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У роботі повідомляється про вплив включення Fe на структурні та оптоелектронні властивості тонких плівок ZnO, отриманих методом центрифугування. Номінальне співвідношення Fe/Zn у розчині становило 7 %. Рентгенограми плівок показали, що леговане включення призводить до істотних змін структурних характеристик плівок ZnO. Усі плівки мають полікристалічну структуру з переважним зростанням вздовж площини (002) плівки ZnO. Розмір кристалітів був розрахований за відомою формулою Шеррера і виявився в діапазоні 22-17 нм. Найбільше середнє значення оптичного пропускання у видимій області спектру належало плівці ZnO, легованій Fe. Результати Раманівського розсіювання підтвердили спостереження методів XRD та УФ-спектроскопії появою цих місць на ділянках Zn+2. Ці результати пояснюються теоретично і порівнюються з тими, про які повідомляється іншими дослідниками. Результати Холівських вимірювань тонких плівок ZnO та ZnO:Fe виявляють високу концентрацію електронів приблизно 1016 см – 3 та їх низьку рухливість 2.6 см2/Вс. Усі вирощені зразки демонструють неоднозначний тип провідності носіїв (p- або n-тип) в автоматичних Холівських вимірюваннях Ван-дер Поу. Аналогічний результат спостерігався раніше іншими групами у плівках ZnO, легованих Li та As. Однак, охарактеризувавши зразки рентгено-електронною спектроскопією (XPS), ми продемонстрували, що неоднозначний n-тип носіїв у наших плівках ZnO не є внутрішньою поведінкою зразків, а обумовлений стійким ефектом фотопровідності в ZnO. This paper reports the effect of Fe incorporation on structural and electro-optical properties of ZnO thin films prepared by spin coating techniques. The Fe/Zn nominal volume ratio was 7 % in the solution. X-ray diffraction patterns of the films showed that doped incorporation leads to substantial changes in the structural characteristics of ZnO films. All the films have polycrystalline structure, with a preferential growth along the ZnO (002) plane. The crystallite size was calculated using a well-known Scherrer’s formula and found to be in the range of 22-17 nm. The highest average optical transmittance value in the visible region was belonging to the Fe doped ZnO film. The results of the Raman scattering confirmed the observations of XRD and UV-Vis analysis techniques by the appearance of these occupancies at Zn+2 sites. These results are explained theoretically and are compared with those reported by other workers. The results of Hall measurement of ZnO and ZnO:Fe thin films reveal a high electron concentration around 1016 cm – 3 and low mobility 2.6 cm2/Vs. All as-grown samples show ambiguous carrier conductivity type (p-type and ntype) in the automatic Van der Pauw Hall measurement. A similar result has been observed in Li-doped ZnO and in As-doped ZnO films by other groups before. However, by characterizing our samples whit XPS, we have demonstrated that the ambiguous carrier type n in intended our ZnO films is not intrinsic behavior of the samples. It is due to the persistent photoconductivity effect in ZnO.

The aging and deterioration of highway bridges requires the development and implementation of technologies that provide enhanced resilience in short period of time. Fiber-reinforced polymers can be used as an effective resilience enhancement strategy for critical bridge components that provide rapid recovery of strength, ductility and minimize disruption of traffic. This paper introduces three measures of bridge resilience, namely load carrying capacity, ductility and rapid recovery of function, which can be used for the design and management of highway bridges.An example illustrates the modeling of the performance of corrosion-damaged reinforced concrete columns and how different rapid rehabilitation approaches can contribute to achieve resilient highway bridge structures., 6th International Symposium on Life-Cycle Civil Engineering, IALCCE 2018, October 28-31, 2018, Ghent, Belgium

