• Coupled systems mechanics
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• 제6권3호
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• pp.229-249
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• 2017

A new technique to mitigate irregular buildings with soil structure interaction (SSI) effect subjected to critical seismic waves is presented. The L-shape in plan irregular building for various reasons was selected, subjected to seismic a load which is a big problem for structural design especially without separation gap. The L-shape in plan building with different dimensions was chosen to study, with different rectangularity ratios and various soil kinds, to show the effect of the irregular building on the seismic response. A 3D building subjected to critical earthquake was analyzed by structural analysis program (SAP2000) fixed and with SSI (three types of soils were analyzed, soft, medium and hard soils) to find their effect on top displacement, base shear, and base torsion. The straining actions were appointed and the treatment of the effect of irregular shape under critical earthquake was made by using tuned mass damper (TMD) with different configurations with SSI and without. The study improve the success of using TMDs to mitigate the effect of critical earthquake on irregular building for both cases of study as fixed base and raft foundation (SSI) with different TMDs parameters and configurations. Torsion occurs when the L-shape in plan building subjected to earthquake which may be caused harmful damage. TMDs parameters which give the most effective efficiency in the earthquake duration must be defined, that will mitigate these effects. The parameters of TMDs were studied with structure for different rectangularity ratios and soil types, with different TMD configurations. Nonlinear time history analysis is carried out by SAP2000 with El Centro earthquake wave. The numerical results of the parametric study help in understanding the seismic behavior of L-shape in plan building with TMDs mitigation system.

• 국제초고층학회논문집
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• 제4권4호
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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.

• Advances in Computational Design
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• 제5권1호
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• pp.35-54
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• 2020

One of the prevailing structural systems in high-rise buildings is the core-wall system. On the other hand, the existence of one or more underground stories causes the perimeter below-grade walls with the diaphragm of grade level to constitute of a very stiff box. In this case or a similar situation, during the lateral response of a tall building, underground perimeter walls and diaphragms that provide an increased lateral resistance relative to the core wall may introduce a prying action in the core that is called backstay effect. In this case, a rather great force is generated at the diaphragm of the grade-level, acting in a reverse direction to the lateral force on the core-wall system, and thus typically causes a reverse internal shear. In this research, in addition to review of the results of the preceding studies, an improved relationship is proposed for prediction of backstay force. The new proposed relationship takes into account the effect of foundation flexibility and is presented in a non-dimensional form. Furthermore, a specific range of the backstay force to lateral load ratio has been determined. And finally, it is shown that although all suggested formulas are valid in the elastic domain, yet with some changes in the initial considerations, they can be applied to some certain non-linear problems as well.

• 국제초고층학회논문집
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• 제13권2호
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• pp.113-145
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• 2024

Bamboo is seen as a low cost, lightweight, widely available and environmental-friendly material. In Vietnam, it also connects deeply to our culture. However, it wasn't seen as a viable material for large structures before VTN Architects. Furthermore, Vietnamese cities are facing the same environmental problems as many developing metropolises in the world. Globally, climate change is a serious issue. The need for sustainable construction material is clear. The increasing development of eco-tourism in Vietnam and Asia is also a background. These become the background to the foundation and the development of bamboo architecture by VTN Architects. The journal analyses our development of bamboo construction, joints, structures, and how to use them to realise space and to create eco-friendly architecture. We will talk about our process of bamboo procurement, our construction methods, our unique joint system, how we make a frame unit and how we construct VTN bamboo structures from units.

