Seismic risk assessment of code-noncompliant reinforced concrete (RC) frames faces significant challenges due to structural heterogeneity and the complex interplay of site-specific hazard conditions. This study aims to introduce a novel framework that integrates three key concepts specifically targeting these challenges. Central to the methodology are fragility fuses, which employ a triplet of curves-lower bound, median, and upper bound-to rigorously quantify within-class variability in seismic performance, offering a more nuanced representation of code-noncompliant building behavior compared to conventional single-curve approaches. Complementing this, spectrum-consistent transformations dynamically adjust fragility curves to account for regional spectral shapes and soil categories, ensuring site-specific accuracy by reconciling hazard intensity with local geotechnical conditions. Further enhancing precision, the framework adopts a nonlinear hazard model that captures the curvature of hazard curves in log-log space, overcoming the oversimplifications of linear approximations and significantly improving risk estimates for rare, high-intensity events. Applied to four RC frame typologies (2-5 stories) with diverse geometries and material properties, the framework demonstrates a 15-40 % reduction in risk estimation errors through nonlinear hazard modeling, while spectrum-consistent adjustments show up to 30 % variability in exceedance probabilities across soil classes. Fragility fuses further highlight the impact of structural heterogeneity, with older, non-ductile frames exhibiting 25 % wider confidence intervals in performance. Finally, risk maps are presented for the four frame typologies, making use of non-linear hazard curves and spectrumconsistent fragility fuses accounting for both local effects and within-typology variability.

Seismic fragility denotes the probabilities of a system exceeding some prescribed damage levels under a range of seismic intensities. Classical seismic fragility studies in slope engineering usually construct fragility functions by making some assumptions for fragility curve shape, and always neglect spatial variability of soil materials. In this study, an assumption-free method on the basis of probability density evolution theory (PDET) is proposed for seismic fragility assessment of slopes. The random input earthquakes and spatially-variable soil parameters in slope are simultaneously quantified. By the proposed method, assumption-free fragility curves of a slope are established without limiting the fragility curve shape. The obtained fragility results are also compared with those from two classic parametric fragility methods (linear regression and maximum likelihood estimation) and Monte Carlo simulation. The results demonstrate that the proposed assumption-free method has potential to gives more rigorous and accurate fragility results than classical parametric fragility analysis methods. With the proposed method, more reliable fragility results can be obtained for slope seismic risk assessment.

Destructive earthquakes result in significant damage to a wide variety of buildings. The resulting damage data is crucial for evaluating the seismic resilience of buildings in the region and investigating urban resilience. Field damage data from 38 destructive earthquakes in Sichuan Province were collected, classified, and statistically analysed according to the criteria of the latest Chinese seismic intensity scale for evaluating building damage levels. Meanwhile, the construction features and seismic damage characteristics of these buildings were also examined. These results facilitated the development of a damage probability matrix (DPM) for various building typologies, such as raw-soil structures (RSSs), stone-wood structures (SWSs), brick-wood structures (BWSs), masonry structures (MSs), and reinforced concrete frame structures (RCFSs). The damage ratio was employed as the parameter for vulnerability assessment, and a comprehensive analysis was performed on the differences in damage levels among all buildings in various intensity zones and time frames. Furthermore, the DPMs were further refined by simulating additional data from high-intensity zones to more accurately represent the seismic resistance of existing buildings in multiple-intensity zones. Vulnerability prediction models were developed using the biphasic Hill model, which elucidates varying damage trends across different construction typologies. Finally, empirical fragility curves were established based on horizontal peak ground acceleration (PGA) as the damage indicator. This study is based on multiple seismic damage samples from various regions, accounting for the influence of earthquake age. The DPMs, representative of the regional characteristics of Sichuan Province, were developed for different building types. Furthermore, multidimensional vulnerability regression models and empirical fragility curves are established based on these DPMs. These models and curves provide a theoretical foundation for seismic disaster scenario simulations and the seismic capacity analysis of buildings within Sichuan Province.

