Hazard Scenarios Research Articles

Time-Variation of Shear Forces Affecting the Impact Resistance of Reinforced Concrete Beams

One of the most hazardous scenarios for reinforced concrete (RC) members is due to the actuation of impact loads. Such impacts may be either accidental or induced events. Experimental research has demonstrated that the failure mode of RC beams is strongly governed by shear, due either to the formation of a shear plug close to the impact point or to the full development of inclined shear-bending cracks along the shear span. In order to analyze the shear strength under impact conditions, it is essential to understand how the development of inertia forces leads to a time-dependent distribution of shear forces and bending moments which differs significantly to those produced by quasi-static loads. In the paper, an experimentally-based determination of shear forces and follow-up of crack pattern is presented for RC beams tested under impact loads. A Digital Image Correlation technique supported by a high-speed camera is used to understand the evolution of shear forces at critical sections and to discuss the ultimate shear strength provided by M-V interaction diagrams.

Multiscenario flood hazard assessment using probabilistic runoff hydrograph estimation and 2D hydrodynamic modelling

In this paper, we aim to define a procedure of flood hazard assessment applicable to large river basins in which flood events can be induced/sustained by the full basin area or by fractions of the total area as functions of the extent of the triggering precipitation event. The proposed procedure is based on a combined approach accounting for (1) the reconstruction of intensity–duration–frequency curves expressing the magnitude in terms of intensity for multiple return periods; (2) the application of the soil conservation service method for runoff estimation from a selected rainfall scenario considering some characteristics of the basin (i.e. soil type, land use/treatment, surface condition, and antecedent moisture conditions); (3) 2D hydrodynamic modelling conducted by the HEC-RAS model using runoff hydrographs as hydrological input data; (4) the reconstruction of flood hazard maps by overlaying multiple inundation maps depicting flood extent for different return periods. To account for the variability in the extent of the triggering precipitation event and the resulting input hydrograph, multiple contributing areas are considered. The procedure is tested at the archaeological site of Sybaris in southern Italy, which is periodically involved in flood events of variable magnitude. The obtained results highlight that the variable extent of the floodable area is strongly conditioned by the extent of the contributing area and return period, as expected. The archaeological site is always involved in the simulated flooding process, except for the smallest contributing area for which only a 300-year event involves this part of the site. Our findings may be useful for developing and supporting flood risk management plans in the area. The developed procedure might be easily exported and tested in other fluvial contexts in which evaluations of multiple flood hazard scenarios, due to the basin geometry and extent, are needed.

Estimation of the influence of protective behaviour on expected injuries in transport accidents with hazardous materials

The release of hazardous materials due to transport accidents can have major health consequences for bystanders. The number of casualties will partly be determined by their protective behaviour.This study describes a three-step approach to predict health consequences of protective behaviour (for example, hiding or escaping) of bystanders in the first minutes of a transport accident with hazardous material. First, a discrete choice experiment (DCE) was used to predict protective behaviour. Second, a gas dispersion model (SeReMo) was used to estimate the distribution of casualties for different protective behaviours. Third, results of the DCE and SeReMo were combined to estimate the distribution of casualties in the population-at-risk. This approach was applied to a hypothetical marine accident with different hazardous material scenarios on a large waterway in a close vicinity of a beach/quay with bystanders.An important finding of our study was that in general a short reaction time and escaping in cross-wind direction, as protective behaviours, are of vital importance to reduce the number of casualties. A scenario with a short reaction time and a visible cloud towards the beach/quay resulted in a protective behaviour with the largest reduction of casualties.A dynamic risk assessment approach considering that people threatened by hazardous material are not ‘stationary observers’, but will exhibit protective behaviour, and a risk assessment that takes into account empirical information on expected protective behaviour will present a more realistic estimate of the number and severity of casualties when a large transport accident with hazardous materials would occur.

