Internal soil erosion in urban environments is a significant factor contributing to the chronic uneven settlement of subway stations. This paper investigates the seismic failure mechanisms of subway stations affected by prior soil internal erosion. Erosion is modeled via a practical approach based on the Cap plasticity model. A 2D finite element model of a two-layer, three-span subway station is developed to simulate its seismic response under various factors, including the seismic incidence angle, soil erosion, and earthquake motions. The vertical load transfer and damage assessment of the vertical elements are thoroughly analyzed across all the scenarios. The results show that after the adverse internal force redistribution caused by soil erosion in the corners of the underlying soil, the subway station experiences a progressive seismic failure process. As the seismic incidence angle increases, the deformation mode of the station shifts from a bilateral shear mode to a unilateral pushover mode, requiring more seismic energy for structural collapse.

This paper presents a comprehensive on-site decision-making framework for assessing the structural integrity of a jacket-type offshore platform in the Gulf of Mexico, installed at a water depth of 50 m. Six critical analyses-(i) static operation and storm, (ii) dynamic storm, (iii) strength-level seismic, (iv) seismic ductility (pushover), (v) maximum wave resistance (pushover), and (vi) spectral fatigue-are performed using SACS V16 software to capture both linear and nonlinear interactions among the soil, piles, and superstructure. The environmental conditions include multi-directional wind, waves, currents, and seismic loads. In the static linear analyses (i, ii, and iii), the overall results confirm that the unity checks (UCs) for structural members, tubular joints, and piles remain below allowable thresholds (UC < 1.0), thus meeting API RP 2A-WSD, AISC, IMCA, and Pemex P.2.0130.01-2015 standards for different load demands. However, these three analyses also show hydrostatic collapse due to water pressure on submerged elements, which is mitigated by installing stiffening rings in the tubular components. The dynamic analyses (ii and iii) reveal how generalized mass and mass participation factors influence structural behavior by generating various vibration modes with different periods. They also include a load comparison under different damping values, selecting the most unfavorable scenario. The nonlinear analyses (iv and v) provide collapse factors (Cr = 8.53 and RSR = 2.68) that exceed the minimum requirements; these analyses pinpoint the onset of plasticization in specific elements, identify their collapse mechanism, and illustrate corresponding load-displacement curves. Finally, spectral fatigue assessments indicate that most tubular joints meet or exceed their design life, except for one joint (node 370). This joint's service life extends from 9.3 years to 27.0 years by applying a burr grinding weld-profiling technique, making it compliant with the fatigue criteria. By systematically combining linear, nonlinear, and fatigue-based analyses, the proposed framework enables robust multi-hazard verification of marine platforms. It provides operators and engineers with clear strategies for reinforcing existing structures and guiding future developments to ensure safe long-term performance.

The present study proposes a rapid visual screening methodology for multi-hazard vulnerability assessment (termed as MH-RVS) of reinforced concrete (RC) buildings in the Indian Himalayan region considering earthquakes, debris flow, debris flood, and soil subsidence. An extensive field survey of 1200 buildings was conducted in three hill towns situated in the Northwestern Indian Himalayan region to identify prevalent multi-hazard vulnerability attributes. The presented MH-RVS methodology is statistically developed based on the information obtained from the current field survey and existing post-hazard reconnaissance studies. The proposed methodology effectively addresses the concern of underpredicting the expected damage states of RC buildings situated in hilly regions subjected to multi-hazard scenarios when they are assessed using RVS methodologies of seismic vulnerability assessment. Further, a simplified MH-RVS form is developed to collect field data and conveniently segregate the RC buildings based on their expected damage state under multi-hazard scenarios involving earthquakes, debris flow, debris flood, and soil subsidence. Stakeholders and decision-makers can use the proposed MH-RVS methodology to assess the perceived vulnerability of RC buildings in the Indian Himalayan region and devise timely strategies for structural strengthening and risk mitigation.

This paper presents a comprehensive method for analyzing prestressed concrete bridges subjected to multiple concurrent dynamic loads, incorporating soil-structure interaction (SSI) and seismic wave propagation effects. The study develops a comprehensive numerical framework that simultaneously accounts for traveling seismic waves, train-induced vibrations, and soil-foundation dynamics. Three-dimensional finite element modeling captures the complex interaction between the bridge structure, foundation system, and surrounding soil medium. The investigation considers the spatial variability of ground motion and its influence on the bridge's dynamic response, particularly examining how different wave velocities and coherency patterns affect structural behavior. Advanced material constitutive models based on damage mechanics theory are implemented to represent both linear and non-linear structure responses under dynamic loading conditions. The analysis reveals that traditional simplified approaches, which neglect SSI, train, and seismic loading combinations, and traveling wave effects may significantly misestimate the structural demands. The results demonstrate how wave passage effects can either amplify or attenuate the combined response depending on the relationship between seismic wave velocity, the frequency content of the ground motion recordings, and the local soil conditions. These findings could contribute to the development of more reliable design methodologies for prestressed bridges in seismically active regions with significant railway traffic.

