• 국제초고층학회논문집
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• 제7권3호
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• pp.187-195
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• 2018

Buckling-restrained braces (BRBs) are widely used as highly ductile seismic devices, with the first building using BRBs completed in 1989 in Tokyo, and thousands more now in Japan, USA, Taiwan, China, New Zealand and other countries. Although design codes of several countries specify BRB performance criteria, detailed design provisions are not necessarily provided, as BRBs are typically treated as a manufactured device. This paper briefly reviews the early history of BRB research and offers state-of-the-art views on the design criteria required to obtain stable and reliable performance. Representative project examples and up-to-date studies relevant to tall buildings are summarized.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.330-337
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• 2002

The objective of the earthquake resistant design of structures is to satisfy on the one side the minimization of damage requirement under earthquakes with high probability of occurrence during the design life and on the other side the no collapse requirement under the design seismic event with low probability of occurrence. The two requirements are satisfied with the minimum strength of substructure as well as the ductile failure mechanism presented in the codes. In this study seismic performance is evaluated with two bridges which have steel box superstructures and T type, II type piers as substructures. In order to satisfy the two requirements redesign of both substructures and steel bearings are carried out.

• Structural Engineering and Mechanics
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• 제9권6호
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• pp.589-600
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• 2000

This paper attempts to provide a theoretical basis for the design of high-strength concrete columns in terms of the spacing of lateral reinforcement. In order to achieve this, important concepts had to be addressed such as the choice of a measure of ductile behaviour and a realistic high-strength concrete stress-strain model, as well as limiting factors such as longitudinal steel buckling and lateral steel fracture. A design method incorporating above factors are suggested in the paper. It is shown that both buckling of longitudinal steel and hoop fracture will not demand a reduction in spacing of lateral ties with increase in compressive strength of concrete.

• Structural Engineering and Mechanics
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• 제3권5호
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• pp.475-495
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• 1995

In the past, physical models have been proposed, in compliance with the concept of the compressive-force path, for the realistic design of various statically determinate structural concrete members. The present work extends these models so as to encompass indeterminate RC structural forms. Pilot tests conducted on continuous beams and fixed-ended portal frames have revealed that designing such members to present-day concepts may lead to brittle types of failure. On the other hand, similar members designed on the basis of the proposed physical models attained very ductile failures. It appears that, unlike current design approaches, the compressive-force path concept is capable of identifying those areas where failure is most likely to be triggered, and ensures better load redistribution, thus improving ductility. The beneficial effect of proper detailing at the point of contraflexure in an indeterminate RC member is to be noted.

• Steel and Composite Structures
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• 제20권2호
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• pp.337-355
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• 2016

Steel coupling beam in reinforced concrete (RC) coupled shear wall system is a proper substitute for deep concrete coupling beam. Previous studies have shown that RC coupled walls with steel or concrete coupling beam designed with strength-based design approach, may not guarantee a ductile behavior of a coupled shear wall system. Therefore, seismic performance evaluation of RC coupled shear wall with steel or concrete coupling beam designed based on a strength-based design approach is essential. In this paper first, buildings with 7, 14 and 21 stories containing RC coupled shear wall system with concrete and steel coupling beams were designed with strength-based design approach, then performance level of these buildings were evaluated under two spectrum; Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE). The performance level of LS and CP of all buildings were satisfied under DBE and MCE respectively. In spite of the steel coupling beam, concrete coupling beam in RC coupled shear wall acts like a fuse under strong ground motion.

• Earthquakes and Structures
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• 제10권1호
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• pp.73-89
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• 2016

The seismic performance of moment frames could vary according to the rotation capacity of their connections. The minimum rotation capacity of moment connections for steel intermediate moment frames (IMF) was defined as 0.02 radian in AISC 341-10. This study evaluated the seismic performance of IMF frames with connections having a rotation capacity of 0.02 radian. For this purpose, thirty IMFs were designed according to current seismic design provisions considering different design parameters such as the number of stories, span length, and seismic design categories. The procedure specified in FEMA P695 was used for conducting seismic performance evaluation. It was observed that the rotation capacity of 0.02 radian could not guarantee the satisfactory seismic performance of IMFs. This study also conducted seismic performance evaluation for IMFs with connections having the rotation capacity of 3% and ductile connections for proposing the minimum rotation capacity of IMF connections.

