• Earthquakes and Structures
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• v.18 no.6
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• pp.691-707
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• 2020

One of the most important issues in structural systems is evaluation of the margin of safety in low and mid-rise buildings against the progressive collapse mechanism due to the earthquake loads. In this paper, modeling of collapse propagation in structural elements of RC frame buildings is evaluated by tracing down the collapse points in beam and column structural elements, one after another, under earthquake loads and the influence of column removal is investigated on how the collapse expansion in beam and column structural members. For this reason, progressive collapse phenomenon is studied in 3-story and 5-story intermediate moment resisting frame buildings due to the corner and edge column removal in presence of the earthquake loads. In this way, distribution and propagation of the collapse in progressive collapse mechanism is studied, from the first element of the structure to the collapse of a large part of the building with investigating and comparing the results of nonlinear time history analyses (NLTHA) in presence of two-component accelograms proposed by FEMA_P695. Evaluation of the results, including the statistical survey of the number and sequence of the collapsed points in process of the collapse distribution in structural system, show that the progressive collapse distribution are special and similar in low-rise and mid-rise RC buildings due to the simultaneous effects of the column removal and the earthquake loads and various patterns of the progressive collapse distribution are proposed and presented to predict the collapse propagation in structural elements of similar buildings. So, the results of collapse distribution patterns and comparing the values of collapse can be utilized to provide practical methods in codes and guidelines to enhance the structural resistance against the progressive collapse mechanism and eventually, the value of damage can be controlled and minimized in similar buildings.

• 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 Korean Association for Spatial Structures
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• v.21 no.4
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• pp.73-80
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• 2021

A mid-story isolation system was proposed for seismic response reduction of high-rise buildings and presented good control performance. Control performance of a mid-story isolation system was enhanced by introducing semi-active control devices into isolation systems. Seismic response reduction capacity of a semi-active mid-story isolation system mainly depends on effect of control algorithm. AI(Artificial Intelligence)-based control algorithm was developed for control of a semi-active mid-story isolation system in this study. For this research, an practical structure of Shiodome Sumitomo building in Japan which has a mid-story isolation system was used as an example structure. An MR (magnetorheological) damper was used to make a semi-active mid-story isolation system in example model. In numerical simulation, seismic response prediction model was generated by one of supervised learning model, i.e. an RNN (Recurrent Neural Network). Deep Q-network (DQN) out of reinforcement learning algorithms was employed to develop control algorithm The numerical simulation results presented that the DQN algorithm can effectively control a semi-active mid-story isolation system resulting in successful reduction of seismic responses.

• Earthquakes and Structures
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• v.15 no.3
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• pp.307-317
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• 2018

The current study explores the soil-structure interaction (SSI) effect on the potential seismic damage of mid-rise non-seismically designed reinforced concrete frames retrofitted by Fibre Reinforced Polymer (FRP). An 8-storey reinforced concrete frame poorly-confined due to transverse reinforcement deficiency is selected and then retrofitted by FRP wraps to provide external confinement. The poorly-confined and FRP retrofitted frames with/without SSI are modelled using hysteretic nonlinear elements. Inelastic time history and damage analyses are performed for these frames subjected to different seismic intensities. The results show that the FRP confinement significantly reduces one or two damage levels for the poorly-confined frame. More importantly, the SSI effect is found to increase the potential seismic damage of the retrofitted frame, reducing the effectiveness of FRP retrofitting. This finding, which is contrary to the conventionally beneficial concept of SSI governing for decades in structural and earthquake engineering, is worth taking into account in designing and evaluating retrofitted structures.

• International Journal of High-Rise Buildings
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• v.3 no.3
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• pp.173-183
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• 2014

Nakanoshima Festival Tower is a 200 m high-rise complex building which contains a renewed 2700-seat capacity concert hall known as "Festival Hall" and offices including headquarter of a news company. In order to build up an office tower on the hall which requires large open space, a giant truss system is employed. The giant trusses being composed of mega-trusses and belt-trusses support all the building weight above them and transfer the load to the outside of the hall. The building also requires high seismic resistance performance for a news company. Application of mid-story seismic isolation enables the building to satisfy high-level seismic resistance criteria.