• 한국강구조학회 논문집
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• 제26권6호
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• pp.537-547
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• 2014

골조 유닛 모듈러 구조 형식은 기 제작된 유닛 구조물을 적층하여 건물을 보다 간편히 건설을 할 수 있어 중, 고층 건물에 적용이 확대되고 있다. 이러한 유닛 모듈러 구조 형식은 외력에 의하여 발생하는 축력과 휨모멘트를 지반에 잘 전달시켜야 함으로 각각의 유닛구조물은 기초와 적절히 연결되어야 한다. 본 연구에서는 새로운 형태의 매입형 유닛-기초 접합부를 제안하였으며, 제안된 접합부의 성능을 일련의 실험 연구를 통하여 평가하였다. 총 5개의 실물 크기의 실험체를 제작하여 실험을 수행하였으며, 매입 길이와 엔드 플레이트와 같은 제안된 유닛-기초 접합부의 휨거동에 영향을 미칠 수 있는 인자들의 영향을 살펴보았다. 실험결과, 모든 실험체에서 강성은 최소한 반강접의 강성을 상회하는 것으로 나타났으며, 기둥의 매입길이는 본 연구에서 수행한 실험체에서 약 200mm가 적절한 것으로 파악되었다.

• Geomechanics and Engineering
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• 제20권2호
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• pp.87-101
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• 2020

The construction of combined pile-raft foundations is considered as the main option in designing foundations in high-rise buildings, especially in soils close to the ground surface which do not have sufficient bearing capacity to withstand building loads. This paper deals with the geotechnical report of the Northern Fereshteh area of Tabriz, Iran, and compares the characteristics of the single pile foundation with the two foundations of pile group and geogrid. Besides, we investigate the effects of five principal parameters including pile diameter and length, the number of geogrid layers, the depth of groundwater level, and pore water pressure on vertical consolidation settlement and pore water pressure changes over a year. This study assessed the mechanism of the failure of the soil under the foundation using numerical analysis as well. Numerical analysis was performed using the two-dimensional finite element PLAXIS software. The results of fifty-four models indicate that the diameter of the pile tip, either as a pile group or as a single pile, did not have a significant effect on the reduction of the consolidation settlement in the soil in the Northern Fereshteh Street region. The optimum length for the pile in the Northern Fereshteh area is 12 meters, which is economically feasible. In addition, the construction of four-layered ten-meter-long geogrids at intervals of 1 meter beneath the deep foundation had a significant preventive impact on the consolidation settlement in clayey soils.

• 한국건설관리학회논문집
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• 제18권4호
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• pp.3-16
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• 2017

초고층 개발사업의 불확실한 리스크 요인을 고려한 재무타당성을 분석하기 위해 확률론적 접근방법을 통한 몬테카를로 시뮬레이션을 적용하기 위해서는 먼저 타당성 분석 시 고려되어야 하는 리스크 인자에 대한 식별이 이루어 져야 한다. 이 부분은 선행연구에서 식별된 초고층 개발사업의 단계별 리스크 요인들을 고려하고자 하며, 추출된 리스크 인자 중에서 개발사업의 수익을 저하시키는 리스크 인자들을 2차 식별하여 각 인자별 데이터의 특성을 잘 표현할 수 있는 확률분포를 추정하여 몬테카를로 시뮬레이션을 적용하였다. 이렇게 도출된 시뮬레이션 결과를 통하여 현실에서 사업타당성 검토 중인 여러 초고층 개발사업의 추후 운영 시 수익성을 예측하는 자료로 적용 가능한 대안을 찾아보고자 한다. 분석 결과, 아파트를 포함한 통합 현금흐름으로 추정한 초고층부의 평균 NPV와 IRR은 흑자 수익구조를 가지고 있다. 이는 아파트 분양수익으로 호텔 및 오피스에서 오는 적자를 상쇄시켜 주기 때문으로 보인다. 초고층부 시설 중 사업성에 미치는 영향력은 전망대 1차년도 매출액이 가장 크며, 다음으로 운영기간에 따른 오피스 공실률이 큰 영향을 미치고 있음을 알 수 있었다. 또한 초고층 개발사업의 수익성을 높이기 위한 최적의 포트폴리오 구성은 매우 중요함을 알 수 있다.

