Browsing by Author "Echaveguren, Tomas"

Now showing 1 - 12 of 12
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    Estimation of Exceedance Probability of Scour on Bridges Using Reliability Principles
    (2021) Contreras-Jara, Manuel; Echaveguren, Tomas; Chamorro, Alondra; Vargas-Baecheler, Jose
    Scour is one of the most relevant causes of bridge collapse. Most existing scour models have been focused on estimating scour depth as input for bridge design. This estimation is mainly deterministic. Parameter uncertainty has been considered to estimate expected scour as well. This framework is suitable for bridge design but has limitations for risk analysis of bridge networks, in which exceedance probabilities are needed. In this paper we use the first-order reliability method to estimate the probability that the actual scour will exceed the design scour, considering the uncertainty in hydraulic and hydrological parameters. The procedure was applied to a case study in Chile using the flood-flow history between 30 and 60 years of eight fluviometric stations. The local, contraction, and general scour were estimated for return periods between 2 and 500 years. The exceedance probability obtained was highly dependent on the uncertainty in annual maximum flow, Froude's number, top width, and riverbed longitudinal slope.
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    Fragility curves for road embankments exposed to adjacent debris flow
    (2023) Nieto, Natalia; Chamorro, Alondra; Echaveguren, Tomas; Escauriaza Mesa, Cristian Rodrigo
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    Friction reliability criteria applied to horizontal curve design of low-volume roads
    (SAGE PUBLICATIONS INC, 2007) de Solminihac, Hernan E.; Echaveguren, Tomas; Vargas, Sergio
    Design of road horizontal curves usually considers geometric characteristics and surface pavement condition by means of friction, superelevation, and speed equations in a deterministic point of view: a unique radius and superelevation are selected, considering a uniform behavior of drivers and pavement surface condition. However, empirical evidence shows that operating speed usually exceeds design speed when design speed is lower than 100 km/h. This means that the aggregated friction demand exceeds the design friction. The friction threshold and variability are not considered in design at the present time. Therefore, the designer does not know the remaining friction available and cannot estimate the margin of safety provided by the design. This problem is important in low-volume roads (LVRs) because the design speed usually considered is lower than 100 km/h. In this paper a methodology to design horizontal curves for LVRs is proposed, considering the variability of skid resistance, pavement texture, driver behavior, and geometric design elements. Critical speed is obtained for two conditions: consistency between design and operational conditions and consistency between friction thresholds considered for the pavement surface and operational condition. For this purpose, a reliability index is estimated by using the Hasofer-Lind method. Results show that a more realistic design is obtained when an aggregated friction demand based on driver behavior is considered. A good design is obtained when design speed ranges around 60 km/h and the standard deviation of curve radius is lower than 20% of the mean radius.
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    Long-term behaviour model of skid resistance for asphalt roadway surfaces
    (CANADIAN SCIENCE PUBLISHING, 2010) Echaveguren, Tomas; de Solminihac, Hernan; Chamorro, Alondra
    Skid resistance (SR) is relevant to road safety. Several researchers have showed that SR diminishes its value over time depending on the traffic-aggregated interactions, and the presence of heavy vehicles in the traffic stream. The classical SR model shows that its value drops from a starting value to an equilibrium value over time. However, this behaviour in low-volume roads is not entirely true. In this paper, an SR model in a single mathematic specification is proposed, which considers the polishing effect of heavy traffic through the polishing equivalence factor. The model was calibrated by using data measured with a SCRIM device from 1100 test sections in Chile. Considering speed and temperature factors calibrated for Chile, data were processed and corrected. It was concluded that the model for long-term behaviour of SR is satisfactory, but it is necessary to include the seasonal effects for a more realistic model.
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    Natural hazard risk management in the Chilean drinking water industry: Diagnosis and recommendations
    (2023) Molinos-Senante, Maria; Chamorro, Alondra; Contreras, Marta; Echaveguren, Tomas
    Disaster risk management in water infrastructure is still a world challenge. In this study, we present and discuss the results of an extensive survey conducted to Chilean water companies focused on disaster risk management in the production of drinking water. The main conclusions were: i) there is significant heterogeneity in the practices applied by water companies; ii) water companies use a large variety of tools to manage natural disasters; iii) earthquake is the one more relevant hazard for water companies. Based on the main conclusions of the survey, a set of recommendations for the Chilean water industry are proposed.
