Self-centering Energy Dissipation Research Articles

A Novel Self-centering Braced Double-column Rocking Bent for Seismic Resilience

ABSTRACT A novel self-centering braced double-column rocking bent (SBRB) consisting of a double-column rocking bent and traditional or self-centering energy dissipation braces is developed analytically and numerically to enhance the seismic resilience. The analytical model of the SBRB is established, and numerical models of the SBRB are built to evaluate its seismic performance. Numerical results indicate that the SBRB is featured by prominent seismic performance including high lateral stiffness and strength, stable energy dissipation ability and good self-centering capability. The parameters of braces, axial force ratio, tendon prestress, and confinement play significant roles in the seismic responses of SBRB.

Seismic design and performance of a steel frame-shear plate shear wall with self-centering energy dissipation braces structure

The steel plate shear wall with self-centering energy dissipation braces (SPSW-SCEDB) is a new seismic lateral resistant component. This paper outlines the performance requirements of the steel frame-shear plate shear wall with self-centering energy dissipation braces (SF-SCSPSW) structure and presents a direct displacement-based seismic design method for the structure. A combined strip model of the SPSW-SCEDB that considers the effect of the bolted connection on the wall plate is established. The comparison of the simulated and experimental results shows that the model can accurately predict the strength and hysteretic behavior under cyclic loading. The 8- and 15-story prototype buildings were designed using the presented method. The results of nonlinear dynamic analysis showed that larger inter-story deformations occurred on the lower floors, and the inter-story ratios gradually decreased with an increase in the number of floors. The maximum inter-story drift ratio (1.73%) of the 8-story structure under mega earthquakes and the maximum residual drift ratio (0.018%) of the 15-story structure under large earthquakes were less than the limit values (2% and 0.5%). Local yielding occurred between the brace connection and the column under mega earthquakes, but the columns remained in an elastic state. The seismic responses of the SPSW-SCEDBs in the two structures met the performance requirements of being elastic and suffering light and moderate and serious damage under frequent, medium, large, and mega earthquakes, respectively. The effectiveness of the proposed design method was verified.

Dual-Objective Control of Maximum and Residual Drift Ratios of Super-Tall Buildings Based on Self-Centering Energy Dissipation Outriggers

It is critical to ensure the seismic resilience of super-tall buildings using high performance materials. The seismic resilience of these buildings can be enhanced by simultaneously controlling the maximum and residual inter-story drift ratios. To realize such dual-objective control, a prevailing trend is to adopt self-centering energy dissipation outriggers. In this study, taking a real engineering practice as the prototype building, super-tall building study cases with energy dissipation outriggers, and with self-centering energy dissipation outriggers are designed. Based on nonlinear time-history analysis, the seismic performances of these study cases are evaluated and compared with emphasis on the maximum, and residual inter-story drift ratios. The dual-objective control effect of self-centering energy dissipation outriggers and energy dissipation outriggers are analyzed and compared. The results indicate that self-centering energy dissipation outriggers are more effective than energy dissipation outriggers for achieving the dual-objective control of the maximum and residual drift ratios of super-tall buildings.

Assembled self-centering energy dissipation braces and a force method-based model

A pre-pressed spring self-centering energy dissipation (PS-SCED) bracing system has significant energy dissipation and re-centering abilities, although many welds result in a lengthy manufacturing process and reduce the machining accuracy to an unacceptable level. An assembled pre-pressed spring self-centering energy dissipation (A-PS-SCED) bracing system that uses disc spring groups to provide a re-centering ability and a friction device to dissipate energy, is presented in this paper to simplify production and maintenance. A novel force method-based (FMB) hysteretic analysis model governing the distribution of the internal force is proposed and verified by a numerical model of the A-PS-SCED brace and tests of the PS-SCED brace specimen. The simulation results indicate that the A-PS-SCED brace exhibits sufficient and steady energy dissipation and re-centering capacities. The FMB model agrees well with the numerical model with a maximum bearing force difference of 2% and has steady hysteretic responses under random excitations. The FMB model is used to determine the mechanisms of the stiffness and contact status change during a typical loading process. Additionally, the FMB model accurately predicts the cyclic loading test results of an existing PS-SCED brace specimen, and the average bearing force differences are 6% and 2% at friction force of 200 kN and 300 kN, respectively.

