Self-centering Energy Dissipation Research Articles

Development and experimental study of a self-centering variable damping energy dissipation brace

A new self-centering variable damping energy dissipation (SC–VDED) brace is proposed to reduce the activation force and sudden change in stiffness after activation of self-centering energy dissipation braces. The brace uses the combination disc springs to provide self-centering capability and the structural design of a magnetorheological (MR) fluid device to realize variable damping energy dissipation. The mechanics of the SC–VDED brace and the equations governing its design and hysteretic responses are presented. A brace specimen with a total length of 1.365 m was designed and fabricated, and a series of cyclic tests were carried out under the sinusoidal excitation with different frequencies and amplitudes. Results demonstrate that the brace exhibits full quasi-flag-shaped hysteretic responses, a small activation force, few sudden change in stiffness, and large energy dissipation. The pre-pressed force of the combination disc springs should be larger than the initial damping force, and their stiffness should be increased to give full play to the self-centering and energy dissipation capabilities of the brace. Fatigue and destructive test results indicate that the behaviors of the brace are stable enough to provide self-centering and energy dissipation capabilities, and the loose and severe stress concentration of the outer tube clamps cause the brace to fail.

Experimental behavior and analysis of self-centering steel brace with pre-pressed disc springs

Quasi-static reversed cyclic loading tests and finite element analyses of a pre-pressed spring self-centering energy dissipation brace are conducted. The proposed steel bracing system combines a mechanism of pre-pressed disc springs for self-centering with friction devices for energy dissipation. The mechanics and the basic equations governing the design and distribution of internal force are presented. The results demonstrate that the bracing system exhibits stable and repeatable self-centering hysteretic responses with effective energy dissipation, and no residual deformation occurs when the initial pre-pressed force of disc springs is greater than the friction force provided by the energy dissipation devices. The forces at the surface of the inner and outer tubes are distributed as expected. The inverse calculation method is proposed to predict the hysteretic responses employing the strain data, the comparative analyses of behaviors obtained from experiments, finite element analyses, and inverse calculation are conducted, and good agreements are observed.

Parametric Analysis and Direct Displacement-Based Design Method of Self-Centering Energy-Dissipative Steel-Braced Frames

The self-centering energy-dissipative (SCED) brace is a novel bracing element that can substantially reduce the residual deformation and enhance the reparability of structures. In this paper, nonlinear dynamic analyses have been conducted on a 4- and a 12-story steel-braced frame with SCED braces to study the effect of four important design parameters on the seismic performance of the SCED frames and recommendations are given for selection of the parameters. The parameters considered include the response modification coefficient [Formula: see text], the stiffness ratio of the brace [Formula: see text], the strength ratio of the brace [Formula: see text], and the fuse activation story drift [Formula: see text]. The relationship between the residual story drift and the peak story drift of the SCED frames is obtained based on these statistics. Finally, based on the equivalent linearization theory, a direct displacement-based design method applicable to the SCED frames, regarding both the peak story drift and residual story drift as the design objectives, is proposed.

Development and experimental verification of a pre-pressed spring self-centering energy dissipation brace

The present study develops and experimentally verifies a new type of earthquake-resilient bracing system. The proposed pre-pressed spring self-centering energy dissipation (PS-SCED) bracing system combines friction energy dissipation devices between inner and outer tube members with a mechanism of pre-pressed disc springs that provides a self-centering capability and additional energy dissipation. Two large-scale PS-SCED braces with different types of inner tube members are designed, fabricated, and tested under low cyclic reversed loadings, and the results demonstrate that the PS-SCED braces exhibit stable and repeatable flag-shaped hysteretic responses with excellent self-centering capabilities, effective energy dissipation, large ultimate bearing capacity, and appreciable ductility. The residual deformation of the brace is controlled by adjusting the ratio of the initial pre-pressed force of the disc springs to the friction force provided by the energy dissipation devices. The energy dissipation and ductility of the PS-SCED brace constructed with a circular inner tube are better than those of the brace constructed with an X-shaped inner tube. A restoring force model for the PS-SCED brace is proposed, and the predicted hysteretic responses agree well with the experimental results.

