Josée Bastien

BRIDGE INTEGRITY ASSESSMENT BY CONTINUOUS WAVELET TRANSFORMS

The potential of continuous wavelet transforms for damage assessment of existing bridges is investigated herein. Different types of continuous wavelet transforms have been under investigation and the most effective ones have been introduced in a toolbox to automate the damage assessment procedure. In this paper, the performance of the wavelet approach and the influence of different parameters in the damage assessment procedures are studied through two examples: a simply supported beam and a three-span concrete bridge. Applying the wavelet transforms to a structures static and/or dynamic response showed promising results with regard to localization of structural modification or damage. This paper underlines the high sensitivity of the wavelet analysis to damage intensity and its ability to be applied directly to the damaged data. These key characteristics could lead to this approach becoming one of the best for structural health monitoring of existing bridges in the near future.

Measuring infrastructure investment option value

Purpose - – The purpose of this paper is to propose a risk-based framework to estimate the option value of infrastructure investment, accounting for the stochastic behavior of both financial and physical (engineering) variables. Design/methodology/approach - – This study uses a real-options approach and computes the optimal investment dates and option values using Least Squares Monte Carlo, both the original Longstaff – Schwartz algorithm and the constrained Least Squares approach of Le tourneau – Stentoft. Findings - – Real-option value for infrastructure investment is substantial. It is beneficial to model jointly financial and engineering risks to better understand the timing and real-option value of infrastructure investment. The analysis further shows which variables are option value drivers. Research limitations/implications - – Future work could integrate financing constraints into the model, consider path dependency in the physical state variables or integrate sovereign risk, expropriation risk, operational risk or other project risks. Practical implications - – Financial practitioners and investment managers interested in infrastructure risk finance or project finance will benefit from a novel framework to analyze infrastructure investments in which engineering and financial risks interact in a tractable way. Social implications - – Public decision-makers will benefit from a better understanding of what determines the value of infrastructure investments, how real-option value affects optimal investment timing and how both are determined by financial and engineering risks. Originality/value - – The analysis considers financial and engineering risks in a single framework to better understand option value in infrastructure investment. The framework and findings are useful both to risk finance and project finance practitioners and investors as well as engineers and public sector decision-makers.

Effects of Delamination on the Performance of Two-Way Reinforced Concrete Slabs

Tests on two-way reinforced concrete slab-column connections with simulated delamination are reported. The experimental results are compared with test results of companion specimens to investigate the effects of significant delamination on the punching and postpunching responses of the specimens, as well as the effects of structural integrity reinforcement on the postpunching behavior of delaminated specimens. The results are also compared with predictions of punching shear resistance and postpunching shear resistance predictions. Significant delamination of the top reinforcement caused decreases in prepunching stiffness, punching shear resistance, and postpunching shear resistance of the specimens. The provision of structural integrity reinforcement allowed for the development of a postpunching shear resisting mechanism, increasing the postpunching shear resistances and ultimate deflections.

Multi-media learning tool for teaching mathematics

A pedagogical tool created for the teaching and learning of applied engineering mathematics is presented and described herein. The tool, which uses the World Wide Web (WWW) as the means of dissemination, is a didactic software made up of three hypertext linked modules. These modules are a tutorial, an exerciser and a simulator. The design of the tool was made using the experience from other systems and from education specialists. The tools most important features lie with its user interaction and its diagnostic capabilities. Results of a survey held with a group of students is also discussed.

Flexible decision analysis procedures for optimizing the sustainability of ageing infrastructure under climate change

Abstract Currently, there is significant interest in ensuring the sustainability and serviceability of infrastructure systems in the context of climate change. Indeed, a large proportion of existing structures already are in an advanced state of deterioration, thus affecting the sustainability and usefulness of these structures, and highlighting the need for better planning and decision analysis tools. Such tools would benefit from improved models to predict the residual life of structures, to estimate benefits derived from infrastructures, to account for uncertainties associated with physical and financial processes, and to provide more flexibility in decision-making strategies. These concepts are investigated through application of a risk-based decision-making model for reinforced concrete bridge decks in Montreal to estimate the optimal timing for deck repairs. A probabilistic deterioration model is used to predict the residual life of concrete decks as a function of exposure to de-icing salts using historical data and predictions from climate change scenarios. Historical data are used to validate model assumptions by comparing predicted condition states to observations from periodic inspections, while the climate scenarios are used to evaluate the impact of climate change on deterioration rates assuming that current deck design and de-icing salt management strategies are not modified. In this instance, the optimal timing for the first major repair is influenced by the uncertainty involved with climate change predictions and the future availability of funds, while ensuring the safety of users and the required level of service. The proposed framework, based on a cost-benefit analysis, is applicable to any infrastructure project.

Methods for Shear Strengthening of Thick Concrete Slabs

AbstractThis paper presents different strengthening techniques to improve the shear capacity of existing thick concrete slab structures that were constructed without shear reinforcement. Reinforcing bars are installed into vertical drilled holes and anchored with epoxy adhesive to increase the shear capacity. Experiments on retrofitted beams, representing slab strips, showed that all of the strengthening techniques investigated resulted in increased shear capacities. The shear failure mechanisms of the strengthened beams showed that, as expected, current evaluation methods for elements with conventional, well-anchored stirrups can lead to an overestimation of the shear capacities. The efficiency of the strengthening techniques is strongly influenced by the performance of the end anchorage of the drilled-in bars. The effectiveness of the epoxy-bonded bars is a function of their embedded length and they can, in some cases, debond before they reach their yield strength. By using the maximum bar spacing requi...

Robustness of Shrinkage-Compensating Repair Concretes

Drying shrinkage is one of the least desirable properties of repair concrete, because in restrained conditions, it may lead to shrinkage cracking and thus adversely affect its durability. Shrinkage compensating concretes (ShCCs) made with expansive mineral admixture represent an attractive alternative to prevent shrinkage cracking. This paper outlines a project devoted to the study of ShCC repair material robustness as a function of selected parameters. Two types of expansive agents were used, a calcium sulfoaluminate-based admixture (Type K) and a calcium oxide-based (Type G) one. The assessment of robustness addressed the influence of both the mixture design parameters (cement composition, type and dosage of expansive agent, w/cm ratio) and the curing conditions (moist curing conditions, temperature) upon the ShCC expansive behavior, the bond between ShCC repairs and concrete substrates, and ShCC frost durability. Overall, the results yielded in this study demonstrate interesting potential of ShCCs as crack-resistant and durable repair materials.