Disc Springs Research Articles

Tests of double-stage SMA slip friction damper

This study presents a new type of self-centering damper, termed the double-stage shape memory alloy (SMA) slip friction damper, which mainly comprises of the grooved center and cap plates, stacked disc springs, and SMA bars. The double-stage behavior is realized by the serial connection of the stacked disc springs and the SMA bars, with the purposes of adjusting stiffness and damping for varied seismic hazard levels. The configuration and working mechanism are firstly presented, along with the analytical equations governing the force-displacement relationship. As the key components, the SMA bar, the friction mechanism, and the disc springs were tested separately. And then, the proof-of-concept tests of the reduced-scale damper were conducted. From the testing results, the damper exhibited a symmetric double-stage self-centering damping behavior. Some hysteretic parameters of interest were then quantified. Three-dimensional numerical models were established and were further used for parametric analysis. Both the analytical method and numerical model agree well with the experimental data.

Development and experimental verification for the coaxially formed self-centering buckling-restrained brace

The development for a new construction of self-centering buckling restrained braces (SCBRBs) was made by letting either an assembled steel BRB part or an integrally formed composite BRB part coaxially pass through an outer self-centering (SC) part with steel disc springs, and tests on the SCBRBs were conducted to validate the seismic performance and the configurations, mainly including the pattern of BRBs and that of pull rods in SC parts to keep the initial stiffness under two loading sides as close as possible. Tests show that, contrary to BRBs, the SCBRBs presenting flag-shape hysteretic curves have a significant reduction of residual drifts. Variation laws show that the residual drifts of the SCBRBs at horizontal drift levels of 2% are almost within 0.5% if self-centering ratios exceed 0.66. Besides, when the ratios under drift levels of 2% are close to 1.0, the residual drifts are approximately within the start displacements of the specimen with a SC part only. For the four SCBRBs adopting the same SC part within the drifts from 2% to 3.5%, approximately 56–73% axial strength and about 13–21% energy dissipation are from the SC part. Both types of BRB parts work stably. Except for tension fracture of plate braces, other members remain intact in SCBRBs, facilitating replacement of plate brace and reuse of intact SC part. Moreover, the interaction between two tubes in the SC part provides additional energy dissipation and horizontal resistance. Both tests and theoretical predictions reveal that the adjustment of pull rods in the SC part can adjust its initial stiffness in tension, and the pattern of employing two groups of six rods applying tension forces by two stages is preferred to decrease the difference between the initial stiffness in tension and that in compression.

Seismic performance of a new precast concrete frame joint with a built-in disc spring

A new, precast concrete frame beam-column connection is designed in this research. The connection adopts the assembly mode of the precast column and seam area jointly to maintain the integrity of the joint area and increase the assembly efficiency. Based on the conventional grouting sleeve connection, a disc spring device is constructed on the beam end to improve the ductility of the joint. Ten connecting specimens were tested under low cyclic loads, including two monolithic connections, four ordinary precast connections, and four new precast connections. The test parameters included the joint type and axial pressure ratio, and the difference in the seismic performance was determined by evaluating the failure mode, hysteresis characteristics, stiffness degradation, energy dissipation, and shear deformation of the joint area. Compared to monolithic connections, conventional precast connections display similar hysteresis characteristics. Although their ductility is slightly lower, their bearing capacity is higher. Compared with the previous two connections, the new connection with the built-in disc spring device has superior seismic performance. The axial pressure ratio is a significant aspect in determining the failure mode of the precast connection, and the specimen exhibits less shear damage at a larger axial pressure ratio.

Exact shell solutions for conical springs. II. Radial cylindric curb

Actual manuscript examines the disk springs with constant material thickness. The kinematic hypothesis is used for modelling. Motivating feature is the possibility to calculate the disk springs of with free gliding edges and the edges with the constrained radial movement. Variation formulations are used for derivation. The developed equations are suitable for springs made of isotropic materials, as spring steel and light metal alloys. The advantage of the methodology is the derivation of closed form solutions with restrictions on radial movement of inner and outer edges. The developed formulas are recommended for industrial calculations of free and restricted Belleville washers.

