The study, published in the Journal of Materials Science by Mahdieh Sabbaghian and Mohammad Zaman Kabir, focuses on a copper-aluminum-manganese alloy with a composition of 15.8 percent aluminum and 11 percent manganese by atomic fraction. Copper-based shape memory alloys have attracted attention for decades precisely because their raw materials are cheap and abundant compared with nickel and titanium. Yet they have historically suffered from a critical weakness: in polycrystalline form, meaning materials made of many small crystals rather than a single crystal, they tend to crack along grain boundaries during repeated elastic cycling. The intergranular brittleness has been the Achilles heel that kept them confined to laboratory curiosities and niche applications.

The Iranian team approached this challenge through the lens of thermomechanical processing, the art and science of combining heat treatment with mechanical deformation to sculpt a material’s internal structure. They compared several processing routes applied to the same base alloy: hot rolling followed by quenching, conventional annealing, and a more exotic procedure called cyclic heat treatment, in which the material is repeatedly heated and cooled through a critical temperature range. Each route leaves a distinct fingerprint on the microstructure, and the researchers set out to map exactly how those fingerprints translate into functional performance.

Characterization was carried out with an impressive battery of techniques. Differential scanning calorimetry measured the temperatures at which the alloy transforms between its high-temperature austenite phase and its low-temperature martensite phase, the reversible crystallographic shift that underpins all shape memory behavior. X-ray diffraction identified the phases present, while optical and scanning electron microscopy revealed the grain structures, and microhardness testing probed local mechanical resistance. Superelasticity itself was evaluated through cyclic tensile testing, in which specimens are stretched and unloaded repeatedly while stress-strain curves are recorded, and the shape memory effect was assessed through bending recovery experiments in which pre-strained samples are heated and their recovery angle measured.

The physics here deserves a moment of explanation. Superelasticity is not ordinary elasticity. In a superelastic alloy, applying stress at a temperature above the austenite finish temperature triggers a stress-induced transformation from austenite to martensite. The material yields at a nearly constant stress plateau as the transformation proceeds, absorbing enormous strain, sometimes several percent, which would permanently deform an ordinary metal. When the load is removed, the martensite becomes unstable and reverts to austenite, and the material snaps back almost completely. The catch is that this reversible transformation must sweep through entire grains without generating damaging stress concentrations at grain boundaries. Large grains, and ideally single crystals, make this far easier, which is why grain size control is the central battleground for polycrystalline shape memory alloys.

This is where cyclic heat treatment enters the story, and it is the most striking part of the new work. The technique, pioneered by researchers including Takashi Omori and Ryosuke Kainuma at Tohoku University, exploits a phenomenon called abnormal grain growth. Under normal circumstances, heating a metal causes its grains to grow uniformly and modestly. But under specific cyclic conditions, a select few grains develop a growth advantage, consuming their neighbors until they dominate the entire microstructure. The result can be grains centimeters long, effectively transforming a polycrystal into an oligocrystal or even a single crystal without any of the expensive directional solidification or crystal-pulling methods traditionally required. The mechanism is thought to involve the repeated dissolution and reprecipitation of phases during each thermal cycle, which selectively favors grains with particular orientations or defect structures.

Applying cyclic heat treatment to their Cu-Al-Mn alloy, the researchers achieved dramatic results. Differential scanning calorimetry of the treated specimens revealed austenite finish temperatures below zero degrees Celsius, a crucial finding because it means the alloy is fully austenitic, and therefore superelastic, at room temperature. Cyclic tensile testing then showed that the cyclically heat treated material exhibited pronounced superelasticity, with a recoverable strain of 6.24 percent, more than five times that of the untreated control specimen. For a polycrystalline copper-based alloy, that is an extraordinary figure, and it demonstrates that the abnormal grain growth strategy transfers effectively from the iron-manganese-aluminum-nickel systems where it was first demonstrated to the copper-based family.

