• Earthquakes and Structures
• /
• v.23 no.1
• /
• pp.35-57
• /
• 2022

This article presents a computationally efficient framework for multi-objective seismic design optimization of steel moment-resisting frame (MRF) structures based on the nonlinear dynamic analysis procedure. This framework employs the uniform damage distribution philosophy to minimize the weight (initial cost) of the structure at different levels of damage. The preliminary framework was recently proposed by the authors based on the single excitation and the nonlinear static (pushover) analysis procedure, in which the effects of record-to-record variability as well as higher-order vibration modes were neglected. The present study investigates the reliability of the previous framework by extending the proposed algorithm using the nonlinear dynamic design procedure (optimization under multiple ground motions). Three benchmark structures, including 4-, 8-, and 12-story steel MRFs, representing the behavior of low-, mid-, and high-rise buildings, are utilized to evaluate the proposed framework. The total weight of the structure and the maximum inter-story drift ratio (IDRmax) resulting from the average response of the structure to a set of seven ground motion records are considered as two conflicting objectives for the optimization problem and are simultaneously minimized. The results of this study indicate that the optimization under several ground motions leads to almost similar outcomes in terms of optimization objectives to those are obtained from optimization under pushover analysis. However, investigation of optimal designs under a suite of 22 earthquake records reveals that the damage distribution in buildings designed by the nonlinear dynamic-based procedure is closer to the uniform distribution (desired target during the optimization process) compared to those designed according to the pushover procedure.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.10a
• /
• pp.541-546
• /
• 1998

The objective of this research is to observe the actual response of low-rise nonseismic moment-resisting infilled reinforced concrete frame subjected to varied levels of earthquake ground motions. First of all, the reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used. This model was, then, subjected to the shaking table motions simulating Taft N21E component earthquake ground motions, whose peak ground accelerations(PGA`s) were modified to 0.12g, 0.2g, 0.3g, and 0.4g. The global behavior and failure mode were observed. The lateral accelerations and displacements at each story and local deformations at the critical portions of structure were measured. Before and after each earthquake simulation test, free vibration tests were performed to find the changes in the natural period of the model.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.04b
• /
• pp.427-432
• /
• 1998

The objective of this research is to observe the actual response of low-rise nonseismic moment-resisting reinforced frame subjected to varied levels of earthquake ground motions. First of all, the reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used. This model was, then, subjected to the shaking table motions simulating Taft N21E component earthquake ground motions, whose peak ground accelerations(PGA's) were modified to 0.12g, 0.2g, 0.3g, and 0.4g. The global behavior and failure mode were observed. The lateral accelerations and displacements at each story and local deformations at the critical portions of structure were measured. The base shear was measured by using specially made load cells. Before and after each earthquake simulation test, free vibration tests were performed to find the changes in the natural period and damping ratio of the model.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.04b
• /
• pp.481-486
• /
• 1998

In this paper, elastic and inelastic behavior of exterior joint of moment-resisting R.C frame with non-seismic detail subjected to reversed cyclic lateral load such as earthquake excitations was investigated. 1/2-scals subassemblage exterior beam-column joint including slab was manufactured based on similitude law. Then, pseudo static test under the displacement control was performed. The results of 1)crack pattern and failure mode, 2)degradation stiffness and strength, energy dissipation capacity from load-displacement hysteresis curve, 3)strain of steel were analysed.

• International Journal of Concrete Structures and Materials
• /
• v.7 no.2
• /
• pp.135-153
• /
• 2013

This study investigates the direct displacement based design (DDBD) approach for different types of reinforced concrete structural systems including single moment-resisting, dual wall-frame and dual steel-braced systems. In this methodology, the displacement profile is calculated and the equivalent single degree of freedom system is then modeled considering the damping characteristics of each member. Having calculated the effective period and secant stiffness of the structure, the base shear is obtained, based on which the design process can be carried out. For each system three frames are designed using DDBD approach. The frames are then analyzed using nonlinear time-history analysis with 7 earthquake accelerograms and the damage index is investigated through lateral drift profile of the models. Results of the analyses and comparison of the nonlinear time-history analysis results indicate efficiency of the DDBD approach for different reinforced concrete structural systems.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.10a
• /
• pp.466-472
• /
• 1996

The nonlinear analysis was perforned for a 2-bay 2-story moment-resisting reinforced concrete plane frame with seismic detail using KDARC 2D program. The analytical models consist of the material model, the member model, the hysteretic model, and the damage model etc. The conclusion based on the results of analysis is as following. : (1) Story shear-displacement relationship is similar to the experiment result but from the energy point of view, the analysis relationship is similar to the experiment result but from the energy point of view, the analysis result was different from the experiment result. (2) Plastic hinges were found to occur mainly in beams at first story while all the columns had plastic hinges throughout the structure. (3) Failure mode is a little different from experiment result in the yielding mechanism. (4) Damage index isabout 0.25. This means that the degree of damage is moderate and can be repairable.