Seismic performance of modular steel buildings (MSBs) equipped with resilient slip friction joints (RSFJs)

Modular construction is becoming a prevalent technique combining off-site construction and on-site assembly to provide fast, reliable and high-quality permanent buildings. The modular method is a good alternative to traditional on-site construction when the layout consists of repetitive units such as hotels and multifamily dwellings, and when the construction schedule is tight. The dynamic performance of Modular Steel Buildings (MSBs) has not yet been fully studied, and a limited number of investigations on the nonlinear dynamic behavior of MSBs showed that they are susceptible to damage during strong ground motions. This paper considers the use of a self-centering energy dissipation device, called Resilient Slip Friction Joint (RSFJ), in MSBs to avoid seismic damage, enable immediate occupancy, and reduce the repair costs after a severe earthquake event. Two different configurations of RSFJs (namely tension-compression and tension-only configurations) were introduced to Seismic Force Resisting Systems (SFRSs) of 6- and 12-story MSBs. This study presents a step-by-step design procedure by following the capacity design for RSFJs in accordance to National Building Code of Canada (NBCC). The dynamic performances of both configurations were evaluated by performing bi-directional Nonlinear Time History Analysis (NLTHA). In addition to global response of MSBs, component level maximum demands of RSFJs were assessed to shed a light on the overall performance of MSBs under three different hazard levels. It was shown that low- and mid-rise MSBs can efficiently be equipped with RSFJ to mitigate earthquake-induced vibrations and minimize the damage to the structural members.

Modeling of Disc Spring Self-Centering Energy Dissipation Braces from Inactive State to Design Limit State

AbstractThis paper focuses on modeling the hysteretic behavior of disc spring self-centering energy dissipation braces (DS-SCEDBs) from the inactive state to the design limit state, and proposes tw...

Study on prediction method of initial stiffness of self-centering energy dissipation braces

The self-centering energy dissipation (SCED) brace is an innovative structural component of seismic-resistant systems that provides a flag-shaped response with good energy dissipation and self-centering capacity. The initial stiffness of the SCED brace is a crucial parameter for brace design and a braced frame system. The current use of SCED braces is limited by the significant discrepancy between the actual and theoretically predicted initial stiffnesses. In this paper, the sources resulting in the inaccurate prediction are identified as the accuracy of the theoretical governing equations and the practical fabrication tolerances of the braces. The accuracies of the governing equations with different levels of complexity are analyzed and compared based on a typical SCED brace. To investigate the reduction effect of fabrication tolerances on the effective axial stiffness, a large number of numerical simulations are conducted on an axially loaded tube member with different tolerance characteristics, including the fundamental length tolerance, contact surface nonuniformity, and load level. According to the trends of the effective axial stiffness, a valid stiffness reduction factor is defined. It can provide good estimates of the reduced axial stiffness under different tolerance parameters. Additionally, the stiffness reduction factor is incorporated into a refined governing equation of an experimental SCED brace to verify the accuracy of the predicted initial stiffness when the effect of the fabrication tolerances is considered. It is shown that the modified governing equation estimates well the actual initial stiffness. Moreover, this prediction equation can be easily extended to other types of SCED braces once the tolerance parameters have been determined.

