• Structural Engineering and Mechanics
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• 제61권4호
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• pp.483-496
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• 2017

Earthquake excitations may induce important amount of seismic energy into structures. Current design philosophy mainly deals with the plastic deformations of replaceable energy dissipating devices rather than damages accumulated on structural members. Since earthquake damage is substantially concentrated on these devices they could be replaced after severe earthquakes. In this study, the efficiency of steel cushion (SC) on seismic improvement of a vulnerable reinforced concrete (RC) frame is determined by means of several numerical simulations. The cyclic shear behaviors of SCs were determined by performing quasi-static tests. The test results were the main basis of the theoretical model of SCs which were used in the numerical analysis. These analyses were performed on three types of RC frames namely bare frame (BF), full-braced frame (F-BF) and semi-braced frame (S-BF). According to analysis results; implementation of SCs has considerable effects in reducing the storey shear forces and storey drifts. Moreover plastic energy demands of structural elements were reduced which indicates a significant improvement in seismic behavior of the RC frame preventing damage accumulation on structural elements. Full-braced frame having SCs with the thickness of 25 mm has better performance than semi-braced frame interms of energy dissipation. However, global energy dissipation demand of S-BF and F-BF having SCs with the thickness of 18 mm are almost similar.

• Structural Engineering and Mechanics
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• 제74권1호
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• pp.19-32
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• 2020

Metallic energy-dissipation dampers are widely used in structures. They are comprised of an added damping and stiffness (ADAS) device with many parallel, diamond-shaped hole plates, the neck width of which is an important parameter. However, no studies have analyzed the neck width's influence on the ADAS device's performance. This study aims to better understand that influence by conducting a pseudo-static test on ADAS, with three different neck widths, and performing finite element analysis (FEA) models. Based on the FEA results and mechanical theory, a design neck width range was proposed. The results showed that when the neck width was within the specified range, the diamond-shaped hole plate achieved an ideal yield state with minimal stress concentration, where the ADAS had an optimal energy dissipation performance and the brittle shear fracture on the neck was avoided. The theoretical values of the ADAS yield loads were in good agreement with the test values. While the theoretical value of the elastic stiffness was lower than the test value, the discrepancy could be reduced with the proposed modified coefficient.

• Steel and Composite Structures
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• 제45권5호
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• pp.683-695
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• 2022

Conventional braces are often used to provide stiffness to structures; however due to buckling they cannot be used as seismic energy dissipating elements. In this study, a seismic energy dissipation device is proposed which is comprised of a bracing member and a steel hysteretic damper made of steel hexagonal plates. The hexagonal shaped designated fuse causes formation of plastic hinges under axial deformation of the brace. The main advantages of this damper compared to conventional metallic dampers and buckling-restrained braces are the stable and controlled energy dissipation capability with ease of manufacture. The mechanical behavior of the damper is formulated first and a design procedure is provided. Next, the theoretical formulation and the efficiency of the damper are verified using finite element (FE) analyses. An analytical model of the damper is established and its efficiency is further investigated by applying it to seismic retrofit of a case study structure. The seismic performance of the structure is evaluated before and after retrofit in terms of maximum interstory drift ratio, top story displacement, residual displacement, and energy dissipation of dampers. Overall, the median of maximum interstory drift ratios is reduced from 3.8% to 1.6% and the residual displacement decreased in the x-direction which corresponds to the predominant mode shape of the structure. The analysis results show that the developed damper can provide cost-effective seismic protection of structures.

• Structural Engineering and Mechanics
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• 제89권1호
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• pp.93-102
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• 2024

Using negative Poisson's ratio materials, an innovative metallic-yielding damper is introduced for the first time in this study. Through the use of ABAQUS commercial software, a nonlinear finite element analysis is conducted to determine the performance of the proposed system. Mild steel plates with elliptical holes are used for these types of dampers, which dissipate energy through an inelastic deformation of the constitutive material. To assess the capability of the proposed damper, nonlinear quasi-static finite element analyses have been conducted on the damper with a variety of geometric parameters. According to the results, the proposed system is ductile and has a high capacity to dissipate energy. The proposed auxetic damper has a specific energy absorption of 910.8 J/kg and a ductility of 33.6. Therefore, this damper can dissipate a large amount of earthquake input energy without buckling by increasing the buckling load of the brace with its ductile behavior. In addition, it was found that by incorporating auxetic dampers in the steel frame, the frame was made harder, stronger, and ductile and its energy absorption increased by 300%.

• Journal of Korean Association for Spatial Structures
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• 제15권1호
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• pp.85-94
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• 2015

SAFE damper is a hybrid damper which is comprised of a friction damper and a metallic damper. These two dampers combine to resist external energy in stages. Under minor earthquake loads, the friction damper operates alone. However, the friction damper and metallic damper dissipate the energy together when a severe earthquake occurs. In comparison with other methods for seismic retrofitting, the SAFE damper has many advantages. The SAFE damper doesn't cause damage to façade of the building, and the construction period can be reduced when retrofitting. This paper describes experiments evaluating the structural performance of the SAFE damper. From the results, it was found that the structural performance of a conventional RC bare frame can be significantly improved by the installation of the SAFE damper.

