Search Results (587)

Proto-AGI describes the intermediate stage of artificial intelligence between narrow task-specific tools and fully autonomous general intelligence. This paper presents the first formal operationalisation of Proto-AGI traits within a cross-domain digital workflow for structural engineering and demonstrates it through a four-domain computational ecosystem applied to seismic vulnerability assessment. Viktor.ai processes cone penetration test data to stratify a three-layer soil profile, identifying a compressible intermediate stratum at 5 to 12 m depth with amplification characteristics in the 0.3 to 0.7 second period range, based on the depth and stiffness contrast of the weak layer rather than a formal site response analysis. The Fayaz RotD script computes orientation-independent RotD50 and RotD100 response spectra for two contrasting ground motion records: the near-fault Northridge record (RSN 1086, Mw 6.69) delivers RotD50 = 2.00 g and RotD100 = 2.79 g at the structural natural period of 0.41 s, a 39.6% directional uplift; the moderate-distance Kobe record (RSN 1107, Mw 6.9) delivers RotD50 = 0.591 g and RotD100 = 0.795 g at the same period. OpenSeesPy nonlinear dynamic analysis of a five-storey reinforced concrete frame produces peak inter-storey drifts of 0.45% and 0.34% under the two records respectively, both within the FEMA 356 Immediate Occupancy threshold of 1.0%. A 3.4-fold spectral demand difference produces only a 1.32-fold drift difference, reflecting the combined effects of frequency content, pulse characteristics, duration and nonlinear structural response under the two contrasting records. The Viktor.ai RC Section Analyzer yields a curvature ductility factor of 2.3 under ACI 318-25, identifying deformation capacity as the governing constraint under more severe future demands. These four findings form a causal chain connecting site conditions, spectral demand, structural response and sectional capacity that no single domain produces independently—the emergent ecosystem intelligence that defines Proto-AGI in structural engineering practice. Full article

To address the insufficient load-bearing capacity and overall stiffness of timber truss roofs in brick–timber and earth–timber structures in rural areas, as well as the requirements for preserving traditional architectural characteristics, a steel–timber composite roof system was proposed. The system was developed through rational integration of timber and steel components to enhance the overall mechanical performance of the structure. At the joint level, flexural performance tests were conducted on cramp-iron joint, gusset–plate joint, and steel–timber joint. The moment–rotation relationships, failure modes, and ductility characteristics of the three joint types were systematically investigated. Based on the experimental results, a trilinear moment–rotation model was established. Furthermore, a finite element model of the roof structure was established using SAP2000 (26.2.0), and the stress distribution and load–displacement responses under horizontal static loading were analyzed through numerical simulation. The influence of different joint configurations on the mechanical performance of the roof structure was evaluated from an overall structural perspective. The results demonstrated that the peak bending moment of the steel–timber joint was increased by approximately 163.50% and 3.74% compared with those of the cramp-iron joint and gusset–plate joint, respectively. The ductility coefficient was enhanced by approximately 9.33% and 62.91%, respectively. In the finite element model of the roof structure, the peak load of the roof system with the steel–timber joint was increased by approximately 114.96% and 9.54%, while the corresponding displacement capacity was improved by approximately 76.62% and 43.41%, compared with the other two roof systems, respectively. Future studies will focus on further evaluating the seismic performance of steel–timber composite roof systems through cyclic loading experiments, dynamic response analysis, and full-scale structural validation, thereby providing a more comprehensive understanding of their long-term applicability in earthquake-prone rural buildings. Full article

To reduce the modeling effort and computational cost of assembled composite shear walls with C-shaped steel frames in global structural analysis, this study proposes an engineering-oriented simplified mechanical analysis method. Three representative specimens—a C-shaped steel-frame composite shear wall (CSCSW), a rectangular steel-frame composite shear wall (RSCSW), and a T-shaped, C-shaped steel-frame composite shear wall with a vertical connection (VTCSWC)—are decomposed into functional modules according to their load-transfer mechanisms. Simplified models comprising axial springs, diagonal braces, and a modified three-vertical-line-element model are established. Degrading bilinear Clough and trilinear Takeda models are adopted as the restoring-force relationships, and the governing parameters are determined through mechanical equilibrium analyses. The three simplified wall models are implemented in OpenSees to obtain hysteresis curves, skeleton curves, and stiffness-degradation responses. Comparisons with quasi-static test results show that the errors in peak load and secant stiffness are both within 10%, while the models reproduce the stiffness degradation and pinching characteristics of the specimens. Relative to refined three-dimensional solid finite element models, the proposed approach substantially reduces computational cost without compromising engineering accuracy, providing an efficient tool for structural design and seismic performance assessment of assembled C-shaped steel-framed composite shear-wall systems. Full article

