The work arrives at a pivotal moment. The second generation of Eurocode 8, the European seismic design standard, is shifting masonry verification toward displacement-based methods. In this framework, engineers no longer simply check whether wall stresses stay below allowable limits; instead they build a capacity curve for the entire building, tracing how lateral force evolves with increasing roof displacement. The accuracy of that curve depends directly on how well the drift capacity of each individual shear wall is known. Yet the codified approaches available until now assign drift limits according to predefined failure modes, separating walls into shear-dominated or flexure-dominated categories, a distinction that laboratory evidence increasingly shows to be artificial.

Experiments over the past two decades have demonstrated that drift capacity is governed by the coupled effects of axial load ratio, wall slenderness and the distribution of bending moment along the wall height. These factors interact continuously, producing gradual transitions between shear, hybrid and flexural response mechanisms. When a design code forces every wall into one of two boxes, the predicted drift capacity can jump discontinuously as a wall crosses an arbitrary classification boundary, even though the physical behavior changes smoothly. The Aachen team set out to replace this step-function logic with a mechanically transparent formulation that reflects the true, continuous nature of the transition.

The foundation of the study is a newly compiled European database of in-plane cyclic shear wall tests, the Modern Masonry Shear-wall DataBase, or MoMaS-DB. It builds on earlier datasets published by researchers at EPFL and the University of Pavia, which together supplied 225 tests used to derive the drift limits in the second-generation Eurocode, and expands them with additional campaigns on vertically perforated clay units, calcium silicate units, lightweight aggregate concrete units and concrete blocks. In total, the database contains 353 cyclic shear wall tests spanning hollow clay, solid clay, calcium silicate bricks and blocks, autoclaved aerated concrete, lightweight aggregate concrete and concrete block masonry, with thin-layer mortar emerging as the predominant joint type. Each test record captures material properties, wall geometry, loading conditions, observed failure modes and the key points of the experimental load-displacement curve.

Because even a database of this size cannot fill the entire parameter space uniformly, the researchers complemented the experiments with an extensive numerical simulation campaign. They built a simplified micro-model of a hollow clay masonry wall in LS-DYNA, representing the units as nonlinear solid elements and the mortar joints as contact interfaces governed by a stress-based failure criterion with cohesive softening. The model was calibrated against small-scale component tests and validated against 13 wall tests drawn from the database, reproducing maximum horizontal forces with good agreement and capturing the governing failure modes reliably. With the validated model in hand, the team systematically varied wall length from 1.00 to 4.00 meters, axial load ratio from 3 to 30 percent of the characteristic masonry compressive strength, and moment distribution factor from 0.5 to 1.5, generating 300 simulation variants that would have been prohibitively expensive to test physically.

From this simulation matrix, the researchers distilled the study’s central innovation: a normalized shear slenderness parameter that combines wall geometry, boundary conditions and vertical load level into a single quantity. Low values of this parameter correspond to heavily compressed, squat walls with restrained rotations, where shear-controlled behavior dominates and drift capacity is limited. High values indicate slender walls under low axial load, where rocking and flexural deformation become significant and drift capacity grows. Plotting the simulation results against this parameter revealed a clear physical picture: below a critical value of roughly 5, the response is shear-dominated; beyond it, hybrid mechanisms emerge and eventually give way to flexural failure, while the load-bearing capacity asymptotically approaches the theoretical rocking limit derived from rigid-body equilibrium.

The proposed drift capacity formulation follows directly from this observation. It consists of a constant range for shear-dominated behavior, where the drift at the Significant Damage limit state takes a fixed value, and a linear range with a calibrated slope that captures the progressive increase in drift capacity as hybrid and flexural mechanisms take over. The slope was determined through an unbiased lognormal regression procedure in linear space, minimizing the deviation of the mean predicted-to-observed ratio from unity without imposing penalty terms or artificial regularization on the scatter. This purely data-driven calibration yielded a slope of 0.053 for the simulation data, and the same procedure was subsequently applied to the filtered experimental database, which retained 210 representative tests after excluding short piers, walls with drift capacities above 2 percent associated with rocking, eccentrically loaded specimens and pseudo-dynamic tests.

The comparison with the failure-mode-dependent procedure of the draft Eurocode 8 part 1-2 is revealing. For the simulated hollow clay walls, the new approach reduced the mean absolute error at the Significant Damage limit state from 0.36 to 0.17, halving the scatter while eliminating the systematic overestimation of drift capacity for flexural and hybrid failure modes. On the experimental data, the two methods performed more comparably once the standard’s conservative upper drift limits were applied, but the new approach achieved this accuracy without needing empirical caps, because it explicitly accounts for the parameters that drive the response. Selected wall tests underscored the difference: for four-meter-long hollow clay walls, the normative approach overestimated drift capacities by a factor of roughly 2.2 to 3.0, while the new approach overestimated them by only 1.2 to 1.6, largely because the normative method neglects wall slenderness for realistic moment distributions that often exceed unity in actual buildings.

The practical significance of the work was tested at the building scale. Applying both approaches to a three-storey masonry building with autoclaved aerated concrete walls showed that the failure-mode-dependent method produced drift capacities strongly constrained by its predefined limits, with the flexural cap of 0.6 percent governing most shear-failing walls. The new approach, by contrast, captured the higher drift capacity of short walls and walls under low axial stress, following established mechanical principles rather than empirical restrictions. The method has already been incorporated as an alternative procedure in the final draft of FprEN 1998-1-2, giving European designers a validated option for deformation-based masonry design, with partial safety factors derived from the statistical scatter of the database to maintain reliability at the structural level.

The authors are candid about the limitations that remain. The experimental database is unevenly distributed across wall slenderness, moment distribution factors and masonry types, so the linear part of the formulation partly relies on extrapolation at high normalized shear slenderness values, and some masonry types still lack sufficient tests for material-specific calibration. Future work, they note, should expand the database with additional cyclic tests, particularly for large slenderness values, moment distribution factors greater than one, and underrepresented materials, and should address hybrid failure modes, cyclic degradation and wall-to-slab interaction at the building level. Even so, the study marks a decisive step away from the brittle logic of failure-mode classification toward a continuous, physics-based description of how masonry walls deform, promising more realistic capacity curves and, ultimately, safer masonry buildings in earthquake-prone regions.

Subject of Research: Seismic drift capacity estimation of unreinforced masonry shear walls using a normalized shear slenderness parameter

Article Title: A novel approach for the estimation of seismic drift capacity in unreinforced masonry (URM) shear walls based on governing structural parameters

Article References: Mukattash, N., Butenweg, C., Kubalski, T., & Klinkel, S. (2026). A novel approach for the estimation of seismic drift capacity in unreinforced masonry (URM) shear walls based on governing structural parameters. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02697-1

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02697-1

Keywords: unreinforced masonry, shear walls, drift capacity, Eurocode 8, displacement-based design, normalized shear slenderness, axial load ratio, moment distribution, cyclic shear wall tests, MoMaS-DB, nonlinear simulation, earthquake engineering

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