Innovative Shape Memory Alloy Research Articles

Displacement-based seismic design of SMA cable-restrained sliding lead rubber bearing for isolated continuous girder bridges

The sliding of isolation bearings in a bridge structure can reduce bridge pier damage, but bearing sliding under the strong earthquake may cause excessive displacement of the girders or even falling girders. This study proposes an innovative shape memory alloy (SMA) cable-restrained sliding lead rubber bearing (SMA-SLRB), which can maximise the sliding advantages of the bearing whilst combining the displacement-limiting capacity and self-centering capacity of the SMA cable. The working mechanism of the SMA-SLRB is firstly revealed, and the mechanical model of the SMA-SLRB is verified by tests. Then, the multilevel fortification performance target of isolated continuous girder bridges with SMA-SLRB is proposed. A displacement-based seismic design (DBSD) method for the SMA-SLRB isolated continuous girder bridge is established. Next, with the single pier model of a five-span isolated continuous girder bridge taken as an example, the displacement-based design is implemented, and the seismic performance of the bridge is evaluated. Finally, the seismic responses of bridges with SMA-SLRB and SLRB under extremely rare earthquakes are compared. Results show that the energy dissipation capacity and stiffness of SMA-SLRB are improved to varying degrees compared with SLRB. The bridge basically achieves the design target displacement and meets the requirements of multilevel fortification performance, which confirms the effectiveness of the DBSD method. Under extremely rare earthquakes, the SMA-SLRB can effectively reduce the maximum displacement and residual displacement of the girder compared with the SLRB.

Seismic mitigation performance of shape memory alloy flexible circumferential joint in shield tunnel

AbstractThe circumferential joint of a shield tunnel is prone to damage under strong earthquakes, affecting the safety of the tunnel. This paper adopts an innovative shape memory alloy (SMA) flexible circumferential joint for longitudinal seismic mitigation of the tunnel. The SMA joint is composed of SMA ring springs and ordinary bolts. The SMA joint design is performed for a shield tunnel, and a simplified model of the SMA joint is proposed. Based on the generalised response displacement method, the longitudinal seismic mitigation analysis of the tunnel is conducted, the arrangement of SMA joints is discussed, and the seismic mitigation performance is evaluated. Results show that the SMA joint design method can efficiently complete the joint design, and the SMA joint model can accurately reflect the joint performance. SMA joints can reduce the stiffness of tunnel joints and have a good energy dissipation effect, which is suitable for shield tunnel seismic mitigation. An appropriate SMA joint arrangement can concentrate the tunnel joint deformation and effectively reduce the opening width between the tunnel segment rings. It can also dissipate energy and reduce the internal force of the tunnel joint, thus enhancing the seismic safety of the tunnel.

Development and investigation of an innovative shape memory alloy cable‐controlled self‐centering viscoelastic coupling beam damper for seismic mitigation in coupled shear wall structures

AbstractTo improve the seismic performance of coupled shear walls in high‐rise buildings and to eliminate the problems of large residual deformation and relatively small initial stiffness and damping properties of the traditional viscoelastic coupling beam damper (TVCBD), an innovative shape memory alloy (SMA)‐cable‐controlled self‐centering viscoelastic coupling beam damper (SVCBD) with energy dissipation and self‐centering capabilities was designed and investigated in this study. The construction form and operating principles of the SVCBD were proposed, relevant material performance tests of the cables were performed, and good results were obtained. Finally, the contribution of the SVCBD to seismic mitigation of a 10‐story reinforced concrete coupled shear wall structure was verified by seismic time‐history analyses. The results indicated that compared with TVCBD, SVCBD possesses fuller hysteretic curves, showing stronger energy dissipation capacity, higher initial stiffness, and much smaller residual deformation. The initial strain and cross‐sectional area of the SMA cables and the shear area of the viscoelastic plates affect the energy dissipation and self‐centering performance of SVCBD significantly. The seismic response and post‐earthquake residual deformation of the coupled shear wall structure and the plastic damage of the main components can be effectively controlled by utilizing the proposed SVCBD.