The tall building construction sector has recently exhibited an increasing development, especially in Europe. This activity is aligned with European policies regarding soil conservation and social housing. Due to their slenderness, such structures are particularly sensitive to wind and earthquake loads. Nevertheless, current building codes, standards, and most scientific literature neglect the interaction of these events as simultaneity has always been considered a rare design case due to the limited effect on the structural elements. The present work carries out a careful statistical investigation on the occurrence of strong earthquakes accompanied by a wind load event, characterized by non-negligible daily mean-wind velocities in Italy, where more than onethird of its area is occupied by high mountains, limiting the urban development to confined zones. Subsequently, the effect of the simultaneous occurrence of earthquake and wind loads has been studied, both from the numerical and experimental points of view (i.e., shaking table and wind tunnel tests) to evaluate the consequences on structural and non-structural elements (e.g., fa & ccedil;ades) of a building case study. Results show that the cumulative effect of typical and noncatastrophic daily mean wind velocity (i.e., in the range of 5-10 m/s at 10 m from the ground) and a typical and non-catastrophic seismic daily shock (i.e., with magnitude in the range of 3-5), can trigger large inter-story drift ratio values and fatigue, causing damage to non-structural elements - like fa & ccedil;ades - and consequently a risk for occupants and high economic losses.

Historically, it has been demonstrated that bridges may be vulnerable to fire, and in many circumstances, resulting damage might not be apparent, and bridges could maintain acceptable levels of serviceability. In the absence of proven assessment tools and given the limited research that addresses bridge fire, research that better understands response and strives to improve highway bridge resiliency to fire is needed. Extending the work carried out during an earlier research stage, the present study focused on investigating performance of bridge pier columns that survive fire under coupled vehicle collision and air blast. Numerical models of single reinforced concrete columns supported by a pile foundation system and surrounded by air and soil volumes were created using LS-DYNA. As explicit solvers such as those available in LS-DYNA are infrequently used for fire analysis, an indirect two-step approach that integrated heat transfer and structural analyses was developed and validated against published fire-induced impact and blast test results. A parametric study that examined the effects of various fire exposure conditions and column diameters was completed. Performance was comprehensively assessed based on various structural response parameters, which included failure modes, lateral displacement, residual axial capacities, and shear demand-to-capacity ratios. Column damage was then categorized into six levels to qualitatively assess column performance under the aforementioned multi-hazards. The developed modeling approach was shown to be viable, and results indicated that larger column diameters could potentially remain in service in their final damage states after being repaired for fire durations of less than 120 min.

This study aims to advance knowledge on multi-hazard damage to shallow foundation bridges subjected to simultaneous scour, earthquake, and vehicular loads. While most water-crossing bridges have deep foundations, still, a significant number of water-crossing bridges have shallow foundations. In addition, there is limited research focusing on damage assessment of bridges with shallow foundations under multi-hazard scenarios. Therefore, this study proposes a probabilistic multi-hazard damage assessment framework for bridges with shallow foundations exposed to seismic, scour, and vehicular loadings. The proposed framework includes steps for hazard modeling, multi-hazard finite element modeling, non-linear time history analysis, and multi-hazard fragility modeling, and it was showcased on Chemin des Dalles Bridge, which is a typical bridge located in the Province of Quebec in Canada. Demand and fragility models parameterized on hazard and soil parameters were developed for the bridge components and a system fragility model was also developed using a series system assumption. The results from the analysis of these damage and fragility models indicated that scour notably increases component- and bridge-level response in typical shallow foundation bridges. However, until the scour depth is lower than the foundation height, the increased damage does not impose a significant threat to the bridge's safety. It was observed that earthquakes had the highest influence on the bridge components' response followed by scour and vehicular loads. Overall, the proposed framework can be used to facilitate policy-making toward informed bridge maintenance and retrofitting to aid in disaster mitigation planning and emergency response.

A hazard is a natural occurrence that might harm humans, animals or the environment. It may cause loss of life, illness or other health consequences, property damage, social and economic crisis or environmental degradation. Many places of the world are at risk from one or more disasters. Although many studies have concentrated on single hazards, there is a need for integrated evaluations of multi-hazards for more effective land management. A selection of datasets and methods, such as meteorological data, satellite images, and GIS, were used to create the risk assessment maps. The parameters for multi-hazard assessment are mainly considered as rainfall, slope, elevation, and land use/land cover and create a map in a GIS environment. For a particular region, multi-hazards can be produced by integrating maps of several hazard assessments. The objective of this study is an integration of geospatial and fuzzy-logic techniques for multi-hazard mapping. Extensive parts of Gujarat state (India) experience a wide range of natural hazards: floods, soil erosion, drought, and earthquakes. This research creates and evaluates individual and group multi-hazard maps to visualize the spatial variation of hazards in Gujarat state, India. The calculated four individual hazard maps have been categorised into five classes: very-low, low, moderate, high, and very high. The multi hazard map has been classified into sixteen classes using the GIS unsupervised. This study aims to improve disaster preparedness, enhance land management, or guide decisionmaking for disaster risk reduction. This study can be helpful in the future to engineers, planners, and local governments in the field of spatial planning and natural disaster management.