Optimal Vibration Control Design of Antenna Mast on Super High-Rising Structures Against Multi-Hazards of Earthquake and Wind

Antenna mast structures are usually set on top of modern super high-rising structures to meet the requirements of communication and aesthetics, and such buildings are highly sensitive to horizontal loads that can greatly increase the acceleration and displacement responses during their life-cycles owing to the inherent high flexibility and low damping. As a result, the antenna masts with small mass and stiffness may suffer serious whiplash effect under the earthquake or wind excitations. In this paper, a multi-hazard protective system with hybrid isolated and energy-dissipated devices of isolation bearing, viscous damper and mild steel damper is presented for the typical inserted antenna mast structures on super high-rising structures. To determine the optimum parameters of the hybrid system that maximize the structural control efficiency under a single hazard of earthquake or wind load, as well as the coupled conditions of these two hazards, an optimization method based on the genetic algorithm is developed for the presented hybrid control system to resist various hazard scenarios. Objective functions are further proposed to penalize the accelerations and relative displacements at the top of the antenna mast structure. Taking a super-tall TV tower as an example, the OpenSeesPy platform is employed to establish the finite element (FE) model. The numerical results show that the optimization scheme for the hybrid energy-dissipated antenna mast system under a single hazard is not suitable for the other hazard condition, while the optimized results for the multi-hazard condition can give consideration to the effects of both earthquake and wind. Moreover, the sensitive analysis is performed to investigate the effects of each parameter of the hybrid system on the objective functions. It can be concluded that the proposed hybrid system performs well under earthquake, wind and coupled multi-hazards, which is of practical significance for the vibration control of antenna masts on super high-rising structures.

Imagining and assessing future risks: A dynamic scenario‐based social vulnerability analysis framework for disaster planning and response

AbstractWhile social vulnerability assessments should play a crucial part in disaster management, there is a lack of assessment tools that retain sensitivity to the situation‐specific dynamics of vulnerabilities emerging in particular hazard scenarios. We developed a novel scenario‐based vulnerability assessment framework together with practitioners in crisis management and assessed the suitability of its components in three past crises and their scenario‐based derivations: a large‐scale power outage, the COVID‐19 pandemic, and a cyber‐attack. Rather than deterministically concluding about vulnerability based on prefixed factors, the framework guides relevant stakeholders to systematically think through categories of vulnerability pertinent to a scenario. We used a table‐top exercise, interviews, and focus groups to demonstrate how the framework broadens the crisis managers’ understanding of the scope of factors that may cause vulnerability, the related sources of information and enables to identify individuals burdened by certain vulnerability mixes. The new framework could be applied to different types of crises to enhance preparedness, demand‐driven relief and rescue during critical events.

Building-scale flood loss estimation through vulnerability pattern characterization: application to an urban flood in Milan, Italy

Abstract. The vulnerability of flood-prone areas is determined by the susceptibility of the exposed assets to the hazard. It is a crucial component in risk assessment studies, both for climate change adaptation and disaster risk reduction. In this study, we analyse patterns of vulnerability for the residential sector in a frequently hit urban area of Milan, Italy. The conceptual foundation for a quantitative assessment of the structural dimensions of vulnerability is based on the modified source–pathway–receptor–consequence model. This conceptual model is used to improve the parameterization of the flood risk analysis, describing (i) hazard scenario definitions performed by hydraulic modelling based on past event data (source estimation) and morphological features and land-use evaluation (pathway estimation) and (ii) the exposure and vulnerability assessment which consists of recognizing elements potentially at risk (receptor estimation) and event losses (consequence estimation). We characterized flood hazard intensity on the basis of variability in water depth during a recent event and spatial exposure also as a function of a building's surroundings and buildings' intrinsic characteristics as a determinant vulnerability indicator of the elements at risk. In this sense the use of a geographic scale sufficient to depict spatial differences in vulnerability allowed us to identify structural vulnerability patterns to inform depth–damage curves and calculate potential losses from mesoscale (land-use level) to microscale (building level). Results produces accurate estimates of the flood characteristics, with mean error in flood depth estimation in the range 0.2–0.3 m and provide a basis to obtain site-specific damage curves and damage mapping. Findings show that the nature of flood pathways varies spatially, is influenced by landscape characteristics and alters vulnerability spatial distribution and hazard propagation. At the mesoscale, the “continuous urban fabric” Urban Atlas 2018 land-use class with the occurrence of at least 80 % of soil sealing shows higher absolute damage values. At microscale, evidence demonstrated that even events with moderate magnitude in terms of flood depth in a complex urbanized area may cause more damage than one would expect.

