• Earthquakes and Structures
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• 제23권3호
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• pp.271-282
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• 2022

Seismic resisting self-centering bridge piers with high energy dissipation and negligible residual displacement after an earthquake event are focus topics of current structural engineering. The energy dissipation components of typical bridge piers are often relatively single; and exhibit a certain level of damage under earthquakes, leading to large residual displacements and low cumulative energy dissipation. In this paper, a novel socket self-centering bridge pier with a hybrid energy dissipation system is proposed. The seismic resilience of bridge piers can be improved through the rational design of annular grooves and rubber cushions. The seismic response was evaluated through the finite element method. The effects of rubber cushion thickness, annular groove depth, axial compression ratio, and lateral strength contribution ratio of rubber cushion on the seismic behavior of bridge piers are systematically studied. The results show that the annular groove depth has the greatest influence on the seismic performance of the bridge pier. Especially, the lateral strength contribution ratio of the rubber cushion mainly depends on the depth of the annular groove. The axial compression ratio has a significant effect on the ultimate bearing capacity. Finally, the seismic design method is proposed according to the influence of the above research parameters on the seismic performance of bridge piers, and the method is validated by an example. It is suggested that the range of lateral strength contribution ratio of rubber cushion is 0.028 ~ 0.053.

• Steel and Composite Structures
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• 제33권5호
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• pp.641-652
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• 2019

This paper investigates the effect of aftershocks on the seismic performance of self-centering (SC) prestressed concrete frames using the probabilistic seismic demand analysis methodology. For this purpose, a 4-story SC concrete frame and a conventional reinforced concrete (RC) frame are designed and numerically analyzed through nonlinear dynamic analyses based on a set of as-recorded mainshock-aftershock seismic sequences. The peak and residual story drifts are selected as the demand parameters. The probabilistic seismic demand models of the SC and RC frames are compared, and the SC frame is found to have less dispersion of peak and residual story drifts. The results of drift demand hazard analyses reveal that the SC frame experiences lower peak story drift hazards and significantly reduced residual story drift hazards than the RC frame when subjected to the mainshocks only or the mainshock-aftershock sequences, which demonstrates the advantages of the SC frame over the RC frame. For both the SC and RC frames, the influence of as-recorded aftershocks on the drift demand hazards is small. It is shown that artificial aftershocks can produce notably increased drift demand hazards of the RC frame, while the incremental effect of artificial aftershocks on the drift demand hazards of the SC frame is much smaller. It is also found that aftershock polarity does not influence the drift demand hazards of both the SC and RC frames.

• Structural Engineering and Mechanics
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• 제71권1호
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• pp.45-56
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• 2019

A modified mechanical model of pre-pressed spring self-centering energy dissipation (PS-SCED) brace is proposed, and the hysteresis band is distinguished by the indication of relevant state variables. The MDOF frame system equipped with the braces is formulated in an incremental form of linear acceleration method. A multi-objective genetic algorithm (GA) based brace parameter optimization method is developed to obtain an optimal solution from the primary design scheme. Parameter sensitivities derived by the direct differentiation method are used to modify the change rate of parameters in the GA operator. A case study is conducted on a steel braced frame to illustrate the effect of brace parameters on node displacements, and validate the feasibility of the modified mechanical model. The optimization results and computational process information are compared among three cases of different strategies of parameter change as well. The accuracy is also verified by the calculation results of finite element model. This work can help the applications of PS-SCED brace optimization related to parameter sensitivity, and fulfill the systematic design procedure of PS-SCED brace-structure system with completed and prospective consequences.

• Steel and Composite Structures
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• 제31권2호
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• pp.149-158
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• 2019

The force-deformation behavior, strain distribution and failure modes of a variable damping self-centering brace (VD-SCB) are theoretically analyzed, experimentally studied, and numerically simulated to guide its design. The working principle of the brace is explained by describing the working stages and the key feature points of the hysteretic curve. A large-scale brace specimen was tested under different sinusoidal excitations to analyze the recentering capability and energy dissipation. Results demonstrate that the VD-SCB exhibits a full quasi-flag-shaped hysteretic response, high ultimate bearing capacity, low activation force and residual deformation, and excellent recentering and energy dissipation capabilities. Calculation equations of the strain distribution in different parts of the brace are proposed and are compared with the experimental data and simulated results. The developments of two failure modes are compared. Under normal circumstances, the brace fails due to the yielding of the spring blocking plates, which are easily replaced to restore the normal operating conditions of the brace. A brief description of the design procedure of the brace is proposed for application.