Earthquake-induced fracturing and microcrack development in subsurface strata are widely recognized as important processes influencing seepage and the hydrological behaviour of surface water bodies, particularly in tectonically active mountainous terrains. However, the hydrogeological response to repeated low-magnitude (<4) seismic events remains poorly understood. This study presents an integrated geoelectrical and remote sensing investigation of the Nagi Lake region in the Sikkim Himalaya, India, based on Vertical Electrical Sounding (VES) surveys conducted in May 2022 and March 2026, following a seismic sequence of 74 low-magnitude earthquakes recorded during February 2026. Comparative analysis of four VES profiles (VES1–VES4), supported by validatory factor analysis, reveals spatially heterogeneous changes in subsurface electrical characteristics between the two survey periods. VES1, VES2, and VES3 indicate reduced signatures of pre-existing microcracks that are consistent with sediment densification and partial sealing, whereas VES4 suggests localized development or persistence of microfractures. Because the surveys span approximately four years, these changes likely reflect the combined influence of long-term hydrogeological, environmental, and geomorphic processes, with the February 2026 seismic sequence representing one potential contributing factor rather than the sole driver. To further evaluate ground deformation, Sentinel-1A Synthetic Aperture Radar (SAR) data acquired between January 2019 and March 2026 were analysed using Persistent Scatterer Interferometric SAR (PS-InSAR). The results indicate cumulative Line-of-Sight (LOS) displacements ranging from −17.9 cm (movement away from the satellite) to +3.5 cm (movement toward the satellite) in the vicinity of Nagi Lake, reflecting localized surface deformation with millimetre-scale precision. These observations provide complementary evidence of ongoing subsurface adjustment that may promote sediment compaction and microcrack modification. Overall, the study demonstrates measurable temporal changes in the subsurface structure of the Nagi Lake area and suggests that repeated low-magnitude seismicity may contribute to subsurface restructuring alongside other environmental processes. The findings highlight the value of integrating geophysical monitoring and satellite-based deformation analysis for understanding groundwater–surface water interactions and supporting the sustainable management of vulnerable Himalayan water bodies. Full article

Welded reinforcement cages (WRCs), which connect longitudinal reinforcement and stirrups through welding, have attracted increasing attention for industrialized construction of reinforced concrete (RC) structures. However, the welding process may introduce heat-affected zones, residual stresses, and local metallurgical changes in reinforcing bars, raising concerns regarding the potential influence of welded longitudinal-bar-to-stirrup connections on the seismic performance of RC bridge piers. This study experimentally investigates this issue through quasi-static cyclic tests on two large-scale RC bridge pier specimens with identical reinforcement layouts but different reinforcement connection methods. One specimen adopted conventional tied connections between longitudinal reinforcement and stirrups, whereas the other employed welded connections. The seismic responses of the specimens were evaluated in terms of failure mode, hysteretic behavior, skeleton curve, strength, ductility, stiffness degradation, energy dissipation, residual displacement, and strain development. The results showed that both specimens exhibited flexure-dominated failure with similar crack propagation and concrete-cover spalling characteristics. The differences in yield and peak strengths were within 5%, and the cumulative energy dissipation differed by only 2.1%, indicating comparable global seismic performance. The welded specimen exhibited a slightly larger ultimate displacement (12.8%) and ductility coefficient (9.4%), while the stiffness degradation characteristics remained nearly identical. Although several weld spots detached during the post-peak loading stage, no fracture or necking of the longitudinal reinforcement was observed, suggesting that the adopted welding procedure did not adversely affect the cyclic deformation behavior of the reinforcement. Within the scope of the tested specimens, the results demonstrate that welded longitudinal-bar-to-stirrup connections can maintain the seismic performance of RC bridge piers and provide experimental evidence for the potential application of WRCs in industrialized bridge construction. Further studies involving additional specimens and broader design parameters are required to validate the general applicability of these findings. Full article

