Search

Modern structural design codes assume a statistically stationary climate. However, it is now known that the climate is changing at a rate that calls into question the stationarity assumption. This study was undertaken to explore various methods of accounting for climate nonstationarity. The geographical domain of this study covers most of Canada, intending to explore how best to update future climatic variables in the National Building Code of Canada (NBC). Outputs from future climate simulations for North America by Environment and Climate Change Canada (ECCC) and the Pacific Climate Impacts Consortium (PCIC) were used, focusing on a representative concentration pathway (RCP) scenario, namely the RCP8.5 emissions scenario. Surface hourly mean wind speeds and ground snow amounts were extracted from the simulations and used to detect and quantify trends in the extreme climatic variables from 1950 through 2100. This study reviewed different concepts for evaluating climatic design variables under stationary and nonstationary climates. It was found that within the range of linear nonstationarity detected for grid points within Canada, the results predicted using these nonstationary methods are close. Therefore, a simpler approach, namely Minimax design life level, was adopted to estimate the design wind speeds for 1/50 and 1/500 annual probability of exceedance and the design ground snow loads for 1/50 and 1/1,000 annual probability of exceedance. Design values derived based on nonstationary approaches were compared with the results estimated using the conventional return period concept between 1986 and 2016 and a moving-time-window method between 2060 and 2090 centered at 2075. [ABSTRACT FROM AUTHOR]

This paper presents a uniform and consistent semi-quantitative classification of consequences of failure of buildings as part of a multi-level seismic risk management framework for existing buildings to help building owners make risk-informed decisions for the seismic evaluation and retrofit of existing buildings to minimise the life safety risk. The management framework consists of three levels of risk assessment, namely: (i) Level 1: Preliminary seismic screening; (ii) Level 2: Semi-quantitative seismic risk screening; and (iii) Level 3: Quantitative seismic evaluation. The proposed classification consists in general of three classes, namely: (i) Consequence Class – Low (CC-L), (ii) Consequence Class – Medium (CC-M); and (iii) Consequence Class – High (CC-H). These consequence classes are based on semi-quantitative criteria, including building occupancy, number of people at risk, building area, number of storeys, and mobility and ability to escape. The proposed classification can be used to refine the building importance classification in many codes, standards and guides to yield more uniform classification of consequences of failure that can be integrated with the seismic risk management framework to determine more uniform risks of failure. An example illustrating the application of the proposed classification is provided for the case of office buildings. [ABSTRACT FROM AUTHOR]

The development of infrastructure systems that are sustainable and resilient is a challenging task that involves a broad range of performance indicators over the system lifecycle that affect system functionality and recovery. Sustainability indicators address economic, social, and environmental performance metrics and resilient indicators address strength, functionality, and recovery-time metrics following a hazard event. Sustainable systems consider environmental impact and conservation of nonrenewable resources over the life of the system. Resilient systems consider performance levels relative to potential damage levels and recovery times from events. Both concepts address adequate system performance and lifecycle costs, but put a different emphasis on other indicators. Numerous sources of uncertainties associated with the lifecycle performance of infrastructure systems require the use of a risk-informed decision-making approach to properly account for uncertainties and to identify cost-effective strategies to manage risk. A framework for risk-informed decision making for the lifecycle performance of infrastructure facilities that includes consideration of sustainability and resilience is presented. Separate examples are provided for the same highway bridge deck system to illustrate sustainable and resilient performance objectives with the design and rehabilitation of highway bridge decks. The sustainability assessment considers the effect of corrosion degradation mechanisms on lifecycle costs, environmental impact (CO2 and waste), and social impacts (accidents and user time) while maintaining service life and structural safety. The resilience assessment considers the effect of seismic hazard events on structural damage levels and recovery time while maintaining system functionality and structural safety. [ABSTRACT FROM AUTHOR]

The aging and deterioration of highway bridges and the new requirements for sustainable infrastructures and communities require innovative approaches for their management that can achieve an adequate balance between social, economic and environmental sustainability. This paper presents a multi-objective decision-making approach for the sustainable design and management of highway bridge decks, which can consider several and conflicting objectives, such as the minimisation of owner's costs, users costs, and environmental impacts and uses goal setting and compromise programming to determine the satisficing and compromise solutions that yield the best trade-off between all competing objectives. The proposed approach is based on robust reliability-based mechanistic models of the deterioration and service life of reinforced concrete bridge decks, which include diffusion models for the prediction of chloride ingress into concrete and steel corrosion and thick-walled cylinder models for the prediction of stresses induced by the accumulating corrosion products in the concrete cover. The proposed approach is illustrated on the life cycle design and management of highway bridge decks using normal and high performance concrete. It is shown that the high performance concrete deck alternative is a Pareto optimum, while the normal concrete deck is found to be a dominated solution in terms of life cycle costs and environmental impacts. [ABSTRACT FROM AUTHOR]