• Earthquakes and Structures
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• 제22권3호
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• pp.319-330
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• 2022

Retrofit of soft-story buildings due to seismic loads using Gap-Inclined-Brace (GIB) system is considered a new retrofit technique that aims to maintain both strength and stiffness of structure. In addition, it provides more ductility and less P-delta effect, and subsequently better performance is observed. In this paper, the effect of the eccentricity between GIB and the retrofitted column due to installation on the efficiency of the retrofitting system is studied. In addition, a modification in the determination method of GIB properties is introduced to reduce the eccentricity effect. Also, the effect of GIB system on the seismic response of mid-rise buildings with different heights considering soft-story at various heights has been studied. A numerical model is developed to study the impact of such system on the response of retrofitted soft-story buildings under the action of seismic loads. To achieve that goal, this model is used to perform a numerical investigation, by considering five case study scenarios represent several locations of soft-story of two mid-rise reinforced concrete buildings. At first, Non-linear static pushover analysis was carried out to develop the capacity curves for case studies. Then, Non-linear time history analyses using ten earthquake records with five peak ground accelerations is performed for each case study scenario before and after retrofitting with GIB. The results show that large GIB eccentricity reduce the ultimate lateral resistance and deformation capacity of the retrofitting system. Moreover, the higher the retrofitted building, the more deformation capacity is observed but without significant increase in ultimate lateral resistance.

• 한국지진공학회논문집
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• 제10권3호
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• pp.65-75
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• 2006

건물의 지진응답을 평가하기 위하여 비선형 푸시오버 해석을 수행한다. 구조물의 비탄성 지진응답을 정확히 예측하기 위해서는, 비선형해석에 사용되는 층하중분포가 구조물의 시간이력 지진응답 동안 실제로 발생되는 지진하중분포를 나타낼 수 있어야 한다. 본 연구에서는 건축물의 지진하중분포를 예측하기 위하여 새로운 모드조합법을 개발하였다. 개발된 모드조합법에서는 모드조합계수를 곱한 각 모드의 스펙트럼응답을 조합하여 다수의 지진하중분포를 예측한다. 모멘트 골조와 켄틸레버 벽체에 대한 변수연구를 수행하였다. 변수연구 결과를 토대로, 각 고유모드가 구조물의 지진응답에 미치는 영향을 나타내는 모드조합계수를 정의하였다. 다양한 정형 및 수직 비정형 구조물에 대하여 제안된 계수모드조합법을 적용하였다. 그 결과 제안된 모드조합법은 시간이력 응답 동안 구조물에 실제로 발생되는 지진하중분포를 정확히 예측할 수 있었다.

• Earthquakes and Structures
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• 제6권3호
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• pp.301-316
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• 2014

This paper is devoted to investigate the effects of SSI on strength reduction factor of multistory buildings. A new formula is proposed to estimate strength reduction factors for MDOF structure-soil systems. It is concluded that SSI reduces the strength reduction factor of MDOF systems. The amount of this reduction is relevant to the fundamental period of structure, soil flexibility, aspect ratio and ductility of structure, and could be significantly different from corresponding fixed-base value. Using this formula, measuring the amount of this error could be done with acceptable accuracy. For some practical cases, the error attains up to 50%.

• Structural Engineering and Mechanics
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• 제40권1호
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• pp.1-11
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• 2011

Ambient vibration tests were carried out to evaluate the dynamic properties of an asymmetric steel building with semi-rigid connections. The test case has many non-structural elements, constructed in the city of Tehran (Iran). The tests were conducted to obtain natural frequencies, mode shapes and damping ratio of the structure and then Fourier transform were used to analyze the velocity records obtained from the tests. The first and second natural periods of the building were obtained as 1.37 s and 1.28 s through the test and damping ratio for the first mode was calculated as 0.047. However, Natural periods obtained from finite element model have higher values from those gained from ambient vibration. Then the model was calibrated by modeling of the in-fill masonry panels at their exact locations and considering the boundary conditions by modeling two blocks near the block No. 3, but the differences were existed. These differences may be due to some hidden stiffness of nonstructural elements in the low range of elastic behavior, showing the structure stiffer than it is in reality.

• Structural Engineering and Mechanics
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• 제52권3호
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• pp.573-593
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• 2014

Pounding between adjacent buildings is a significant challenge in metropolitan areas because buildings of different heights collide during earthquake excitations due to varying dynamic properties and narrow separation gaps. The seismic responses of adjacent buildings of varying height, coupled through soil subjected to earthquake-induced pounding, are evaluated in this paper. The lumped mass model is used to simulate the buildings and soil, while the linear visco-elastic contact force model is used to simulate pounding forces. The results indicate while the taller building is almost unaffected when the shorter building is very short, it suffers more from pounding with increasing height of the shorter building. The shorter building suffers more from the pounding with decreasing height and when its height differs substantially from that of the taller building. The minimum required separation gap to prevent pounding is increased with increasing height of the shorter building until the buildings become almost in-phase. Considering the soil effect; pounding forces are reduced, displacements and story shears are increased after pounding, and also, minimum separation gap required to prevent pounding is increased.

