ production of composite precast concrete members, a detailed plan for production, curing, and installation is needed. However, it needs to be confirmed that the space is sufficient to produce the precast concrete members on-site before planning those activities. Therefore, this study proposes in-situ production analysis of composite precast concrete members of Green Frame with the evaluation of structural safety and available area on the parking structure. The result of this study shows that the in-situ production of precast concrete members is possible through a case study.

• Advances in Computational Design
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• v.8 no.1
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• pp.13-36
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• 2023

The Puebla-Morelos Earthquake (Mw 7.1) occurred in Mexico in 2017 causing 44 buildings to collapse in Mexico City. This work evaluates the non-linear response of a 6-story reinforced concrete (RC) frame prototype model with masonry infill walls on upper floors. The prototype model was designed using provisions prescribed before 1985 and was subjected to seismic excitations recorded during the earthquakes of 1985 and 2017 in different places in Mexico City. The building response was assessed through a damage index (DI) that considers low-cycle fatigue of the steel reinforcement in columns of the first floor, where the steel was modeled including buckling as was observed in cases after the 2017 earthquake. Isocurves were generated with 72 seismic records in Mexico City representing the level of iso-demand on the structure. These isocurves were compared with the location of 16 collapsed (first-floor column failure) building cases consistent with the prototype model. The isocurves for a value greater than 1 demarcate the location where fatigue failure was expected, which is consistent with the location of 2 of the 16 cases studied. However, a slight increase in axial load (5%) or decrease in column cross-section (5%) had a significant detrimental effect on the cumulated damage, increasing the intensity of the isocurves and achieving congruence with 9 of the 16 cases, and having the other 7 cases less than 2 km away. Including column special detailing (tight stirrup spacing and confined concrete) was the variable with the greatest impact to control the cumulated damage, which was consistent with the absence of severe damage in buildings built in the 70s and 80s.

• Earthquakes and Structures
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• v.5 no.4
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• pp.379-394
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• 2013

Post-earthquake fire (PEF) can lead to a rapid collapse of buildings damaged partially as a result of prior earthquake. Almost all standards and codes for the design of structures against earthquake ignore the risk of PEF, and thus buildings designed using those codes could be too weak when subjected to a fire after an earthquake. An investigation based on sequential analysis inspired by FEMA356 is performed here on the Immediate Occupancy, Life Safety and Collapse Prevention performance levels of structures, designed to the ACI 318-08 code, after they are subjected to an earthquake level with PGA of 0.35g. This investigation is followed by a fire analysis of the damaged structures, examining the time taken for the damaged structures to collapse. As a point of reference, a fire analysis is also performed for undamaged structures and before the occurrence of earthquake. The results indicate that the vulnerability of structures increases dramatically when a previously damaged structure is exposed to PEF. The results also show that the damaging effects of post-earthquake fire are exacerbated when initiated from the second and third floor. Whilst the investigation is made for a certain class of structures (conventional buildings, intermediate reinforced structure, 3 stories), the results confirm the need for the incorporation of post-earthquake fire into the process of analysis and design, and provides some quantitative measures on the level of associated effects.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.465-468
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• 2004

The first thing in remodelling of an apartment is the enlargement of living area, which is usually attained through extending balcony or corridor to the outside of the building. As a reasonable solution to the extension of floor a method of rigid connection in which steel bars are injected into the existing slab and concrete of newly building slab is installed with proper reinforcement is proposed in this research. To verify the structural performance of the method bending tests have been carried out for seven slab specimens.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.236-237
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• 2021

In the waterproofing of the rooftop of reinforced concrete buildings, it is difficult to solve perfectly according to the proficiency of waterproofing materials, methods, and mechanics. Therefore, this study applies a Tricot Fabric Mesh to the behavior of the bottom concrete. In addition, it responds to the behavior of the concrete cracking, and the waterproofing and protective layer has developed a method to provide convenience for rooftop floor use by adhesion between the base and the waterproof layer with the use of high viscosity urethane to effectively move the surface deformation and surface vapor and install a airvent device on the wall.

• Structural Engineering and Mechanics
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• v.64 no.3
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• pp.339-346
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• 2017

Slabs prevent harmful effects of fire that may occur in any floor. However, it is necessary to protect the slabs from fire. Insulation materials may be appropriate to protect reinforced concrete (RC) slab from elevated temperature. In the present study, a model has been developed in artificial neural network (ANN) to predict the moment capacity ($M_r$) of RC slabs exposed to fire with insulation material. 672 data were obtained for ANN model through author's prepared program. Input layer in model consisted of seven input parameters; such as effective depth (d), ratio of d'/d, thermal conductivity coefficient ($k_{insulation}$), insulation materials thickness ($L_{insulation}$), reinforcement area ($A_{st}$), fire exposure time ($t_{\exp}$), and concrete compressive strength ($f_c$). The predicted $M_r$ by ANN was consistent with the obtained $M_r$ by author. It is proposed to ease computational complexity in determining $M_r$ using ANN. The effects of using insulation material on the moment capacity in RC slabs were also investigated. Insulating material with low thermal conductivity has been found to be more effective for durability to high temperature.

• Computers and Concrete
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• v.27 no.4
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• pp.343-353
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• 2021

In this study, in order to improve the seismic performance of existing reinforced concrete (RC) framed structures, various external attachment of corner steel frame configurations was considered as a user-friendly retrofitting method. The external steel frame is designed to contribute to the lateral stiffness and load carrying capacity of the existing RC structure. A six-story building was taken into account. Four different external corner steel frame configurations were suggested in order to strengthen the building. The 3D models of the building with suggested retrofitting steel frames were developed within ABAQUS environment using solid finite elements and analyzed under horizontal loadings nonlinearly. Horizontal top displacement vs loading curves were obtained to determine the overall performance of the building. Contributions of steel and RC frames to the carried loads were computed individually. Load/capacity ratios for the ground floor columns were presented. In the study, 3D rendered images of the building with the suggested retrofits are created to better visualize the real effect of the retrofit on the final appearance of the façade of the building. The analysis results have shown that the proposed external steel frame retrofit configurations increased the lateral load carrying capacity and lateral stiffness and can be used to improve the seismic performance of RC framed buildings.