Over the past few decades, engineering research has increasingly focused on the reliability assessment of transport infrastructures and their critical components when faced with multiple natural hazards. This trend stems from recognizing the substantial direct and indirect economic losses associated with infrastructure damage and the resulting downtime. The increasing frequency of intense hazard occurrences, as a consequence of climate change, coupled with the time-intensive nature of post-event bridge inspections, highlights the need for an efficient approach to assess bridge fragility to hazards that occur either as single abrupt events or in compounds, i.e., multiple hazard perturbations or combined incremental deterioration. This approach should account for the order of hazards and the accumulation of damage to bridge components. Within this context, we introduce an analytical method for evaluating the fragility of bridges affected by independent or multiple successive and independent natural hazards. The proposed method is demonstrated through a case study in which a riverine bridge is evaluated considering different sequences of hazards. Initially, the fragility of the bridge under individual hazards, such as earthquakes or floods, is calculated. Subsequently, multi-hazard fragility curves are constructed to capture the combined effects of these events. This approach is a comprehensive method for generating fragility curves for bridges, considering all structural components involved in the resisting system of the structure. These curves are based on a detailed estimation of thresholds for different limit states, encompassing multiple failure modes and accounting for soil-structure interaction (SSI) effects. The method employs a probabilistic framework to manage uncertainties in both the demand on the structure and its capacity to withstand single hazards. The framework is extended to include scenarios involving multiple hazards that occur separately or in series, emphasizing how cumulative damage influences the overall bridge fragility. The findings indicate a significant increase in the probability of damage for all the limit states examined, underscoring the importance of considering the cumulative effect of multiple hazards in the fragility analysis of bridges. The fragility models can be used in life-cycle risk assessment of aging bridges exposed to multiple hazards to inform decision-making and prioritization of investments for risk mitigation and climate adaptation.

The lateral cyclic bearing characteristics of pile foundations in coastal soft soil treated by vacuum preloading method (VPM) are not well understood. To investigate, static lateral cyclic loading tests were conducted to assess the impact of treatment durations and sealing conditions on pile performance. Results indicated that vacuum preloading significantly improved soil properties, with undrained shear strength (S-u) increasing by up to 36.5 times, especially in shallow layers. Longer treatment durations boosted the ultimate lateral bearing capacity by up to 125%, although the effect decreased with depth, suggesting an optimal duration. Sealing conditions had minimal impact on capacity but affected S-u distribution and pile behaviour. Analysis of p-y curves revealed that longer durations improved soil resistance in shallow layers, while shorter durations provided consistent resistance across depths. Sealed conditions enhanced displacement capacity. The API specification predicted soil resistance accurately for lateral displacements under 0.1D but showed errors for larger displacements. These findings emphasise the need for optimising VPM parameters to enhance pile-soil interaction and lateral cyclic performance. The study offers guidance for applying VPM in soft soil foundation engineering and balancing performance with cost efficiency.

This study analyzed seismic responses of shallow rectangular tunnels within the framework of soil-structure-soil interaction. The idealized soil profile and properties were derived from site-specific investigation reports. Racking curves, typically used in design, were reevaluated to reflect local soil conditions, nonlinear soil behavior, and seismic influences. Results differed significantly from traditional literature findings, emphasizing the importance of localized factors. Finite element methods enabled nonlinear soil parameter modeling and time-history analysis of soil-structure systems. Literature reviews and case studies identified potential damage states with discrete damage levels. The findings quantified probabilities of these damage states and established recurrence relationships for system damages. Fragility curve analyses, widely employed in structural engineering, were used to develop graphical representations of damage probabilities. This study's outcomes provide insights into the seismic behavior of tunnels under localized conditions and enhance reliability in geotechnical and structural engineering designs.

