• Steel and Composite Structures
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• v.20 no.2
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• pp.317-335
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• 2016

Concentrically braced steel frames (CBFs) can be optimised during the seismic design process by using lateral loading distributions derived from the concept of uniform damage distribution. However, it is not known how such structures are affected by uncertainties. This study aims to quantify and manage the effects of structural and ground-motion uncertainty on the seismic performance of optimum and conventionally designed CBFs. Extensive nonlinear dynamic analyses are performed on 5, 10 and 15-storey frames to investigate the effects of storey shear-strength and damping ratio uncertainties by using the Monte Carlo simulation method. For typical uncertainties in conventional steel frames, optimum design frames always exhibit considerably less inter-storey drift and cumulative damage compared to frames designed based on IBC-2012. However, it is noted that optimum structures are in general more sensitive to the random variation of storey shear-strength. It is shown that up to 50% variation in damping ratio does not affect the seismic performance of the optimum design frames compared to their code-based counterparts. Finally, the results indicate that the ground-motion uncertainty can be efficiently managed by optimizing CBFs based on the average of a set of synthetic earthquakes representing a design spectrum. Compared to code-based design structures, CBFs designed with the proposed average patterns exhibit up to 54% less maximum inter-storey drift and 73% less cumulative damage under design earthquakes. It is concluded that the optimisation procedure presented is reliable and should improve the seismic performance of CBFs.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.55-58
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• 2005

From the development of residential flat plate system, continuously bended shear reinforcements were applied in the joint performance test. The testing parameters are shear reinforcement types, which are no reinforcement, studrail reinforcement, and rebar type reinforcement. To verify the lateral resisting capacity, cyclic load is applied in the constant vertical load condition. From the test results, the resisting capacity of developed shear reinforcement system has a good performance behavior in the story drift ratio.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.209-216
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• 2003

The purpose of this study is to investigate the response characteristics of pushover analysis of upper wall-lower frame system with X and Y-directions' lateral load Pushover analysis estimates initial elastic stiffness, post-yielding stiffness, and plastic hinges on each story of structures through three-dimensional nonlinear analysis program. The conclusions of this study are as follows; (1) As a result of pushover analysis, the magnitude of nonlinear response and distribution of yield hinge in lower structure are similar with both X and Y directions, but not in upper structure because of different relative stiffness. (2) The maximum drift ratio of roof is larger for X-direction than for Y-direction with respect to magnitude of shear wall areas in upper structure.

• Earthquakes and Structures
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• v.5 no.1
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• pp.1-22
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• 2013

Soft storey failure mechanism is a common collapse mode for masonry-infilled (MI) reinforced concrete (RC) buildings subjected to severe earthquakes. Simple analytical equations correlating global with local ductility demands are derived from pushover (PO) analyses for seismic assessments of regular MI RC frames, considering the critical interstorey drift ratio, number of storeys and lateral loading configurations. The reliability of the equations is investigated using incremental dynamic analyses for MI RC frames of up to 7 storeys. Using the analytical ductility relationship and a coefficient-based method (CBM), the response spectral accelerations and period shift factors of low-rise MI RC frames are computed. The results are verified through published shake table test results. In general applications, the analytical ductility relationships thus derived can be used to bypass the onerous PO analysis while accurately predicting the local ductility demands for seismic assessment of regular MI RC frames.

• Structural Engineering and Mechanics
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• v.70 no.5
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• pp.591-600
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• 2019

Steel tubular buckling controlled braces are well known as being simple, practical and cost-effective lateral force resisting systems. Although these system features have gained the attention of the researchers over the last decade, steel tubular buckling controlled braces currently have limited application. Indeed, only a few steel tubes tightly encased within each other exist in the steel industry. In this paper, a new and practical design method is proposed in order to better promote the widespeared application for current steel tubular buckling controlled brace applications. In order to reach this goal, a holed-adapter made with polyoxymethylene adaptable to all round and square steel sections, was developed to use as infiller. The research program presents designing, producing and displacement controlled cyclic loading tests of a conventional tubular brace and a buckling controlled composite brace. In addition, numerical analysis was carried out to compare the experimental results. As a result of the experimental studies, buckling was controlled up to 0.88 % drift ratio and the energy dissipation capacity of the conventional tubular brace increased 1.46 times due to the proposed design. The main conclusion of this research is that polyoxymethylene is a highly suitable material for the production of steel tubular buckling controlled braces.