Seismic performance of novel RC shear wall with replaceable self-centering energy-dissipation components

A novel reinforced concrete (RC) shear wall with replaceable self-centering energy-dissipation components (RSECs) symmetrically installed at the bottom corner of the wall panel is proposed in this study. The RSEC consists of self-centering part and energy-dissipation part, which not only dissipates most of the seismic energy but also provides the restoring force for the wall to return initial position after yielding of the component. The RC wall with RSECs is designed to reduce the damage to the main part of structural wall and the residual deformation of the structure. The structural details and design considerations of the RC shear wall with RSECs are introduced. To verify the seismic performance of RC shear walls with the new replaceable corner components, the numerical mode is developed for the new type of shear wall and validated by experimental results. Parametric studies of RC wall with RSECs are then conducted to investigate the effects of the stiffness and pre-pressure force of disc spring group, the bearing capacity ratio of RSEC, and the thickness of embedded steel plate. The results indicate that the RC wall with RSECs has moderate bearing capacity and lateral stiffness, good energy-dissipation capacity, excellent self-centering capability and the characteristics of low damage. The function of the RC wall with RSECs can be quickly restored by replacing RSECs after the strong earthquake.

Study on the dynamics characteristics and screening performance of the disc spring vibration screen

The disc spring system is applied to the vibration screen, which can effectively reduce the exciting force and improve screening capacity. In this work, the dynamic characteristics and screening performance of the disc spring vibration screen are studied. The modal simulation and experimental results show that the model vibration direction at first natural frequency is consistent with the working direction of the vibration screen. Moreover, the trajectory analysis and discrete element screening simulation prove that the disc spring vibration screen has better screening performance than the coil spring vibration screen. Eventually, by comparing required exciting force under the same amplitude, fatigue life of the spindle bearing, and energy consumption between the coil spring and disc spring vibration screen, it can be found that disc spring vibration screen has better mechanical properties, higher reliability, and lower energy consumption.

Seismic design and performance study of self‐centering moment‐resisting frames with sliding rocking beams and preloaded disc springs

AbstractThis paper focuses on the seismic analysis and performance assessment of the self‐centering moment‐resisting frames with sliding rocking beams (SCMRF‐SRB) through a nonlinear numerical simulation study. In the SCMRF‐SRB systems, the beam is comprised of three segments with the rocking beam placed in the middle segment. The beam growth (expansion) problem due to the gap‐opening in the rocking joint is counteracted by the sliding movement of the rocking beam inside the beam brackets. The restoring force of such SCMRF‐SRBs is generated by two sets of preloaded disc springs mounted on each side of the web of the beam and the energy dissipation is provided by replaceable hysteretic dampers (RHD). The relative movement of the rocking beam inside the brackets generates a friction force that contributes to the energy dissipation capacity and strength of the system based on prior experimental observations. Load vs. displacement relationships of an SCMRF‐SRB modular structure were formulated and verified with nonlinear finite element analysis results. A three‐story building located in downtown Seattle was designed and its seismic performance was studied through nonlinear static and dynamic analyses. According to the results of the nonlinear dynamic analyses, the prototype structure met the expected performance criteria in terms of inter‐story drift ratio (IDR), re‐centering behavior, and responses of the frame member at design basis earthquake (DBE). In different parametric studies, the effect of the length and location of the rocking beam on the seismic performance of the prototype structure was investigated. Moreover, the effects of the energy dissipation capacity and post‐yielding stiffness on the structural responses of the prototype buildings were studied. It was also shown that an SCMRF‐SRB structure with a large energy dissipation ratio of up to 90% can be utilized without adversely affecting the self‐centering performance of the system.

Performance evaluation of a nonlinear energy sink with quasi-zero stiffness property for vertical vibration control

The advantages of nonlinear energy sink (NES) have been proven to effectively reduce vibrations in the horizontal direction. The application of NES devices to suppress vertical vibration is still at an early stage. In this study, a new type of NES that works in the vertical direction, where disc springs and viscous dampers are utilized to connect an additional mass with the primary structure, is proposed. The NES device can provide a cubic restoring force characterized by the quasi-zero stiffness (QZS) property. Initially, the equations of motion of the primary structure supplemented with NES were established. Then, the force and displacement transmissibility curves were obtained via the steady-state analysis for the NES-controlled, tuned mass damper (TMD)-controlled, and uncontrolled systems. Analytical results revealed that the targeted energy transfer (TET) property of the NES can absorb the kinetic energy within the operating range without amplifying the response in the lower and higher frequency ranges. In contrast, TMD is more efficient within the operating range. Finally, a practical large-span floor structure was adopted to compare the operating performance of NES and TMD. External vibration includes track-induced vibration, vertical earthquake, and human-induced vibration. Numerical results show that the NES performs better than traditional TMD in controlling the vertical response. Moreover, the addition of a NES device will not potentially amplify the response on some occasions.

