Experimental study on steel hysteretic column dampers for seismic retrofit of structures

Mohammad Mahdi Javidan,Seungho Chun,Jinkoo Kim 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.4

In this research, the seismic performance of a steel column damper is evaluated using cyclic loading tests of two one-story one-bay reinforced concrete (RC) frames before and after retrofit. The theoretical formulation and design procedure of the damper are explained first and then the details of the tests are described. The seismic performances of the test frames are evaluated in terms of hysteretic behavior, energy dissipation, crack pattern, failure mechanism, and damper behavior. The analytical model of the damper is established and verified using the experimental data. In order to further investigate the applicability of the developed damper for seismic retrofit, a case-study structure is chosen and retrofitted using the proposed damper. The seismic performance of the structure is evaluated and compared before and after retrofit in detail using pushover, nonlinear time-history, and fragility analyses. The results show that the presented damper can efficiently reduce inter-story drifts and damage of the structure. The details of modeling techniques and simulations given in this study can provide guidelines and insight into nonlinear analysis and retrofit of RC structures.

Full-scale tests of two-story RC frames retrofitted with steel plate multi-slit dampers

Mohammad Mahdi Javidan,Mohammad Seddiq Eskandari Nasab,Jinkoo Kim 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.5

There is a growing need of seismic retrofit of existing non-seismically designed structures in Korea after the 2016 Gyeongju and 2017 Pohang earthquakes, especially school buildings which experienced extensive damage during those two earthquakes. To this end, a steel multi-slit damper (MSD) was developed in this research which can be installed inside of partition walls of school buildings. Full-scale two-story RC frames were tested with and without the proposed dampers. The frames had structural details similar to school buildings constructed in the 1980s in Korea. The details of the experiments were described in detail, and the test results were validated using the analysis model. The developed seismic retrofit strategy was applied to a case study school building structure, and its seismic performance was evaluated before and after retrofit using the MSD. The results show that the developed retrofit strategy can improve the seismic performance of the structure to satisfy a given target performance level.

Steel hexagonal damper-brace system for efficient seismic protection of structures

Mohammad Mahdi Javidan,Jinkoo Kim 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.5

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.

A ductile steel damper-brace for low-damage framed structures

Mohammad Mahdi Javidan,Jinkoo Kim 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.3

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.

Development of Viscoelastic Column Dampers for Seismic Retrofit of Structures

Javidan, Mohammad Mahdi(모하마드 자비단),Assefa, Jonathan Dereje(아세파 조나단),Kim, Jinkoo(김진구) 대한건축학회 2022 대한건축학회 학술발표대회 논문집 Vol.42 No.2

Computationally efficient framework for probabilistic collapse analysis of structures under extreme actions

Javidan, Mohammad Mahdi,Kang, Hyungoo,Isobe, Daigoro,Kim, Jinkoo Elsevier 2018 ENGINEERING STRUCTURES Vol.172 No.-

<P><B>Abstract</B></P> <P>Currently there is a growing need for a versatile framework consisting of analytical and surrogate models to ensure both accuracy and computational efficiency of collapse analysis under extreme actions. However training metamodels for highly nonlinear structural responses requires large number of samples to achieve enough accuracy. In this research a method is developed to achieve computational efficiency by implementing the adaptively shifted integration-Gauss technique in conjunction with a core neural network metamodel. The analytical model is validated by experimental data and its accuracy is further evaluated by detailed finite-element analysis. The applicability and efficiency of the provided tool for highly nonlinear analyses are investigated using collapse assessment of a steel framed structure subjected to code-stipulated vehicle impact loads. Thorough probabilistic analyses are carried out including reliability assessment, fragility analysis, and two different sensitivity tests. The analysis results show the superiority and precision of this framework compared to detailed finite-element analysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Efficient probabilistic collapse assessment under extreme actions. </LI> <LI> Utilizing ANN with the ASI-Gauss technique for reliability analysis. </LI> <LI> ANN-based Global sensitivity analysis under vehicle impact loads. </LI> <LI> Comparison between Tornado diagram analysis and Global sensitivity analysis. </LI> <LI> Fragility analysis under vehicle impact loads. </LI> </UL> </P>

Steel hysteretic column dampers for seismic retrofit of soft-first-story structures

Mohammad Mahdi Javidan,Jinkoo Kim 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.3

In this study a new hysteretic damper for seismic retrofit of soft-first story structures is proposed and its seismic retrofit effect is evaluated. The damper consists of one steel column member and two flexural fuses at both ends made of steel plates with reduced section, which can be placed right beside existing columns in order to minimize interference with passengers and automobiles in the installed bays. The relative displacement between the stories forms flexural plastic hinges at the fuses and dissipate seismic energy. The theoretical formulation and the design procedure based on plastic analysis is provided for the proposed damper, and the results are compared with a detailed finite-element (FE) model. In order to apply the damper in structural analysis, a macromodel of the damper is also developed and calibrated by the derived theoretical formulas. The results are compared with the detailed FE analysis, and the efficiency of the damper is further validated by the seismic retrofit of a case study structure and assessing its seismic performance before and after the retrofit. The results show that the proposed hysteretic damper can be used effectively in reducing damage to soft-first story structures.

Seismic retrofit of structures using added steel column friction dampers

Mohammad Mahdi Javidan,Asad Naeem,Jinkoo Kim 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.49 No.3

In this study, the feasibility and applicability of a friction damper with a vertical installation scheme are investigated. This device is composed of a steel section and two friction hinges at both ends which dissipate seismic energy. Due to its small width and vertical installation scheme, the proposed damper can minimize the interference with architectural functions. To evaluate the performance of the proposed damper, its mechanical behavior is theoretically evaluated and the required formulas for the yield strength and elastic stiffness are derived. The theoretical formulas are verified by establishing the analytical model of the damper in the SAP2000 software and comparing their results. To further investigate the performance of the developed damper, the provided analytical model is applied to a 4-story reinforced concrete (RC) structure and its performance is evaluated before and after retrofit under the Maximum Considered Earthquake (MCE) hazard level. The seismic performance is thoroughly evaluated in terms of maximum interstory drift ratio, displacement time history, residual displacement, and energy dissipation. The results show that the proposed damper can be efficiently used to protect the structure against seismic loads.