Driver’s Attention Allocation and Mental Workload at Different Random Hazard Points on Prairie Highway

To identify the characteristics of driver’s visual perception and measure the mental workload at different random hazard points on prairie highway, an on-road study was conducted with 28 drivers. The I view X HED eye tracker and MP150 multichannel physiological recorder were used to collect the driver’s eye movement and ECG data at different hazard scenarios synchronously. The gaze transfer theory and statistical methods were used to make comparative analysis of typical visual and mental workload evaluation indicators of drivers at different random risk points. The results show that no matter what kind of random risk is confronted, the percentage of drivers’ fixation duration to the current lane drops, where random risk belongs to increase. The distribution of eye glance transition proportions shows that drivers highly bias their scanning attention by only focusing on transferring between forward and the areas where the random belongs to. Compared with off-road risk points, the driver’s gaze transfer is more frequent when facing on-road risk points, and the gaze transfer path is fixed, indicating that on-road risks have higher requirements for drivers’ perception and greater information processing load. There are obvious differences in the degree of influence of the types of random risk points on driver’s psychology. The heart rate growth rate is the largest when drivers were confronted with overtaking cut-in (37.9%) and forward parking (38%), whereas the index RMSSD changes in the opposite way. It reaches the minimum value when the random risks are overtaking cut-in (22.679 ms) and forward parking (22.907 ms). Meanwhile, the driving speed shows larger fluctuation at risk points on the road. This study reveals that on-road hazards pose greater threats to drivers, and it can contribute to a better understanding of the potential hazards on the prairie highways and provide suggestions for future application of advanced driver assistance systems which can warn drivers about potential hazards.

Identification and Improvement of Hazard Scenarios in Non-Motorized Transportation Using Multiple Deep Learning and Street View Images.

In the prioritized vehicle traffic environment, motorized transportation has been obtaining more spatial and economic resources, posing potential threats to the travel quality and life safety of non-motorized transportation participants. It is becoming urgent to improve the safety situation of non-motorized transportation participants. Most previous studies have focused on the psychological aspects of pedestrians and cyclists exposed to the actual road environment rather than quantifying the objective safety hazards, which has led to a non-rigorous evaluation of their basic safety situation. An integrated processing approach is proposed to comprehensively and objectively evaluate the overall safety level of non-motorized transportation participants on each road segment. Our main contributions include (1) the universal approach is established to automatically identify hazard scenarios related to non-motorized transportation and their direct causing factors from street view images based on multiple deep learning models; (2) a seed points spreading algorithm is designed to convert semantic images into target detection results with detail contour, which breaks the functional limitation of these two types of methods to a certain extent; (3) The safety situation of non-motorized transportation on various road sections in Gulou District, Nanjing, China has been evaluated and based on this, a series of suggestions have been put forward to guide the better adaptation among multiple transportation participants.

Developing landslide hazard scenario using the historical events for the Kashmir Himalaya

Developing landslide hazard scenario using the historical events for the Kashmir Himalaya

Physics-based simulations of multiple natural hazards for risk-sensitive planning and decision making in expanding urban regions

Rapid urban expansion in many parts of the world is leading to increased exposure to natural hazards, exacerbated by climate change. The use of physics-based models of natural hazards in risk-informed planning and decision-making frameworks may provide an improved understanding of site-specific hazard scenarios, allowing various decision makers to more accurately consider the consequences of their decisions on risks in future development. We present results of physics-based simulations of flood, earthquake, and debris flow scenarios in a virtual urban testbed. The effect of climate change, in terms of increasing rainfall intensity, is also incorporated into some of the considered hazard scenarios. We use our results to highlight the importance of using physics-based models applied to high-resolution urban plans to provide dynamic hazard information at the building level for different development options. Furthermore, our results demonstrate that including building elevations into digital elevation models is crucial for predicting the routing of hazardous flows through future urban landscapes. We show that simulations of multiple, independent hazards can assist with the identification of developing urban regions that are vulnerable to potential multi-hazard events. This information can direct further modelling to provide decision-makers with insights into potential multi-hazard events. Finally, we reflect on how information derived from physics-based hazard models can be effectively used in risk-sensitive planning and decision-making.