Hot rolling, meanwhile, delivered a different but complementary set of benefits. The rolled specimens showed ultimate tensile strength and cumulative energy density to fracture increased by approximately 74 percent and 39 percent respectively compared with the control. Rolling refines the microstructure, breaks up casting defects, and can introduce beneficial texture, aligning the crystallographic grains in ways that accommodate the transformation strain more gracefully. The most exciting result, however, came from combining the two processes. A route that paired hot rolling with cyclic heat treatment promoted pronounced abnormal grain growth while simultaneously enhancing strength, ductility, and superelasticity, yielding an ultimate tensile strength of up to 572 megapascals, a total strain at fracture of up to 15.4 percent, and a recoverable superelastic strain of up to 6.86 percent. Achieving all three properties together is rare; usually improving one comes at the expense of another.

The implications extend well beyond the laboratory. Shape memory alloys are increasingly specified in civil infrastructure, where their superelasticity allows them to absorb seismic energy and re-center structures after earthquakes, and where their shape memory effect lets them apply permanent prestressing forces to concrete elements as they are heated. Reviews of the field have highlighted applications ranging from bridge shear reinforcement to column retrofitting and vibration damping systems. In these large-scale structural uses, the cost of nickel-titanium is often prohibitive, since tonnage quantities would be required. A copper-based alternative with competitive functional properties, produced from inexpensive raw materials through conventional rolling and furnace treatments, could change the economics of resilient infrastructure design entirely.

There are, of course, questions that future work must address. Cyclic heat treatment schedules can be time-consuming, and scaling the abnormal grain growth process from laboratory coupons to commercial bar and plate stock will demand careful process control. Fatigue behavior over thousands of superelastic cycles, corrosion resistance in realistic environments, and compatibility with welding and joining methods all remain to be fully characterized for the processed alloy. Still, the demonstration that a simple combination of rolling and thermal cycling can coax a cheap copper alloy into delivering nearly seven percent recoverable strain alongside 572 megapascals of strength marks a genuine advance. It suggests that the era of superelastic metals may not belong exclusively to nickel and titanium after all, and that with clever processing, some of the oldest and most familiar metals in human history still have remarkable new tricks to teach us.

Subject of Research: Thermomechanical processing and cyclic heat treatment of Cu–Al–Mn shape memory alloys to enhance superelasticity

Article Title: Adapting superelasticity in Cu–Al–Mn shape memory alloys via thermomechanical processing and cyclic heat treatment

Article References: Sabbaghian, M., & Kabir, M. Z. (2026). Adapting superelasticity in Cu–Al–Mn shape memory alloys via thermomechanical processing and cyclic heat treatment. Journal of Materials Science, 61(43), 34049-34087. https://doi.org/10.1007/s10853-026-13738-0

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13738-0

Keywords: shape memory alloys, superelasticity, Cu–Al–Mn, cyclic heat treatment, abnormal grain growth, thermomechanical processing, hot rolling, martensitic transformation, grain size, structural materials, seismic resilience, Journal of Materials Science

The research team developed two distinct connection configurations, both designed to provide continuity and core reinforcement at the critical slab-to-beam interface. The first, designated Continuity and Core reinforcement – Combined (CC-C), integrates the continuity and core reinforcement within a combined arrangement, while the second, Continuity and Core reinforcement – Discrete (CC-D), separates these reinforcement functions into discrete elements. Both connections incorporate a 75 millimetre ledge width, a dimension chosen deliberately to comply with the minimum ledge support advised by New Zealand standards, which have long been regarded as among the most demanding seismic detailing provisions in the world following that country’s devastating earthquake experiences with precast flooring.

The significance of the ledge dimension cannot be overstated. In past earthquakes, most notably the Northridge earthquake of 1994 and the Canterbury earthquake sequence in New Zealand, hollow core floors suffered failures traced to insufficient bearing length and inadequate connection detailing. When a building sways laterally during strong ground shaking, the ends of precast slabs experience alternating positive and negative bending moments, and if the supporting ledge is too narrow or the reinforcement poorly arranged, the slab end can crack, lose its seating, and ultimately drop. The New Zealand requirement for minimal ledge support therefore represents a hard-won lesson from forensic investigations of real failures, and the Indian research team’s decision to adopt it signals a commitment to internationally recognized best practice.