COMPARATIVE SEISMIC PERFORMANCE ASSESSMENT OF UHPC JACKETING AND SCED BRACING TECHNIQUES

Observed damage to existing pre-seismic code buildings in previous earthquakes has raised interest among the engineering community for improving the performance of these structures using different seismic retrofit measures. This paper throws light on contemporary techniques for the seismic retrofit of RC buildings, namely ultra-high-performance concrete (UHPC) jacketing and self-centering energy dissipative (SCED) braces. Detailed fiber-based numerical modeling of a benchmark structure is undertaken to evaluate the effectiveness of the selected retrofit measures. The case study structure is a two-story pre-seismic code residential building designed for gravity and wind loads, exhibiting poor seismic performance. Along with the two retrofit strategies investigated, several parameters are also considered. Inelastic static pushover and incremental dynamic analyses are conducted to select the retrofit measures and assess their effects on seismic performance. Using a collection of far-field earthquake records and a set of performance criteria, fragility functions are constructed to assess the vulnerability of the benchmark structure with and without the retrofit solutions. The study shows that the adopted index that links cost to the seismic performance obtained from the fragility functions can provide a rational ranking of the selected retrofit approaches relative to the existing building and support selecting the most effective and economical alternative.

Quantification of higher mode effects of steel frame and control method using dual self-centering variable friction damper brace

Self-centering energy dissipation braced frames (SCEDFs) have been developed to satisfy the requirements of resilience. However, low post-yield stiffness in such systems often leads to a higher mode effect, resulting in a significant deformation concentration that may exceed the design objectives. A novel dual self-centering variable friction damper (DSC-VFD) brace with high post-yield stiffness and enhanced energy dissipation capability was proposed. Its hysteretic behavior, characterized by a loading stiffness that is larger than the unloading stiffness, was developed by incorporating the C++ language into the OpenSees platform. To evaluate the higher mode effect in different types of frames, a quantification measure based on the higher mode results of the steel frames, considering the seismic responses around the peak value, was therefore established. Then, the seismic responses of the DSC-VFD frames (DSC-VFDFs) using the proposed uniaxial material were calculated and compared with those of the traditional moment resisting frame (MRF) and SCEDF with the same design process. Finally, the four parameters, including the first stiffness modification coefficient α1, second stiffness ratio α2, strength ratio β, and fourth stiffness ratio α4, were considered to evaluate their influences on nonlinear seismic responses and the higher mode effect of the DSC-VFDF by the above-mentioned quantification measures. The results indicate that the influence of higher modes should not be ignored in the design of self-centering braced frames, and the higher mode quantification results of base shear are more sensitive than those of effective displacement. The DSC-VFD brace can more effectively improve the seismic responses and control the higher mode effect than the traditional SCEDF.

Parametric analysis and failure mode of steel plate shear wall with self-centering braces

A steel plate shear wall with self-centering energy dissipation braces (SPSW-SCEDB) is developed and tested. The SPSW-SCEDB is prefabricated and replaceable. The effects of various design parameters on the hysteretic behavior of the SPSW-SCEDB without the effects of the frame are investigated. The experimental results show that the residual deformations of the wall plate are eliminated by the restoring force of braces, and the SPSW-SCEDB exhibits high initial stiffness, stable post-yield stiffness, and good energy dissipation capability. The SPSW-SCEDB with a thicker and wider wall plate has better energy dissipation capacity and higher post-yield stiffness. The wider wall plate reduces the lateral force contribution of the braces to the SPSW-SCEDB, resulting in the weakening of the overall strength of the SPSW-SCEDB. The SPSW-SCEDB has a good self-centering capability when the ratio of the horizontal restoring force of the braces to the compressive force of the wall plate is larger than 1.3. Compared with the size of the wall plate, the effect of the friction force on the SPSW-SCEDB is relatively small. The destructive test results demonstrate that the SPSW-SCEDB maintains stable lateral force resistance, energy dissipation and self-centering capabilities, even though the lateral drift is 4% and many wrinkles that cannot be smoothed out occur on the wall plate. In addition, the test results highlight the assembly capability and the replaceability of the components of the SPSW-SCEDB.