Development and application of a deformation-amplified self-centering energy dissipation device

Suitable seismic response reduction devices can substantially improve the seismic performance of engineering structures. However, devices with wide applicability and multi-function are lacking. A novel deformation-amplified self-centering energy dissipation (DA-SCED) device suitable for reducing the seismic response of different engineering structures is proposed in this paper. Self-centering of the device is achieved by a pre-pressed combined steel disc spring. The elastic–plastic hysteretic deformation of the lead rod is used to dissipate the earthquake energy. The shear deformation of the lead rods is amplified because the arc lengths of the lead rod embedded points and the connecting rod hinged point are proportional to the distances of both to the disc center when the steel disc rotates; the former distance is designed to be larger than the latter. Pseudo-static tests were conducted under reciprocating tension and compression of a full-scale model to determine the mechanical properties and seismic energy dissipation capacity of the device. A numerical simulation was performed to analyze the factors influencing mechanical performance. In addition, a restoring force model of the device was established and verified, and the seismic energy dissipation capacity was studied using a prefabricated segment pier. The results indicate that the DA-SCED device has good self-centering and energy dissipation abilities. Its hysteresis curves show flag-shaped characteristics, and the maximum residual displacement after unloading is only 0.97 mm. The self-centering capacity can be improved by increasing the disc spring pre-pressure, and the energy dissipation capacity can be enhanced by increasing the deformation amplification ratio and the diameter and number of the lead rods. The proposed restoring force model can describe the mechanical properties of the device accurately. Furthermore, the DA-SCED devices used in the prefabricated segment pier have satisfactory energy dissipation and self-centering performance under seismic action. After installing the device at the bottom of the pier, the transverse and longitudinal opening deformations between the cushion cap and bottom segment are decreased by 41.52 % and 46.75 %, the displacements of the pier top are reduced by 16.34 % and 31.63 %, and the shear forces of the pier bottom are reduced by 12.26 % and 11.96 %, respectively. The device can reduce the seismic responses and the level of damage to the pier, and improve the self-centering ability and seismic performance of the structure.

Self-Centering Rotational Joints for Seismic Resilient Steel Moment Resisting Frame

A novel self-centering rotational joint (SCRJ) was proposed to replace the plastic hinge at the beam end to achieve a seismic resilient frame without diminishing the structural usability. The quasi-static cyclic tests of the SCRJs with different sets of friction components and disc springs were conducted, with the results showing that the precompressive force, stiffness of the compressive force, and slope angle of the right helicoid surfaces can significantly affect the hysteresis behavior. The hysteresis curve of the SCRJ demonstrates a flag shape with four characteristic states: activation state, ultimate state, reversal activation state, and deactivation state. The displacement-based design approach was adopted for the resilient steel moment resisting frame structure with the SCRJs based on which a six-story resilient frame structure was designed with the SCRJs at the beam ends. The nonlinear dynamic analysis shows that the interstory drift ratio and residual interstory drift ratio of the resilient frame structure can meet the design objectives, in which the SCRJs reach the plastic state (caused by geometric nonlinearity) more easily than conventional plastic hinges (caused by material plasticity), resulting in larger deformations, and can effectively dissipate seismic energy and protect the main frame from yielding under the rarely occurring earthquake (ROE) level.