• Geomechanics and Engineering
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• 제30권2호
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• pp.169-185
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• 2022

The urbanization and increasing rate of population demands effective means of transportation system (basement and tunnels) as well as high-rise building (resting on piled foundation) for accommodation. Therefore, it unavoidable to construct basements (i.e., excavation) nearby piled foundation. Since the basement excavation inevitably induces soil movement and stress changes in the ground, it may cause differential settlements to nearby piled raft foundation. To understand settlement and load transfer mechanism in the piled raft due to excavation-induced stress release, numerical parametric studies are carried out in this study. The effects of excavation depths (i.e., formation level) relative to piled raft were investigated by simulating the excavation near the pile shaft (i.e., H_e/L_p=0.67), next to (H_e/L_p=1.00) and below the pile toe (H_e/L_p=1.33). In addition, effects of sand density and raft fixity condition were investigated. The computed results have revealed that the induced settlement, tilting, pile lateral movement and load transfer mechanism in the piled raft depends upon the embedded depth of the diaphragm wall. Additional settlement of the piled raft due to excavation can be account for apparent loss of load carrying capacity of the piled raft (ALPC). The highest apparent loss of piled raft capacity ALPC (on the account of induced piled raft settlement) of 50% was calculated in in case of H_e/L_p = 1.33. Furthermore, the induced settlement decreased with increasing the relative density from 30% to 90%. On the contrary, the tilting of the raft increases in denser ground. The larger bending moment and lateral force was induced at the piled heads in fixed and pinned raft condition.

• Earthquakes and Structures
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• 제9권6호
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• pp.1193-1219
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• 2015

The purpose of this study is to evaluate the seismic performance of high-rise reinforced concrete (RC) box-type wall structures commonly used for most residential buildings in Korea. For this purpose, an analytical model was calibrated with the results of the earthquake simulation tests on a 1:5 scale 10-story distorted model. This calibrated model was then transformed to a true model. The performance of the true model in terms of the stiffness, strength, and damage distribution through inelastic energy dissipation was observed with reference to the earthquake simulation test results. The model showed high overstrength factors ranging from 3 to 4. The existence of slab in this box-type wall system changed the main resistance mode in the wall from bending moment to tension/compression coupled moment through membrane actions, and increased the overall resistance capacity by about 25~35%, in comparison with the common design practice of neglecting the slab's existence. The flexibility of foundation, which is also commonly neglected in the engineering design, contributes to 30~50% of the roof drift in the stiff direction containing many walls. The possibility of concrete spalling and reinforcement buckling and fracture under the maximum considered earthquake (MCE) in Korea appears to be very low when compared with the case of the 2010 Concepcion, Chile earthquake.

• Geomechanics and Engineering
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• 제18권3호
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• pp.267-275
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• 2019

Tabriz is a large Iranian city and the capital of the East Azerbaijan province. The bed rock of this city is mainly consisted of marl layers. Marl layers have some outcrops in the northern and eastern parts of city that mainly belong to the Baghmisheh formation. Based on their colors, these marls are classified into three types: yellow, green, and gray marls. The city is developing toward its eastern side wherein various civil projects are under construction including tunnels, underground excavation, and high-rise building. In this regard, the swelling behavior assessment of these marls is of critical importance. Also, in lightweight structures with foundation pressure less than swelling pressure, several problems such as walls cracking and jamming of door and windows may occur. In the present study, physical properties and swelling behavior of Baghmisheh marls are investigated. According to the X-ray diffractometer (XRD) results, the marls are mainly composed of Illite, Kaolinite, Montmorillonite, and Chloride minerals. Type and content of clay minerals and initial void ratio have a decisive role in swelling behavior of these marls. The swelling potential of these marls was investigated using one-dimensional odometer apparatus under stress level up to 10 kPa. The results showed that yellow marls have high swelling potential and expansibility compared to the other marls. In addition, green and gray marls showed intermediate and low swelling potential and swelling pressure, respectively.