• Magazine of the Korea Concrete Institute
• /
• v.9 no.6
• /
• pp.255-266
• /
• 1997

본 논문의 목적은 내진상세를 가진 철근콘크리트 골조의 비탄성 거동 예측에서 현재 사용되고 있는 해석적 방법이 가지는 신뢰성을 검토하고 실험에서 실측할 수 없었던 내부 힘의 분포 및 변화과정을 관찰하는 것이다. 이를 위하여 이미 실험이 수행된 2경간 2층 내진상세 모멘트-저항 철근콘크리트 평면골조(1)를 대상으로 ICARC 2D 프로그램(3)을 사용하여비탄성해석을 수행하였다. 해석결과가 실험결과에 최대한 일치하도록 관련 모델 변수들을 조절하였다. 이러한 해석결과가 실험결과와 어느 정도 일치하는 지 비교하였으며, 해석결과 얻어진 내부 힘의 발전과정을 관찰한결과 다음과 같은 결론에 도달하였다. (1)전체 횡력-횡변위 관계는 실험결과에 매우 유사하게 해석결과를 얻을 수 있다. (2)구조물의 힘의 분포 및 재분재 과정에 관련하여 해석은 구체적인 정보를 제사하였으며 실험결과 나타난 균열 및 변형결과와 대체로 일치한 소성힌지 발생과 파괴메카니즘을 나타내어 그 유용성을 입증하고 있다. (3)해석결과가 대체로 실험결가아 일치하나 국부거동과 관련하여 일부분 실제거동과 상당한 차이를 나타내어, 보다 정확한 모델을 개발할 필요성을 느낀다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2006.03a
• /
• pp.225-232
• /
• 2006

Three building structures haying piloti frames in the lower two stories were selected as prototypes and were analyzed using nonlinear static analysis to investigate the seismic capacity of these buildings. The first one has a symmetrical moment resisting frame (Model 1), the second has an infilled shear wall in the central frame (Model 2), and the third has an infilled shear wall only in one of exterior frames (Model 3), The analytical results were compared with those of shaking table tests with regards to the overstrength and ductility of the irregular buildings. Infilled shear wall in Model 2 and Model 3 induced large overstrength factors, 6.8 and 6.0, respectively, which are about two times larger than that of Model 1, 3.5. The displacement ductility ratio in Model 2 was only 2.5, due to the shear failure of wall in the piloti stories, whereas those of Model 1 and Model 3 reached 3.2.

• Earthquakes and Structures
• /
• v.16 no.4
• /
• pp.425-436
• /
• 2019

Successive ground motions having short time intervals have occurred in many earthquakes so far. It is necessary to investigate the effects of this phenomenon on different types of structures and to take these effects into consideration while designing or retrofitting structures. The effects of seismic sequences on the structures with combined reinforced concrete shear wall and moment resisting frame system have not been investigated in details yet. This paper has tried to analyse the seismic performance of structures with such structural systems subjected to mainshock-aftershock sequences. The effects of the seismic sequences on the investigated models are evaluated by strong measures such as IDA capacity and fragility and vulnerability curves. The results of this study show that the seismic sequences have a significant effect on the investigated models, which necessitates considering this effect on designing, retrofitting, decision making, and taking precautions.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.3 no.4
• /
• pp.61-70
• /
• 1999

Cracking was observed in beam-to-column connections of many steel building frames during the 1994 Northridge and 1995 Kobe earthquakes. Thus extensive experimental researches are currently being conducted to improve the seismic performance of steel frames. A value of 0.015 radian was considered as a reasonable estimate of beam plastic rotation demand in steel moment-resisting frames subjected to severe earthquakes. The objective of this research is to develop a type of connection detail which moves the plastic hinge region in the beam away from the face of the column and can prevent cracking at the welded flange of the beam-to-column connection under seismic loading. An experimental investigation was undertaken on five beam-to-column connection specimens to study the performance of the connections with proposed details. The experiemental results showed that the flexural strength and rotational ductility of the beam connections were adequate for the seismic resistance steel frames to prevent possible cracks at the connections.