To evaluate the seismic efficiency of the two novel connections, the researchers subjected full-scale specimens to reverse cyclic loading, the standard laboratory method for simulating the back-and-forth deformation demands that an earthquake imposes on a structure. The testing regime allowed the team to assess a comprehensive suite of performance indicators, including ductility, load capacity, energy dissipation capacity, damping characteristics, hysteretic response properties, stiffness degradation, load ratios, elastic stiffness, and strain distribution. Each of these parameters tells part of the story of how a connection behaves as damage accumulates: ductility measures how far the joint can deform beyond its elastic limit, energy dissipation reflects its capacity to absorb seismic energy, and stiffness degradation tracks how the connection softens through repeated cycles.

The headline result is striking. Both the CC-C and CC-D connections effectively sustained both positive and negative moments without losing support, even under lateral drift levels reaching ±5.36 per cent. To put that figure in perspective, modern seismic design codes typically expect structures to remain standing at drift levels of around 2 to 3 per cent, and acceptance criteria for moment frames tested under standards such as ACI 374.1-05 demand stable performance at considerably smaller deformations. A connection that retains its slab seating at more than five per cent drift has demonstrated a remarkable margin of safety, one that would translate directly into life-safety performance during a severe earthquake. The fact that neither configuration lost support at any point in the testing suggests that the ductile detailing successfully transformed a traditionally brittle failure mode into a ductile, energy-absorbing one.

Complementing the laboratory programme, the team carried out a thorough three-dimensional nonlinear finite element simulation using ABAQUS software, one of the most widely used platforms for advanced structural analysis. The numerical models employed the concrete damaged plasticity framework, a constitutive approach rooted in the plastic-damage theories developed by Lubliner and colleagues and later extended by Lee and Fenves, which captures both the crushing and cracking behaviour of concrete under cyclic loading. The simulations showed strong agreement with the experimental findings, with discrepancies remaining within 10 per cent, a level of correlation that validates the modelling approach and opens the door to using such models for future design studies without the expense of physical testing for every variant.

Beyond simply reproducing the test results, the numerical investigation yielded critical insights into the modelling aspects that govern the accuracy of finite element predictions for these assemblies. The researchers examined element size sensitivity, confirming that mesh resolution materially affects the computed response, a well-known but frequently underestimated issue in nonlinear concrete analysis. They also investigated material dilation properties, which control how concrete expands as it shears and which influence confinement effects within the connection zone, and the role of viscosity coefficients, the numerical regularization parameters that help convergence in softening materials without artificially stiffening the response. These findings provide practical guidance for other researchers and engineers seeking to model precast connections reliably, addressing pitfalls that can otherwise lead to misleading predictions.

The strain distribution measurements from the experiments added another layer of understanding, revealing how forces flow through the connection detailing and where the reinforcement is most heavily engaged. Such data are essential for confirming that the design philosophy behind the connections, namely that yielding should occur in the ductile reinforcement rather than through brittle concrete failure at the slab bearing, is actually realized in practice. The hysteretic loops recorded during cyclic testing, together with the damping characteristics derived from them, indicate how effectively each configuration dissipates seismic energy cycle after cycle, a property directly linked to how quickly a building’s vibrations decay during an earthquake.

The broader implications of this work extend well beyond the laboratory in Chennai. Precast and prestressed concrete construction is growing rapidly worldwide, driven by demands for speed, quality, and sustainability, and hollow core slabs remain a flagship product of the precast industry, supplied in this study by TEEMAGE PRECAST in Kancheepuram. In seismically active regions from India to the Mediterranean to the Americas, the vulnerability of slab-to-beam connections has been a persistent obstacle to confident adoption of precast flooring in high-seismic zones. Connection solutions that are both ductile and practical to construct, using conventional materials and detailing techniques compatible with codes such as IS 13920 for ductile detailing and IS 15916 for prefabricated concrete construction, could substantially expand the safe use of these efficient floor systems.

