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.

Offshore wind turbines (OWTs) empoly various foundation types, among which Jacket-type offshore wind turbines (JOWTs) are often used in shallow waters with challenging soil conditions due to their lattice framework foundations and multiple anchoring points. However, prolonged exposure to harsh marine environments (e.g. storms) and age-related degradation issues like corrosion, fatigue cracking, and mechanical damage increases failure risks. To address these issues, this paper introduces a Digital Healthcare Engineering (DHE) framework, which provides a proactive strategy for enhancing the safety and sustainability of JOWTs: (1) Real-time health monitoring using IoT; (2) Data transmission via advanced communication technologies; (3) Analytics and simulations using digital twins; (4) AI-powered diagnostics and recommendations; as well as (5) Predictive analysis for maintenance planning. The paper reviews recent technological advances that support each DHE module, assesses the framework's feasibility. Additionally, a prototype DHE system is proposed to enable continuous, early fault detection, and health assessment.

Granular soils creep and age. Previous findings on the time-dependent phenomena under deviatoric stress are summarized and extended with the results of an experimental investigation. Multi-stage triaxial compression tests with creep phases at different deviatoric loading on medium-dense and dense samples of a uniformly graded silica sand confirm an increase in stiffness after creep phases. Contact maturing, contact homogenization, and stabilization of the soil structure are known causes for ageing reported in the literature. As other results found in the literature, the volumetric creep behavior can be dilatant, contractant or of negligible strain close to zero and depends on the trend of the volumetric strain resulting from deviatoric loading at the beginning of creep. By the triaxial tests it is shown that dilatant creep results in an increase of the radial strain due to grain rearrangements. The axial strain rates during creep and changes of the small-strain shear modulus (ageing) follow a power law with time. According to the experiments, the exponent of the proposed power law describing the development of strain and shear modulus at small strain during creep is independent of the density and stress state. The small-strain shear stiffness and the associated soil structure at the onset of creep determine the subsequent ageing behavior. A linear dependency was found between the related ageing rates and axial strain rates during creep, which can be used to predict ageing of granular materials in combination with rate-dependent constitutive models.

For rock structures exposed in the natural condition, water-induced weakening (including water softening and chemical weathering) is thought to be the main reason for its' stiffness and strength degradation, thus it is of great significance to study the mechanical properties of rocks under the influence of water. In this study, a hexagonal close-packed particle assembly (2D) composed of bonded circular particles with same diameter is considered to approximate a typical soft rock, where the composite contact model for rock materials considering the water-induced wakening is adopted to define the microscopic mechanical reactions between particles. Based on homogenisation theory and lattice model, the stress-strain relationship and strength criteria for rock considering water-induced weakening, as well as the quantitative correlation between macroscopic elastic and strength parameters with microscopic parameters are obtained. The effects of water softening and chemical weathering respectively characterised by saturation and mass loss ratio on macroscopic mechanical behaviours of rock are analysed in detail. The long-term ageing effects of water-induced weakening are also analysed. All results are in good agreement with the laboratory test results, verifying the applicability of the theoretical solution for analysing the effect of water-induced weakening on mechanical behaviours of rock.

Biochar provides a sustainable carbon sequestration technology, an effective fertilizer in agriculture, a step forward for the profitable and safe disposal of bio-wastes, reduced carbon dioxide emissions and global warming, and a renewable energy source. Using biochar as a bitumen modifier in asphalt pavement construction is under active research. It can prove a sustainable and environmentally friendly alternative, provided it meets the efficiency, strength, and economy challenge. This review focused on the available literature on utilizing biochar as a bitumen modifier for the construction of asphaltic roads. The studies show that biochar's physical and chemical nature has helped project it as a promising bitumen modifier. The biochar, being porous and fibrous, provides a strong, stiff frame in the asphaltic mast and results in the enhancement of both stiffening point and viscosity. This, in turn, leads to a reduction in penetration or increased deformation resistance. This is perhaps the reason for the high performance of biochar-modified asphalt at high temperatures. The increase in viscosity of asphaltic masts was also observed due to biochar amendment, making asphalt more sensitive to temperature. The two important factors, the complex modulus and the rutting factor of the asphalt, were noticed to increase with the addition of 10% biochar. The biochar amendments of up to 20% increased fatigue resistance temperature by 4.6 degrees C. The improvement in the resistance to deformation at high temperatures, probably due to a reduction of phase angle due to adding biochar, is also seen as a significant function of biochar. However, biochar applicability in the field is mainly related to its cost efficiency and performance as a bitumen modifier for asphaltic pavements. So far as the cost economy is concerned, the mean price for biochar (as per available literature) was very high, from $2.65 to $0.09/kg for blended biochar. The price was as high as $3.29/kg in the Philippines to $0.08/kg in India and in the US to $13.48/kg, implying that the market price of biochar is variable worldwide and dependent mainly on the biochar feedstock, cost of labor/living of the area and land costs. On the other hand, its efficiency has not yet been satisfactory at low temperatures. The other noticeable limitations that need to be explored in further research are long-term effects on strength, rutting resistance, and ageing. Also, field studies to support the research and, more importantly, cost economy viz-a-viz other available modifiers need exploration.