The risk of failure of concrete infrastructures built in corrosive environments is increasing due to use of deicing salts, increased loads, inadequate maintenance and increased rate of deterioration due to climate change. Climate change leads to an increase in temperatures, which in turn leads to an increase in chloride diffusivity and rate of corrosion that yield an increase in probability of corrosion of reinforcing steel, concrete damage and a shortening of service life of concrete structures. The impact of temperature rise due to climate change on diffusivity is modeled using the Arrhenius relationship. Uncertainties in the parameters governing the service life, such as concrete cover depth, chloride threshold, chloride diffusion coefficient, surface chloride content are considered by modeling them as random variables. The optimum service life of concrete structures can be defined as the time at which the probability of corrosion reaches an acceptable value for different types of concrete, reinforcing steel and concrete cover depths. The time-dependent probability of corrosion of reinforcing steel embedded in concrete structures is formulated as a nonlinear optimization problem that is solved by the projected Lagrangian algorithm. The example of a concrete bridge deck is used to illustrate that the timedependent probability of corrosion increases with temperature by 37% and 77% for life cycle temperature rises of 3◦C and 6◦C, respectively compared to the reference case at 23◦C. To reduce this probability of corrosion, corrosion-resistant steel reinforcement, high performance or/and higher concrete cover depth can be used. For the case of bridge decks reinforced with corrosion-resistant steel, the corrosion probability is reduced by half after 40 years compared to that associated with black steel for the climate scenario with 6◦C temperature rise. The final selection of an optimal design should take into account the life cycle costs incurred during the service life or life cycle of concrete infrastructures., 6th International Symposium on Life-Cycle Civil Engineering, IALCCE 2018, October 28-31, 2018, Ghent, Belgium

One-third of Canada’s 75,000 highway bridges have structural or functional deficiencies and a short remaining service life. With 20 million light vehicles, 750,000 trucks and 15,000 public transit buses using Canadian bridges annually, they are essential for the efficient movement of commercial goods within the country and across international borders. Owners of bridges and critical concrete infrastructure are seeking to reduce operating costs during their service life. Canadian industry dealing with the construction and maintenance of concrete bridges is exploring advances in materials science, fault detection and automation to develop and improve their products and tools to meet bridge owners’ needs. Canadian firms are already at work helping to develop long-life structures. However, they are facing technical barriers that are challenging the adoption of new products and technologies, such as early failure of materials used for rehabilitation and unreliable technologies for initial and long-term assessment.

The development of an effective strategy for the inspection and monitoring of the nation?s critical bridges has become necessary due to aging, increased traffic loads, changing environmental conditions, and advanced deterioration. This article presents the development of a probabilistic mechanistic modeling approach supported by durability monitoring to obtain improved predictions of service life of concrete bridge decks exposed to chlorides. The application and benefits of this approach are illustrated on a case study of a reinforced concrete barrier wall of a highway bridge monitored over 10 years. It is demonstrated that service life predictions using probabilistic models calibrated with selected monitored field data can provide more reliable assessments of the probabilities of reinforcement corrosion and corrosion-induced damage compared to using deterministic models based on standard data from the literature. Such calibrated probabilistic models can help decision makers optimize intervention strategies as to how and when to repair or rehabilitate a given structure, thus improving its life cycle performance, extending its service life and reducing its life cycle cost.

Ultra high performance fibre-reinforced concrete (UHPFRC) is a newly developed concrete material that provides very high strength and very low permeability. The renewal of aging highway bridges and the construction of new bridges using ultra high performance concrete can yield structurally efficient long life bridges, which will require minimum maintenance and low life cycle costs. A simplified flexural design approach of UHPFRC girders and a comparative study of the structural efficiency of UHPFRC and conventional precast prestressed concrete girder bridges are presented in this paper, and to compare its structural efficiency to conventional slab-on- concrete girder bridges. The proposed design approach is consistent with the Canadian Bridge Design Code (CHBDC) and is based on the state-of-the-art design recommendations for UHPFRC and checked using a three-dimensional finite element analysis. It is found that the use of UHPFRC in precast/prestressed concrete girders can yield a reduction of up to two girder lines with smaller girder sizes when compared to conventional concrete girders bridge. UHPC results in a significant reduction in concrete volume that can reach 40%, which turn leads to a more efficient design of the superstructure and a significant reduction in the dead loads on the substructure, which is very important for the safety of aging bridge substructures., 8th International Conference on Short & Medium Span Bridges: 03 August 2010, Niagara Falls, Ontario, Canada

The design and preservation of bridges have been driven, for a long time, by the concerns tominimize costs and improve asset condition. The growing concerns for environmental protection and theshift towards achieving sustainable transportation infrastructure are now requiring the use of approaches thatseek to achieve an adequate balance between social, economic and environmental performance over the entirelife cycle of the bridge. This paper discusses some performance indicators, such as safety, serviceability,costs, traffic disruption, greenhouse gas emissions, which can be used for life cycle design of highwaybridges. An example, taken from the North American context, illustrates how different design and rehabilitation approaches can contribute to achieve the desirable balance between social, economic and environmental sustainability criteria., IABMAS 2010: Bridge Maintenance, Safety, Management and Life-Cycle Optimization: 11 July 2010, Philadelphia, USA

