• Earthquakes and Structures
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• v.10 no.4
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• pp.939-963
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• 2016

According to the new directives about the rational and efficient use of energy, thermal bridges in buildings have to be avoided, and the thermal insulation (TI) layer should run without interruptions all around the building - even under its foundations. The paper deals with the seismic response of multi-storeyed reinforced concrete (RC) frame building structures founded on an extruded polystyrene (XPS) layer placed beneath the foundation slab. The purpose of the paper is to elucidate the problem of buildings founded on a TI layer from the seismic resistance point of view, to assess the seismic behaviour of such buildings, and to search for the critical parameters which can affect the structural and XPS layer response. Nonlinear dynamic and static analyses were performed, and the seismic response of fixed-base (FB) and thermally insulated (TI) variants of nonlinear RC building models were compared. Soil-structure interaction was also taken into account for different types of soil. The results showed that the use of a TI layer beneath the foundation slab of a superstructure generally induces a higher peak response compared to that of a corresponding system without TI beneath the foundation slab. In the case of stiff structures located on firm soil, amplification of the response might be substantial and could result in exceedance of the superstructure's moment-rotation plastic hinge capacities or allowable lateral roof and interstorey drift displacements. In the case of heavier, slenderer, and higher buildings subjected to stronger seismic excitations, the overall response is governed by the rocking mode of oscillation, and as a consequence the compressive strength of the XPS could be insufficient. On the other hand, in the case of low-rise and light-weight buildings, the friction capacity between the layers of the applied TI foundation set might be exceeded so that sliding could occur.

• Wind and Structures
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• v.21 no.5
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• pp.537-564
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• 2015

Excessive motions in buildings cause occupants to become uncomfortable and nervous. This is particularly detrimental to the tenants and ultimately the owner of the building, with respect to financial considerations. Serviceability issues, such as excessive accelerations and inter-story drifts, are more prevalent today due to advancements in the structural systems, strength of materials, and design practices. These factors allow buildings to be taller, lighter, and more flexible, thereby exacerbating the impact of dynamic responses. There is a growing need for innovative and effective techniques to reduce the serviceability responses of these tall buildings. The current study considers a case study of a real building to show the effectiveness and robustness of the TLD in reducing the coupled lateral-torsional motion of this high-rise building under wind loading. Three unique multi-modal TLD systems are designed specifically to mitigate the torsional response of the building. A procedure is developed to analyze a structure-TLD system using High Frequency Force Balance (HFFB) test data from the Boundary Layer Wind Tunnel Laboratory (BLWTL) at the University of Western Ontario. The effectiveness of the unique TLD systems is investigated. In addition, a parametric study is conducted to determine the robustness of the systems in reducing the serviceability responses. Three practical parameters are varied to investigate the robustness of the TLD system: the height of water inside the tanks, the amplitude modification factor, and the structural modal frequencies.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.101-112
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• 1999

Structural walls have been mostly used for the design of reinforced concrete buildings in seismic areas because they play a role as an efficient bracing system and offer great potential for lateral load resistance and drift control. The lateral resistance system for the earthquake load should be designed to have enough ductility and stable hysteretic response in the critical regions where plastic deformation occurred beyond yielding. The behavior of the reinforced concrete element to experience large deformation in the critical areas by a major earthquake is affected by the performance of the confined core concrete. Thus, the confinement of concrete by suitable arrangements of transverse reinforcement results in a significant increase in both the strength and ductility of compressed concrete. This paper reports the experimental results of reinforced concrete structural walls for wall-type apartment structure under axial loads and cyclic reversal of lateral loads with different confinement of the boundary elements. The results show that confinement of the boundary element by open 'U'-bar and cross tie is effective. The shear strength capacity is not increased by the confinement but deformation capacity is improve.

• Journal of the Korean Society of Industry Convergence
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• v.15 no.1
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• pp.29-36
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• 2012

Reinforced concrete shear walls and X-type steel braces were applied in seismic retrofit techniques for seismic performance evaluation of school buildings constructed in accordance with standard design announced by the ordinance of the ministry of construction in 1980s. Seismic performance evaluation was based on FEMA 356 using response spectrum as elastic analysis and conducted to pushover analysis with nonlinear static analysis. The maximum displacement ratio between floors in 4th and 3rd floors of the existing school buildings was less than 1.0%, which was functioning level in FEMA 356. However, because plastic hinge occurs somewhat in structural members according to the results of pushover analysis, partial reinforcement will be required. X-direction of the maximum lateral displacement of reinforced concrete shear walls than X-type steel braces was 45% and 32% in 4th and 3rd floors of school buildings, and Y-direction was 18% and 17%, respectively.