• Steel and Composite Structures
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• 제47권2호
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• pp.185-201
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• 2023

Despite the high lateral stiffness and strength of the Concentrically Braced Frame (CBF), due to the buckling of its diagonal members, it is not a suitable system in high seismic regions. Among the offered methods to overcome the shortcoming, utilizing a metallic damper is considered as an appropriate idea to enhance the behavior of Concentrically Braced Frames (CBFs). Therefore, in this paper, an innovative steel damper is proposed, which is investigated experimentally and numerically. Moreover, a parametrical study was carried out to evaluate the effect of the mechanism (shear, shear-flexural, and flexural) considering buckling mode (elastic, inelastic, and plastic) on the behavior of the damper. Besides, the necessary formulas based on the parametrical study were presented to predict the behavior of the damper that they showed good agreement with finite element (FE) results. Both experimental and numerical results confirmed that dampers with the shear mechanism in all buckling modes have a better performance than other dampers. Accordingly, the FE results indicated that the shear damper has greater ultimate strength than the flexural damper by 32%, 31%, and 56%, respectively, for plates with elastic, inelastic, and plastic buckling modes. Also, the shear damper has a greater stiffness than the flexural damper by 43%, 26%, and 53%, respectively, for dampers with elastic, inelastic, and plastic buckling modes.

• Journal of the Korea institute for structural maintenance and inspection
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• 제17권2호
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• pp.62-70
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• 2013

The purpose of this study is the displacement and velocity dependence evaluation of clamped shape metallic damper, which were evaluated superior in energy dissipation capacity than straight type slit damper. For this purpose, 6 metallic damper specimens are prepared and dependence test are performed. Test variables are displacement dependence and velocity dependence. According to displacement dependence test results, larger target displacement (50mm) shows lower cyclic numbers and cumulated energy dissipated area than lower target displacement (25mm). Also it shows higher strength and early failure than short target displacement. In velocity dependence evaluation, fast target velocity (60mm/sec) shows lower cyclic numbers and cumulated energy dissipated area than slow target velocity (40mm/sec). Therefore the hysteresis dependence of metallic damper were evaluated as close relation to the loading displacement and velocity conditions.

• Steel and Composite Structures
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• 제44권3호
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• pp.325-337
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• 2022

In this research, an earthquake-resistant structural system consisting of a pin-connected steel frame and a bracing with metallic fuses is proposed. Contrary to the conventional braced frames, the main structural elements are deemed to remain elastic under earthquakes and the seismic energy is efficiently dissipated by the damper-braces with an amplification mechanism. The superiority of the proposed damping system lies in easy manufacture, high yield capacity and energy dissipation, and an effortless replacement of damaged fuses after earthquake events. Furthermore, the stiffness and the yield capacity are almost decoupled in the proposed damper-brace which makes it highly versatile for performance-based seismic design compared to most other dampers. A special attention is paid to derive the theoretical formulation for nonlinear behavior of the proposed damper-brace, which is verified using analytical results. Next, a direct displacement-based design procedure is provided for the proposed system and an example structure is designed and analyzed thoroughly to check its seismic performance. The results show that the proposed system designed with the provided procedure satisfies the given performance objective and can be used for developing highly efficient low-damage structures.

• Land and Housing Review
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• 제5권2호
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• pp.107-114
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• 2014

Passive energy dissipation systems for seismic applications have been under development for a number of years with a rapid increase in implementations starting in the mid-1990s in many countries. A metallic hysteretic damper has most commonly been used for seismic protection of structures in domestic area because they present high energy-dissipation potential at relatively low cost and easy to install and maintain. This paper presents an analytical case study of the effectiveness of isotropic hysteretic metallic damper(IHMD) called Kagome as a passive dissipative device in reducing structural response during seismic excitation. An eighteen-story RC framed apartment building is studied with and without IHMD. Results demonstrate the feasibility of these techniques for seismic mitigation. The inclusion of supplemental passive energy dissipation devices in the form of IHMD proved to be a very effective method for significantly reducing the seismic response of the building investigated.

• Smart Structures and Systems
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• 제26권6호
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• pp.765-779
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• 2020

Collapse of bridges in recent earthquakes demonstrates the need to deepen the understanding of the behaviour of these structures against seismic actions. This paper presents a highly detailed numerical model of an actual bridge subjected to extreme seismic action which results in its collapse. Normally, nonlinear numerical models have high difficulties to achieve convergence when reinforced concrete is intended to be represented. The main objective of this work is to determine the efficiency of different passive control strategies to prevent the structural collapse of an existing bridge. Metallic dampers and seismic isolation by decoupling the mass were evaluated. The response is evaluated not only in terms of reduction of displacements, but also in increasing of shear force and axial force in key elements, which can be a negative characteristic of the systems studied. It can be concluded that the use of a metallic damper significantly reduces the horizontal displacements and ensures the integrity of the structure from extreme seismic actions. Moreover, the isolation of the deck, which in principle seems to be the most effective solution to protect existing bridges, proves inadequate for the case analysed due to its dynamic characteristics and its particular geometry and an unpredictable type of axial pounding in the columns. This unexpected effect on the isolation system would have been impossible to identify with simplified models.