Research on design and numerical simulation of self-centering prefabricated RC beam-column joint with pre-pressed disc spring devices

To improve the resilience performance of precast concrete frame structure, a novel self-centering prefabricated concrete beam-column joint with controllable plastic hinge (PJ-CPH) is proposed in this manuscript. Controllable plastic hinge is an innovative connection configuration composed by pin shaft, rotational friction damper and disc spring self-centering devices. The rotational friction damper is used for withstanding bending moment and dissipating seismic energy. The disc spring self-centering device is used for withstanding bending moment and providing restoring force, while the pin shaft is merely used for withstanding shear force. A detailed design procedure was presented by introducing self-centering ratio α and moment amplification factor β. A flag-shaped hysteretic model of PJ-CPH was proposed, simultaneously, a numerical model was developed based on the OpenSees computational platforms. The numerical simulation analysis was carried out for four PJ-CPH models with different parameters and one cast-in-situ beam-column joint model under low cyclic loading. Analysis results indicate that the hysteretic curve obtained by theoretical calculation are in good agreement with the numerical simulation results. Consequently, the effectiveness of the established hysteretic model was verified. Compared with the cast-in-situ beam-column joint, PJ-CPH achieves the damage-free connection and exhibits the superior resilience performance. The simulation results suggest that self-centering ratio α values should be assumed approximately in the range 1.00–1.30, moment amplification factor β values in 1.30–1.40, which can induce damage to concentrate in controllable plastic hinge, protect the main structure from damage and reduce repair costs.

Emerging superelastic SMA core damping elements for seismic application

Structural and non-structural damage reported after recent strong earthquakes promotes a fundamental shift in structural design target from “collapse resistance” to “fast structural function recovery”. A unique class of metal called superelastic shape memory alloy (SMA) has been emerging as a promising solution to enhance the seismic resilience of structures. SMA core damping elements are the basic constituents of many newly-proposed seismic resistant members or devices, and they are directly responsible for the safety, integrity, and economical efficiency of the structures using them. This mini-review paper offers a comprehensive summary of the emerging SMA core damping elements recently developed, covering SMA monofilament wires, fibers, bars, flat plates, U-shaped plates, angles, cables, rings, helical springs, disc springs, and friction springs. These SMA core elements are suitable for various seismic application scenarios, and their efficiency have been verified through either full-scale or proof-of-concept experimental studies. The basic working principles, advantages, and potential shortcomings of these elements are discussed, and future research needs are outlined.

Development and experimental verification of self-centering disc slit damper for buildings

The damage avoidance design (DAD) philosophy is oriented towards the low-damage design of building structures compared to the previous conventional ductile design. Low-damage structures with supplemental damping and self-centering ability are one of the main aspects of the DAD philosophy to decrease irreparable damage and enhance the seismic performance of structures. This research proposes an efficient, double-acting self-centering hysteretic damper by combining the widely used steel slit dampers and prestressed disc springs for building structures. The proposed seismic protection device is called Self-Centering Disc Slit Damper (SC-DSD), which consists of two square standard hollow steel sections, nested together with an assembly of prestressed disc springs within the steel sections. The performance of SC-DSD is assessed experimentally through a static cyclic loading test to evaluate the global system's dissipation capacity, self-centering ability, and hysteresis loop. A simplified numerical model is developed to predict the self-centering force-displacement relationship of the proposed device. Finally, the seismic force bearing capacity of the proposed damper is compared with the conventional slit damper.

Self-centering beam-column joints with variable stiffness for steel moment resisting frame

Different from the self-centering joint with constant post-yield stiffness (CS joint), self-centering joint with various post-yield stiffness (VS joint) is proposed to control the seismic responses and improve the seismic resilience of frame structures under the extremely rarely occurring earthquake (EROE) level. The angle steel connectors and disc springs are adopted to provide the energy dissipation and self-centering capacities of the VS joint, respectively. First, theoretical study and pseudo-static tests are conducted, the results show that the VS joint has two stages of stiffness after the joint gap opens; the joint can deform and dissipate energy during the first stage with ordinary post-yield stiffness when the rotation angle of the joint is small; with the increase of the joint rotation angle, the weak stack of disc springs is flattened, causing the joint to enter the second stage with strengthened post-yield stiffness. It is found that the smaller the deformation capacity of the preloaded weak stack, the smaller the begin rotation angle of the second stage; the larger the stiffness of the strong stack, the larger the strengthened post-yield stiffness. Then, the updated displacement-based design method suitable for the frame structure with the VS joints (VSF structure) is also proposed. The non-linear dynamic time analysis results show that the plastic damage of the general moment resisting frame structure (GF structure) is severe and exceeds the extent of repairability under the EROE level; both the frame structure with the CS joints (CSF structure) and VSF structure have similar structural responses under the frequently occurring earthquake (FOE), the moderately occurring earthquake (MOE) and the rarely occurring earthquake (ROE) levels, and both can avoid plastic damage and have good self-centering capability even under the EROE level; due to the strengthened post-yield stiffness of the VS joints, the displacement responses of the VSF structure under the EROE level can be effectively controlled, while this is difficult for the CSF structure, whose responses exceed the performance target.