• 소성∙가공
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• 제21권7호
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• pp.412-419
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• 2012

The ingot-breakdown scheme of a tower flange material (low-alloy steel) for offshore wind turbine was investigated using finite element (FE) simulations and experimental analyses. Based on compression test results of the low-alloy steel, a deformation processing map was generated using the superposition approach between the dynamic materials model (DMM) and Ziegler's instability criterion. The deformation processing map allowed determination of the optimum process conditions for the tower flange material. Within the FE simulations of the ingot breakdown process, the Cockcroft-Latham criterion, which considers ductile fracture, was used to predict the possibility of forming defects during the hot working process. In general, the critical value for the ductile fracture of steel is 0.74. During the ingot-breakdown under optimum process conditions, the actual tower flange forgings exhibited a relatively uniform shape without any forming defects.

• 한국정밀공학회지
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• 제16권12호
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• pp.168-173
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• 1999

It is investigated that internal defect of planetary gear which consists of two gears with different number of teeth on both side. The internal defect, central burst, begin to form at the place of adiabatic shear band which usually has maximum ductile fracture value during the forming operation, forward and backward extrusion. It makes the plastic forming of planetary gear difficult. The prediction of defect to minimize the cost to produce the planetary gear. The finite element simulation code DEFORM is applied to analyze the defects. In the analysis, the toothed gears are assumed as axisymmetric cylinders whose diameters are equal to those of pitch circles of the each gears. Experiments were carried out with the SCM415 alloy steel as billet material and AIDA 630-ton knuckle-joint press. The calculated results and experimental inspections are compared to design a die and blank without defects and the results are useful to predict the internal defect.

• International Journal of Concrete Structures and Materials
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• 제1권1호
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• pp.11-18
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• 2007

In the recent design of high ductile engineered cementitious composites (ECC), optimizing both processing and mechanical properties for specific applications is critical. This study employs a method to develop useful ECC produced with slag particles (slag-ECC) in the field, which possesses different fluid properties to facilitate diverse types of processing (i.e., self-consolidating or spray processing). Control of rheological modulation was regarded as a key factor to allow the performance of the desired processing while retaining the ductile material properties. To control the rheological properties of the composite, the basic slag-ECC composition was initially obtained, determined based on micromechanics and steady-state cracking theory. The stability and consequent viscosity of the suspensions were then mediated by optimizing the dosage of the chemical and mineral admixtures. The rheological properties altered through this approach were revealed to be effective in obtaining ECC-hardened properties, represented by pseudo strain-hardening behavior in uniaxial tension, allowing the readily achievement of the desired function of the fresh ECC.

• KCI Concrete Journal
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• 제12권2호
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• pp.73-84
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• 2000

A new form of construction utilizing structural steel as the boundary elements in ductile flexural concrete walls is proposed to solve the bar congestion problems in such a heavily reinforced region, while maintaining the ductility and energy absorption capacity comparable to their traditional form. Two wall specimens containing rectangular hollow structural sections (HSS) and channels at their ends respectively, and one companion standard reinforced concrete wall specimen with concentrated end reinforcement were constructed and tested under reversed cyclic loading to evaluate the construction process as well as the structural performance. Initially, all three specimens were chosen and detailed with some caution to have approximately the same flexural capacity without change of the original shape and dimension of a rectangular cross section correction. Analysis and comparison of test results indicated that the reversed cyclic responses of three walls showed similar hysteretic properties, but in those with steel boundaries, local buckling of the corresponding steel webs and flanges following significant yielding was a dominant factor to determine the hysteretic response. The monotonic and cyclic responses predicted based on a sectional approach was also presented and found to be in good agreement with measured results. Design recommendations considering local instability of the structural steel elements and the interaction between steel chords and a concrete web member in such a composite wall are presented.