• Steel and Composite Structures
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• 제3권3호
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• pp.185-198
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• 2003

The concept of performance based seismic design has been gradually accepted by the earthquake engineering profession recently, in which the cost-effectiveness criterion is one of the most important principles and more attention is paid to the structural performance at the inelastic stage. Since there are many uncertainties in seismic design, reliability analysis is a major task in performance based seismic design. However, structural reliability analysis may be very costly and time consuming because the limit state function is usually a highly nonlinear implicit function with respect to the basic design variables, especially for the complex large-scale structures for dynamic and nonlinear analysis. Understanding statistical properties of the structural inelastic deformation, which is the aim of the present paper, is helpful to develop an efficient approximate approach of reliability analysis. The present paper studies the statistical properties of the maximum elastoplastic story drift of steel frames subjected to earthquake load. The randomness of earthquake load, dead load, live load, steel elastic modulus, yield strength and structural member dimensions are considered. Possible probability distributions for the maximum story are evaluated using K-S test. The results show that the choice of the probability distribution for the maximum elastoplastic story drift of steel frames is related to the mean value of the maximum elastoplastic story drift. When the mean drift is small (less than 0.3%), an extreme value type I distribution is the best choice. However, for large drifts (more than 0.35%), an extreme value type II distribution is best.

• 한국지진공학회논문집
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• 제9권6호
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• pp.21-30
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• 2005

본 연구에서는 지진하중을 받는 탄성구조물을 대상으로 층전단력 분포에 기초한 마찰감쇠기의 설계방법을 제시하였다. 먼저 마찰감쇠기의 슬립하중(slip-load)을 정규화하는 방법 별로 단자유도 시스템의 수치해석을 수행하고 비교하였다. 이를 통해 슬립하중과 가새 강성의 영향을 파악하였으며, 설치용 가새와 원구조물의 최적강성비를 찾았다. 다음으로는 다양한 고유주기와 층수를 갖는 구조물을 대상으로 수치해석을 통해 마찰감쇠기의 설치 층수와 위치의 결정방법 및 슬립하중의 분배 방법을 도출하였다. 이 과정에서 설치 층수가 포함된 성능지수를 사용하여 슬립하중의 총합으로부터 최적의 설치 층수를 도출하는 경험식을 제시하였다. 마지막으로 실제 지진하중을 사용한 수치해석을 통해 기존의 최적설계 방법과 비교하여 제안된 방법의 우수성을 입증하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.525-530
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• 1998

The objective of this experiment is to observe the elastic and inelastic behaviors of high-rise reinforced concrete frames with nonseimic details. To do this, a building frame designed according to Korean seismic code and detailed in the Korean conventional manner was selected. An 1:12 scale plane frame model was manufactured according law. Reversed lateral load tests and monotonic push-over test were performed under the displacement control. To simulate the earthquake effect, the lateral force distribution was maintained to be an inversed triangular by using whiffle tree. From the tests, story displacements, lateral story forces, local plastic rotations and the relations between inter-story drift versus story shear are obtained. Based on the test results, conclusions on the characteristics of the elastic and behaviors of a high-rise reinforced concrete frame with nonseismic details are drawn.

• Steel and Composite Structures
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• 제41권5호
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• pp.663-679
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• 2021

To elucidate the differences in the collapse behavior between a single-story beam-column assembly and multi-story frame, two 1/3-scale two-bay composite frames, including a single-story composite beam-column assembly and a three-story composite sub-frame, were designed and quasi-statically tested. The load-displacement responses, failure modes, and internal force development of the two frames were analyzed and compared in detail. Furthermore, the resistance mechanisms of the two specimens were explored, and the respective contributions of different load-resisting mechanisms to the total resistances were quantitatively separated to gain deeper insights. The experimental tests indicated that Vierendeel action was present in the two-dimensional multi-story frames, which led to an uneven internal force distribution among the three stories. The collapse resistance of TSDWA-3S in the flexural stage was not significantly increased by the structural redundancy provided by the additional story, as compared to that of TSDWA-1S. Although the development of the load response was similar in the two specimens at flexural stage, the collapse mechanisms of the multi-story composite frame were much more complicated than those of the single-story beam-column assembly, and the combined action between stories was critical in determining the internal force redistribution and rebalancing of the remaining structure.

• Steel and Composite Structures
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• 제27권5호
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• pp.623-632
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• 2018

Performance-Based Plastic Design (PBPD) method has been recently developed to evaluate the behavior of structures in different performance levels. The PBPD method utilizes a base shear force and a lateral load pattern that are estimated based on energy and yielding mechanism concepts. Using of current lateral force pattern results in weak structural members in upper stories of a structure so that the values of the story drift in these stories are larger than the target drift, particularly in high-rise buildings. Therefore, such distribution requires modifications to overcome this drawback. This paper proposes a modified lateral load pattern for steel Eccentrically Braced Frames (EBFs) based on parametric study. In order to achieve the modified load pattern, a group of 26 EBFs has been analyzed under a set of 20 earthquake ground motions. Additionally, results of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to derive the new load pattern. To prove the efficiency of present study, three EBFs as examples were designed by modified pattern and current PBPD distribution. Inelastic dynamic analyses results showed that the story drifts using modified lateral load pattern were well within the target values in comparison with current pattern in PBPD, particularly where the effect of the height is significant. The modified load pattern reduces the possibility of underdesigning in upper levels and overdesigning in lower levels of the frames.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.529-536
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• 1999