The need to upgrade the large number of aging reinforced concrete (RC) structures that are exposed to aggressive environments, such as de-icing salts in cold regions and sea water requires the development of innovative solutions that will lead to the construction of long life RC structures with low life cycle costs. In this paper, the impacts of using high performance reinforcing steels (HPS), such as 316 LN, 304 and 2205 duplex stainless steels and ASTM - 1035 (or chromium) steel on the service life and structural behaviour of RC structures are investigated. In terms of resistance to chloride attack, 316 LN stainless steel provided the highest value, followed by 2205 duplex steel, chromium steel and then carbon steel. In terms of yield and ultimate strengths, chromium steel exhibited the highest values followed by 316 LN and 22065 duplex steels then carbon steel. In terms of ductility, the RC beams reinforced with 316 LN steel exhibited the highest capacity to deform before fracture, followed by duplex 2205 steel, carbon steel, and then chromium steel. In terms of flexural design of RC beams reinforced with HPS, the same flexural capacity is achieved by using much lower areas of reinforcement for chromium steel, followed by stainless steel and then carbon steel. This suggests that greater savings in material, labour, and maintenance costs are possible when using chromium steel and stainless steel as a reinforcement for RC structures built in aggressive environments, such as highway bridge decks, parking structures, marine and offshore structures., 3rd Congress of the International Federation for Structural Concrete (FIB) and PCI Convention: 29 May 2010, Washington, D.C.

Aussi disponible en français: Cadre de travail modèle pour l'évaluation des infrastructures publiques de base au Canada

8th TRB National Conference on Transportation Asset Management: 19 October 2009, Portland, OR

Paper presented orally only (not for publication), 8th TRB National Conference on Transportation Asset Management: 19 October 2009, Portland, OR

Performance indicators are an essential part of modern road asset management. The basic rationale for having measureable performance indicators is that limited availability of resources makes it necessary to allocate these resources as effectively as possible among competing alternatives; moreover, that considerations of safety, capacity, serviceability, functionality and durability are explicitly recognized.A comprehensive approach to developing performance indicators should consider the basic rationale, a balance in use and reporting, efficiency and effectiveness, a tie to transportation values, objectivity in the measurements used and the stakeholders involved in the development of a framework., Annual Conference of Transportation Association of Canada: 18 October 2009, Vancouver, B.C.

The ageing and deterioration of highway bridges can have very serious consequences in terms of reduced safety, serviceability and functionality. Many bridges built in the 1960's and 1970's are considered deficient by today's standards. The widespread deterioration and some recent failures have highlighted the importance of developing and implementing effective inspection strategies, including structural health monitoring systems, which can identify structural problems before they become critical and endanger public safety. Continuous monitoring is becoming necessary due to ageing of bridges, increased traffic loads, changing environmental conditions, and reduced capacities, especially for medium and long-span bridges given the severe consequences of failure. The implementation of monitoring programs can assist in optimizing the in-depth inspection, maintenance, rehabilitation, and replacement of bridge structures. The continuous and simultaneous measurements at critical discrete points of a bridge system will allow the assessment of its performance with respect to different limit states, including safety and serviceability. Prediction models, updated from such monitoring data, can optimize intervention strategies as to how and when to repair or rehabilitate thus extending service life and reducing life-cycle costs.The objectives of this paper are: (i) to present an approach for the efficient use of structural health monitoring into the durability and structural reliability assessment process; (ii) to highlight the applicability of the approach to short, medium and long-span bridges; and (iii) to demonstrate the effective use of field monitoring data for the calibration and updating of service life prediction models. A case study on a medium-span concrete highway bridge is also presented and used to illustrate the approach., 4th International Conference on Structural Health Monitoring of Intelligent Infrastructure (SHMII-4): 22 July 2009, Zurich, Switzerland

This paper presents an approach for a multi-objective-based management of aging critical highway bridges to improve their life cycle performance with emphasis on improving public safety and security. The proposed multi-objective optimization framework is presented as an effective approach that overcomes some of the limitations and complexities of cost-benefit or risk analyses, where all consequences need to be expressed in monetary terms. The framework prioritizes first the critical bridges and then identifies the risk mitigation measures that can be used to satisfy several possible management objectives such as maximizing public safety and public security, minimizing traffic disruption and minimizing costs. Risk mitigation strategies can include more frequent and/or more in-depth inspections, load rating, monitoring of the structural performance and security of bridges, rehabilitation and strengthening of damaged elements, and protection of weak and vulnerable components against extreme shocks due to natural hazards or intentional attacks. A multi-objective criticality index is proposed as a prioritization criterion that achieves an adequate best trade-off between all identified and conflicting objectives. The implementation of the proposed approach is demonstrated on three examples that illustrate the prioritization process on a hypothetical network of ten critical bridges and the use of different risk mitigation measures, such as health monitoring and deterioration prediction models on bridge structures., Aging Infrastructures Workshop: 21 July 2009, Columbia University, New York City

