Prefabricated reinforced concrete construction occupies a distinctive place in structural engineering. Unlike cast-in-place buildings, whose columns and beams are monolithically poured, precast structures are assembled from factory-produced elements joined on site. This makes them fast and economical to build, but it concentrates seismic vulnerability in the connections. In the classic Turkish precast industrial building, roof girders rest on column corbels, typically through dowel bars and elastomeric bearing pads, and the entire lateral load path depends on how well these joints hold together when the ground lurches. The 2023 Kahramanmaraş earthquake sequence, with its pulse-like near-fault motions and unusually high vertical accelerations, tested those joints as severely as any event in Turkish history.

The research team began with field investigations in the affected region, documenting damage patterns across prefabricated buildings exposed to the twin shocks. Their reconnaissance identified a recurring catalogue of construction deficiencies: inadequate dowel detailing at girder-corbel connections, missing elastomeric bearing pads, substandard grout applications, and insufficient confinement reinforcement in columns and joints. Each of these defects, individually modest in appearance, proved capable of triggering or accelerating structural failure. Where bearing pads were absent, girders pounded directly against concrete corbels, crushing the bearing surfaces and losing their ability to accommodate the relative displacements that near-fault shaking imposes. Where dowels were poorly anchored or under-reinforced, the connections that should have tied roof girders to columns simply gave way.

These observations align with a long history of lessons from Turkish earthquakes. Precast structures were damaged in the 1998 Ceyhan earthquake, the 1999 Kocaeli earthquake, the 2011 Van earthquake, and the 2020 Sivrice earthquake, and in each event the same weak points surfaced: connections, corbels, and the detailing that modern codes require but field practice does not always deliver. What distinguishes the new study is that it does not stop at cataloguing damage. It converts the field evidence into quantitative fragility models, the statistical machinery that engineers use to estimate the probability that a structure will exceed a given damage state at a given level of ground shaking intensity.

Fragility analysis works by subjecting numerical models of a structure to suites of ground motion records and tracking how often a governing limit state, such as the onset of significant connection damage or loss of lateral load capacity, is exceeded as shaking intensity increases. The team built detailed nonlinear models of representative reinforced concrete prefabricated buildings and ran them through ground motions representative of the Kahramanmaraş sequence, including records with the velocity pulses and strong vertical components characteristic of near-fault sites. The resulting fragility curves provide a probabilistic portrait of vulnerability, allowing engineers to compare design variants on a common, defensible footing rather than relying on anecdote alone.

The single most striking quantitative finding concerns the roof girder-to-corbel connection. When the dowels connecting girders to columns were bolted, the seismic resilience of the structure improved dramatically: the median ground motion intensity at which the governing limit state was exceeded nearly doubled compared with structures relying on unbolted dowel connections. In practical terms, a building with bolted dowel connections could withstand roughly twice the shaking intensity before reaching its critical damage threshold. That is not an incremental improvement; it is the difference between a structure that survives a near-fault event and one that does not, achieved through a connection detail that costs comparatively little to implement.

The study also examined the role of infill walls, the masonry or precast panels that fill the bays between columns. In general, infill walls improved seismic resistance, stiffening the frames and sharing lateral load that would otherwise concentrate entirely on the columns. But the analysis revealed a crucial caveat: the benefit depended heavily on the integrity of the connections between the walls and the surrounding frame. Where those connections were robust, the walls acted as effective seismic fuses and load-sharing elements. Where the connections were poor, the walls detached early, their contribution vanished, and in some scenarios the falling panels introduced additional hazards. The lesson is that infill walls are not a passive benefit that can be assumed; they are only as good as the detailing that ties them into the structural system.

Near-fault effects emerged as a decisive amplifier of all these vulnerabilities. Earthquakes that rupture directly beneath or very close to a site produce ground motions with forward directivity, meaning a long-period velocity pulse arrives with much of the fault’s slip concentrated in a single large cycle of motion. The Kahramanmaraş events, including documented episodes of supershear rupture, delivered exactly this kind of pulse-like loading, along with vertical accelerations strong enough to degrade the friction and bearing capacity of simply supported precast elements. For connections already weakened by missing pads or deficient dowels, the combination of horizontal pulses and vertical acceleration was punishing. The study’s numerical results make clear that fragility assessments for precast buildings in near-fault zones must explicitly account for these motion characteristics rather than relying on generic record sets.