Development and validation of a versatile hysteretic model for pre-compressed self-centering buckling-restrained brace

Due to the preferable self-centering and energy dissipation capabilities, self-centering energy dissipation (SCED) braces have become an emerging structural component in earthquake engineering. In this paper, an innovative self-centering steel buckling-restrained brace (SC-SBRB) consisting of two independent and complementary systems, i.e., a buckling-restrained energy-dissipation system and a pre-compressed disc spring self-centering system, is proposed. The working mechanism and mechanics of the SC-SBRB are investigated under one cycle of cyclic loading. A versatile self-centering hysteretic model (SCHM) is developed based on the working principle of the SC-SBRB to accurately characterize the energy dissipation and self-centering properties of the SC-SBRB under repeated cyclic loading. The SCHM is a path-dependent model that allows for straightforward parameter interpretation of the mechanics of the SC-SBRB. Numerical simulations are conducted on four SC-SBRBs with different self-centering ratios to validate the prediction results obtained from the SCHM. A good agreement between the simulation results and the prediction results confirm the validity of the proposed SCHM. Simulation results also demonstrate that the SC-SBRB can provide a stable and repeatable flag-shaped hysteretic response, as well as substantial energy dissipation and self-centering ability. Additionally, the SCHM is reasonably extended to other SCED braces with similar hysteretic rules. Further validation of the SCHM is performed by comparing the experimental results of the SCED braces with the SCHM results. It is concluded that the proposed SCHM has excellent applicability and can describe the responses of other SCED braces.

Variable-friction self-centering energy-dissipation braces (VF-SCEDBs) with NiTi SMA cables for seismic resilience

This study introduces a Variable-Friction Self-Centering Energy-Dissipation Brace (VF-SCEDB) incorporating pre-tensioned superelastic NiTi shape memory alloy (SMA) cables and novel Variable Friction Devices (VFDs). The motivation behind the proposed member is to promote reliable energy dissipation without compromising the self-centering capability. In addition, the strength and the loading/unloading plateau stiffness of the brace can be adjusted separately by an appropriate combination of the NiTi SMA cables and the VFDs. The concept, configuration, and fundamental working principle of the VFD and VF-SCEDB are first presented. An experimental study on a proof-of-concept VF-SCEDB specimen is then conducted to understand its fundamental cyclic behavior. The results confirm that the proposed VF-SCEDB has the potential for exhibiting both excellent energy-dissipation and self-centering capabilities. Analytical models for predicting the hysteretic response of the VFD and the brace are also developed, and the prediction agrees well with the experimental results. Following the experimental program, a system-level analysis considering a series of 3-story concentrically braced steel frames employing different self-centering braces including the new VF-SCEDBs, is carried out. The results show that the frames can well control the residual deformation, but compared with other types of self-centering braces, the VF-SCEDB can more effectively reduce the peak deformation of the structures.

Lateral Seismic Response and Self-Centering Performance of a Long-Span Railway Continuous Beam-Arch Bridge

Based on the seismic isolation design concept of functional separation, a seismic isolation system with bearings and braces combination for railway bridge was proposed. The sliding bearings afford the vertical loads, and the self-centering energy dissipation brace (SCED) and buckling restrained brace (BRB) control the horizontal displacement of the beam, so the functional separation was achieved under the combined action. Taking a long-span railway continuous beam-arch bridge as an example, the corresponding analysis model was established to study lateral seismic response and the girder’s displacement pattern of the continuous beam-arch bridge under the earthquake excitations. The seismic response of bridges with different seismic isolation schemes was studied. The result showed that the presence of arch rib in a continuous beam-arch bridge amplifies the transverse displacement response of the girder compared with that in a continuous beam bridge of equal mass. The seismic isolation system with sliding bearings and energy dissipation braces can control the relative displacement between the pier and beam greatly, and the SCED can reduce or even eliminate the residual displacement between pier and beam. Furthermore, under the strong ground motions, the combined use of SCED and BRB can achieve the seismic isolation to the maximum extent when the self-centering force ratio ζ, the ratio of self-centering force to superstructure weight, is 0.074.

