Simulating interacting multiple natural-hazard events for lifecycle consequence analysis

Among different types of natural-hazard interactions (simply multi-hazard interactions hereinafter), some occur through the nature of the hazards themselves, regardless of the presence of any physical assets: they are often called ﾓLevel Iﾔ (or occurrence) interactions. In such cases, one hazard event triggers or modifies the occurrence of another (e.g., severe wind and flooding; liquefaction and landslides triggered by an earthquake), thus creating a dependency between the parameters characterising such hazard events. They differ from ﾓLevel IIﾔ (or consequence) interactions, which instead occur through impacts/consequences on physical assets/components and systems (e.g., accumulation of physical damage or social impact due to earthquake sequences, landslides due to the earthquake-induced collapse of a retaining structure). Multi-hazard Life Cycle Analysis (LCA) aims to quantify the consequences (e.g., repair costs, downtime, and casualty rates) expected throughout a systemﾒs service life, accounting for both Level I and Level II interactions. Nevertheless, the available literature generally considers these interactions mainly defining relevant taxonomies, often qualitatively, without providing a computational framework to simulate a sequence of hazard events in terms of their occurrence times and features and resulting consequences. This paper aims to partly fill this gap by identifying modelling approaches associated with different Level I interactions. It describes a simulation-based approach for generating multi-hazard scenarios (i.e., a sequence of hazard events and associated features through the systemﾒs life cycle) based on the theory of competing Poisson processes. The proposed approach incorporates the different types of interactions in a sequential Monte Carlo sampling method. The method outputs potential sequences of events throughout a systemﾒs life cycle, which can be integrated into LCA frameworks to quantify interacting hazard consequences. A simple application is presented to illustrate the potential of the proposed method.

WARP^2: Wind assessment of roofs to pullout & pullover for priority cultural heritage structures in the Philippines

Cultural tourism is one of the priority sectors by which the Government of the Philippines aims to foster inclusive and sustainable socio-economic development, due to its potential for job creation. Filipino cultural heritage (CH) assets are particularly vulnerable to natural hazards (e.g., earthquake ground shaking, strong wind, and flooding) due to their age and type of construction. In particular, non-engineered CH roofs have been recognized as the most vulnerable component in the building envelope due to typhoon-induced wind uplift. Consequently, they may cause large amount of economic loss and disruption to CH assets. This paper introduces a simulation-based approach for non-engineered CH roof fragility derivation, i.e., to assess the probability of different levels of damage experienced by CH roofs over a range of wind hazard intensities. In this approach, two limit states are considered, corresponding to roof-panel pullout and pullover failure modes. An illustrative application of the proposed procedure is finally presented with reference to 17 priority CH buildings across the Philippines

Surface glazing of concrete using a 2.5 kW high power diode laser and the effects of large beam geometry

Interaction of a 2.5 kW high power diode laser (HPDL) beam with the ordinary Portland cement (OPC) surface of concrete has been investigated, resulting in the generation of a tough, inexpensive amorphous glaze. Life assessment testing revealed that the OPC glaze had an increase in wear life of 1.3 to 14.8 times over an untreated OPC surface, depending upon the corrosive environment. Also, variations in the width of the HPDL beam were seen to have a considerable affect on the melt depth. Furthermore, the maximum coverage rate that it may be possible to achieve using the HPDL was calculated as being 1.94 m2/h. It is a distinct possibility that the economic and material benefits to be gained from the deployment of such an effective and efficient large area coating on OPC could be significant