While a high content of reclaimed asphalt in road construction is targeted, recycled bitumen has often undergone chemical and physical damages characterized as ageing. This can be counteracted with additives denoted as rejuvenators and by controlling the heating process during mix production. This study investigated the surface and base layers of three asphalt variants with different levels of reclaimed asphalt and rejuvenator. Asphalt samples were heated either through conventional heat conduction or through dielectrical heating using radio waves. Bitumen analyses included Ring-and-Ball, Needle Penetration, Dynamic Shear Rheometry and Fourier Transform Infrared Spectroscopy while asphalt performance was assessed by Cyclic Indirect Tensile Test. Ageing indicators were derived and correlated quantitatively, revealing high correlation among bitumen analysis results and lower correlation of asphalt analysis results. Some of the test methods explicitly supported the hypothesis that radio wave heating may induce a lower ageing than conventional heating combined with rejuvenation.

This study aims to explore the effects of biochar ageing on its surface properties and the bioavailability of heavy metals in soil. The biochar was subjected to chemical oxidation/dry-wet cycles (CDWs), chemical oxidation/freeze-thaw cycles (CFTs), and natural ageing (NT) to analyze changes in the elemental composition, pH, specific surface area, pore volume, and surface functional groups. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were applied to characterize the functional groups and microstructure, and the BCR sequential extraction method was employed to demonstrate the fractionation distribution of Cu, Cd, and Pb. The results showed that the CDWs and CFTs treatments significantly reduced the carbon content of the biochar (with a maximum reduction to 47.70%), increased the oxygen content (up to 49.17%), and notably increased the specific surface area and pore volume. The pH decreased significantly from 9.91 to 4.92 and 4.99 for the CDWs and the CFTs, respectively. The FTIR analysis indicated notable changes in hydroxyl and carboxyl functional groups, and the SEM revealed severe microstructural damage in biochar after the CDWs and CFTs treatments. The heavy metal fractionation analysis indicated that exchangeable Cu, Cd, and Pb significantly increased after the CDWs treatment, reaching 31.40%, 5.25%, and 6.79%, respectively. In conclusion, biochar ageing significantly affects its physicochemical properties and increases the bioavailability of heavy metals, raising concerns about its long-term remediation effectiveness.

Light absorbing organic carbon, a.k.a., brown carbon (BrC) is an important contributor to air quality deterioration and global radiative forcing. This work studied optical, chemical properties and sources of BrC in fine particles (PM2.5) collected in Yangzhou, China. The light absorption coefficient at 365 nm of methanol-soluble organics (Abs(365,WSOC)) and water-soluble organics (Abs(365,WSOC)) were 13.50 +/- 7.03 M/m and 6.08 +/- 4.30 M/m, respectively. Mass absorption efficiency at 365 nm (MAE(365)) of methanol-soluble BrC (1.12 +/- 0.35 m(2)/gC) was also higher than water-soluble BrC (0.75 +/- 0.29 m(2)/g C). For water-soluble BrC, both Abs(365) and MAE(365) generally decreased with increases of its oxygen-to-carbon (O/C) ratios and oxidation states (OSc), indicative of photo-bleaching upon chemical ageing. Positive responses of Abs(365,WSOC) and MAE(365,WSOC) to nitrogento-carbon (N/C) ratios and water-soluble organic nitrogen (ON) contents reveal that ON species are important BrC chromophores. A multiple linear regression model was applied to apportion Abs(365,WSOC) to contributions of different factors resolved from positive matrix factorization on water-soluble organic aerosols (OA), and obtained MAE(365) values of different OA factors. Overall, primary OA sources including traffic (18.9%), biomass burning (23.7%), and cooking-related OA (10.5%) together dominated the AbS(365,WSOC) despite their total mass contribution was only about one third (31.9%). The largest single contributor of Abs(365,WSOC) however, was the less-oxidized secondary OA (33.8%); the more-oxidized secondary OA factor dominated water-soluble OA mass (50.8%), yet its light absorptivity was the weakest and contributed only 13.1% of Abs(365,WSOC).