Performance of prestressed T-type self-centering energy-dissipation brace

In this study, high-strength cables were used to create a prestressed T-type self-centering energy-dissipation brace (PTSEB), which can be used for multi-story and high-rise frame structures. The brace can dissipate energy through friction, provide lateral stiffness through prestressed cables, and automatically return to its original position under the action of cable tension after the external load disappears. Lever action is used to significantly amplify the deformation ability of the brace. Moreover, the energy-dissipation ability of the brace is considerably better than that of a traditional self-centering brace. A test and a finite element analysis were performed on the PTSEB, and the results indicated that the brace had a strong energy-dissipation ability, as well as a high deformation capacity and self-centering capacity. ABAQUS was used to analyze and compare the performance of braces with different sizes. The results showed that in a certain range, as the shell height increased, the seismic performance of the PTSEB was improved significantly; however, an increase in the shell width did not improve the seismic performance of the PTSEB significantly. Reasonable sizes for the PTSEB were proposed based on a finite element parameter analysis to ensure that the brace would have improved energy-dissipation and self-centering abilities. A restoring force model of the PTSEB was constructed, and the key points of the restoring force model were obtained using some proposed formulas. The design parameters of the PTSEB could be determined based on these formulas.

SEISMIC PERFORMANCE STUDY OF REINFORCED CONCRETE FRAME WITH SELF-CENTERING BRACES

A mechanical model is proposed accurately describe the hysteretic behavior of pre-pressed spring self-centering energy dissipation (PS-SCED) brace. The state variables are introduced to distinguish different stages of PS-SCED brace and then its mechanical responses are determined. The secondary development of the mechanical model is carried out based on ABAQUS. The simulation results of the developed PS-SCED brace element are compared with the test results of the brace, and the seismic performances of a 3-story reinforced concrete frame structure with PS-SCED braces are analyzed. The results indicate that the hysteretic curves obtained from the brace element simulation agree well with the test results, and the brace element is accurate enough to describe the mechanical performance of the brace under dynamic loads. The seismic energy dissipates sufficiently and the plastic deformation of the structure is controlled effectively by PS-SCED braces subjected to strong earthquake. Additionally, the residual deformations of frame structure with PS-SCED braces are reduced by 72.1%~92.1% compared with the original frame structure. The PS-SCED brace exhibits full hysteretic performances with good energy dissipation capacity and self-centering behavior, which significantly improves the seismic performances of reinforced concrete frame structures.

Theoretical analysis and experimental investigation of hysteretic performance of self-centering variable friction damper braces

Traditional buildings, even with normal self-centering energy dissipation (SCED) braces, might suffer from large deformations and high mode effects under an extremely strong earthquake, leading to a concentration of inter-story drift in upper floors. To satisfy the requirements of resilience, larger post-yield stiffness and higher energy dissipation, a novel brace with pretensioned basalt fiber-reinforced polymer (BFRP) tendons and variable friction dampers (VFDs) was developed, and this brace was termed the self-centering variable friction damper (SC-VFD) brace. The variable stiffness and sliding force of the VFD system were theoretically analyzed. This was followed by quasi-static experiments on two VFD and two SC-VFD braces with different parameters. The theoretical analysis and experimental results revealed the same tendencies, demonstrating the reliability and feasibility of SC-VFD braces. The hysteretic curve of the SC-VFD braces exhibited stable and normal flag-shape behavior before the second activation, while the hysteresis curve indicated a variable flag-shape behavior with second activation, variable friction force, and larger post-yield stiffness when the brace slid at slope section. Compared with the VFD brace, the SC-VFD brace had the same energy dissipation ability but less residual displacement and lower equivalent viscous damping ratio. More combinations of disc springs in series resulted in smaller axial forces and lowers post-yielding stiffness, thereby decreasing the energy dissipation capability.