Dry-connected prefabricated composite walls have been increasingly used in steel structures owing to the development of building industrialization and the demand for rapid and efficient construction. However, the respective influences of dry-connection configuration and wall panel material on the seismic response of prefabricated composite walls require further clarification. To address this issue, full-scale quasi-static tests, continuum damage mechanics (CDM) analysis, and finite element simulations were conducted. Six specimens were tested under low-cycle reversed loading. The influence of connection type was evaluated by comparing MRC walls with U-type and Z-type connections, whereas the influence of wall panel material was evaluated by comparing MRC and SFC walls under U-type connections. For the tested MRC walls, the deformation capacity of the connections strongly influenced the failure mode. The U-type rigid connections provided limited deformation buffering, resulting in stress concentration at the wall ends, initial cracking at displacements of 8–10 mm, rapid crack propagation, and semi-brittle failure. In contrast, the Z-type flexible connections released deformation demand through the slip and rotation mechanisms of the slotted holes. The maximum tested displacements of the Z-type specimens were approximately 2.58–2.78 times the ultimate displacements of the corresponding U-type specimens. The Z-type specimens maintained stable load-carrying behavior with limited panel damage throughout the tested displacement range. Furthermore, a restoring-force calculation method was established based on CDM theory, and the predicted peak loads were generally consistent with the experimental results. This study identifies the load-transfer, deformation, and energy-dissipation characteristics of the tested connection–panel configurations and provides comparative evidence for the further development of prefabricated composite wall systems. Full article

Viscoelastic dampers, leveraging the synergistic mechanism of viscous dissipation and elastic recovery, simultaneously reduce seismic-induced structural displacement and acceleration responses while offering the advantages of simple construction and ease of installation, which hold broad prospects in both the seismic design of new buildings and the retrofitting of existing structures. This work aims to propose a rapid optimization design method for viscoelastic dampers considering torsional effect for three-dimensional solid structures. First, a full-scale prefabricated assembled viscoelastic damper was developed, and mechanical property tests were conducted under a series of loading conditions. Based on the test results, a genetic algorithm is employed to optimize the design scheme of viscoelastic dampers through co-simulation using MATLAB R2022a and OpenSees. The optimization objectives consider both the inter-story drift ratio and acceleration response of the structure, with particular emphasis on the influence of torsional effects. Given that the proposed optimization scheme accounts for structural dynamic characteristics, building functionality, and the universality of seismic excitations, it serves as a design reference for the optimization analysis of other damped structures. Full article

The basement lithology in the northern South China Sea remains poorly constrained because of the lack of drilling data, which creates major challenges for predicting bedrock buried-hill reservoirs. This study is based on 2D and 3D seismic data, together with gravity and magnetic data, and is constrained by previous studies on the regional tectonic framework and lithologic distribution of the northern South China Sea. We investigated the basement lithologic composition of the XS area, established an integrated gravity–magnetic–seismic interpretation framework for basement lithology, and discussed the possible geological controls on basement lithologic distribution. The results show the following: (1) The basement in the study area is mainly composed of granite intrusive bodies, metamorphic rocks, and volcanic rocks. Granite bodies are characterized by irregular to intrusive seismic geometries, strong double-peak reflections at the upper boundary, and weak-amplitude, medium- to low-frequency internal reflections, reflecting their intrusive characteristics. Metamorphic rocks show diverse external seismic geometries, single-peak or weak reflections at the upper boundary, and medium- to strong-amplitude parallel internal reflections that intersect the upper boundary at high angles. Their gravity and magnetic responses show considerable overlap with those of granitic rocks. Volcanic rocks commonly show mound-shaped or lenticular seismic geometries and medium- to strong-amplitude, moderately continuous internal reflections. Intermediate–mafic volcanic rocks are associated with relatively stronger gravity and magnetic anomaly responses, whereas felsic volcanic rocks generally exhibit weak to moderate gravity and magnetic responses. These characteristics provide an integrated seismic–gravity–magnetic constraint framework for basement lithology interpretation in the South China Sea. (2) Integrated gravity–magnetic–seismic interpretation indicates that, near the present top of the pre-Cenozoic basement in the XS area, granite intrusive bodies are the dominant lithology. Metamorphic rocks mainly occur as discontinuous basement remnants in local structural lows or erosional windows, whereas volcanic rocks are mainly distributed near fault intersections or occur as bead-like bodies along fault zones. (3) The distribution of granite intrusive bodies and metamorphic basement is interpreted to be related to Indosinian–Yanshanian magmatic activity, tectonic deformation, and subsequent denudation. Faults formed during Early Yanshanian compression were later reactivated during the Himalayan period and may have acted as magma conduits, promoting the development of volcanic edifices along fault zones. Full article

