• International Journal of High-Rise Buildings
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• v.11 no.4
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• pp.331-346
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• 2022

Reproducing the horizontally homogeneous atmospheric boundary layer in computational wind engineering is essential for predicting the wind loads on structures. One of the important issues is to use fully developed inflow conditions, which will lead to the consistence problem between inflow condition and internal roughness. Thus, by analyzing the previous results of computational fluid dynamic modeling turbulent horizontally homogeneous atmospheric boundary layer, we modify the past hypotheses, detailly derive a new type of inflow condition for standard k-ε turbulence model. A group of remedial approaches including formulation for wall shear stress and fixing the values of turbulent kinetic energy and turbulent dissipation rate in first wall adjacent layer cells, are also derived to realize the consistence of inflow condition and internal roughness. By combing the approaches with four different sets of inflow conditions, the well-maintained atmospheric boundary layer flow verifies the feasibility and capability of the proposed inflow conditions and remedial approaches.

• International Journal of High-Rise Buildings
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• v.12 no.4
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• pp.299-306
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• 2023

An overview of seismic isolation and structural control in Japan is presented. The paper includes a mention of the history of aseismic technology and the earthquake threat in Japan, summarizes the merits of seismic isolation and response control, and discusses the types of devices used and some recent project examples. The projects presented are mostly examples of response control used for high-rise buildings. These types of buildings are not amendable to seismic isolation, and are a challenge to applying damping devices, as their high aspect ratio means that their dominant deformation mode is bending. Japanese engineers have developed a range of unique techniques to apply response control to these types of structures. Concluding remarks discuss some of the current challenges to expanding the use of seismic isolation and response control technologies.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.45-46
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• 2016

As the demand for super tall buildings is currently increased in domestic and foreign countries, some kinds of ultra-high strength concretes are being developed actively. Since the cross section of concrete becomes smaller thanks to such kinds of ultra-high strength concretes, the concrete structures can be much bigger, more gigantic and much ultra-high. And as another benefit which is generated thanks to the enhancement of the durability performance, the maintenance expenses are also saved. However, since low W/B ultra-high concrete has a high possibility that many cracks can occur in the initial period due to the self-shrinkage caused by the self-desiccation as one of the blending characteristics, the problem becomes bigger by influencing the safety of a structure. Therefore, in this study, it is intended to analyze the effects of substituting some limestone-based ultra-high strength mortar with electric arc furnace oxidizing slag fine aggregates on the self-shrinkage of mortar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.37-44
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• 2020

This research aimed to propose the more proper equation than the leading and existing equations to predict the optimum location of offset outrigger. In this study, a 79 existing models of offset outrigger system were examined. And the key factors in the existing offset outrigger models were the stiffness of shear wall and offset outrigger system, the stiffness of exterior column connected in offset outrigger, the frame stiffness, the ratios of lateral stiffness of frame in shear wall-frame structures, and all that. This paper proposed the modified equation of predicting the optimal location of offset outrigger system. Additionally, the findings of this study provided the important structure engineering materials of the optimal offset outrigger position in tall building.

• International Journal of High-Rise Buildings
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• v.4 no.4
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• pp.283-290
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• 2015

Crack control remains a primary concern for mass concrete structures, where the majority of cracking is caused by temperature changes during the hydration process. One-time pouring is a useful construction method for mass concrete structures. The suitability of this method for constructingon of the Shanghai Tower's mass concrete foundation slab of Shanghai Tower is considered here by a numerical simulation method based on a 6- meter- thick slab. Some of the conclusions, which can be verified by monitoring results conducted during construction, are as follows. The temperature gradient is greater in the vertical direction than in the radial direction, therefore, the vertical temperature gradient should be carefully considered for the purpose of crack control. Moreover, owing to cooling conditions at the surfaces and the cement mortar content of the slab, the temperatures and temperature gradients with respect to time vary according to the position within the slab.