Modified flag-shaped model for self-centering system and its equivalent linearization and structural optimization for stochastic excitation

The analysis and design of self-centering structural systems have attracted substantial attention from researchers for the seismic design of structures. The flag-shaped hysteretic model has been widely used in the design and structural response analysis of self-centering devices. In this research, a modified flag-shaped (MFS) model is proposed to describe the hysteretic characteristics of self-centering energy dissipation (SCED) braces, which are commonly used in self-centering structures. The MFS model comprises three parts: a linear elastic part, a bilinear elastic part, and an elasto-plastic part with a slip zone. The effectiveness of the MFS model is validated based on the results of the quasi-static and hybrid simulation tests available in the literature. Equivalent linearization is carried out on the MFS model for stochastic earthquakes, and closed-form solutions are obtained for the linearized parameters. A one-degree-of-freedom braced system is used to verify the equivalent linearization of the MFS model in comparison with Monte Carlo simulation results. Finally, an SCED-braced five-story frame structure is optimized by minimizing the maximum ductility demand for the SCED braces using the equivalent linearization of the MFS model. The optimized design by the MFS model is observed to exhibit uniform ductility demands along the height. This can be considered as the ideal optimal solution. The responses of the multi-degree-of-freedom structure also demonstrate the effectiveness of the proposed MFS model and its equivalent linearization.

Numerical Studies on the Seismic Performances of RC Two-Column Bent Bridges with Self-Centering Energy Dissipation Braces

AbstractBridges may suffer large residual displacements after strong earthquakes. These large residual displacements may increase the reinforcement cost and even lead to the collapse of the bridge....

Seismic design and behavior of self-centering energy dissipation braced steel frame

A self-centering energy dissipation (SCED) brace that utilized disc springs to provide self-centering capability and friction pads to dissipate energy was developed. Based on Bouc–Wen model and the working principle of SCED brace, a restoring force model is developed to describe the mechanical behavior of the brace. Comparisons between the cyclic loading tests and predicted results are conducted. Results show that the restoring force model can accurately predict both the energy dissipation and self-centering capabilities of SCED brace. A performance-based design method for frame structures with SCED braces is developed corresponding to the four-level seismic fortification objective, that is, no damage under minor and moderate earthquakes, replaceable or repairable under major earthquakes, and no collapse under mega earthquakes. A typical SCED braced steel frame was designed, and nonlinear time-history analysis was conducted to analyze the seismic performance and resilience of the braced frame. It is demonstrated that the SCED braced frame has superior resilience with small residual deformation under the moderate and major earthquakes due to the self-centering capability provided by the SCED brace. The collapse of the structure is also effectively avoided due to the stable energy dissipation and lateral stiffness provided by the SCED brace.

Development and experimental validation of a steel plate shear wall with self-centering energy dissipation braces

Abstract A new type of steel plate shear wall with self-centering energy dissipation braces (SPSW-SCEDB) was developed. Validation tests of the wall plate and the pre-pressed spring self-centering energy dissipation (PS-SCED) braces were conducted and a single-bay, single-story, 1:3-scale SPSW-SCEDB specimen was designed, fabricated, and tested under cyclic loadings. The results demonstrated that the SPSW-SCEDB exhibited a stable flag-shaped hysteretic response with high initial stiffness, appreciable ductility, and excellent self-centering and energy dissipation capabilities due to the synergistic effects of the wall plate and the PS-SCED braces. The proposed theoretical equations of the compressive force of the wall plate, the ultimate lateral load capacity, and the remaining restoring force of the SPSW-SCEDB were verified. The PS-SCED braces reduced the stiffness degradation of the wall plate and improved the lateral force resistance and the stability of the SPSW-SCEDB system. The wall plate provided more energy dissipation than the PS-SCED braces. The remaining restoring force of the PS-SCED braces should be as small as possible to maximize the energy dissipation of the PS-SCED braces while ensuring that it overcomes the compressive force of the wall plate.