By pairing rigorous physical testing with validated high-fidelity simulation, the Anna University team has delivered a template for how connection research should be conducted: propose a detailing innovation grounded in lessons from past failures, verify it under realistic cyclic demands against international acceptance benchmarks, and then distil the behaviour into numerical models that designers can trust. The demonstration that hollow core slab-to-beam connections can survive drift levels exceeding five per cent without losing support marks a meaningful advance in precast seismic engineering, and the detailed modelling guidance ensures that the findings will ripple outward, informing future designs, code provisions, and the ongoing effort to make precast buildings as resilient as they are efficient.

Subject of Research: Seismic performance of ductile hollow core slab-to-beam connections in precast concrete buildings

Article Title: Seismic resilience of hollow core slab – beam connections with novel ductile detailing: experimental and numerical simulations

Article References: Vinutha, D., Vidjeapriya, R., & Jaya, K. P. (2026). Seismic resilience of hollow core slab – beam connections with novel ductile detailing: experimental and numerical simulations. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02681-9

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02681-9

Keywords: hollow core slabs, precast concrete, seismic resilience, ductile detailing, reverse cyclic loading, finite element analysis, ABAQUS, connection design, drift capacity, energy dissipation, New Zealand standards, earthquake engineering

The study, led by Zhaoxun Yuan of Guangdong Polytechnic of Water Resources and Electric Engineering together with Guiqiang Hao, Junxian Zhao of South China University of Technology, Wei Han, and Jiulin Bai of Chongqing University, focuses on a seismic-resilient connection for precast concrete moment frames that the same research group had previously proposed and tested. The concept is elegant: instead of allowing an earthquake to crack and crush the concrete beam itself, the design deliberately concentrates all the damage into sacrificial steel components that can be unbolted and swapped out after a quake, much like replacing a blown fuse in an electrical panel.

The connection is installed at the splice location along the beam — the point that corresponds to the inflection point of the beam under gravity loading, where bending demands are naturally lowest. At the top of the beam, vertical steel plates known as shear tabs are embedded across the splice section and extend into the adjacent precast beam segments. These tabs perform two simultaneous jobs: they act as the rotational center of the connection, allowing the beam ends to rock and rotate under seismic motion, and they transfer shear forces between the beam segments. Shear studs welded onto the embedded portions of the tabs help anchor the forces into the surrounding concrete. At the bottom of the beam, two buckling-restrained braces, or BRBs, serve as the replaceable fuse. A BRB is a steel yielding core wrapped in a restraining mechanism that prevents the brace from buckling in compression, allowing it to yield repeatedly in both tension and compression and dissipate seismic energy in a stable, predictable way — a technology with a well-documented track record in steel braced frames.

Previous experimental work by the team had validated the broader damage-control philosophy of the system: the fuses yield, the concrete stays essentially intact, and the building snaps back into service with only a quick component replacement required. But a critical question remained unanswered. The shear tabs are not simple elements — they simultaneously carry axial forces, shear forces and bending moments between the beam segments while themselves rotating as the connection rocks. If a designer sizes the tabs incorrectly, they can either fail to transmit the forces reliably or fracture prematurely under the relentless back-and-forth of cyclic earthquake loading. Before this new study, no systematic design criteria existed for these components, leaving the innovative connection without an engineering pathway from proof-of-concept into actual building codes and practice.

To close that gap, the researchers constructed detailed finite element models of the connection, carefully calibrated against the earlier test data so that the simulations reproduced the observed behavior with confidence. With a validated digital replica in hand, they used it as a virtual laboratory to dissect the force transfer mechanism inside the shear tabs — mapping how axial, shear and flexural demands flow through the steel plates and into the welded shear studs and surrounding concrete. Understanding this internal load path was the essential prerequisite for writing any rational design rule, because a design criterion is only trustworthy if it reflects what the component is actually experiencing, rather than what an idealized diagram suggests.