From these findings the authors draw a clear retrofitting agenda for the existing stock of reinforced concrete prefabricated structures. Priority measures include upgrading connection details, particularly bolting dowel connections at girder-corbel joints; adding elastomeric bearing pads where they are missing; and installing properly designed precast infill walls with reliable connections. Beyond the physical interventions, the study emphasizes the need for clear design guidelines and rigorous field assessment protocols so that existing buildings, especially in regions exposed to near-fault seismicity, can be systematically evaluated and reinforced before the next earthquake rather than after. The authors note that implementing these strategies would substantially enhance the seismic resilience of the precast building stock, reducing potential future human and economic losses.

The broader significance of the work extends beyond Türkiye. Precast industrial construction is common across seismic regions worldwide, from the Mediterranean to the Americas, and the failure modes documented after Kahramanmaraş echo those observed after the 2012 Emilia earthquakes in Italy, the 1994 Northridge earthquake in California, and the 1995 Kobe earthquake in Japan. The Turkish study adds a quantitative dimension to that international record, demonstrating with fragility curves just how much performance hinges on a handful of connection details. For engineers, the message is disarmingly simple: in prefabricated construction, the earthquake finds the joints. Bolting a dowel, seating a bearing pad, or grouting a connection properly may look like minor line items in a construction budget, but the difference they make, roughly a doubling of the shaking a building can survive, is the kind of margin on which lives and livelihoods depend when the fault finally slips.

Subject of Research: Seismic fragility and construction deficiencies of reinforced concrete prefabricated buildings in the 2023 Kahramanmaraş earthquakes

Article Title: Seismic performance assessment of reinforced concrete prefabricated structures during the 2023 Kahramanmaraş earthquakes: fragility analysis and construction deficiency evaluation

Article References: Seismic performance assessment of reinforced concrete prefabricated structures during the 2023 Kahramanmaraş earthquakes: fragility analysis and construction deficiency evaluation. (n.d.). https://doi.org/10.1007/s10518-026-02712-5

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02712-5

Keywords: prefabricated concrete, Kahramanmaraş earthquakes, fragility analysis, seismic performance, dowel connections, corbel connection, elastomeric bearing pads, infill walls, near-fault ground motion, retrofitting, East Anatolian Fault, Bulletin of Earthquake Engineering

Hybrid buildings occupy an awkward middle ground in structural engineering. They combine reinforced concrete frame elements, columns and beams, with load-bearing masonry walls in ways that do not fit the textbook definitions of either a pure concrete frame or a pure masonry structure. In these buildings, the stiff masonry walls and the more flexible concrete frames share the task of resisting lateral earthquake forces, producing complex load transfer paths and highly uneven stiffness distributions. Engineers have long known from laboratory studies that infill masonry walls can dramatically alter how a concrete frame responds to shaking, sometimes protecting it and sometimes triggering brittle failures. But when it comes to regional risk assessments, buildings like these are typically forced into one of the two standard categories, and their distinctive behavior is effectively erased from the statistics.

The February 2023 sequence made the cost of that simplification painfully visible. The magnitude 7.8 Pazarcık earthquake and the magnitude 7.6 Elbistan event struck hours apart, subjecting cities across Hatay, Gaziantep, and Kahramanmaraş provinces to some of the strongest ground motions ever recorded in Türkiye. In the aftermath, teams from the Ministry of Environment, Urbanization and Climate Change carried out rapid visual damage inspections across hundreds of thousands of structures, tagging each building with a damage class. That enormous dataset, normally used simply to prioritize demolitions and aid, became the raw material for the new analysis.

From the official field assessments, the researchers filtered out 169 low-rise hybrid buildings of one to three stories located in the Antakya and Nurdağı regions. For each building, they derived a coordinate-based estimate of short-period spectral acceleration, a standard measure of ground shaking intensity at the periods relevant to stiff, low-rise structures. The values came from the USGS ShakeMap rasters for both main shocks, and for every building the team adopted the larger of the two estimates as the maximum envelope demand, a conservative choice that reflects the cumulative assault of the two events on the same structure.

The damage picture in the sample was grim. Nearly 60 percent of the 169 buildings, 59.76 percent exactly, had been classified as heavily damaged, requiring urgent demolition, or had collapsed outright. The authors are careful to stress that this figure describes their filtered sample, not the region as a whole. Because the representativeness of the field data could not be established, the proportion should not be read as an estimate of how widespread severe damage was across all hybrid buildings in the affected areas. Still, the sheer concentration of severe outcomes in a dataset drawn from official inspections underscores why the researchers felt these structures warranted dedicated analysis.