Selection of representative natural hazard scenarios for engineering systems

AbstractRepresentative hazard scenarios are essential for many tasks in risk management, such as preparedness and emergency response planning. However, criteria and methods for systematically selecting such scenarios for natural hazards are lacking. From a risk perspective, such scenarios should be selected considering the losses they incur. Hence, we propose to define a scenario that is representative for a certain degree of loss, for example, the 100‐year loss, as the most likely one among all possible scenarios leading to this loss. Taking basis in a generic model of natural hazards and their impact on engineering systems, we formally introduce the representative scenarios. We then develop algorithms that enable an efficient evaluation of these scenarios. The method and algorithms are demonstrated on a hypothetical example considering a spatially distributed infrastructure system subjected to earthquakes.

The 2020 earthquake sequence and seismic hazard scenario of Mizoram state in northeast India

The Mizoram state of India lies in close proximity to the active Indo-Burma subduction zone and had experienced several moderate to large earthquakes, including the M7 event in 1938. Since 2015, only two events with 5<M<6 have occurred in the area, however, a sudden enhancement of earthquake activity (M3.0–M5.7) was observed from June to August 2020 in the eastern part of the Mizoram state, including the four events of M ≥ 5.0. We analysed the waveform data of 21 events recorded by the local and regional BBS to estimate the source parameters. The focal depth of these events varies from 13 to 45 km, while other parameters such as corner frequency, source radius, stress drop, and scalar seismic moment of the events are found in the range of 0.45–3.36 Hz, 0.77–5.58 km, 1.3–193 bars, and 3.98107E+13 to 6.30957E+17 Nm, respectively. The seismicity pattern shows two distinct clusters along the well-demarcated faults in the region, and most of them are generated by strike-slip movements. The Churachandpur-Mao Fault (CMF) is found to be the most active tectonic element in the study area. Hence, an M8 event has been simulated on the same fault using the stochastic simulation technique. The technique was validated by simulating the three M+5 events on the same source zone and comparing the simulated PGA, frequency, and response spectrum with the observed data. The simulation reveals that a PGA ∼480 gals is expected near the fault zone. The easternmost districts of Mizoram, such as Champai, Serchhip, Lunglei, Saiha, and Aizawl, may experience severe PGA (250–450 gals). The response spectral acceleration corresponding to single-storey, double-storey, 3–4 storey, and 5–6 storey buildings has also been estimated in the present study and it is found to vary in the range of 1,400–200 gals. The result of the present study will be useful in various engineering applications and help reduce the loss of lives and damage to infrastructure due to future large events in the region.

Assessment of urban flood risk based on data-driven models: A case study in Fuzhou City, China

In response to the growing threat of urban flooding, this study developed an integrated method to evaluate the flood risk of the study area (Fuzhou City, China) to different types of urban flooding. First, a coupled hydrological–hydrodynamic model was developed to obtain the key dynamic flood factors forced by typical rainstorm events with river levee overtopping and pipeline transportation. Second, an integrated framework was developed to assess urban flood vulnerability under different flood hazard scenarios. Fifteen features were selected and their relative importance was analyzed by using the XGBoost model. Finally, a cloud model was used to realize qualitative to quantitative characterization of subregions of urban flood risk. The results highlighted the flooding nodes, and the inundation areas presented increasing trends with the increase of return periods. The inundation degree was divided into four categories based on the inundation degree, for which the flooding area was 324.30, 177.81, 43.42, and 20.93 ha, respectively. Six explanatory variables with greater importance were recognized in all schemes. The risk level of subregions changed dynamically, when the rainfall intensity increased, the risk level of subregions showed an increasing trend. Areas with intermediate and high risk were concentrated in the central and western of the study area. At the drainage subregion scale, two types of subareas are essential in urban flood management, respectively, the subregions with high risk in specific rainfall, and the subregions easily transforming into high-risk areas when rainfall increases. This study provides promising references in urban flood risk management.