• Wind and Structures
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• v.7 no.3
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• pp.203-214
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• 2004

This paper describes a method for developing a multi-degree-of freedom aero-elasto-plastic model of a base-isolated mid-rise building. The horizontal stiffness of isolators is modeled by several tension springs and the vertical support is performed by air pressure from a compressor. A lead damper and a steel damper are modeled by a U-shaped lead line and an aluminum line. With this model, the frequency ratio of torsional vibration to sway vibration, and plastic displacements of isolation materials can be changed easily when needed. The results of isolation material tests and free vibration tests show that this model provides the object performance. The peak displacement factors are about 4.5 regardless of wind speed in wind tunnel tests, but their gust response factor decreases with increment of wind speed.

• International Journal of High-Rise Buildings
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• v.9 no.2
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• pp.175-185
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• 2020

Currently, few studies have been conducted to comprehend the seismic reliability of post-tensioned (PT) CLT shear wall structures, due to the complexity of this kind of structural system as well as due to lack of a reliable structural model. In this paper, a set of 4-, 8-, 12-, and 16-storey benchmark PT CLT shear wall structures (PT-CLTstrs) were designed using the direct displacement-based design method, and their calibrated structural models were developed. The seismic reliability of each PT-CLTstr was assessed based on the fragility analysis and based on the response surface method (RSM), respectively. The fragility-based reliability index and the RSM-based reliability index were then compared, for each PT-CLTstr and for each seismic hazard level. Results show that the RSM-based reliabilities are slightly less than the fragility-based reliabilities. Overall, both the RSM and the fragility-based reliability method can be used as efficient approaches for assessing the seismic reliabilities of the PT-CLTstrs. For these studied mid- and high-rise benchmark PT-CLTstrs, following their fragility-based reliabilities, the 8-storey PT-CLTstr is subjected to the least seismic vulnerability; while, following their RSM-based reliabilities, the 4-storey PT-CLTstr is subjected to the least seismic vulnerability

• 건축구조
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• v.20 no.2
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• pp.25-28
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• 2013

• Earthquakes and Structures
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• v.16 no.4
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• pp.469-485
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• 2019

A numerical investigation regarding local (${\mu}_L$) and story (${\mu}_S$) ductility demand evaluation of steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF), is conducted in this study. The interior connections are modeled, firstly as perfectly pinned (PP), and then as semi-rigid (SR). Three models used in the SAC steel project, representing steel buildings of low-, mid-, and high-rise, are considered. The story ductility reduction factor ($R_{{\mu}S}$) as well as the ratio ($Q_{GL}$) of $R_{{\mu}S}$ to ${\mu}_L$ are calculated. ${\mu}_L$ and ${\mu}_S$, and consequently structural damage, at the PMRF are significant reduced when the usually neglected effect of SR connections is considered; average reductions larger than 40% are observed implying that the behavior of the models with SR connections is superior and that the ductility detailing of the PMRF doesn't need to be so stringent when SR connections are considered. $R_{{\mu}S}$ is approximately constant through height for low-rise buildings, but for the others it tends to increase with the story number contradicting the same proportion reduction assumed in the Equivalent Static Lateral Method (ESLM). It is implicitly assumed in IBC Code that the overall ductility reduction factor for ductile moment resisting frames is about 4; the results of this study show that this value is non-conservative for low-rise buildings but conservative for mid- and high-rise buildings implying that the ESLM fails evaluating the inelastic interstory demands. If local ductility capacity is stated as the basis for design, a value of 0.4 for $Q_{GL}$ seems to be reasonable for low- and medium-rise buildings.

• International Journal of High-Rise Buildings
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• v.12 no.2
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• pp.163-168
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• 2023

Today 55 percent of the population in the world lives in urban areas which is expected to increase to 68 percent by the year 2050. In the cities, high-rise buildings as symbols of the modern cityscape are dominating the skylines, but the data to demonstrate their embodied energy and environmental impacts are scarce, compared to low- or mid-rise buildings. Reducing the embodied energy and environmental impacts of buildings is critical as about 42 percent of primary energy use and 39 percent of the global greenhouse gas (GHG) emissions come from the building sector. However, it is an overlooked area in embodied energy and environmental impacts of high-rise buildings. Life cycle assessment (LCA) is a widely used tool to quantify the embodied energy and environmental impacts of the building sector. LCA combined with Building Information Modeling (BIM) can simplify data acquisition of the building as well as provide both tools with feedback. Several studies recognize that the integration of BIM and LCA can simplify data acquisition of the building as well as provide tools with feedback. This article provides an overview of literature on BIM-based of embodied energy and environmental impacts of high-rise buildings. It also compares with different LCA methodologies. Finally, major strategies to reduce embodied energy and environmental impacts of high-rise buildings, research limitations and trends in the field are covered.