• Smart Structures and Systems
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• v.18 no.6
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• pp.1251-1267
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• 2016

In this paper, Simple Adaptive Control (SAC) is used to enhance the seismic response of nonlinear tall buildings based on acceleration feedback. Semi-active MR dampers are employed as control actuator due to their reliability and well-known dynamic models. Acceleration feedback is used because of availability, cost-efficiency and reliable measurements of acceleration sensors. However, using acceleration feedback in the control loop causes the structure not to apparently meet some requirements of the SAC algorithm. In addition to defining an appropriate SAC reference model and using inherently stable MR dampers, a modification in the original structure of the SAC is proposed in order to improve its adaptability to the situation in which the plant does not satisfy the algorithm's stability requirements. To investigate the performance of the developed control system, a numerical study is conducted on the benchmark 20-story nonlinear building and the responses of the SAC-controlled structure are compared to an $H_2/LQG$ clipped-optimal controller under the effect of different seismic excitations. As indicated by the results, SAC controller effectively reduces the story drifts and hence the seismically-induced damage throughout the structural members despite its simplicity, independence of structural parameters and while using fewer number of dampers in contrast with the $H_2/LQG$ clipped-optimal controller.

• Smart Structures and Systems
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• v.22 no.5
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• pp.547-560
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• 2018

This paper investigates the operation of the $H_{\infty}$ static output-feedback controller to reduce dynamic responses under seismic excitation on the five-story and benchmark 20 story building with parametric uncertainties. Linear matrix inequality (LMI) control theory is applied in this system and then to achieve the desired LMI formulations, some transformations of the LMI variables is used. Conversely uncertainties due to material properties, environmental loads such as earthquake and wind hazards make the uncertain system. This problem and its effects are studied in this research. Also to decrease the transition of large amount of data between sensors and controller, avoiding the disruption of whole control system and economy problems, the operation of the decentralized controllers is investigated in this paper. For this purpose the comparison between the performance of the centralized, fully decentralized and partial decentralized controllers in uncoupled and coupled cases is performed. Also, the effect of the changing the number of stories in substructures is considered. Based on the numerical results, the used control algorithm is very robust against the parametric uncertainties and structural responses are decreased considerably in all the control cases but partial decentralized controller in coupled form gets the closest results to the centralized case. The results indicate the high applicability of the used control algorithm in the tall shear buildings to reduce the structural responses and its robustness against the uncertainties.

• International Journal of High-Rise Buildings
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• v.5 no.3
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• pp.195-203
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• 2016

Shear wall structures have been widely used in high-rise buildings during the past decades, mainly due to their good overall performance, large lateral stiffness, and high load-carrying capacity. However, traditional reinforced concrete wall structures are prone to brittle failure under seismic actions. In order to improve the seismic behavior of traditional shear walls, this paper presents three different metal energy-dissipation shear wall systems, including coupled shear wall with energy-dissipating steel link beams, frame with buckling-restrained steel plate shear wall structure, and coupled shear wall with buckling-restrained steel plate shear wall. Constructional details, experimental studies, and calculation analyses are also introduced in this paper.

• Journal of the Korean GEO-environmental Society
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• v.10 no.3
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• pp.63-71
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• 2009

The movement of in-situ walls has become very important as construction in large cities moves upward, instead of outward. Tall structures typically have deep excavations not on1y to provide extra space for parking, but also to reduce the potential settlement of the building. These large excavations require a robust bracing system to resist the lateral earth pressures as the depth increases. Methods to predict deflections of the retaining systems are of utmost importance because wall movements allow potentia1 settlement of adjacent structures. Case studies will be analyzed and measured waI1 def1ections will be compared with predictions from empirica1ly derived charts.

• Earthquakes and Structures
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• v.15 no.2
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• pp.145-153
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• 2018

Extensive reinforced concrete interior beam-column joints with beams of different depths have been used in large industrial buildings and tall building structures under the demand of craft or function. The seismic behavior of the joint, particularly the relationship between deformation and strength in the core region of these eccentric reinforced concrete beam-column joints, has rarely been investigated. This paper performed a theoretical study on the effects of geometric features on the shear strength of the reinforced concrete interior beam-column joints with beams of different depths, which was critical factor in seismic behavior. A new model was developed to analyze the relationship between the shear strength and deformation based on the Equivalent Strut Mechanism (ESM), which combined the truss model and the diagonal strut model. Additionally, this paper developed a simplified calculation method to estimate the shear strength of these type eccentric joints. The accuracy of the model was verified as the modifying analysis data fitted to the test results, which was a loading test of 6 eccentric joints conducted previously.