Performance-Based Assessment of Bridges with Novel SMA-Washer-Based Self-Centering Rocking Piers.

This study discussed a novel self-centering rocking (SCR) bridge system equipped with shape memory alloy (SMA)-based piers, with a particular focus on the benefit of the SCR bridge system in a life-cycle context. The study commences with an introduction of the SCR bridge system; subsequently, a life-cycle loss and resilience assessment framework for the SCR bridge system is presented. Specifically, the seismic fragility, resilience, and life-cycle loss associated with the SCR and conventional bridge systems were addressed. The proposed life-cycle assessment framework was finally applied to two highway bridges with and without SMA washer-based rocking piers, considering the representative hazard scenarios that could happen within the investigated regions. The results revealed that the novel SCR pier bridge system slightly increased the bearing displacement but extensively reduced the pier curvature ductility due to the rocking mechanism. The SCR bridge system kept a lower life-cycle loss level and exhibited more resilient performance than the conventional bridge, especially in the region with higher seismic intensities. Indirect loss can be significantly larger than the direct loss, specifically for the earthquakes with a relatively low probability of occurrence. The SCR bridge system outperformed the conventional system in terms of recovery time, where a quick recovery after an earthquake and drastically decreased the social and economic losses.

Modeling the dispersion and mixing of light gases in enclosed spaces using the Method of Moments

Leakage of light flammable gases in buildings or enclosed spaces may cause significant environmental and safety hazards. This study proposes a transient reduced-order model for the dispersion and mixing of light gases in closed rooms using the Method of Moments (MoM). The MoM model solves the moments of the species pdf transport equation in the vertical direction of the room. The evaluated moments are used to generate the horizontal distribution of the species at any time and height in the room. This provides a better representation of the species distribution in the room compared to a well-known analytical model called the ‘filling-box model’ and computationally faster model compared to CFD alternatives. The MoM model is demonstrated for a buoyant methane release in a closed room. The results are benchmarked by using Fire Dynamics Simulator (FDS), which is a computational fluid dynamics (CFD) model used for buoyancy-driven flows, including fire. The MoM model represents good performance compared to FDS in significantly faster time (4 min on a single core vs. 4 days and 7 h on 33 cores in parallel). The model can be used to investigate toxicity, fire, or explosion hazard scenarios, which helps developing prevention systems and mitigation strategies.

UAV-based pipeline inspection system with Swin Transformer for the EAST

The regular inspection of pipelines is not only a requirement to ensure the stable operation of the EAST, but also a strict safety regulation to decrease the probability of accidents caused by gas or liquid leakage. The main issues facing manual inspection are the length of the pipeline, inaccessible areas, and hazardous scenarios, which makes this task extremely difficult and time-consuming. This paper proposes a UAV inspection system for pipeline inspection missions. Loose bolts within a given pipeline are used as detection objects during experimentation to create a dataset and conduct further analysis on the accuracy of the loose-bolt detection with Swin Transformer. The results verify the effectiveness and accuracy of the UAV pipeline inspection system in terms of loose-bolt detection. The UAV inspection system proposed in this study can provide useful reference value and guidance for the regular inspection of the EAST or other pipeline inspection missions.

Empirical Comparison of Learning Effectiveness of Immersive Virtual Reality–Based Safety Training for Novice and Experienced Construction Workers

Statistics show that novice and experienced construction workers face different risks of construction accidents. However, there is very little work on this topic. This study conducted empirical experiments to quantifying the effectiveness of immersive virtual-reality-based safety training (IVST) across 6 worker specialties in terms of facing 17 hazardous scenarios at real construction sites. An immersive virtual reality–based safety training system (IVSTS) is proposed to measure the effectiveness of IVST programs with regard to six specialties in 2 controlled groups: (1) novice workers (40 college students), and (2) experienced workers (40 randomly selected construction practitioners). The study results indicate that the proposed IVSTS improved the safety performance index of all 80 participants by 14.12% in terms of correct selection of personal protection equipment, and by 28.95% in terms of hazardous scenario identification. The improvement of safety learning performance of the novice workers was better than that of the experienced workers, especially for hazardous scenario identification, with a 15.90% higher improvement index. The improvement suggestions for the existing IVST program were summarized according to the influence of the individual characteristics of the trainees on the learning effect between the novice and the experienced IVST programs.