• Wind and Structures
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• 제37권3호
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• pp.245-254
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• 2023

In this paper, the wind-induced response of Jiayuguan wooden building (world cultural heritage) in Northwest China was studied. ANSYS finite element software was used to establish four kinds of building models under different working conditions and carry out modal analysis. The simulation results were compared with the field dynamic test results, obtaining the model which reflects the real vibration characteristics of the wooden tower. Time history data of fluctuating wind speed was obtained by MATLAB programming. Time domain method and ANSYS were used to analyze the wind-induced vibration response time history of Jiayuguan wooden building, obtaining the displacement time history curve of the structure. It was suggested that the wind-induced vibration coefficient of Jiayuguan wooden building is 1.76. Through analysis of the performance of the building under equivalent static wind load, the maximum displacement occurs in the three-story wall, gold column and the whole roof area, and the maximum displacement of the building is 5.39 cm. The ratio of the maximum stress value to the allowable value of wood tensile strength is 45 %. The research results can provide reference for the wind resistant design and protection of ancient buildings with similar structure to Jiayuguan wooden tower.

• Smart Structures and Systems
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• 제15권3호
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• pp.863-879
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• 2015

This paper experimentally investigates the effectiveness and applicability of the time delay control (TDC) algorithm, which is simple and robust to unknown system dynamics and disturbance, for an active mass damper (AMD) system to mitigate the excessive vibration of a building structure. To this end, the theoretical background including the mathematical formulation of the control system is first described; and then, a thorough experimental study using a shaking table system with a small-scale three-story building structural model is conducted. In the experimental tests, the performance of the proposed control system is examined by comparing its structural responses with those of the uncontrolled system in the free vibration and forced vibration cases. It is clearly verified from the test results that the TDC algorithm embedded AMD system can effectively reduce the structural response of the building structure.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.823-837
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• 2020

In this research, the idea of improving the seismic response of an existing steel structure with use of friction dampers between external walls and the structure is discussed. The main difference of this method with other methods of seismic rehabilitation is that interior spaces of the existing structure remain untouched and new parts including external walls and dampers are added outside of the structure. Three frames having 3, 6 and 9 stories are modeled in SAP2000 software before and after seismic retrofit and responses of the system are investigated under the effect of seven earthquake records. Initially, different ratios of seismic weight of stories are presumed for slip forces of the dampers with a distribution based on given equations. The optimized capacity of dampers is obtained by investigating the average of maximum displacement, acceleration and base shear of the structure caused by earthquakes. For this optimized values, maximum inter-story drifts and acceleration are obtained through numerical models. Results show that in 3, 6 and 9-story frames peak roof displacement decreased up to 80%. Maximum roof acceleration and base shear of the frames also decreased 46, 40 and 32% and 84, 67 and 65%, respectively for three building structures.

• 건축역사연구
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• 제18권6호
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• pp.127-144
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• 2009

This thesis aims to analyze the architectural form for the restoration of noogak(樓閣), Boje-roo(普濟樓) which was constructed at the central court of Beomeo-sa(梵魚寺). The results are as follow; 1. Boje-roo was established in 1700. By the constructional records and poetic essays of the times, the architectural of the establishment building was consisted fo two stories structure. The passage system for the approach to the court was the nuha-jinip(樓下進入), that is to say, one might walk between the columns of lower story of the building. And one could ascent the upper stairs and approach to the upper level, inner court. 2. By the remodelling in 1812, the building was varied to one story structure. Therefore the passage system for the approach to the inner court transformed from the nuha-jinip to the ugak-jinip(隅角進入), that is to say, one might ascent the atairs of the podium and could approach the inner court through the both sides of the building. 3. Under the Japanese imperialistic rule, the structure of it's roof and walls of Boje-roo were altered to the Japanese style. In 1965, the wooden columns were shifted to the concreted column, and the wooden wall-panels were shifted to the brick wall attached stone slates. 4. Conclusively speaking, for the restoration of Boje-roo, the establishment form in 1700 is the more proper than the remodelling form in 1812.

• 국제초고층학회논문집
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• 제12권3호
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• pp.215-224
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• 2023

This paper presents the structural design and response control system of the JR MEGURO MARC building, a 70 meters high office building with steel structure located in Tokyo (Figure 1). In order to achieve high earthquake resistance and useable office space, this building integrates a centralized response control system with deformation amplification mechanisms and tuned viscous mass dampers on the lower floor. Moreover, buckling-restrained braces (BRB) are installed on the upper floors to increase the effectiveness of centralized response control system and to reduce damage of the main frames in the event of a major earthquake. It features an efficient centralized response control system by amplifying the deformation of the dampers without creating a soft story.