ACTIGRAPHIC ASSESSMENT OF SLEEP-ACTIVITY CYCLE IN PHYSIOPATHOLOGY: EXPERIMENTAL AND METHODOLOGICAL STUDIES

The principal objective of my research during my PhD has been the investigation of the rest-activity circadian rhythms in physiopathology, dealing with both experimental and methodological issues. On the experimental side, the focus of my research program was centered on the investigation of the rest-activity circadian rhythms in patients with binge eating disorders. On the methodological side, my activity was aimed at exploring the relationships between the actigraphy-based assessment of circadian rhythmicity and the questionnaire-based assessment of circadian typology. The thesis is organized in 11 Chapters. Chapter 1 provides a short introduction to chronobiology and to the components of a circadian rhythm. Chapter 2 describes the two most common methods used to evaluate the circadian rhythmicity, namely actigraphy and self-administered questionnaires. These two approaches have remarkable strengths and weaknesses. Actigraphy is a non-invasive method (usually based on a small, wearable actigraphic unit) that allows one to monitor the activity levels during the 24 hours, to detect the rest-activity circadian rhythm, to evaluate the activity levels during the nocturnal sleep and to assess the quality and quantity of sleep by specific sleep parameters. One alternative approach to assessment of the circadian typology of a subject is based on self-administered questionnaires. Questionnaires are obviously less objective than actigraphy-based assessments, but have the advantage of being simple and cost-effective. Chapter 3 provides a general overview of all the research projects I have taken part in throughout my PhD course. This chapter has been written with the reader in mind and aims to succinctly describe the structure and function of the subsequent chapters, 4 through 11. In Chapters 4 to 7, I will focus on the experimental core of my research activity during my PhD course, which is the chronobiological investigation of obese patients suffering from binge eating disorder. First, I will provide an overview of the features characterizing this disorder. Then, I will describe three experimental studies that were carried out in these patients with the purpose of i): quantifying their rest-activity circadian rhythm (RARs); ii) describing their sleep behaviour; iii) evaluating the effectiveness of a physical activity program as an auxiliary therapeutic approach to the traditional treatment for BED. In Chapters 8 to 10, I will illustrate the methodological core of my research activity during my PhD which aims to develop predictive formulas - based on linear regression - enabling investigators to use the questionnaire-based assessment of circadian typology (Morningness-Eveningness Questionnaire, MEQ) as a surrogate of the actigraphy-based assessment of circadian rhythmicity. A methodological project of this kind was successful is showing that both MEQ and its reduced version rMEQ are appropriate for the prediction of the actigraphy-based acrophase and this may prove useful when actigraphy-based measurements are not applicable, in so far as they result either too complex or time-consuming. Chapter 11, the final chapter, is concerned with providing concise summaries of the other studies I have been involved in during my PhD course. Seven experimental studies are described in relation to: i) the influence of chronotype on circadian rhythm (RARs), on sleep, on physical activity and on cardiac autonomic function; ii) the effects of aerobic physical activity on sleep and on markers of insulin resistance in breast cancer women; iii) the effects of short and prolonged exposure to cave environments on human physiology. The thesis also comprises an appendix containing the list of all the scientific papers that I co-authored in the course of my PhD thesis. The list reports both the published and the submitted articles

Seismic Fragility Analysis of Deteriorating Reinforced Concrete Buildings from a Life-Cycle Perspective

Structural systems in seismically-active regions typically undergo multiple ground-motion sequences during their service life (including multiple mainshocks, mainshocks triggering other earthquakes on nearby fault segments, mainshock-aftershock, and aftershock-aftershock sequences). These successive ground motions can lead to severe structural/non-structural damage and significant direct/indirect earthquake-induced losses. Nevertheless, the effects of a pre-damaged state during ground-motion sequences are often neglected in assessing structural performance. Additionally, environmentally-induced deterioration mechanisms may exacerbate the consequences of such groundmotion sequences during the structural system’s designed lifetime. Yet, such combined effects are commonly overlooked. This paper proposes an end-to-end computational methodology to derive timeand state-dependent fragility relationships (i.e., explicitly depending on time and the damage state achieved by a system during a first shock) for structural systems subjected to chloride-induced corrosion deterioration and earthquake-induced ground-motion sequences. To this aim, a vector-valued probabilistic seismic demand model is developed. Such a model relates the dissipated hysteretic energy in the ground-motion sequence to the maximum inter-storey drift induced by the first shock and the intensity measure of the second shock for a given corrosion deterioration level. Moreover, a vectorvalued generalised logistic model is developed to estimate the probability of collapse, conditioning on the same parameters as above. An appropriate chloride-penetration model is then used to model the timevarying evolution of fragility relationships’ parameters using a plain Monte-Carlo approach, capturing the continuous nature of the deterioration processes (i.e., gradual and shock deterioration). The significant impact of such a multi-hazard threat on structural fragility is demonstrated by utilising a casestudy reinforced concrete building. Due to deteriorating effects, reductions up to 33.3% can be noticed in the fragility median values

A Markovian framework for multi-hazard life-cycle consequence analysis of deteriorating structural systems

Multiple-hazard (or simply multi-hazard) interactions are either disregarded or addressed inadequately in most existing computational risk modelling frameworks for natural hazards, leading to inaccurate life-cycle consequence estimates. This, in turn, can lead to ineffective risk-informed decisionmaking for disaster-mitigation strategies and/or resilience-enhancing policies. Probabilistic multi-hazard life-cycle consequence (LCCon) analysis (e.g., assessment of repair costs, downtime, and casualties over an asset’s service life) enables optimal life-cycle management of critical assets under uncertainties. However, despite recent advances, most available LCCon formulations fail to accurately incorporate the damage-accumulation effects due to incomplete (or absent) repairs in between different hazard events. This paper introduces a Markovian framework for efficient multi-hazard LCCon analysis of deteriorating structural systems, appropriately accounting for complex interactions between hazards and their effects on a system’s performance. The proposed framework can be used to test various risk management and adaptation pathways. Specifically, the Markovian assumption is used to model the probability of a system being in any performance level (e.g., damage or functionality state) after multiple hazards inducing either “shock deterioration” or “gradual deterioration”, as well as after potential repair actions given such deteriorating processes. The expected LCCon estimates are then obtained by combining the performance level distribution with suitable system-level consequence models. The proposed framework is illustrated for a case-study reinforced concrete building considering earthquake-induced ground motions and environmentally-induced corrosion deterioration during its service life

Energy-based procedures for seismic fragility analysis of mainshock-damaged buildings