Reservoir-triggered seismicity (RTS) is commonly associated with stress perturbations induced by reservoir loading and pore-pressure diffusion within fractured rock masses. Shortly after the initial impoundment of the Irapé Hydropower Plant (Minas Gerais, Brazil), a sequence of induced earthquakes was recorded, providing an opportunity to investigate the compatibility between reservoir loading and the observed seismic response. This study presents a first-order hydromechanical assessment integrating finite element modelling, analytical elasticity solutions, and pore-pressure diffusion theory to evaluate the spatial distribution of stress perturbations and the characteristic diffusion times associated with reservoir impoundment. A two-dimensional elastic model was developed to simulate stress redistribution induced by the maximum reservoir load, while a parametric diffusion analysis was performed for representative hydraulic diffusivities and hypocentral depth scenarios between 1 and 6 km. Numerical results showed excellent agreement with the analytical elasticity solution (RMSE = 14.36 kPa, MAE = 11.08 kPa, mean relative error = 1.38%, and R² = 0.999), supporting the reliability of the numerical model. The simulations indicate that vertical stress perturbations decrease from approximately 1.8–2.0 MPa immediately beneath the reservoir to about 0.01–0.1 MPa at kilometer-scale depths, where the recorded seismicity is presumed to occur. The diffusion analysis indicates that pore-pressure propagation to these depths generally requires substantially longer times than the interval between reservoir filling and the onset of seismic activity. Nevertheless, owing to uncertainties in hydraulic diffusivity, fracture connectivity, and hypocentral depth estimates, the diffusion results are interpreted as a first-order sensitivity analysis rather than a site-specific prediction. Overall, the results support the temporal compatibility and physical plausibility of rapid elastic stress redistribution as a potential triggering mechanism, while recognizing that the available geological and seismological data are insufficient to establish a direct causal relationship or demonstrate fault reactivation. Full article

High-voltage porcelain column-type equipment systems comprise various equipment units whose porcelain columns generally have circular cross-sections and approximately axisymmetric geometries. Although this geometric symmetry results in nominally equivalent lateral mechanical properties at the component level, differences among equipment types and multiple uncertainty sources may lead to heterogeneous seismic responses at the system level. To investigate the combined effects of ground-motion randomness and uncertainties in the elastic modulus and diameter of porcelain sleeves and damage control indices, Latin hypercube sampling was employed to generate 100 structural models with different modeling parameters. These models were randomly paired one-to-one with 100 selected ground-motion records, and uncertainty in the damage control indices was incorporated into the dynamic response and fragility analyses. The results indicate that the variability in structural seismic responses arises from the combined effects of modeling-parameter uncertainty and ground-motion randomness. These effects are propagated to the fragility curves through changes in the median ground-motion intensity and total logarithmic standard deviation of the fragility functions. The fragility curves accounting for multiple uncertainty sources generally fluctuate around the baseline curves considering ground-motion randomness alone, without exhibiting a consistent upward or downward shift. No strictly monotonic relationship was observed between the coefficients of variation in the uncertain parameters and the total dispersion of the fragility results, although larger parameter variability produced greater deviations from the baseline in some cases. Nevertheless, the overall differences remained limited, with a maximum absolute difference of 0.043. From the perspective of symmetry, the results demonstrate that component-level geometric symmetry coexists with system-level response heterogeneity and cannot alone eliminate the effects of equipment-specific characteristics and stochastic uncertainties on seismic fragility. Within the scope of this study, fragility curves considering ground-motion randomness alone may therefore provide a reasonable approximation for engineering assessment. Full article