Hysteretic behavior studies of self-centering energy dissipation bracing system

This paper presents a new type of pre-pressed spring self-centering energy dissipation (PS-SCED) bracing system that combines friction mechanisms between the inner and outer tube members to provide the energy dissipation with the pre-pressed combination disc springs installed on both ends of the brace to provide the selfcentering capability. The mechanics and the equations governing the design and hysteretic responses of the bracing system are outlined, and a series of validation tests of components comprising the self-centering mechanism of combination disc springs, the friction energy dissipation mechanism, and a large scale PS-SCED bracing specimen were conducted due to the low cyclic reversed loadings. Experimental results demonstrate that the proposed bracing system performs as predicted by the equations governing its mechanical behaviors, which exhibits a stable and repeatable flag-shaped hysteretic response with excellent self-centering capability and appreciable energy dissipation, and large ultimate bearing and deformation capacities. Results also show that almost no residual deformation occurs when the friction force is less than the initial pre-pressed force of disc springs.

Design, Testing, and Detailed Component Modeling of a High-Capacity Self-Centering Energy-Dissipative Brace

AbstractThe self-centering energy-dissipative (SCED) brace is an innovative cross brace for buildings that provides a nonlinear response with good energy dissipation and postyield stiffness while minimizing residual drift after an earthquake. This provides a high level of seismic performance by allowing structures to remain operational even after major seismic events. Recently, the SCED brace has been improved through the design and experimental evaluation of a high-capacity SCED (HC-SCED) that has an axial capacity similar to some of the largest available conventional cross braces for buildings. This prototype HC-SCED satisfied testing protocols for buckling-restrained braces and exhibited full self-centering behavior during cycles up to 1.5% drift. To characterize the hysteretic response of the brace in detail, a new analytical approach is developed. This new approach is necessary because simplified stiffness estimates do not provide good predictions of the low-amplitude displacement response and initia...

Design and Testing of an Enhanced-Elongation Telescoping Self-Centering Energy-Dissipative Brace

AbstractThe self-centering energy-dissipative (SCED) brace is a new steel bracing member that provides both damping and recentering capability to a structure, while reducing or eliminating residual building deformations after major seismic events. Previous SCED brace designs exhibited full self-centering capability over frame lateral deformations ranging from 1.5 to 2.0% of a typical building story height owing to the elongation capacity of the tendons comprising the system. To overcome this limitation, a new enhanced-elongation telescoping SCED (T-SCED) brace has been developed that allows for self-centering response over two times the range achieved with the original SCED bracing system. A prototype design of this proposed system was fabricated and tested quasi-statically and dynamically in a full-scale vertical steel frame. It exhibited full self-centering behavior in a single story frame that was laterally deformed to 4% of its story height. This new T-SCED brace also satisfied standard testing protoc...

Mechanisms to limit higher mode effects in a controlled rocking steel frame. 2: Large‐amplitude shake table testing

SUMMARYThis paper presents the results of 56 large‐amplitude shake table tests of a 30% scale eight‐storey controlled rocking steel frame. No significant damage or residual deformations were observed after any of the tests. The frame had four possible configurations on the basis of combinations of two higher mode mitigation mechanisms. The first mitigation mechanism was formed by allowing the upper section of the frame to rock, so as to better control the mid‐height overturning moment. The second mitigation mechanism was formed by replacing the conventional first‐storey brace with a self‐centering energy dissipative (SCED) brace, so as to better control the base shear. The mechanisms had little effect during records where higher mode effects were not apparent, but they substantially reduced the shear and overturning moment envelopes, as well as the peak floor accelerations, during more demanding records. The reduction in storey shears led to similarly reduced brace force demands. Although the peak force demands in the columns were not reduced by as much as the frame overturning moments, using an upper rocking joint allowed the column demands to be estimated without the need to assume a lateral force distribution. The tests demonstrated that multiple force‐limiting mechanisms can be used to provide better control of peak seismic forces without excessive increases in drift demands, thus enabling more reliable capacity design. These results are expected to be widely applicable to structures where the peak seismic forces are significantly influenced by higher mode effects. Copyright © 2012 John Wiley & Sons, Ltd.