To convert the paired observations of shaking intensity and damage into something predictive, the team turned to binary logistic regression, a statistical technique widely used in empirical fragility work. For each of three damage thresholds, slight-or-worse, moderate-or-worse, and heavy-or-worse, they fitted a continuous fragility function that expresses the probability of exceeding that threshold as a function of the spectral acceleration demand. Fragility curves of this kind are the workhorses of earthquake loss estimation: feed in an expected ground motion and the curve returns the likelihood that a typical building of the class will sustain at least a given level of damage.

The resulting median capacities are strikingly close together. The spectral acceleration at 0.3 seconds corresponding to a 50 percent probability of exceedance came out at 1.238 g for the slight-or-worse threshold, 1.405 g for moderate-or-worse, and 1.490 g for heavy-or-worse. In many building classes, these medians would be spread much further apart, reflecting a gradual progression from cosmetic cracking to structural distress. The tight clustering here suggests that once short-period shaking in these hybrid buildings crosses a certain band, damage can escalate rapidly from mild or moderate levels to heavy damage, leaving little margin between repairable and irreparable states. The authors caution that part of this pattern may also reflect uncertainties in the dataset, including the coarse binary and rapid visual damage classifications on which the models rest, and they note that the relationship for the lowest threshold showed only marginal statistical significance.

Even with those caveats, the implications for seismic risk assessment are significant. If hybrid buildings can jump from moderate to severe damage within a narrow range of demand, then treating them as ordinary reinforced concrete frames or as masonry buildings could seriously misestimate both expected losses and the number of structures likely to need demolition after a major event. The study argues that low-rise hybrid structures should be evaluated as a candidate separate vulnerability group, one whose models explicitly account for infill-wall and frame interaction, stiffness mismatch between the two structural materials, and discontinuities in the load path. Such an approach would bring regional risk models closer to the behavior that laboratory experiments on infilled frames have documented for decades, from the pioneering experimental evaluations of masonry-infilled concrete frames to recent work on confined masonry and mixed construction.

The methodology itself is a template for post-earthquake science. Rather than waiting years for detailed structural surveys, the researchers showed that official rapid assessment data, when combined with coordinate-matched ShakeMap intensity values, can yield usable fragility functions for a building class that would otherwise remain invisible. This approach echoes statistical procedures developed for earthquake damage fragility curves over the past two decades and complements recent empirical fragility studies of reinforced concrete buildings in the same earthquake. It also aligns with a broader movement toward faster, data-driven damage assessment, including machine learning frameworks that infer ground-level damage from aerial imagery.

The authors are explicit about the limits of their findings. The dataset is geographically concentrated in two districts, and the ground motions it reflects carry the specific signature of the 2023 sequence, including directivity effects and site conditions particular to the region. The fragility curves should therefore be interpreted as broad statistical indicators of relative vulnerability rather than precise predictive tools for any individual building. Data availability is also constrained: the underlying damage records can be obtained from the corresponding author upon reasonable request, subject to permission from the Turkish ministry that collected them. Nevertheless, as Türkiye rebuilds and as other earthquake-prone countries confront their own stocks of informal, mixed-construction buildings, the message of the study is hard to ignore. The buildings that defy easy classification are precisely the ones that risk models most often get wrong, and the 2023 Kahramanmaraş earthquakes have now provided the empirical evidence to prove it.

Subject of Research: Empirical seismic fragility assessment of low-rise hybrid concrete-masonry buildings damaged in the 2023 Kahramanmaraş earthquake sequence in Türkiye

Article Title: Empirical fragility assessment of low-rise hybrid buildings following the 2023 Kahramanmaraş earthquake sequence

Article References: Türer, A., Çağlar, F. A., & Bahçacı, Y. (2026). Empirical fragility assessment of low-rise hybrid buildings following the 2023 Kahramanmaraş earthquake sequence. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02689-1

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02689-1

Keywords: hybrid buildings, empirical fragility, Kahramanmaraş earthquakes, seismic vulnerability, spectral acceleration, logistic regression, infill walls, rapid visual screening, Antakya, Nurdağı, ShakeMap, earthquake damage assessment