A modular approach for vulnerability assessment in Southern Italy: A forest fire hazard scenario.

Vulnerability is an important component for risk assessment, representing the main element in the perception of the risk. This paper shows a methodological approach to describe a composite vulnerability index suitable to be used at the census scale. The aim of this study is threefold: at first, a new administrative limit, "Territorial Context" (TC), for the purpose of the emergency management is investigated. Second, it improves the common vulnerability methods applying different weights and a new approach of vulnerability levels classification by using fuzzy analysis. Finally, it provides vulnerability maps, which represent a simple way to identify areas where the capacity to cope with a hazard, during an event, is strongly influenced by social and territorial conditions and the road infrastructure accessibility. The proposed TC Vulnerability Index (TCVI) aggregates three indices to capture the complex realities of the investigated system that cannot be adequately quantified by a single index. Specifically, two indices measure the social (TCVIpeople) and territorial (TCVIexposure) vulnerability through an inductive approach based on the principal component analysis. The third index (TCVIemergency) provides a measure of the emergency management operating system, essentially based on the possibility of moving to safe areas, for citizens, or to coordination centers and risk areas, for rescuers. Results show notable differences in the spatial distribution of vulnerability, highlighting the multidimensionality and heterogeneity of the census area characteristics. These findings would provide a scientific base for the public decision-makers to implement.

Coastal hazards mapping using high-resolution UAV image and DEM. A Case study in Siung Beach, Gunungkidul, Indonesia

The southern coast of Gunungkidul, which is adjacent to the subduction zone, is prone to various coastal hazards. The increasing number of visitors to the beach leads to more exposure and increases the risks. This study aims to determine the coastal hazards in Siung Beach, Gunungkidul, Yogyakarta. A high-resolution aerial image and DEM were acquired using a low-cost Unmanned Aerial Vehicle. The acquired images were processed using Structure from Motion (SfM) photogrammetry to generate an orthomosaic image with 5cm spatial resolution. A worst-case tsunami hazard scenario (12 m) was executed using raster filtering on the generated UAV-DEM. Based on the tsunami inundation model, most of the buildings are affected by the worst-case tsunami scenario. According to orthomosaic interpretation, rip current hazard is also spotted on the eastern part of the beach. The rip current is considered a channel rip, a stationary rip current affected by the bathymetric condition. Potential rockfall due to slope instability might be occurred on the southern part of the beach, as a former enormous mass movement can be delineated from the orthomosaic image. Siung Beach is formed by the combination of volcanic origin and karst process, resulting in undulating topography. Due to various coastal hazards in Siung beach, disaster management planning should be established to reduce the risks.

Driving Performance of Experienced Young Adult Drivers with and without Autism Spectrum Disorder While Listening to Music on Two Scenarios: Hazards versus Wayfinding

This study explored the effect of music on the driving performance of experienced young adult drivers with and without autism spectrum disorder (ASD) using an interactive driving simulator with two types of scenarios. A 2 (Group: autism/neurotypical) × 2 (Music: music/no music) × 2 (Scenario: hazards/wayfinding) factorial design was used with the order of scenarios and music conditions counterbalanced. Participants were 34 neurotypical drivers and 5 drivers with ASD, all with at least 3 years of driving experience. Paired sample t-tests demonstrated no effect of music for any condition. Overall, the drivers with ASD had higher performance means than the neurotypical group with significant differences in the wayfinding scenario and the category for following regulations. Neurotypical drivers had better performance on the wayfinding scenario than the hazard scenario in maneuvers and being attentive to the environment. Although this study had a low number of drivers with ASD, it suggests drivers with ASD can perform better than neurotypical drivers, possibly because they follow road rule guidelines more consistently than neurotypical peers. In addition, this is the first study to examine wayfinding skills in teens/young adults with and without ASD.