An innovative shape memory alloy flexible circumferential joint for tunnel seismic mitigation

Under strong ground motion, shield tunnels passing through uneven soil layers are easily damaged. Based on the concept of elastic washers, a shape memory alloy (SMA) flexible circumferential joint for longitudinal seismic mitigation of shield tunnels is proposed to achieve seismic mitigation with minimal impact; it is composed of SMA ring springs and ordinary joint bolts. The test performance and influencing factors of SMA ring springs are discussed. Then, based on the analytical solution of the SMA ring spring, the design method of the SMA flexible circumferential joint is proposed. The mechanical properties of the SMA flexible circumferential joint under different loads are studied through the numerical simulation of tunnel joints. Test, analysis and simulation results indicate that SMA ring springs have good energy dissipation and self-recovery effects and can satisfy the mechanical performance requirements of elastic washers. The joint design method can conveniently and efficiently design suitable SMA flexible circumferential joint. Numerical simulations show that under various loads, the joints can reduce the longitudinal stiffness of the tunnel and dissipate energy. The joint can improve the ability of the tunnel to adapt to the soil deformation under earthquakes, reduce the internal force of the structure and at the same time achieve energy dissipation effect, thereby enhancing the seismic safety of the tunnel.

Environmental Performance of Deconstructable Concrete Beams Made with Recycled Aggregates

The construction sector is one of the most energy-intensive and raw-material-demanding human activities and, hence, contributes a significant share of greenhouse gas emissions. As a matter of principle, making the construction sector “greener” is one of the main challenges for policy makers, private companies and the scientific community. For this reason, one of the most promising actions is based on recycling Construction and Demolition Waste (CDW) and converting them into secondary raw materials for the construction sector itself. Moreover, the reduction of the environmental impact can be further amplified through the optimization of the production, assembly and deconstruction/reuse procedures and through the maximization of the service life. In this aim, the present work aims at analyzing the environmental performance of duly sized and designed prefabricated Decontructable and Reusable Beam (DRB) incorporating with Recycled Concrete Aggregates (RCA) assembled by means of an innovative system based on a memory®-steel prestressing technique. The environmental performance is evaluated through Life Cycle Assessment with a cradle-to-gate approach: the analysis of 16 midpoint impact categories was conducted using the methodology proposed by EN15804. In this context, three allocation scenarios for avoided impacts due to reuse (100-0, 50:50 and 0-100) were considered, and a sensitivity analysis was performed. It was verified that due to the higher amount of post-tensioning required for the innovative shape memory alloy steel bars, the DRBs present inferior environmental performance than the Ordinary Beams (ORB). However, when analyzing the reuse scenarios, it was observed that the DRB could have considerably lower impacts, depending on the type of allocation procedure adopted in LCA modeling. This study brings as the main contribution an evaluation and some design guidelines for the development of circular concrete structures based on the principles of Design for Deconstruction (DfD) and the prefabricated process.

High‐Speed Antagonistic Shape Memory Actuator for High Ambient Temperatures

This work presents the development of an innovative shape memory alloy (SMA) actuator principle, which allows high‐speed switching cycles through the decoupling of antagonistically arranged SMA wires. Being optimized for the use at high ambient temperatures up to 65 °C, a possible application area is the active venting of injection molds where it can be used to expel air, which is trapped during the injection mold process. The patented actuator principle is based on a decoupled agonist–antagonist SMA‐spring system and allows a high‐speed closing movement by a compact and lightweight design. Another innovation compared to conventional antagonistic SMA actuator systems is the integrated fail‐safe mechanism, which guarantees a defined closed state in case of power failure. Subsequently, in the motivation the need for active venting valves for injection molding is first described. Second, the novel actuator principle is introduced, and the development of an electronics concept is discussed. Finally, the design process, assembly, and validation of two iterations of the actuator prototype are presented. The final prototype validation measurements showcase high performance by valve strokes of 1 mm within 100 ms at ambient temperature of 65 °C.