Damage-free self-centring links for eccentrically braced frames: development and numerical study

Many recent research studies focused on the development of innovative seismic-resilient structures, chasing the objectives of minimising both seismic damage and repair time, hence allowing the definition of structures able to go back to the undamaged, fully functional condition in a short time. Steel seismic-resilient structures have been widely investigated in the past few years while considering solutions based on moment-resisting and concentrically braced frames. While the first category may be characterised by low stiffness, the second category is often characterised by low ductility. Conversely, eccentrically braced frames (EBFs) represent a compromise between the two and allow both strength and stiffness to be optimised while providing ‘good’ ductility capacity. The present study investigates a solution for damage-free self-centring EBFs relying on damage-free self-centring devices as seismic links (SC-links). The SC-links are based on post-tensioned high-strength steel bars with disk springs to provide the self-centring behaviour, and friction dampers to dissipate the seismic energy. Analytical equations governing the global behaviour of the connection are developed. A four-storey EBF complying with Eurocode 8 provisions is designed with conventional seismic links and upgraded with the proposed SC-link. The third storey of the structure is extracted to develop refined 3-D finite element (FE) models in ABAQUS. The results of the FE simulations are used to investigate the local behaviour of the seismic device and validate the accuracy of the analytical predictions. Moreover, a simplified 2-D FE model is developed in OpenSees to carry out Incremental Dynamic Analysis providing information on the global response of the structure. Residual and peak interstorey drifts and link rotations are monitored as Engineering Demand Parameters, and the seismic performances of the frames are compared.

Test of Novel Self-Centering Energy Dissipative Braces with Pre-Pressed Disc Springs and U-Shaped Steel Plates

ABSTRACT To control the residual displacement of the structure after strong earthquakes, this paper develops and validates a novel brace, i.e. the self-centering energy dissipative brace with pre-pressed disc springs and U-shaped steel plates (SCEDB-U). The pre-pressed disc springs are used for recovering nonlinear deformation and the U-shaped steel plates are used for dissipating energy. Initially, the configuration and working principle are described in detail. Then the analytical equations governing the cyclic behavior of the brace are derived. To confirm the concept, the large-scale bracing specimens are designed and manufactured for the quasi-static cyclic loading tests. In the tests, the varied parameters included the plate width of the U-shaped steel plates and the pre-pressure magnitude of the stacked disc springs. Besides, the high-fidelity three-dimensional finite element (FE) models of SCEDB-U are established. According to the experimental data, the SCEDB-U has typical flag-shaped hysteresis, which is characterized by excellent self-centering capability and stable energy dissipation ability. It also indicates that increasing the plate width of U-shaped steel plates can effectively improve the energy dissipation capacity, but may induce residual displacement; increasing the pre-pressure magnitude of disc springs could improve self-centering ability. The numerical results are in good agreement with the experimental data; hence, the FE models can be further utilized for parametric analysis, initial design and optimization.

Theoretical and experimental investigation on disc spring isolation system with loading rings

A novel disc spring isolation system (DSIS) design for buildings is proposed to isolate vibrations in the vertical direction. The system with nonlinear stiffness consists of disc springs and loading rings that reduce the influence of Coulomb friction between multiple disc springs. Theoretical analysis was first applied to establish a four-curve (FC) model to describe the force-displacement relation of DSIS by considering the influence of slip behavior and Coulomb friction between the loading rings and disc springs. Then, a series of vertical cyclic loading tests were carried out to study the different mechanical properties of DSIS with or without loading rings, and the effectiveness of the loading rings was verified. By comparing with the test results, the accuracy of the proposed FC model was verified. Then, the numerical solution method using the proposed FC model to solve the dynamic response of the single degree of freedom (SDOF) system was investigated. The nonlinear transfer function curves of DSIS with loading rings were compared with those of DSIS without loading rings by numerical analysis. Finally, the comparison study of SDOF for DSIS under the specific harmonic and train-induced vibration was carried out as a case study. The comparison shows that DSIS with loading rings more effectively reduces the start frequency of the isolated system, revealing the significant advantages of adopting DSIS with loading rings in vertical isolation.