Workshop of Canadian Network of Asset Managers-CNAM: 03 May 2009, Calgary, AB

The ageing and deterioration of highway bridges can have serious consequences in terms of reduced safety and serviceability. The objectives of this paper are to present an approach for the structural health monitoring of concrete bridge structures; and to demonstrate the effective use of field monitoring data for the updating of service life prediction models, which accuracy can be significantly improved. A case study on a major highway bridge is also presented and used to illustrate the approach., INFRA 2008: 17 November 2008, Quebec city

A considerable percentage of highway bridges in North America is in a structurally/functionally deficient state due to aging, aggressive environment and increased traffic load and volume. The consequences of this deficiency are numerous, including reduced safety, serviceability and service life, which lead to increased risk of injuries and fatalities; and increased maintenance costs and user costs. Reliable predictions of life cycle performance are critical to the optimization of their design and maintenance that will lead to reduced risks of failure and life cycle costs., Annual Conference of the Transportation Association of Canada (TAC): 21 September 2008, Toronto, Ontario

High performance concrete (HPC) bridge decks are prone to premature cracking if movement is restrained. Internal curing (IC) can reduce shrinkage cracking in structures, thus improving their performance and service life. However, there is very limited information in the literature on the possible extension of service life due to internal curing. This paper addresses this question by using predictive models to estimate the service life and life-cycle costs of a typical bridge deck made with concrete using internal curing as opposed to conventional curing. Four options are compared: (i) normal concrete deck; (ii) HPC deck; (iii) HPC deck with internal curing; and (iv) very high performance concrete deck with internal curing. It was found that the use of internal curing can extend the service life of HPC bridge decks by almost ten years, which is mainly due to due a slower penetration of chlorides as a result of reduced shrinkage cracking. The use of internal curing in HPC decks resulted in a 20% reduction in life-cycle costs, even though the in-place unit cost of internally-cured HPC can be up to 4% higher than that of conventionally-cured HPC. The higher initial investment for the construction of the HPC-IC deck can be offset in only 5 years when compared to that required for normal concrete deck. This is due to a longer service life and less frequent maintenance activities., 50th Brazilian Concrete Congress "Concrete Infrastructure and Environmental Conservation": 04 September 2008, Salvador, Brazil

This paper evaluates relationships between four parameters that govern the time to corrosion initiation of reinforced concrete in chloride-laden environments ' the concrete chloride diffusion coefficient, the steel reinforcement chloride threshold, the concrete cover depth, and the surface chloride exposure condition. A deterministic diffusion-based corrosion initiation model was used to determine numerical, nonlinear relationships between pairs of parameters based on a deterministic, diffusion-based, corrosion initiation model. The relationships can be used to determine the most appropriate combination of the parameter values for an effective design., The 2nd Canadian Conference on Effective Design of Structures: 20 May 2008, Hamilton, Ontario

With its very high strength, high modulus and very low permeability, ultra high performance concrete (UHPC) can provide major improvements over conventional high performance concrete (HPC) in terms of structural efficiency, durability and cost-effectiveness if used in the construction of slab-on-precast prestressed girder bridges. In this study, the optimum use of UHPC is evaluated for the case of simply supported cast in place concrete slab on precast/prestressed UHPC girder bridges. These bridges are designed according to the Canadian Highway Bridge Design Code requirements, including no cracking at the serviceability limit state., Second International Symposium on Ultra High Performance Concrete: 05 March 2008, Kassel, Germany

Workshop on Computational Tools and Technologies for Construction Practitioners: 13 February 2008, London, Ontario

This study investigated the optimum use of ultra high performance concrete (UHPC) for two- and three-lane simply supported bridges. Two designs were investigated: (i) typical cast in place concrete slab on precast/prestressed UHPC girders; and (ii) typical cast in place concrete slab on precast/prestressed UHPC girders. The study measured stress distributions and concentration zones in the girders under dead- and traffic-loads. The concrete quantities and the total areas of prestressing steel were calculated for the UHPC designs and compared to typical concrete designs., 2007 PCI National Bridge Conference: 21 October 2007, Phoenix, Arizona