Innovative dampers as floor isolation systems for seismically-retrofit multi-storey critical facilities

Code provisions are intended to guide engineers to design new buildings adequately protected against structural failures; however, in critical facilities (such as power plants, military headquarters, hospitals, etc.) the post-emergency operability is maintained not only preserving structural integrity but also safeguarding the content functionality. As a result, the present work aims to investigate the use/effectiveness of a method to retrofit existing strategical buildings: in detail, the suggested procedure consists in installing cutting-edge dampers to isolate selected floor systems on a set of multi-storey frames, decoupling fragile nonstructural contents from the seismic source.Initially, taking advantage of peculiar properties of innovative shape-memory alloy materials, we design dampers capable to remain elastic for low-intensity dynamic events, combining 3D finite element numerical simulations to experimental tests performed at the Italian National Research Council (CNR).Subsequently, visco-elastomeric dampers are proposed in order to achieve comparable dissipative performances.Finally, we calibrate equivalent monodimensional FE link-like elements to study building global response and to reproduce the dynamics of floor isolation systems (FISs). Results provide evidence on the local and global seismic response attenuation due to FISs, in terms of stress and deformation reduction. Floor isolation effectiveness is highlighted, comparing visco-elastomeric with SMA dampers, both in a deterministic and in a statistic perspective.

A novel shape memory alloy damping inerter for vibration mitigation

Various shape memory alloy (SMA) dampers have been developed to reduce structural vibration responses. However, the application of SMA dampers has been restricted by the high material costs of SMAs. Therefore, this study developed and tested an innovative SMA damping inerter (SDI) in which an SMA element and an inerter element were arranged in parallel and deployed in series with a supporting spring element. A single-degree-of-freedom structure with an SDI was employed to analyze the effect of vibration mitigation. A theoretical analysis was conducted via an equivalent linearization method, and parameter studies were then used to evaluate the performance of the SDI-fitted structure from perspectives of structural displacement, acceleration, and energy dissipation as well as the most efficient frequency tuning bandwidth. The performances of the SDI and a conventional SMA damper were compared by using a time-domain analysis with recorded and simulated ground motions, revealing clearly superior results for the SDI with respect to structural response mitigation, and seismic energy dissipation. The system proposed here took advantage of the full potential of combining SMA and inerter elements, making the SDI a robust system for mitigating structural vibration with more economical SMA material costs.

Performance of EBFs equipped with an innovative shape memory alloy damper

Given their unique characteristics, Shape Memory Alloys (SMAs) have significant potential for use in different areas of engineering. The phase shift characteristics of these alloys allow them to memorize a certain shape, and if deformed, revert back to that shape through a thermal process. Given the vast potentials of SMAs, they can be utilized to address the limitation of conventional eccentrically braced frames (EBFs) with vertical links in order to achieve better residual and maximum interstory drifts. This paper presents a vibration control system equipped with SMAs to achieve improved operational domain. The Compared to conventional EBFs, the proposed system named recentering damping device (RDD) is easy to fabricate and implement and allows for the redesign of fuse members. A numerical analysis is performed for a 9-story steel frame building using nonlinear analysis program OpenSees to evaluate the system performance. Results of time history analysis demonstrate better self-centering behavior and lower residual interstory drifts of the proposed system as compared to EBF.

Application of an Innovative SMA Ring Spring System for Self-Centering Steel Frames Subject to Seismic Conditions

AbstractThis paper presents an innovative shape memory alloy (SMA) ring spring system used for high-performance steel beam-to-column connections. The ring spring system, which includes a series of ...

A Proof-of-Concept Study on Self-Centering Column Feet Equipped with Innovative Shape Memory Alloy Ring Springs

This paper presents a feasibility study on a self-centering steel column foot equipped with innovative shape memory alloy (SMA) ring springs. The ring spring system includes a series of SMA outer rings and high-strength alloy inner rings stacked in alternation with mating taper faces, and the system is used in conjunction with high-strength bolts in a typical extended end-plate connection to achieve favorable self-centering and energy dissipation performances while ensuring ease of construction. An experimental investigation was first conducted looking into the basic mechanical performance of individual SMA ring springs under cyclic loading. Driven by the superelastic behavior of SMA, excellent self-centering ability with satisfactory energy dissipation is exhibited. Subsequently, a further experimental study on a proof-of-concept column foot specimen is conducted, where the key properties, including ductility, self-centering ability, and energy dissipation capability, are discussed in detail in this paper.