Experimental and Numerical Investigation of a Disc-Spring Damage Avoidance Device in Self-Centering Slotted Beam Connections

ABSTRACT During the past decade damage avoidance initiatives have attracted considerable attention among researchers and earthquake engineers. The paper proposes a Disc Spring Damage Avoidance Device which can practically be implemented in slotted beam connections. It comprises two distinct components for self-centering and energy dissipation. The components are tested under cyclic loading and the device performance in slotted concrete joints is validated using previous experimental and analytical results. Variation in system parameters is investigated using an improved analytical model. The results show that the device can mitigate the residual displacements down to zero while maintaining a reasonable level of energy dissipation.

A generalized method for numerical modeling of seismically resilient friction dampers using flat slider bearing element

There has been a growing interest in recent years by both researchers and industry in developing friction dampers that have enhanced seismic performance by using inclined friction interfaces (i.e., not colinear with the plane of loading) in combination with a re-centering mechanism such as steel disc springs and/or SMA materials. These friction and friction-hybrid dampers provide both energy dissipation and self-centering characteristics. Compared to conventional flat-slider friction dampers (where friction interface is colinear with the plane of loading), numerical modeling of these types of friction devices is not straightforward and requires unique material models or complex element configurations to predict earthquake building responses. This technical note provides a generalized numerical model implemented in the OpenSees structural analyses framework that could be broadly applied to the numerical modeling of seismically resilient type friction dampers. The modeling scheme presented in this study utilizes readily available elements (i.e., flat-slider bearing element), eliminating the need and complexity of creating new material models. Given the increased interest found in the literature in the development of friction dampers with re-centering characteristics, this technical note could be useful for both researchers and engineers. Illustrative examples using two distinctly different seismically resilient friction dampers are presented for validation of the proposed modeling scheme. The first comparison is made with a cross-laminated timber rocking wall detailed with a newly proposed Uplift Friction Damper (UFD). Comparisons are made with both quasi-static cyclic tests and a continuum finite element numerical model in the ABAQUS software program. The second validation example compares results with a quasi-static uniaxial cyclic test of a Friction Spring Damper (FSD) device. Predictions of the proposed generalized numerical model are in good agreement with the results of both validation examples.

Enhancing the Seismic Resilience of Steel Moment Resisting Frame with a New Precast Self-Centering Rocking Shear Wall System

In this paper, a new precast self-centering rocking shear wall system (PSCRSW) mainly composed of precast reinforced concrete (RC) wall, V-shaped steel brace and pre-pressed disc spring friction damper (PDSFD) are proposed to enhance the seismic resilience of steel moment resisting frame (SMRF). The mechanical behavior of PDSFD was investigated and simulated. The skeleton model of PSCRSW was theoretically derived and numerically validated, and the hysteretic performance under different design parameters was discussed and compared with that of the conventional RC shear wall. Based on the analyses, design principles and suggestions for PSCRSW were given. Then, an efficient seismic resilient design method for enhancement of SMRF was proposed, which considers performance objectives of multiple seismic hazard levels and has less design iteration. A typical SMRF was adopted as the prototype to be enhanced by the presented PSCRSW and design method. Reliable numerical models for the prototype and the enhanced SMRF were established, and nonlinear dynamic analyses were performed to assess the effectiveness of enhancing strategy. The results show that PSCRSW can realize approximate yielding behavior, displacement capacity and lateral strength to the conventional shear wall and can significantly lower the residual drift and wall damage. During the design, the ratio of preload to friction force for PSCRSW was suggested to be 1.5~2.0, and the bearing capacity for the wall was suggested to be amplified 1.2 times. Thereby, desirable bearing and self-centering performances can be guaranteed. The presented design method is capable of achieving the inter-story drift ratio targets and the expected roof drift ratios simultaneously, and the seismic resilience of the chosen SMRF was significantly improved by a large margin of reduction in residual inter-story drift and frame member damages.