• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.6
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• pp.241-249
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• 2021

Communication facilities play an essential role in disaster situations. Therefore, communication facilities need to have structural and functional safety during and after earthquakes. Recently, technology for partial seismic isolation has been increasing to protect data facilities and communication equipment installed in buildings from earthquakes. However, excessive displacement may occur in the seismic isolator during an earthquake due to the resonance between the building and the seismic isolator having long-period characteristics, which may cause overturning and separation of the installed equipment. In this study, analytical and experimental studies were conducted to evaluate the safety of seismic isolators installed in high-rise buildings. It was confirmed that damages might occur in buildings' seismic isolator, with resonance characteristics of less than 1 Hz.

• 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.

• International Journal of High-Rise Buildings
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• v.11 no.4
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• pp.301-314
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• 2022

Various studies have been conducted on pedestrian-level wind environments around buildings. With regard to the speed-up mechanism of pedestrian-level winds, there are references to downwash effect due to the vertical pressure gradient of boundary layer flow and venturi effect due to flow blocking by the building. Two factors contribute to increase or decrease of downwash effect: change in twodimensional / three-dimensional air flow pattern (Type 1) and change in downwash wind speed due to building size that does not accompany change in airflow pattern (Type 2). Previous studies have shown that downwash effect has a greater influence in increasing or decreasing the area of strong wind than venturi effect. However, these considerations are derived from the horizontal mean wind speed distribution at pedestrian level and are not the result of three-dimensional flow field around the building. Therefore, in this study, Computational Fluid Dynamics using Large Eddy Simulation were performed to verify the downwash phenomena that contributes to increase in wind speed at pedestrian level.

• International Journal of High-Rise Buildings
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• v.12 no.2
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• pp.121-128
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• 2023

Cities cover only 3% of the planet's surface, yet they are responsible for more than 75% of the global emissions. Given the projected urban built area will double by 2060, the carbon emitted from cities will further increase. SOM proposes the Urban Sequoia concept, for buildings that go beyond 'net zero' and absorb carbon from the atmosphere. This concept combines multiple strategies, including the use of an optimised building form with a highly efficient structural system, modularized prefabrication techniques, holistic integration of facade, MEP and interiors' components, bio-based materials, and Direct Air Capture (DAC) technology, to reduce a 40-storey building's whole life cycle carbon emissions by more than 300% over a 100-year lifespan. Calculations of embodied carbon emissions are performed with SOM's in-house Environmental Analysis (EA) Tool to demonstrate the effectiveness of employing Urban Sequoia's design strategies in the design of new buildings using current technologies.

• Journal of the Korean Institute of Rural Architecture
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• v.26 no.3
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• pp.19-28
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• 2024

This study aims to find the conservation and regeneration plan in terms of preserving and utilizing old wooden houses, regenerating existing buildings, and developing idle land for old dwellings located outside the southern gate of Cheongju, Korea. In the preservation and utilization of old houses, three places in the block where wooden houses clustered are created as conservation houses, and are conversed as cafes, workspaces, and homestays along with the preservation of individual houses. In the regeneration of existing buildings, the street landscape was improved through extension and renovation, new construction after demolition, and exterior renovation for one or two-story buildings facing the roadside. In the development of idle land, it reflects the layout method and open yard space corresponding to the path and orientation of the old house, and the mass was varied and segmented to resolve the medium scale. Accordingly, considering the context, landscape, and environmental aspects of the historical downtown, the development of old dwellings in downtown should shift from a uniform high-rise apartment project-oriented approach to a gradual and continuous regeneration direction.

• International Journal of High-Rise Buildings
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• v.6 no.3
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• pp.227-235
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• 2017

This paper describes some of the challenges for structural design of a mid-story seismic isolated high-rise building, which is located near Tokyo station, completed in 2015. The building is a mixed-use complex and encompasses three volumes: one substructure including basement and lower floors, and a pair of seismic isolated superstructures on the substructure. One is a 136.5m high Main Tower (office use), and the other is a 98.5 m high South Tower (hotel use). The seismic isolation systems are arranged in the $3^{rd}$ floor of the Main Tower and $5^{th}$ floor of the South Tower, so that we call this isolation system as the mid-story seismic isolation. The primary goal of the structural design of this building was to secure high seismic safety against the largest earthquake expected in Tokyo. We adopted optimal seismic isolation equipment simulated by dynamic analysis to minimize building damage. On the other hand, wind-induced vibration of a seismic isolated high-rise building tends to be excited. To reduce the vibration, the following strategies were adopted respectively. In the Main Tower with a large wind receiving area, we adopted a mechanism that locks oil dampers at the isolation level during strong wind. In the South Tower, two tuned mass dampers (TMDs) are installed at the top of the building to control the vibration. In addition, our paper will also report the building performance evaluated for wind and seismic observation after completion of the building. In 2016, an earthquake of seismic intensity 3 (JMA scale) occurred twice in Tokyo. The acceleration reduction rate of the seismic isolation level due to these earthquakes was approximately 30 to 60%. These are also verified by dynamic analysis using observed acceleration data. Also, in April 2016, a strong wind exceeding the speed of 25m/s occurred in Tokyo. On the basis of the record at the strong wind, we confirmed that the locking mechanism of oil damper worked as designed.

