• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.47-54
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• 2001

Unbond brace hysteretic dampers are generally used to prevent or decrease structural damage in building structures subjected to strong earthquake by its energy dissipating hysteretic behavior. In the study, a straightforward design procedure for unbond brace hysteretic dampers was developed. The required amount of equivalent damping to satisfy given performance acceptance criteria was obtained conveniently based on the capacity spectrum method without carrying out time-consuming nonlinear dynamic time history analysis. Then the size of the unbond braces is determined from the required equivalent damping. Parametric study has been performed for the design variables such as natural period, yield strength, the stiffness after the first yield stress of the unbond brace. The procedure was applied to 5-story and 10-story steel frames for verification of the proposed method. According to the earthquake time history analysis results, the maximum displacement of the model structure with unbond braces supplied in accordance with the proposed method corresponds well with the given target displacement.

• Steel and Composite Structures
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• v.28 no.2
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• pp.139-147
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• 2018

Moment frames have considerable ductility against cyclic lateral loads and displacements; however, sometimes this feature causes the relative displacement to exceed the permissible limits. This issue can bring unfavorable hysteretic behavior on the frame due to the reduction in the stiffness and resistance against lateral loads. Most of common bracing systems usually control lateral displacements through increasing stiffness while result in decreasing the capacity for energy absorption. This has direct effect on hysteresis curves of moment frames. Therefore, a system that is capable of both having the capacity of energy absorption as well as controlling the displacements without a considerable increase in the stiffness is quite important. This paper investigates retrofitting of a single-storey steel moment frame using a delayed wire-rope bracing system equipped with the ductile middle steel plate. The steel plate is considered at the middle intersection of wire ropes, where it causes cables to be continuously in tension. This integrated system has the advantage of reducing considerable stiffness of the frame compared to cross bracing systems as a result of which it could also preserve the frame's energy absorption capacity. In this paper, FEM models of a delayed wire-rope bracing system equipped by steel plates with different geometries have been studied, validated, and compared with other researchers' laboratory test results.

• Earthquakes and Structures
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• v.23 no.4
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• pp.363-371
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• 2022

Traditional metal dampers have disadvantages such as a higher yield point and inadequate adjustability. The experimental results show that the low yield point steel has superior energy dissipation hysteretic capacity and can be applied to seismic structures. To overcome these deficiencies, a novel compound metal damper comprising both low yield point steel plates and common steel plates is presented. The optimization objectives, including "maximum rigidity" and "full stress state", are proposed to obtain the optimal edge shape of a compound metal damper. The numerical results show that the optimized composite metal damper has the advantages such as full hysteresis curve, uniform stress distribution, more sufficient energy consumption, and it can adjust the yield strength of the damper according to the engineering requirements. In view of the mechanical characteristics of the compound metal damper, the equivalent model of eccentric cross bracing is established, and the approximate analytical solution of the yield strength and the yield displacement is proposed. A nonlinear simulation analysis is carried out for the overall aseismic capacity of three-layer-frame structures with a compound metal damper. It is verified that a compound metal damper has better energy dissipation capacity and superior seismic performance, especially for a damper with double-objective optimized shape.

• Earthquakes and Structures
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• v.24 no.5
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• pp.365-375
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• 2023

Energy dissipation systems increase the energy dissipation capacity of buildings considerably. In this study, the effect of dampers on a typical 10-storey reinforced concrete structure with a ductile moment-resisting frame was investigated. In this context, 5 different models were created according to the calculation of the slip load and the positions of the dampers in the structure. Nonlinear time-history analyzes using 11 different earthquake acceleration records were performed on the models using the ETABS program. As a result of the analyses, storey displacements, energy dissipation ratios, drift ratios, storey accelerations, storey shears, and hysteretic curves of the dampers on the first and last storey and overturning moments are presented. In the study, it was determined that friction dampers increased the energy dissipation capacities of all models. In addition, it has been determined that positioning the dampers in the outer region of the structures and taking the base shear as a basis in the slip load calculation will be more effective.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.367-374
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• 1999

this paper focuses on the dynamic characteristics of full-scale viscoelastic dampers through the experimental study. Viscoelastic dampers which dissipate the response energy of a building under earthquake excitation make a role of increasing damping capacity of the building. Therefore it is important to recognize the damping behavior of viscoelastic dampers. Full-scale viscoelastic dampers are made of three types of rubbers for experimental test. The hysteretic behavior is obtained through the load-deformation experiment over the various loading frequencies and damper strains The experimental results show the good performance of viscoelastic dampers under earthquake excitations,

• Steel and Composite Structures
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• v.32 no.2
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• pp.199-212
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• 2019