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    Proposal of an Integrated Index for Prioritization of Bridge Maintenance
    (ASCE-AMER SOC CIVIL ENGINEERS, 2010) Valenzuela, Sergio; de Solminihac, Hernan; Echaveguren, Tomas
    The bridge rating used in bridge management systems commonly uses only a structural condition. Factors such as seismic risk, hydraulic vulnerability, and strategic importance are commonly used in an isolated fashion. However, these factors are relevant when there is no possibility to calibrate deterioration models. This research uses the needs-based framework for developing an integrated bridge index (IBI) as an aid for prioritization and decisions made on maintenance and rehabilitation of bridges. The index weighs the structure distresses, hydraulic vulnerability, seismic risk, and strategic importance of the bridge. The index was calibrated using visual inspection, survey to experts, and regression analysis. After, the index was applied on six bridges placed on a primary road of Chile. To organize visual inspection, bridge inventory, and compute IBI and rank bridges, a software was developed. The calibration of the IBI index shows a correlation of 98% and all the parameters obtained were significant. Further research is needed to integrate cost with the proposed index and allocate maintenance activities.
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    Seasonal variability of skid resistance in paved roadways
    (ICE PUBLISHING, 2011) Echaveguren, Tomas; de Solminihac, Hernan
    Skid resistance is relevant for road safety. Past research studies have shown that in the long term, skid resistance oscillates around a trend value. Weather conditions, traffic, microtexture, macrotexture and polishing aggregate susceptibility are factors that contribute to this behaviour. Present models simulate this oscillatory pattern by considering a fixed wavelength adjusted to a calendar year, for a limited number of test sections and considering only heavy traffic. In the present study, an analysis of the long-term fluctuations of skid resistance was performed. Seventeen models were calibrated with different macrotexture levels, traffic and types of pavement surface. The investigation applied the concept of a polishing equivalence factor for traffic modelling in order to evaluate a truck as an equivalent car in terms of polishing. Models were based on a survey of skid resistance and macrotexture developed in the Chilean paved road network. It was concluded that asphalt surfaces were highly sensitive to factors that followed the seasonal pattern. The fluctuation obtained ranged between 0.08 and 0.25. In contrast, fluctuation was valued between 0.04 and 0.11 in cement concrete surfaces. Therefore, skid resistance values should be adjusted considering the season of the year in which they were measured and the type of pavement surface to obtain a value that can be compared with thresholds.
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    Seismic risk evaluation of highway tunnel groups
    (2021) Cartes, Pablo; Chamorro, Alondra; Echaveguren, Tomas
    Tunnels allow the continuity of rural road and urban transportation networks. Their shutdown provokes a loss in the transport system's level service, which entails higher road user costs. Earthquakes are the hazard that most affect the tunnels' serviceability. Depending on the structural damage's magnitude, the serviceability loss can be at different degrees, from marginal changes in traffic flow, associated with minor damages, to traffic interruption, associated with collapsing. Because of seismic phenomena' randomness nature, its effect on tunnel serviceability is estimated in probabilistic terms. Traffic interruption probability was estimated using fragility curves, representing the probability of achieving a specific damage state regarding the seismic hazard intensity. The calibration of tunnel fragility curves requires large samples of damages, seismic intensities, and geological and constructive data, which are not always available, especially in countries with a small number of tunnels in their road network. This work proposes a simplified procedure for evaluating the tunnels' traffic interruption probability due to earthquakes. The approach proposed uses existent seismic exposures maps, a strategy for selecting from existing fragility curves the more suitable, and a simple method to estimate the traffic interruption probability. The procedure analysed 20 tunnels affected by the Maule earthquake in Chile. These tunnels experimented PGA between 0.12 and 0.36 g. The highest risk values were obtained in tunnels without alternative routes and high repairing costs.
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    Sensitivity analysis and uncertainty quantification of a seismic risk model for road networks
    (WILEY, 2021) Allen, Eduardo; Chamorro Giné, Marcela Alondra; Poulos, Alan; Castro, Sebastian; Llera Martin, Juan Carlos de la; Echaveguren, Tomas
    Natural hazards may cause significant disruptions to road infrastructure, subsequently affecting road agencies, users, and productive activities. Despite the existence of infrastructure fragilities to seismic hazard and some operational consequences on network mobility, previous research has not modeled risk in terms of traffic disruptions and consequent travel time delays in subduction environments, analyzing the sensitivity to model parameters and quantified model uncertainty. This study proposes a risk framework to evaluate operational consequences in interurban road networks exposed to seismic hazard using travel time delays and propagate uncertainty in the model. Risk values are evaluated using Monte Carlo simulations, and uncertainty is propagated using a polynomial chaos expansion meta-model. The framework was applied to a very critical interurban network in central Chile. Results demonstrate that the parameters that most significantly influence risk are fragility, loss of road capacity, and traffic volume.