In recent decades, significant research efforts have been devoted to developing fragility and vulnerability models for mainshock-damaged buildings, i.e., depending on the attained damage state after a mainshock ground motion (state-dependent fragility/vulnerability relationships). Displacement-based peak quantities, such as the maximum interstory drift ratio, are widely adopted in fragility analysis to define both engineering demands and structural capacities at the global and/or local levels. However, when considering ground-motion sequences, the use of peak quantities may lead to statistical inconsistencies (e.g., fragility curves’ crossings) due to inadequate consideration of damage accumulation. In this context, energy-based engineering demand parameters (EDPs), explicitly accounting for cumulative damage, can help address this issue. This paper provides an overview of recent findings on the development of aftershock-fragility models of mainshock-damaged buildings. Particular focus is given to state-of-the-art frameworks for fragility analyses based on cumulative damage parameters. Moreover, a literature review on damage indices and energy-based concepts and approaches in earthquake engineering is reported to better understand the main advantages of the mostly adopted energy-based parameters, as well as their limitations. Different refinement levels of seismic response analyses to derive fragility relationships of mainshock-damaged buildings are also discussed. Finally, the benefits of adopting energy-based EDPs rather than, or in addition to, peak quantities in state-dependent fragility analyses are demonstrated on a reinforced concrete frame building. Specifically, a refined lumped plasticity modeling approach is adopted, and sequential cloud-based time-history analyses of a Multi-Degree-of-Freedom (MDoF) model are carried out. The results highlight that energy-based approaches for fragility analysis effectively capture damage accumulation during earthquake sequences without inconsistencies in the obtained statistical models. On the other hand, estimating global or local structural capacity in terms of cumulative EDPs is still challenging. Further experimental data are needed to better calibrate the quantification of energy-based damaged states

Impact of ground-motion duration on nonlinear structural performance: Part II: site- and building-specific analysis

This study’s Part I proved that ground-motion duration could play an important role when assessing the nonlinear structural performance of case-study inelastic single degree-of-freedom systems. However, quantifying duration effects in many practical/more realistic engineering applications is not trivial, given the difficulties in decoupling duration from other ground-motion characteristics. This study’s Part II, introduced in this article, explores the impact of duration on nonlinear structural performance by numerically simulating the structural response of realistic case-study reinforced concrete bare and infilled building frames. Advanced computational models incorporating structural components’ cyclic and in-cycle strength and stiffness deterioration, and destabilizing (Formula presented.) effects are used. The proposed methodology relies on the generalized conditional intensity measure approach to select ground motions. This allows selecting records consistent with the seismic hazard at a target site, both in terms of spectral shape and duration. Those are employed as input to cloud-based nonlinear structural response analyses. Variance analysis is used to quantify the impact of duration on structural response. Furthermore, vector-valued fragility and vulnerability models alternatively using peak- and cumulative-based engineering demand parameters are derived. Results show that higher damage/loss estimates can be attained as ground-motion duration increases. Relative differences up to 44% are found in fragility median values for a pre-code reinforced concrete infilled frame when comparing scalar and vector-valued fragility models conditioned on average pseudo-spectral acceleration and significant durations up to 35 s

Nonlinear static procedures for state-dependent seismic fragility analysis of reinforced concrete buildings

This paper introduces a simplified methodology to develop state-dependent fragility relationships, based on nonlinear static analyses combined with the Cloud Capacity Spectrum Method. Capacity reduction factors for structural members are applied to simulate the attainment of a specific damage state under a mainshock. A cloud-based procedure is adopted to compute fragility analyses. The procedure is illustrated for a case-study building designed for gravity loads only. Results highlight the importance of considering the effect of cumulative damage in the fragility analysis of buildings. The proposed methodology may be used for seismic-risk assessment studies accounting for ground-motion sequences

A Markovian framework to model life-cycle consequences of infrastructure systems in a multi-hazard environment

Existing frameworks for multi-hazard life-cycle consequence (LCCon) analysis typically disregard the interactions between multiple hazards and obtain the total LCCon as the sum of the consequences caused by the individual hazards modelled independently. This practice leads to inaccurate life-cycle consequence estimates and ineffective risk-informed decision-making for disaster-mitigation strategies and/or resilience-enhancing policies. In addition, most available LCCon formulations fail to accurately incorporate the damage-accumulation effects due to incomplete (or absent) repairs between different hazard events. To address these challenges, this paper introduces a Markovian framework for efficient multi-hazard LCCon analysis of deteriorating structural systems, appropriately accounting for complex interactions between hazards and their effects on a system’s performance. The changes in the system’s performance level (e.g., damage or functionality state) are quantified with transition probability matrices following the Markovian assumption and the expected LCCon estimates are obtained by combining the performance level distribution with suitable system-level consequence models, which can include direct asset losses as well as socio-economic consequences. To showcase the framework applicability, a simple road network with a single case-study ordinary reinforced concrete bridge subject to earthquake-induced ground motions and environmentally-induced corrosion deterioration is investigated, estimating consequences in terms of community welfare loss