Informed by that mechanism, the team then formulated two complementary families of design criteria. The first are strength criteria, which ensure that the shear tabs and their stud groups are strong enough to transmit the full complement of forces demanded of them — including the capacity of the replaceable BRB fuses, which are intentionally sized to yield before anything else in the connection. The second are damage-control criteria, which protect the tabs themselves from premature fracture under cyclic loading, guaranteeing that the replaceable fuses remain the sacrificial elements while the permanent load-transfer hardware stays elastic and intact through the design earthquake. In other words, the design ensures the right components break — and only the ones that were meant to.

The researchers then put these proposed design methods through their paces. They generated families of finite element models in which the cross-sectional dimensions of the shear tabs, the height-to-thickness ratios of the plates, and the arrangements and diameters of the welded shear studs were varied systematically. The validation confirmed that the new design equations reliably bounded the behavior across this range of geometries, giving engineers a defensible basis for proportioning real connections rather than relying on trial and error or conservative guesswork. The numerical campaign, illustrated in the paper by more than twenty figures of stress distributions, failure modes and performance comparisons, effectively converts the earlier experimental proof-of-concept into a designable, code-ready structural system.

The broader context makes the work timely. Precast concrete construction — in which beams, columns and walls are factory-cast and assembled on site — offers speed, quality control and reduced labor costs, which is why it dominates industrial construction in many seismically active regions. Yet earthquake after earthquake has exposed the vulnerability of poorly detailed precast connections: the 2012 Emilia earthquake in Italy, the 1999 Turkey earthquake and the 1994 Northridge earthquake all produced characteristic connection failures in precast industrial and commercial buildings, often collapsing roofs even when the rest of the structure survived. Modern seismic design therefore treats the connection, not the member, as the critical link, and decades of research have produced a wide repertoire of alternatives — wet cast-in-place joints, prestressed self-centering systems, slit dampers, friction devices and replaceable energy-dissipation bars — each with its own trade-offs in cost, complexity and recoverability.

What distinguishes the shear-tab-plus-BRB-fuse concept is the way it decouples the two functions that conventional connections force into a single overloaded zone. The steel tabs handle the geometric and force-transfer duties while remaining elastic; the braces handle the energy dissipation and accept the damage. Because the fuses sit at the beam inflection point rather than at the column face, the connection also avoids stressing the critical beam-column joint region, which is notoriously difficult to repair. The result, validated in the team’s earlier experiments, is a frame that experiences minimal residual drift after a design-level earthquake — meaning doors still close, partitions stay uncracked, and the building can be occupied while a small crew bolts in new fuses over a weekend.

The new design methodology for the shear tabs removes what was arguably the last major obstacle to practical implementation of this system for precast concrete frames. With strength and damage-control criteria now validated numerically across a wide parameter space, structural engineers have a complete, documented design procedure for the connection’s every component. The research was funded by the National Natural Science Foundation of China, the Guangdong Basic and Applied Basic Research Foundation, and the Guangdong Provincial Key Laboratory of Modern Civil Engineering Technology. As cities in seismic regions continue to expand with precast construction, designs of this kind point toward a future in which the question after a major earthquake is no longer whether a building can be saved, but simply how quickly the spare parts can be installed.

Subject of Research: Design of shear tabs in seismic-resilient precast concrete moment connections with replaceable buckling-restrained brace fuses

Article Title: Seismic resilient precast concrete moment connections with top shear tabs and bottom replaceable fuses: numerical study on shear tabs detailing

Article References: Yuan, Z., Hao, G., Zhao, J., Han, W., & Bai, J. (2026). Seismic resilient precast concrete moment connections with top shear tabs and bottom replaceable fuses: numerical study on shear tabs detailing. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02666-8

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02666-8

Keywords: seismic resilience, precast concrete, moment frame, shear tabs, replaceable fuse, buckling-restrained brace, finite element analysis, damage-control design, beam-column connection, earthquake engineering, force transfer mechanism, cyclic loading