The objective of the research stated herein is to observe th elastic and inelastic behaviors and ultimate capacity of 1 : 5 scale 3-story reinforced concrete frame. Pushover tests were performed to 1:5 scale 3-story reinforced concrete frames without and with infilled masonry. To simulate the earthquake effect, the lateral force distribution was maintained to be an inverted triangle by using the whiffle tree. From the results of tests, the relations between the total lateral load and the roof drift, the distribution of column shears, the relation between story shear and story drift, and the angular rotations at the critical portions of structures were obtained. The effects of infilled masonry are investigated with regards to the stiffness, strength, and ductility of structures. Final collapse modes of structures with and without infilled masonry are compared.

• KCI Concrete Journal
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• 제11권3호
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• pp.165-174
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• 1999

The objective of the research stated herein is to observe the elastic and inelastic behaviors and ultimate capacity of 1:5 scale 3-story reinforced concrete frame. Pushover tests were performed to 1:5 scale 3-story reinforced concrete frames with and without infilled masonry. To simulate the earthquake effect, the lateral force distribution was maintained by an inverted triang1e by using the whiffle tree. From the test results, the relation ships between the total lateral load and the roof drift, the distribution of column shears, the relation between story shear and story drift, and the angular rotations at the critical portions of structures were obtained. The effects of infilled masonry were investigated with regards to the stiffness, strength, and ductility of structures. Final collapse modes of structures with and without infilled masonry were compared.

• Architectural research
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• 제3권1호
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• pp.53-60
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• 2001

The proposed building upgrading technique employs prestressing cables to function as bracing to improve the seismic performance during future events. A four-story reinforced concrete moment resisting frame damaged from an ultimate limit state earthquake is assessed and upgraded using the proposed technique. Both existing and upgraded buildings are evaluated in regard of seismic performance parameters performing static lateral load to collapse analysis and dynamic nonlinear time history analysis as well. To obtain realistic comparison of seismic performance between existing and upgraded frames, each frame is subjected to its critical ground motion that has strength demand exceeding the building strength supply. Furthermore, reliability of static lateral load to collapse analysis as a substitute to time history analysis is evaluated. The results reveal that the proposed upgrading technique improves the stiffness distribution compared to the ideal distribution that gives equal inter-story drift. As a result, the upgraded building retains more stories that contribute to energy dissipation. The overall behavior of upgraded building beyond yield is also enhanced due to the gradual change of building stiffness as the lateral load increases.

• Earthquakes and Structures
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• 제11권3호
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• pp.407-420
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• 2016

The aim of this study is to investigate the effect of vertical ground motion (VGM) on seismic behavior of reinforced concrete (RC) regular frame with construction joints, and determine more proper modeling method for cast-in-situ RC frame. The four-story RC frames in the regions of 7, 8 and 9 earthquake intensity were analyzed with nonlinear dynamic time-history method. Two different methods of ground motion input, horizontal ground motion (HGM) input only, VGM and HGM input simultaneously were performed. Seismic responses in terms of the maximum vertex displacement, the maximum inter-story drift distribution and the plastic hinge distribution were analyzed. The results show that VGM might increase or decrease the horizontal maximum vertex displacement depending on the value of axial load ratio of column. And it will increase the maximum inter-story drift and change its distribution. Finally, proper modeling method is proposed according to the distribution of plastic hinges, which is in well agreement with the actual earthquake damage.

• Steel and Composite Structures
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• 제21권4호
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• pp.863-882
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• 2016

This study aims to introduce a new bracing system by which even super-wide frames with large openings can be braced. The proposed system, hereafter called Cable-Pulley Brace (CPB), is a tension-only bracing system with a rectilinear configuration. In CPB, a wire rope passes through a rectilinear path around the opening(s) and connects the lower corner of the frame to its opposite upper one. CPB is a secondary load resisting system with a nonlinear-elastic hysteretic behavior due to its initial pre-tension load. As a result, the required energy dissipation would be provided by the MRF itself, and the main intention of using CPB is to contribute to the initial and post-yield stiffness of the whole system. Using a stiffness calibration technique, optimum placement of the CPBs is discussed to yield a uniform displacement demand along the height of the structure. A displacement-based design procedure is proposed by which the MRF with CPB can be designed to achieve a uniform distribution of inter-story drifts with predefined values. Obtained results indicated that CPB leads to significant reductions in maximum and residual deformations of the MRF at the expense of minor increase in the maximum base shear and developed axial force demands in the columns. In the case of a typical 5-story residential building, compared to SMRF system, CPB system reduces maximum amounts of inter-story and residual drifts by 35% and 70%, respectively. Moreover, openings of the frame are not interrupted by the CPB. This is the most appealing feature of the proposed bracing system from architectural point of view.