This paper presents a life cycle-based approach for the design of concrete highway bridges that takes into account physical, economic and environmental performance with emphasis on the reduction of greenhouse gas emissions, construction waste production, and life cycle cost. The analysis considers all the key stages in the life cycle, which include extraction of raw materials, construction, maintenance, repair, rehabilitation, replacement, and disposal. The life cycle analysis compares the life-cycle performance of two concrete highway bridge decks built in corrosive environments - normal concrete is used for one and high performance concrete for the other., 3rd International Conference on Life Cycle Management: 27 August 2007, Zurich, Switzerland

ACI Workshop on Advances in Service Life Models that Consider Multiple Sources of Deterioration, 24 April 2007, Atlanta, Georgia

Aussi disponible en français: Pour une meilleure gestion du cycle de vie des tabliers de ponts routiers

Both owners and users of bridges expect them to have a service life of 50 to 100 years, with only routine maintenance. But demands on most of our bridges have been increasing annually because of growing traffic volumes, higher loads, and harsher environments. These conditions, coupled with the inadequate funding allocated for maintenance, have led to the accelerated aging and extensive deterioration of these critical structures.

This paper presents a comprehensive approach to life cycle cost analysis of reinforced concrete bridges that takes into account all costs incurred by the owners and users during construction, maintenance rehabilitation and replacement. This approach provides also an estimate of the environmental impacts associated with construction and replacement of bridge decks in terms of greenhouse gas emissions and waste production. The analysis considers all the key stages in the life cycle, which include extraction of raw materials, construction, maintenance, repair and rehabilitation, replacement, and disposal. The total life cycle costs are evaluated by using the present value method. In this paper, the long-term economic efficiency of high performance concrete (HPC) containing supplementary cementing materials for the construction and rehabilitation of concrete bridges is evaluated and compared to that of normal performance concrete (NPC) in terms of service life, life cycle cost and environmental impacts., Infra 2006 - Le Québec en chantier : optimiser les interventions

This paper presents a new approach for the maintenance optimization of concrete bridgedecks, which combines a stochastic deterioration model and a multi-criteria optimizationmodel. The stochastic deterioration model is based on the first-order Markov chain thatpredicts the probabilistic time-variation of the condition of bridge decks. The multicriteriaoptimization model takes into account two important and conflicting criteria: theminimization of maintenance costs, and the maximization of the network condition. Thisapproach generates the solution that achieves the best compromise between thesecompeting criteria, while considering the uncertainty in bridge deck deterioration. Thefeasibility and capability of the proposed approach is demonstrated on a network ofbridge decks obtained from the Ministère des Transports du Québec database. Thisexample illustrates the effectiveness of the proposed approach in determining theoptimal set of maintenance alternatives for reinforced concrete bridge decks whenconsidering two or more relevant optimization criteria., 7th International Conference on Short & Medium Span Bridges: 23 August 2006, Montreal, QC.

Publicly owned infrastructure forms a large portion of the existing infrastructure in Canada and elsewhere. Typically, asset managers must make decisions about maintenance and renewal alternatives based on sparse data about the current state of their infrastructure assets, the relative risk of failure of these assets, and the life cycle costs of proposed interventions. The infrastructure in any one organization can consist of a diverse set of assets ranging from bridges to buildings and from buried to overhead utilities. The optimal selection of proposed interventions across this broad spectrum of assets is also problematic, and currently it is performed in a subjective manner. This paper identifies a number of prioritization techniques that can be used to compare and rank repair and renewal projects. This research does not attempt to develop models to select the 'correct projects' or even to identify the best decision model or prioritization technique; rather, it attempts to illustrate by example the results of specific decision-making paradigms., Joint International Conference on Computing and Decision Making in Civil and Building Engineering: 14 June 2006, Montréal, QC.

This paper presents a new approach to optimizing the maintenance of concrete bridge decks. This approach combines a stochastic deterioration model and a multiobjective optimization model. The stochastic deterioration model is based on the first-order Markov chain, which predicts the probabilistic time variation of bridge deck conditions. The multiobjective optimization model takes into account two important and conflicting criteria: the minimization of maintenance costs and the maximization of the network condition. This approach achieves the best compromise between these competing criteria while considering the uncertainty in bridge deck deterioration. The feasibility and capability of the proposed approach are demonstrated with field data for a sample network of bridge decks obtained from the Ministère des Transports du Québec database. This example illustrates the effectiveness of the proposed approach in determining the optimal set of maintenance alternatives for reinforced concrete bridge decks when two or more relevant optimization criteria are taken into consideration.