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    SIGeR-RV: A Web-Geographic Information System-Based System for Risk Management of Road Networks Exposed to Natural Hazards
    (2023) Chamorro, Alondra; Echaveguren, Tomas; Pattillo, Carlos; Contreras-Jara, Manuel; Contreras, Marta; Allen, Eduardo; Nieto, Natalia; de Solminihac, Hernan
    The consequences of natural hazards are frequently estimated by the direct cost of recovering damaged infrastructure and the indirect costs to road users, economic activities, and impacts on society. Road networks are crucial in economic systems, logistic chain continuity, accessibility, mobility, and the evacuation of population during and after extreme events. Risk management systems (RMS) are used to estimate the potential consequences of natural events and to assess strategies for risk reduction. These commonly assess hazards, assets exposure, economic losses, and risk mitigation actions, among others. The general framework of RMS can be adapted to different scenarios. Still, local characteristics, such as the types of hazards and physical assets, cannot always be directly adopted from these systems. This study discusses the development of SIGeR-RV, an RMS developed in Chile for road networks exposed to multiple natural hazards. The RMS was implemented in a web-based geographic information system platform able to display hazard maps, quantify risk levels, prioritize mitigation strategies, and estimate direct and indirect costs and social vulnerability. The content and various capacities of the system are detailed, following the steps marked in its framework. This first version of SIGeR-RV considers seismic hazard, volcanic lahars, and hydro-meteorological hazards that affect road platforms, bridges, tunnels, and cut slopes. The system currently serves as a tool for the Ministry of Public Works of Chile and other decision makers to estimate budget requirements for increasing resilience of the road network, identifying vulnerable road segments, and assessing the socioeconomical impacts of risk reduction.
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    Social vulnerability in Chile: challenges for multi-scale analysis and disaster risk reduction
    (2023) Guerrero Mancilla, Nikole Fernanda; Contreras, Marta; Chamorro Gine, Marcela Alondra; Martínez Reyes, Carolina Del Pilar; Echaveguren, Tomas
    Socio-natural disasters can have profound consequences for countries exposed to natural hazards. Consequently, Disaster Risk Reduction (DRR) management and the development of techniques to measure social vulnerability, such as the Social Vulnerability Index (SoVI), are critical to comprehending and mitigating risk factors. However, the impact of considering different spatial scales to understand and analyze social vulnerability remains largely unknown. The objective of this research is to identify the factors that determine social vulnerability in Chile, the implications of using four different territorial scales, differentiating for urban/rural territory, and the implications in DRR. The research considers the SoVI method, using the national census and the socioeconomic household survey to construct 25 variables at the zone/locality levels, and the use of a GIS platform. On average, eight vulnerability components are defined per model, with an average explanatory variance of 71%. Our analysis shows that soci
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    Traffic interruption risk induced by cut-slope failure: The rainfall effect
    (2023) Jimenez-Ramos, Gustavo; Echaveguren, Tomas; Vargas-Baecheler, Jose; Chamorro, Alondra
    Shallow landslides in road cut-slopes cause traffic disruptions, especially during rainy seasons. Even when the cut slopes are planned for saturation conditions, the variability and uncertainty of the explanatory variables of slope stability combined with pore pressure variation due to rainfall determine the need to probabilistic model the slope stability, considering the effects of rainfall intensity and duration. It is also necessary to know the magnitude of road platform blockage induced by slope failure, which is especially important for rural roads. This paper proposes a method for evaluating the probability of cut-slope landslides and traffic interruption. For this purpose, first-order reliability analysis and a Monte Carlo simulation were used to analyze various slope and rainfall scenarios. The analysis found 24 failure probability curves that were obtained for slope inclination, rainfall intensity, and rainfall duration. Probability values were obtained to achieve "low", "moderate", and "extensive" damage states in terms of roadway blocked due to slope slides and the relationship between roadway blocking width to slope height.