Recent destructive earthquakes have clearly demonstrated that damage distribution in many cities developed on thick alluvial deposits is strongly controlled by local soil amplification and site response effects. Soil conditions therefore play a critical role in determining the characteristics of ground motion and the seismic performance of structures during earthquakes. This study presents the first microzonation-oriented site response assessment for the rapidly urbanizing city of Afyonkarahisar, which is characterized by thick alluvial deposits and a shallow groundwater table. A database consisting of 124 boreholes was compiled to characterize the subsurface stratigraphy of the study area. Shear-wave velocity profiles were verified using both SPT-based correlations and MASW measurements to ensure reliable input parameters for dynamic analyses. One-dimensional equivalent linear and nonlinear site response analyses were performed using the DeepSoil program, employing eleven earthquake ground motion records scaled according to the Turkish Building Earthquake Code. The results indicate that for Earthquake Level-1 (EL-1; 2% probability of exceedance in 50 years) ground motions, nonlinear analyses produce lower amplification factors (1.00–1.62), whereas equivalent linear analyses tend to predict higher amplification values, reaching up to 4.52, owing to their simplified treatment of soil nonlinearity. Under Earthquake Level-2 (EL-2; 10% probability of exceedance in 50 years) motions, both methods yield comparable amplification values ranging from 1.18 to 1.72. GIS-based amplification maps reveal significant spatial variability within the study area and identify zones where local soil conditions may substantially increase seismic demand. The findings suggest that nonlinear site response analysis is more appropriate for representing soil behavior under strong ground motions (EL-1), while both approaches provide comparable results for moderate ground motions (EL-2). Comparisons with Eurocode 8 and NEHRP site classifications further confirm the broader applicability of the results. Overall, this study provides a practical framework for reliable site response assessment that supports earthquake-resistant design and microzonation studies in seismically active regions characterized by complex alluvial environments. Full article

Steel-reinforced concrete (SRC) frame-bent hybrid structures are widely used in conventional island buildings of nuclear power plants because of their favorable seismic performance and economic efficiency. However, the seismic fragility of these structures has not been adequately investigated. In this study, the main turbine building of the CAP1400 nuclear power plant in Rongcheng, Shandong Province, China, was selected as the prototype. A three-bay frame-bent substructure was extracted, and a 1/7-scale model was designed for pseudo-dynamic testing to investigate the evolution of seismic damage and the failure mechanisms of the structure. Based on the experimental results, a refined numerical model was developed in OpenSees. Incremental dynamic analysis (IDA) was subsequently conducted to evaluate the seismic fragility of the SRC frame-bent main turbine building under far-field and near-fault ground motions. The results indicate that the structural stiffness progressively decreases with increasing seismic demand because of concrete cracking and cumulative damage. Damage is primarily concentrated in the short columns, beam-column joints, and column bases. The fragility response also exhibits pronounced directional dependence. Because of the lower lateral stiffness in the X direction, the structure develops larger interstory drift demands and higher probabilities of exceeding the prescribed damage states in the X direction than in the Y direction. For the selected ground-motion suites, near-fault records generally produce slightly higher exceedance probabilities than far-field records at the same peak ground acceleration (PGA), with a maximum difference of 3.68%. However, the magnitude of this difference varies with the damage state, excitation direction, and ground-motion intensity. These findings indicate that pulse-like near-fault ground motions may have a measurable but moderate effect on the seismic fragility of SRC frame-bent main turbine buildings. This study establishes an experimentally validated framework for assessing the seismic fragility of SRC frame-bent structures in nuclear power plants and identifies their vulnerable components, dominant damage mechanisms, and fragility characteristics under different types of ground-motion input. Full article