• International Journal of High-Rise Buildings
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• v.2 no.2
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• pp.141-152
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• 2013

This paper presents a brief overview of the recently developed performance-control method of moment frame design subjected to monotonously increasing lateral loading. The final product of any elastic-plastic analysis is a nonlinear loaddisplacement diagram associated with a progressive failure mechanism, which may or may not be as desirable as expected. Analytically derived failure mechanisms may include such undesirable features as soft story failure, partial failure modes, overcollapse, etc. The problem is compounded if any kind of performance control, e.g., drift optimization, material savings or integrity assessment is also involved. However, there is no reason why the process can not be reversed by first selecting a desirable collapse mechanism, then working backwards to select members that would lead to the desired outcome. This article provides an overview of the newly developed Performance control methodology of design for lateral resisting frameworks with a view towards integrity control and prevention of premature failure due to propagation of plasticity and progressive P-delta effects.

• Journal of Korean Association for Spatial Structures
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• v.23 no.3
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• pp.71-78
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• 2023

Recently, Free-Form and Irregular Shape high-rise buildings are constructed by IT technology development. Tilted shaped high-rise building which is one of Irregular shape high-rise buildings can cause lateral displacement by gravity load and lateral load due to tilted elevation shape. Therefore, it is necessary to review the behavior and structural aspects of the Tilted shape high-rise building by gravity load. In this paper, the dynamic characteristics of a tilted structure with a dual-core were analyzed with the core location as a design variable, and response behavior, vulnerable members, and vulnerable layers to earthquake loads were analyzed. As a result of the analysis, as the location of the core moved in an tilted direction, the eccentric distance and eccentric load decreased, reducing the axial force of the vertical members. However, the location of the core had little effect on the response.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.223-226
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• 2005

The purpose of this study is to discuss how strength and ductility of each system in low-rise R/C buildings combined with extremely brittle, shear and flexural failure systems have influence on seismic capacities of the overall system, which is based on seismic response analysis of SDOF structural systems. To simulate the triple lateral-load resisting system, structures are idealized as a parallel combination of two modified origin-oriented hysteretic models and degrading trilinear hysteretic model that fail primarily in extremely brittle, shear and flexure, respectively. Stiffness properties of three models are varied in terms of story shear coefficients, and structures are subjected to two ground motion components. By analyzing these systems, interaction curves of required strengths of the triple systems for various levels of ductility factors are finally derived for practical purposes.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.499-504
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• 2008

Recently, the problem controlling lateral drift is important in tall buildings for improvement in economic efficiency and habitability. But, the Outrigger System, general used for tall building in Korea, has weak points with the occupancy of special space and the long duration of works. The dampers are applied to actively control building's response by earthquake and wind load in these days. Accordingly, we analyze the effect of the drift control using various dampers to substitute for the Outrigger System as the efficient system in tall buildings.

• Smart Structures and Systems
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• v.13 no.3
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• pp.473-500
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• 2014

Tuned mass dampers (TMDs) have been installed in many high-rise buildings, to improve their resiliency under dynamic loads. However, high-rise buildings may experience natural frequency changes under ambient temperature fluctuations, extreme wind loads and relative humidity variations. This makes the design of a TMD challenging and may lead to a detuned scenario, which can reduce significantly the performance. To alleviate this problem, the current paper presents a proposed approach for the design of a robust and efficient TMD. The approach accounts for the uncertain natural frequency, the optimization objective and the input excitation. The study shows that robust design parameters can be different from the optimal parameters. Nevertheless, predetermined optimal parameters are useful to attain design robustness. A case study of a high-rise building is executed. The TMD designed with the proposed approach showed its robustness and effectiveness in reducing the responses of high-rise buildings under multidirectional wind. The case study represents an engineered design that is instructive. The results show that shear buildings may be controlled with less effort than cantilever buildings. Structural control performance in high-rise buildings may depend on the shape of the building, hence the flow patterns, as well as the wind direction angle. To further increase the performance of the robust TMD in one lateral direction, active control using LQG and fuzzy logic controllers was carried out. The performance of the controllers is remarkable in enhancing the response reduction. In addition, the fuzzy logic controller may be more robust than the LQG controller.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.5
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• pp.117-124
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• 2019

Nonstructural elements are installed according to the function of a building, and refer to the elements other than a structural system that resists external loads. Although the nonstructural elements had the largest part of seismic loss of buildings, seismic design of buildings mainly focuses on structural system and the seismic design of nonstructural elements are rarely conducted. In this study, the seismic design provisions of nonstructural elements presented in Uniform Building Code (UBC) and International Building Code (IBC) were investigated in order to analyze the seismic design considerations of nonstructural elements presented in Korean Building Code (KBC). The results showed that the equivalent static load applied to seismic design of nonstructural elements was revised to take into consideration a total of five items such as effective ground acceleration, vertical amplification factor, response amplification factor, response modification factor, importance factor.