Shape memory alloy actuated accumulator for ultra-deepwater oil and gas exploration

As offshore oil and gas exploration moves further offshore and into deeper waters to reach hydrocarbon reserves, it is becoming essential for the industry to develop more reliable and efficient hydraulic accumulators to supply pressured hydraulic fluid for various control and actuation operations, such as closing rams of blowout preventers and controlling subsea valves on the seafloor. By utilizing the shape memory effect property of nitinol, which is a type of shape memory alloy (SMA), an innovative SMA actuated hydraulic accumulator prototype has been developed and successfully tested at Smart Materials and Structure Laboratory at the University of Houston. Absence of gas in the developed SMA accumulator prototype makes it immune to hydrostatic head loss caused by water depth and thus reduces the number of accumulators required in deep water operations. Experiments with a feedback control have demonstrated that the proposed SMA actuated accumulator can provide precisely regulated pressurized fluids. Furthermore the potential use of ultracapacitors along with an embedded system to control the electric power supplied to SMA allows this accumulator to be an autonomous device for deployment. The developed SMA accumulator will make deepwater oil extraction systems more compact and cost effective.

Theoretical Study on Vibration Control of Symmetric Structure with Shape Memory Alloy (SMA)-Friction Damper

The paper proposed an innovative shape memory alloy (SMA)-friction damper. The damper consisted of the superelastic SMA wire and the friction element in series. According to the working mechanism of the damper, the paper set up the mechanical model of the damper. Seismic elastic-plastic time history response analysis program and energy analysis program of the damped structure were designed. The numerical calculations of the vibration control of a threestory shear-type symmetric structure with the damper were carried out. The results indicated that the damper can decrease the displacement and the inter-story displacement of the structure effectively, but increase the acceleration of the structure comparing with uncontrolled structure. The SMA-friction damper can not only adjust the working status of the energy dissipation elements automatically according to the seismic responses of the structure, but also has some advantages as simple configuration and economical application.

Mitigation of Vertical and Horizontal Seismic Excitations on Bridges Utilizing Shape Memory Alloy System

Vertical seismic excitation has a tremendous effect on bridges and many researchers have pointed out bridges damages occurred during the past significant earthquakes which were direct results of ignoring vertical acceleration of ground motions. Many studies have emphasized the importance of extending practical methods to reduce effects of vertical acceleration of earthquakes besides effects of horizontal accelerations; but no practical method has proposed up to now. In this article, an innovative shape memory alloy system is proposed for bridges that can simultaneously controls effects of vertical and horizontal seismic excitations on bridge and reduce them. To evaluate the effectiveness of the shape memory alloy system, a nonlinear time history analysis is conducted on a detailed three-dimensional model of a multi-span simply supported bridge using a representative ground motion. The results show that the proposed new system is very effective for reducing effects of vertical and horizontal seismic excitations on bridges.

Experimental and numerical behaviour of hysteretic and visco-recentring energy dissipating bracing systems

An extensive program of shaking table tests under the name Project JetPacs (Joint experimental testing on Passive and semi active control systems) has been developed with the goal of assessing the effectiveness of seven different passive and semi-active energy dissipating bracing (EDB) systems in controlling the seismic vibrations of framed buildings. The experimental program, carried out considering a 3D 1/1.5 scaled steel frame, was entirely funded by the Italian Department of Civil Protection as part of the RELUIS 2005–2008 project. The following article focuses on the experimental tests carried out considering only two EDB systems, based on hysteretic dampers (HD) and visco-recentring devices (SMA + VD) respectively. Specially shaped low carbon steel plates were used to provide hysteresis in the HD based devices, while the innovative SMA + VD visco-recentring system was made up of a combination of viscous dampers (VD) and shape memory alloy (SMA) wires. In this paper a displacement focused design procedure based on non linear static analysis has been proposed in order to evaluate the mechanical characteristics of both types of energy dissipating device. The aim of this design procedure is to limit inter-storey drifts after frame yielding. In order to assess the robustness of the design procedure and to evaluate the effects of the viscous and recentring components, two different sets of HD and SMA + VD devices characterized by slight alterations in the mechanical properties have been tested and compared. Finally, the experimental seismic response of the structure equipped with and without the HD and SMA + VD elements is reported and compared with numerical results obtained using non linear time history analysis.