Distributed Acoustic Sensing (DAS) provides dense spatial measurements of the dynamic strain along fiber optic cables, offering high-resolution wave sensing for ground motion monitoring and subsurface imaging applications. However, DAS records the axial strain or strain rate, whereas traditional seismic and engineering ground motion equipment and derived metrics are based on particle displacement, velocity, or acceleration, necessitating reliable strain-to-velocity conversion methods. This study evaluates three widely used conversion approaches: the fk-rescaling, curvelet-based conversion, and slant-stack methods. These approaches are applied to a unique high-energy, near-field, active-source dataset collected at the Birds Landing Site in Sherman Island, California. The dataset includes wavefields generated by a large transmission tower collapse and sledgehammer impacts used for subsurface imaging. The wavefields were recorded simultaneously by a 1.4 km DAS array and 71 collocated nodal stations (NSs). Using 63 DAS–NS pairs, we quantify the strain-to-velocity conversion method performance using amplitude and phase transfer functions (TFs) between DAS-derived and NS particle velocity records, with the root-mean-square error (RMSE) evaluated across three frequency bands: 0.5–100 Hz, 1–10 Hz, and 10–100 Hz. The results show that fk-rescaling provides the most stable amplitude response across both source types, while both the fk-rescaling and slant-stack methods generally yield the best phase agreement. Curvelet-based conversion shows a greater variability and larger RMSE values. All methods yield a poorer amplitude reconstruction at higher frequencies, while the phase content is generally preserved more reliably than amplitudes. Differences between the tower collapse and sledgehammer sources demonstrate the influence of the source characteristics and spatial processing window length on the conversion performance. The findings provide practical guidance for selecting suitable strain-to-velocity conversion methods for active-source DAS applications, particularly where collocated reference sensors are unavailable. Full article

This study aims to elucidate the developmental characteristics of strike-slip fault-controlled Ordovician fault-karst reservoirs (FKRs) in the Yuman area of the Tarim Basin. By integrating regional tectonic settings with high-resolution 3D seismic data, we implemented a comprehensive 3D seismic interpretation strategy. Concurrently, a statistical evaluation of 22 strike-slip fault segments was conducted based on their kinematic attributes, connectivity, and seismic “string-of-beads” responses. The results indicate that the Yuman area is dominated by an interlaced network of NE-striking (sinistral transpressional) and NS-striking (dextral transpressional) faults. Three distinct reservoir-controlling patterns were identified among the 22 FKRs: Type I deep-penetrating transpressional (7 segments), Type II deep-penetrating transtensional (4 segments), and Type III weakly penetrating transpressional (11 segments). Based on reservoir scales and structural positioning, seven high-priority exploration targets were successfully delineated. Furthermore, the results reveal that fault structural maturity, vertical penetration, and kinematic regimes are the pivotal factors controlling FKR quality and stratigraphic distribution. Type I patterns exhibit the highest structural maturity and develop cross-stratigraphic, large-volume reservoirs in shallow sections, representing prime targets. Conversely, Type III reservoirs are deeply buried due to constrained fault growth. Ultimately, reservoir evaluation priority ranges from Type I, through Type II, to Type III, with Targets ① to ④ identified as the most promising candidates for localized exploration breakthroughs. Full article

To investigate the feasibility and effectiveness of seismic repair for prefabricated single-beam column joints in modern Chinese traditional-style buildings (MCTBs), low-cycle reversed loading tests were conducted on two original joints with different T-stub web thicknesses and one repaired joint. A repair strategy was proposed in which damaged T-stub connectors were removed and replaced with welded end-plate connections. The seismic behavior of the joints, including failure mode, hysteretic response, skeleton curve, stiffness degradation, ductility, energy dissipation capacity, and seismic performance comparison between the original and repaired joints, was systematically evaluated. In addition, a refined finite element model was established using ABAQUS and validated against the experimental results to investigate the stress distribution, deformation characteristics, and load-transfer mechanism of the joints. The results indicate that damage in the original joints was mainly concentrated in the T-stub connection region, while the beam and column members remained essentially intact, demonstrating an effective damage-control mechanism. Increasing the T-stub web thickness improved the load-carrying capacity, stiffness, and ductility of the joints. After repair, the load-transfer mechanism changed from a blind-bolted T-stub connection to a welded end-plate connection, resulting in a different damage evolution pattern and failure mode. Nevertheless, the repaired joint exhibited stable hysteretic behavior, satisfactory deformation capacity, and favorable energy dissipation performance. Compared with the original joint, the repaired specimen achieved a moment capacity comparison ratio of approximately 116%, stiffness comparison ratios exceeding 120%, and an energy dissipation comparison ratio of approximately 148%. The finite element results agreed well with the experimental observations and further revealed the evolution of stress concentration regions and load-transfer paths before and after repair. The present experimental results demonstrate the feasibility of the proposed repair method for rehabilitating damaged joints while maintaining satisfactory seismic performance without replacing the primary beam and column members. The proposed repair strategy therefore provides a practical and efficient solution for the post-earthquake rehabilitation of prefabricated joints in MCTBs. Full article