• Journal of the Korea Institute of Building Construction
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• v.21 no.6
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• pp.563-571
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• 2021

Recently, due to the increase in high-rise apartment and residential-commercial complex buildings, a number of mega-class mass concrete members with a thickness of 3m or more have been designed. As the construction of mass concrete such as transfer beam and slab is increasing not only in foundation members but also in special structures, research on reducing temperature cracks in mass concrete is being conducted. To review temperature cracks in mass concrete, it is important to review the thermal properties of concrete, but it is difficult to use an adiabatic temperature rise tester in the field, so the semi-adiabatic temperature rise test is mainly used. In this study, to improve the accuracy of the results of concrete heat characteristics gained by the semi-adiabatic temperature rise test, various factors affecting heat loss compensation and methods were reviewed and presented.

• KIEAE Journal
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• v.14 no.2
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• pp.37-46
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• 2014

University buildings are energy-guzzling facility that consume more than 10,000TOE within a campus annually. Even the consumption is on an upswing trend. Behind such high consumption are there cheap power rates for education facility, lack of high-efficiency equipment and ever-increasing use of various information equipment. Being keenly aware that greenhouse gas emission increases due to such rise of energy consumption, the present study carried out a case study. In the case study, the study chose the buildings of E university from top 10 universities that consume energy most in Seoul and examined the current status of their energy consumption and greenhouse gas emission. And then it set the reduction target of greenhouse gas by year. Putting aside a middle and long-termed strategy for later endeavor, it first established the 1st year's implementation plan (2014) for energy saving and greenhouse gas reduction with limited budget and according to greenhouse gas reduction target. The plan is specified as follows. Targets for energy saving are mainly divided into two sectors: machine equipment and electric equipment. 7 ideas were proposed. Three ideas to improve machine equipment are to replace with high-efficiency boilers and chillers and to adjust the position of the cooling tower. By doing so, it was estimated that energy could be saved by 176.34TOE in total and greenhouse gas could be reduced by 370.771t$CO_2$-eq. Four ideas to improve electric equipment include the replacement with LED lights, LED emergency lights and high-efficiency motors and the installation of motion sensors. It was calculated that such replacement could conserve 1,076.08TOE (electric energy) and reduce 2,181.420t$CO_2$-eq (greenhouse gas).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5525-5533
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• 2012

Because of ultra-high buildings or deeper underground space, recent buildings have the potential that people who have lack of physical strength collapse before arriving at the emergency exits when catastrophes occur. In case of fire, the way to escape is that first, people take the stairs of the adjacent areas and then use the elevator to the remaining distance by road to escape notice or be safe. For this reason, the skyscrapers guidelines of Seoul for information on the elevator for evacuation has been established. Nevertheless, when designing buildings to install a elevator for evacuation separately is not effective, so passenger elevators installation according to the criteria are encouraged to use as evacuation elevators. However, this does not include detailed design guidelines so far. Therefore, this study was to investigate design method to use the passenger elevator for evacuation according to the domestic law and international installation criteria, and to calculated number of lifts and refuge to use the elevator using by the ELVAC+ and PathFinder evacuation program.

• International Journal of High-Rise Buildings
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• v.10 no.4
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• pp.265-283
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• 2021

To ensure that fire induced collapse of a building is prevented it is important to understand the sequence of events that can lead to this event. In this paper, the initiation of collapse mechanisms of generic a multi-storey steel frame subjected to vertical and horizontal travelling fires are analysed computationally by tracking the formation of plastic hinges in the frame and generation of fire induced loads. Both uniform and travelling fires are considered. In total 58 different cases are analysed using finite element software LS-DYNA. For the frame examined with a simple and generic structural arrangement and higher applied fire protection to the columns, the results indicate that collapse mechanisms for singe floor and multiple floor fires can be each split into two main groups. For single floor fires (taking place in the upper floors of the frame (Group S1)), collapse is initiated by the pull-in of external columns when heated beams in end bays go into catenary action. For single floor fires occurring on the lower floors(Group S2), failure is initiated (i.e. ultimate strain of the material is exceeded) after the local beam collapse. Failure in both groups for single floor fires is governed by the generation of high loads due to restrained thermal expansion and the loss of material strength. For multiple floor fires with a low number of fire floors (1 to 3) - Group M1, failure is dominated by the loss of material strength and collapse is mainly initiated by the pull-in of external columns. For the cases with a larger number of fire floors (5 to 10) - Group M2, failure is dominated by thermal expansion and collapse is mainly initiated by swaying of the frame to the side of fire origin. The results show that for the investigated frame initiation of collapse mechanisms are affected by the fire type, the number of fire floors, and the location of the fire floor. The findings of this study could be of use to designers of buildings when developing fire protection strategies for steel framed buildings where the potential for a multifloor fire exists.