This paper presents an investigation on seismic behavior of out-of-code Q690 circular high-strength concrete-filled thin-walled steel tubular (HCFTST) columns made up of high-strength (HS) steel tubes (yield strength $f_y{\geq}690MPa$). Eight Q690 circular HCFTST columns with various diameter-to-thickness (D/t) ratios, concrete cylinder compressive strengths ($f_c$) and axial compression ratios (n) were tested under the constant axial loading and reversed cyclic lateral loading. The obtained lateral load-displacement hysteretic curves, energy dissipation, skeleton curves and ductility, and stiffness degradation were analyzed in detail to reflect the influences of tested parameters. Subsequently, a simplified shear strength model was derived and validated by the test results. Finally, a finite element analysis (FEA) model incorporating a stress triaxiality dependent fracture criterion was established to simulate the seismic behavior. The systematic investigation indicates the following: compared to the D/t ratio and axial compression ratio, improving the concrete compressive strength (e.g., the HS thin-walled steel tube filled with HS concrete) had a slight influence on the ductility but an obvious enhancement of energy dissipation and peak load; the simplified shear strength model based on truss mechanism accurately predicted the shear-resisting capacity; and the established FEA model incorporating steel fracture criterion simulated well the seismic behavior (e.g., hysteretic curve, local buckling and fracture), which can be applied to the seismic analysis and design of Q690 circular HCFTST columns.

• Structural Engineering and Mechanics
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• v.87 no.4
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• pp.391-403
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• 2023

In this study, a new type of self-centering beam-column joint with tapered steel plate links is proposed. Firstly, mechanical property of the basic joint (with the prestressed steel strands only, to provide the self-centering ability) and the combined joint (with both the prestressed steel strands and tapered steel plate links, to provide self-centering and energy dissipation simultaneously) is theoretically analyzed. Then, three joints with different dimensions and combinations of tapered plate links are designed and tested through a series of quasi-static cyclic loading tests. Test results show that a nearly bilinear elastic moment-rotation relationship for the basic joint is obtained. With the addition of tapered steel plate links, typical flag-shape hysteretic curves are obtained, which indicates good self-centering and energy dissipating ability of the combined joint. By installing multiple tapered plate links, stiffness and bearing capacity of the beam-column joint can be enhanced. The theoretical moment-rotation relationships agree well with the test results. A simplified macro model of the proposed joint is developed using OpenSees, which simulates reasonably well its hysteretic behavior.

• Steel and Composite Structures
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• v.24 no.4
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• pp.441-453
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• 2017

In Y-shaped eccentrically braced frame fabricated with high strength steel (Y-HSS-EBF), link uses conventional steel while other structural members use high strength steel. Cyclic test for a 1:2 length scaled one-bay and one-story Y-HSS-EBF specimen and shake table test for a 1:2 length scaled three-story Y-HSS-EBF specimen were carried out to research the seismic performance of Y-HSS-EBF. These include the failure mode, load-bearing capacity, ductility, energy dissipation capacity, dynamic properties, acceleration responses, displacement responses, and dynamic strain responses. The test results indicated that the one-bay and one-story Y-HSS-EBF specimen had good load-bearing capacity and ductility capacity. The three-story specimen cumulative structural damage and deformation increased, while its stiffness decreased. There was no plastic deformation observed in the braces, beams, or columns in the three-story Y-HSS-EBF specimen, and there was no danger of collapse during the seismic loads. The designed shear link dissipated the energy via shear deformation during the seismic loads. When the specimen was fractured, the maximum link plastic rotation angle was higher than 0.08 rad for the shear link in AISC341-10. The Y-HSS-EBF is a safe dual system with reliable hysteretic behaviors and seismic performance.

• Earthquakes and Structures
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• v.16 no.1
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• pp.97-107
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• 2019

The frame structures investigated in this paper is composed of Concrete encased columns with L-shaped steel section and steel beams. The seismic behavior of this structural system is studied through experimental and numerical studies. A 2-bay, 3-story and 1/3 scaled frame specimen is tested under constant axial loading and cyclic lateral loading applied on the column top. The load-displacement hysteretic loops, ductility, energy dissipation, stiffness and strength degradation are investigated. A typical failure mode is observed in the test, and the experimental results show that this type of framed structure exhibit a high strength with good ductility and energy dissipation capacity. Furthermore, finite element analysis software Perform-3D was conducted to simulate the behavior of the frame. The calculating results agreed with the test ones well. Further analysis is conducted to investigate the effects of parameters including concrete strength, column axial compressive force and steel ratio on the seismic performance indexes, such as the elastic stiffness, the maximum strength, the ductility coefficient, the strength and stiffness degradation, and the equivalent viscous damping ratio. It can be concluded that with the axial compression ratio increasing, the load carrying capacity and ductility decreased. The load carrying capacity and ductility increased when increasing the steel ratio. Increasing the concrete grade can improve the ultimate bearing capacity of the structure, but the ductility of structure decreases slightly.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.179-184
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• 1992

Four 3-story 1/2 scaled large concrete panel structures were designed and tested to estimate the seismic resistance capacity of large concrete panel high rise building systems, Test specimens were modeled three story of 24 or 15 story buildings and set up to represent the actural stress of the building . The axial force was constant and the horizontal force was loaded by ductility ratio. Results indicated that the joints of specimens were behavied monolithically to maximum strength. It was shown that the joint box connecting system had lower maximum strength and energy dissipation capacity than welding connection system, but had better deformation capacity.