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During their lifetime, sewer networks face risks of infiltration or exfiltration, restriction of flow capacity, and loss of structural integrity. These factors individually or combined can impact the public health and the environment. This study is aimed at analyzing uncertainties contributing to the service life performance of sewer pipes under compounding effects of corrosion deterioration and traffic loads using a global sensitivity analysis (GSA). The specific goals are to identify significant sources of uncertainty, and to quantify and rank their time-varying significance for extended time horizons. The study considers a comprehensive set of uncertain environmental, structural, and geotechnical variables. Results indicate that among all the material properties, tensile and compressive strength of concrete are the most influential parameters over the entire service life of sewer pipes. According to the results, the significance of environmental variables varies considerably with time. Dissolved sulfide concentration and pH-dependent factor for the proportion of H 2 S in wastewater significantly affect infiltration/exfiltration for pipes that are older than 30 years. Variables contributing to truckload including the truck weight and multiple presence factor are also found to be significant. [ABSTRACT FROM AUTHOR]

Existing bridge performance metrics are limited in their ability to objectively reflect the safety and serviceability of bridges and identify effective Maintenance, Repair and Replacement (MR&R) actions for a large number of bridges in the face of budget constraints. This study presents a comprehensive optimal budget allocation framework with an integer linear programing formulation for a portfolio of bridges based on element-level inspection data. Considering budget constraints, this method determines optimal MR&R actions at element-level such that agency and user costs of repair actions required to have bridges in their like-new state at the next budget allocation year are minimized. The framework incorporates structural safety risks via the probability that the designated structural functionality of a bridge is or deemed to be compromised. The approach is applied to 484 National Highway Systems bridges in district 3 of Ohio. Results indicate that the proposed method can identify work plans comprising the optimal set of MR&R actions that maximize the network-level performance of bridge portfolios, while satisfying budgetary constraints. It is observed that this method consistently assigns higher priority to work plans that reduce structural safety risks of bridges, and to bridges with high traffic demands and long detour lengths. [ABSTRACT FROM AUTHOR]

Identifying key variables that influence crack formation in buried concrete sewer pipes and impact their structural integrity is crucial for evaluating the leakage and collapse vulnerability of these underground structures. The present study performs a comprehensive global sensitivity analysis for these critical pipe responses considering various uncertainties associated with material properties and loading. A high-fidelity three-dimensional nonlinear Finite Element (FE) model of a typical pipe is developed and used to capture pipe behavior. Considering the significantly high computational demand of the generated FE model, a surrogate model using Bayesian Additive Regression Trees (BART) is developed to accurately approximate input-output relationships in this high-dimensional problem. Significant variables are subsequently determined via a global sensitivity analysis based on Sobol's theorem through the application of Markov Chain Monte Carlo simulation to the trained BART model. Results indicate that concrete and backfill soil properties and variables associated with truckloads contribute significantly to the variation of key pipe responses, thereby affecting the likelihood of leakage and collapse. Findings of this study can benefit the design and management of sewer pipes in large wastewater networks and significantly reduce the complexity of assessing the reliability of sewer pipes. [ABSTRACT FROM AUTHOR]

Reliable computational models of transmission towers are key to improved hurricane risk management of transmission systems. However, a comprehensive understanding of involved complexities and their effects on the extreme wind performance of towers is not available. Particularly, buckling effects have not been captured properly and the failure of joints and the post-buckling behaviour of towers have not been investigated. Moreover, contributions of these and other complexities to key tower responses in the presence of uncertainties are not known. This paper presents an approach to modelling lattice towers that captures buckling and post-buckling, and joint slippage and failure and analyses their effects, while considering uncertainties, through a set of probabilistic, nonlinear pushover analyses in OpenSEES. Results for a double circuit vertical lattice tower indicate that buckling can lead to 30% reduction in the load-bearing capacity of towers. Joint slippage reduces the load-bearing capacity of the tower by 6%. It also considerably increases tower displacement. Connection failure can also occur in rare cases and it subsequently, changes tower's failure mode. The proposed modelling approach can be used in risk analysis of transmission systems to investigate various performance levels and improve the design of towers. [ABSTRACT FROM AUTHOR]

As coastal infrastructure systems are continuously exposed to deterioration, it is increasingly crucial to analyse their current and future serviceability performance. This paper investigates effects of chloride corrosion on the lateral force capacity and ductility of a wharf-supporting prestressed concrete marine pile and provides new insights into the state of marine structures. A probabilistically generated finite element modelling approach is developed for piles, which includes discrete concrete pile cross-sectional models connected to steel tendon non-linear elements via a series of non-linear springs that simulate bonding behaviour. Moreover, a prestressed material model is established that incorporates alternate failure modes including stress corrosion cracking and brittle failure to capture chloride-induced pitting corrosion in piles. It is shown that various failure modes cause an overall decrease in the maximum force capacity as piles age. Specifically, the alternate failure modes result in 31 and 56% reductions in the maximum capacity of the pile and associated top pile displacement, respectively, as the age of the pile increases from 25 years to 75 years. The presented methodology and results can greatly assist in decision-making for repair or replacement of wharves and aid in the design of new wharves considering their future performance. [ABSTRACT FROM AUTHOR]