• Structural Engineering and Mechanics
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• v.86 no.4
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• pp.503-518
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• 2023

In tall constructions, the outriggers are regarded as a structural part capable of effectively resisting lateral loads. This study analyses the efficacy of hybrid outrigger system in high rise RCC building for various structural parameters identified. For variations in α, which is defined as the ratio of the relative flexural stiffness of the core to the axial rigidity of the column, static and dynamic analyses of hybrid outrigger system having a virtual and a conventional outrigger at two distinct levels were conducted in the present study. An investigation on the optimal outrigger position was performed by taking the results from absolute maximum inter storey drift ratio (ISD_max), roof acceleration (acc_roof), roof displacement (disp_roof), and base bending moment under both wind and seismic loads on analytical models having 40, 60 and 80 storeys. An ideal performance index parameter was introduced and was utilized to obtain the optimal position of the hybrid outrigger system considering the combined response of ISD_max, acc_roof, disp_roof and, criteria required for the structure under wind and seismic loads. According to the behavioural study, increasing the column area and outrigger arm length will maximise the performance of the hybrid outrigger system. The analysis results are summarized in a flowchart which provides the optimal positions obtained for each dependent parameter and based on ideal performance index which can be used to make initial suggestions for installing a hybrid outrigger system.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.627-634
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• 2004

The purpose of this study is to investigate seismic performance of a bearing wall system for apartment buildings. An 1/3 scale three-story specimen was constructed and tested under cyclic lateral loads. The specimen was consisted of pierced walls and coupling elements as well as floor slabs. The bearing wall system is considered to have a adequate deformation capacity up to $2.0\%$ of roof drift ratio, and the experimental results showed the ductile load-deformation characteristics even though some walls were failed in shear Nonlinear analysis was peformed to compare the load-deformation curve obtained from the experimental program. The result of nonlinear analysis could be useful to predict the actual behavior characteristics of the bearing wall system subjected to lateral loads.

• Structural Engineering and Mechanics
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• v.76 no.3
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• pp.279-291
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• 2020

The seismic design of conventional frame structures is meant to enhance plastic deformations at beam ends and prevent yielding in columns. To this end, columns are made stronger than beams. Yet yielding in columns cannot be avoided with the column-to-beam strength ratios (about 1.3) prescribed by seismic codes. Preventing plastic deformations in columns calls for ratios close to 4, which is not feasible for economic reasons. Furthermore, material properties and the rearrangement of geometric shapes inevitably make the distribution of damage among stories uneven. Damage in the i-th story can be characterized as the accumulated plastic strain energy (W_pi) normalized by the product of the story shear force (Q_yi) and drift (δ_yi) at yielding. Past studies showed that the distribution of the plastic strain energy dissipation demand, W_pi/ΣW_pj, can be evaluated from the deviation of Q_yi with respect to an "optimum value" that would make the ratio W_pi/(Q_yiδ_yi) -i.e. the damage- equal in all stories. This paper investigates how the soil type and ductility demand affect the optimum lateral strength distribution. New optimum lateral strength distributions are put forth and compared with others proposed in the literature.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.53-56
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• 2008

In this investigation, results of laboratory tests on six reinforce concrete flat plate interior connections with elongated rectangular column support which has been used widely in tall residential buildings are presented. The purpose of this study is to evaluate an effect of column aspect ratio(${\beta}$c=$c_1/c_2$) on the hysteretic behavior under earthquake type loading. The aspect ratio of column section was taken as 0.33${\sim}$3($c_1/c_2$=1/3, 1/1, 3/1). Other design parameters such as flexural reinforcement ratio of slab and concrete strength was kept constant as ${\rho}$=1.0%, 1.5% and $f){ck}$=40MPa, respectively. Gravity shear load($V_g$) was applied by 30 percents of nominal vertical shear strength(0.3$V_o$) of the specimen. Experimental observations on punching failure pattern, peak lateral-load and story drift ratio at punching failure, and stiffness degradation were achieved and discussed in accordance with different column aspect ratio.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.129-137
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• 2010

In this study, a five-story steel frame was designed in accordance with KBC2005 to evaluate the effect of the beam-column connection on the structural behavior. The connections were designed as a fully rigid connection and as a semirigid connection. A fiber model was utilized to describe the moment-curvature relationship of the steel beam and column, and a three-parameter power model was adopted for the moment-rotation angle of the semirigid connection. To evaluate the effects of higher modes on structural behavior, the structure was subjected to a KBC2005-equivalent lateral load and lateral loads considering higher modes. The structure was idealized as a separate 2D frame and as a connected 2D frame. The pushover analysis of 2D frames for the lateral load yielded the top displacement-base shear force, design coefficients such as overstrength factor, ductility ratio, and response modification coefficient, demanded ductility ratio for the semirigid connection,and distribution of plastic hinges. The sample structure showed a greater response modification coefficient than KBC2005, the higher modes were found to have few effects on the coefficient, and the lateral load of KBC2005 was found to be conservative. The TSD connection was estimated to secure economy and safety in the sample structure.