Assessment of seismic deformations of geosynthetic reinforced soil (GRS) walls in literature has dealt with unsolved challenges, encompassing time-consuming analyses, lack of probabilistic-based analyses, ignored inherent uncertainties of seismic loadings and limited investigated scenarios of these structures, especially for tall walls. Hence, a novel multiple analysis method has been proposed, founded on over 257,400 machine learning simulations (trained with 1582 finite element method analyses) and numerous performance-based fragility curves, to promptly evaluate the seismic vulnerability. The conducted probabilistic parametric study revealed that simultaneously considering several intensity measures for fragility curves is inevitable, preventing engineering judgement bias (up to 52% discrepancies in damage possibilities). Up to 75% contrasts between failure possibilities of 8 and 20 m walls, especially under earthquakes with common intensities (e.g. PGA <= 0.3g), raised serious concerns in the application of height-independent designing methods of GRS walls (e.g. AASHTO Simplified Method). Decreases in deformation possibilities were nearly the same due to increasing reinforcement stiffness (J) (1000 to 2000 kN/m) and reinforcement length to wall height ratio (L/H) (0.8 to 1.5); a decisive superiority of J variations over increasing L/H, as a remedial plan. The proposed methodology privileges engineers to swiftly assess the seismic deformations of multiple GRS walls at the design stage.

Rubble deposits with a high concentration of rock debris were created after the powerful earthquakes in Jiuzhaigou. Because of the restricted soil resources, water leaks, and nutrient deficits, these deposits pose serious obstacles for vegetation regeneration. The purpose of this study was to investigate the main mechanisms controlling soil water retention and evaluate the effects of different amendments on the hydraulic characteristics and water-holding capacity of collapsed rubble soils. Fine-grained soil, forest humus, crushed straw, and organic components that retain water were added to the altered soils to study the pore structure images and soil-water characteristic curves. Comparing understory humus to other supplements, the results showed a considerable increase in the soil's saturated and wilting water content. The saturated water content and wilting water content rose by 17.9% and 4.3%, respectively, when the percentage of understory soil reached 30%. Additionally, the enhanced soil's microporosity and total pore volume increased by 45.33% and 11.27%, respectively, according to nuclear magnetic imaging. It was shown that while clay particles and organic matter improved the soil's ability to adsorb water, they also increased the soil's total capacity to store water. Fine particulate matter did this by decreasing macropores and increasing capillary pores. These results offer an essential starting point for creating strategies for soil repair that would encourage the restoration of plants on slopes that have been damaged.

In order to accurately measure the internal stress-strain curve of plain concrete specimens and confined concrete specimens under compression, a new measurement method is proposed, which adopts conventional strain gauges to measure the internal strain data of the specimens, and the micro soil pressure box with ultra-large range is developed to measure the internal stress of the specimens. The uniaxial compression tests of 3 plain concrete specimens and 9 confined concrete specimens are completed, and the macroscopic failure process of the specimens and the stress-strain curves at different internal points are obtained. Combined with the experimental results, the accuracy of the calculation results of several classical confined concrete constitutive models is compared, and a modified constitutive model is proposed. Solid finite element analysis is used to analyze the stress-strain curves at different points inside the specimens, and the prediction accuracy of different constitutive models is compared. On this basis, nonlinear finite element analysis is used to verify the quasi-static test of RC columns, and the accuracy of different constitutive models in the nonlinear analysis at the component level is compared and analyzed. The results show that the measurement method proposed in this study can accurately measure the stress-strain data internal the concrete. The calculation results of the modified constitutive model proposed in this study are in the best agreement with the test results, and have a wide range of applications, which can be applied to the measurement of internal stress-strain curves of other different types of specimens.

The siliceous structure that protects diatoms, called frustule, is the main component of diatom sedimentary soils. These particles' physical and mechanical characteristics are challenging, given their geometric conditions of only a few microns. For this evaluation, specialized tools must be used, such as the Scanning Electron Microscope (SEM), the Atomic Force Microscope (AFM) and X-ray dispersion (XRD), among others. The bibliographic references show significant variability in the load-deformation behavior in frustules, diatoms or their organic components. Technical background information usually presents information on a single type of species. This research demonstrated the characterization and micromechanical evaluation of frustules of three morphologically distinguishable species of diatoms (Colombian, Mexican and Peruvian origin). The results showed similarities in the chemical composition of the three samples. The displacement records are variable depending on the species for the same load range. The location of the load application points by AFM on the different types of frustules is presented. The most significant deformation in the Mexican species and the regularity in the results of the Peruvian species stand out. Young's moduli were also calculated by applying the Hertz Model, which had the highest values in the Colombian sample.