• Steel and Composite Structures
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• 제37권6호
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• pp.679-693
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• 2020

This paper investigates the seismic response of buildings equipped with Self-Centering Energy Dissipating (SCED) braces. Two-dimensional models of 3, 6, 12 and 16-story SCED buildings considering both material and geometric nonlinearities are investigated by carrying out pushover and nonlinear time-history analyses. The response indicators of the buildings are studied for weight-scaled ground motions to represent the Design Basis Earthquake (DBE) level and the Maximum Considered Earthquake (MCE) event. The fragility curves of the buildings for two Immediate Occupancy (IO) and Life Safety (LS) performance levels are developed using Incremental Dynamic Analysis (IDA). Results of the nonlinear response history analyses indicate that the maximum inter-story drift occurs at the taller buildings. The mean peak inter-story drift is less than 2% in both hazard levels. High floor acceleration peaks are observed in all the SCED frames regardless of the building height. The overall ductility and ductility demand increase when the number of stories reduces. The results also showed the residual displacement is negligible for all of case study buildings. The 3 and 6-story buildings exhibit desirable performance in IO and LS performance levels according to fragility curves results, while 12 and 16-story frames show poor performance especially in IO level. The results indicated the SCED braces performance is generally better in lower-rise buildings.

• Steel and Composite Structures
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• 제47권4호
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• pp.523-537
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• 2023

This paper proposed a new self-centering brace (SCB), which consists of four post-tensioned (PT) high strength steel strands and energy absorbing steel plate (EASP) clusters. First, analytical equations were derived to describe the working principle of the SCB. Then, to investigate the hysteretic performance of the SCB, four full-size specimens were manufactured and subjected to the same cyclic loading protocol. One additional specimen using only EASP clusters was also tested to highlight the contribution of PT strands. The test parameters varied in the testing process included the thickness of the EASP and the number of EASP in each cluster. Testing results shown that the SCB exhibited nearly flag-shape hysteresis up to expectation, including excellent recentering capability and satisfactory energy dissipating capacity. For all the specimens, the ratio of the recovered deformation is in the range of 89.6% to 92.1%, and the ratio of the height of the hysteresis loop to the yielding force is in the range of 0.47 to 0.77. Finally, in order to further understand the mechanism of the SCB and provide additional information to the testing results, the high-fidelity finite element (FE) models were established and the numerical results were compared against the experimental data. Good agreement between the experimental, numerical, and analytical results was observed, and the maximum difference is less than 12%. Parametric analysis was also carried out based on the validated FE model to evaluate the effect of some key parameters on the cyclic behavior of the SCB.

• Steel and Composite Structures
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• 제51권2호
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• pp.173-183
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• 2024

This study investigates a new seismic retrofit system that utilizes rotational friction dampers and axial springs. The retrofit system involves a steel frame with rotational friction dampers (RFD) at beam-column joints and linear springs at the corners, providing energy dissipation and self-centering capabilities to existing structures. The axial spring acts as a self-centering mechanism that eliminates residual deformations, while the friction damper mitigates seismic damage. To evaluate the seismic performance of the proposed retrofit system, a series of cyclic loading tests were carried out on a steel beam-column subassembly equipped with the proposed devices. An analytical model was then developed to validate the experimental results. A performance point ratio (PPR) was presented to optimize the design parameters of the retrofit system, and a performance-based seismic design strategy was developed based on the PPR. The retrofit system's effectiveness and the presented performance-based design approach were evaluated through case study models, and the analysis results demonstrated that the developed retrofit system and the performance-based design procedure were effective in retrofitting structures for multi-level design objectives.

• 동의생리병리학회지
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• 제18권4호
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• pp.953-956
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• 2004

We studied on the means to ascetic practices centering around Taijiquan. Taijiquan is the means to the self-discipline of the human body. And Taijiquan is the regimen for human health. Therefore according to the continuous training of Taijiquan, we can achieve the purpose of the ascetic practices by the getting over the body's habituations.

• Steel and Composite Structures
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• 제29권3호
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• pp.287-299
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• 2018

The purpose of this study is to investigate the effectiveness of damped cable systems (DCS) to mitigate the earthquake-induced responses of a building frame structure. The seismic performance of the DCS is investigated using the fragility analysis and life cycle cost evaluation of an existing building retrofitted with the DCS, and the results are compared with the structure retrofitted with conventional fluid viscous dampers. The comparison of the analysis results reveals that, due to the self-centering capability of the DCS, residual displacement approximately reaches to zero for the structure retrofitted with the DCS. The fragility analysis shows that the structure retrofitted with the DCS has the least probability of reaching the specific limit states compared to the bare structure and the structure with the conventional fluid viscous damper (VD), especially under the severe ground motions. It is also observed that both the initial and the life cycle costs of the DCS seismic retrofitting technique is lesser compare to the structure retrofitted with the VD.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.980-985
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• 2004

This paper shows a performance analysis for conical type sealless cylinders and rod bearings. The pistons without seal have partly cylindrical and conical shapes. 2 dimensional Reynolds equation and FD(finite differential) numerical techniques are utilized for the performance analysis. The relationship among self-centering forces and leakage flows are investigated. Also, optimal design values for a sealless cylinder are presented. A prototype of sealless cylinder which had rod bearing with four pockets, five pockets, and six pockets was manufactured respectively. Leakage flow test is conducted to evaluate performance of piston and rod bearing in sealless cylinder.