비정형 셀프센터링 가새골조의 비탄성 지진응답

최근 새로운 지진하중 저항시스템으로 셀프센터링(SCED) 가새 시스템이 개발되었다. 진보된 가새 시스템인 비좌굴 가새(BRB) 시스템과는 달리 큰 지진이 발생한 후 구조물의 잔류 변형을 줄이거나 없앨 수 있는 셀프센터링 능력은 SCED 가새 시스템의 장점이다. 본 논문에서는 SCED 가새와 BRB 가새 시스템의 거동에 비틀림의 영향을 조사하기 위하여 세 가지 다른 편심을 가진 3차원 구조물의 응답을 비선형 동적해석을 수행하여 비교하였다. 해석결과에 따르면 층간변위의 높이방향의 변화는 비정형성에 관계없이 SCED 가새골조의 응답이 BRB 가새골조보다 일정하였으며, 잔류 층간변위와 잔류 회전 응답은 비정형성이 증가함에 따라 감소하였다. 중층 구조물에서 SCED 가새골조의 변형집중계수(DCF)는 BRB 가새골조보다 작은 것으로 나타났다. 이것은 SCED 가새골조가 건물 높이에 따라 보다 일정하게 변형함을 의미한다. DCF의 크기에 대한 비틀림 비정형의 효과는 작았다. A self-centering energy-dissipative(SCED) bracing system has recently been developed as a new seismic force resistant bracing system. The advantage of the SCED brace system is that, unlike other comparable advanced bracing systems that dissipate energy such as the buckling restrained brace(BRB) system, it has a self-centering capability that reduces or eliminates residual building deformations after major seismic events. In order to investigate the effects of torsion on the SCED brace and BRB systems, nonlinear time history analyses were used to compare the responses of 3D model structures with three different amounts of frame eccentricity. The results of the analysis showed that the interstory drifts of SCED braced frames are more uniform than those of BRB frames, without regard to irregularity. The residual drift and residual rotation responses tended to decrease as irregularity increased. For medium-rise structures, the drift concentration factors(DCFs) for SCED systems were lower than those for BRB frames. This means that SCED-braced frames deform in a more uniform manner with respect to building height. The effect of the torsional irregularity on the magnitude of the DCFs was small.

Seismic Response of Multistory Buildings with Self-Centering Energy Dissipative Steel Braces

This paper examines the seismic response of 2-, 4-, 8-, 12-, and 16-story steel framed buildings with self-centering energy dissipative (SCED) bracing members. The structures are assumed to be located in Los Angeles, California. Identical buildings equipped with buckling restrained braces (BRB) are also studied for comparison purposes. Incremental static analysis and nonlinear dynamic analysis under ground motion ensembles corresponding to three hazard levels were performed. The SCED frames generally experienced smaller peak story drifts, less damage concentration over the building height, and smaller residual lateral deformations compared to the BRB system. Higher floor acceleration peaks were observed in the SCED frames due to the sharper transitions between elastic and inelastic response assumed in the analysis. The study also indicated that higher design seismic loads may be needed for low-rise SCED and BRB frames in order to improve their collapse prevention performance.

Self-Centering Energy Dissipative Bracing System for the Seismic Resistance of Structures: Development and Validation

Buildings designed according to modern seismic codes are expected to develop a controlled ductile inelastic response during major earthquakes, implying extensive structural damage after a design level earthquake, along with possibly substantial residual deformations. To address this drawback of traditional yielding systems, a new bracing system that can undergo large axial deformations without structural damage while providing stable energy dissipation capacity and a restoring force has recently been developed. The proposed bracing member exhibits a repeatable flag-shaped hysteretic response with full recentering capabilities, therefore eliminating residual deformations. The mechanics of this new system are first explained, the equations governing its design and response are outlined, and one embodiment of the system, which combines a friction dissipative mechanism and Aramid tensioning elements, is further studied. Results from component tests, full-scale (reduced length) quasi-static axial tests, and quasi-static and dynamic seismic tests on a full-scale frame system are presented. Experimental results confirm the expected self-centering behavior of the self-centering energy dissipative (SCED) bracing system within the target design drift. Results also confirm the validity of the design and behavior equations that were developed. It is concluded that the proposed SCED concept can represent a viable alternative to current braced frame systems because of its attractive self-centering property and because the simplicity of the system allows it to be scaled to any desired strength level.