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This master thesis aims to quantify the robustness of post tensioned bridge and to study the effect of corrosion on tendons. A post tensioned bridge has been first design. Concrete with medium compressive strength and steel strands are combined to form the post-tensioned model which provides a very strong and good work structure. The robustness is defined as the structural property that measures the degree of remaining structural performance after the structure has been damaged by corrosion. Corrosion is an electrochemical process which occurs under oxygen and moisture exposure. Many researches have been oriented toward the effect of corrosion on steel bars and toward the consequence on the robustness of the structure. As corrosion leads to reduction of steel area, the robustness of the structure is affected. Indeed, a loss of steel leads to a reduction of strength of the structure. Many definitions of robustness are available but very few practical proposals of a target of threshold value that defines the limit between what is robustness or not do exist. In the past 30 years, different researchers attempted to quantify the robustness. A new approach adequate to structures under deterioration has been used for this case study of a post tensioned bridge affected by corrosion. This approach consists of a robustness indicator IR,D which can be expressed by the area below the curve that defines the normalised structural performance f(D) as a function of the normalised damage D. The higher the robustness index, the more robust the structure is.Through grillage analysis aided by software SAP2000, three damage scenarios have been compared. First, a loss of prestressed area due to corrosion has been applied on the first three most external tendons, secondly on the three middle tendons and finally an equivalent loss of steel area on all the tendons. The index of robustness IR,D have been calculated in function of the damage D for each cases. It has been noticed that the index of robustness is the highest when the corrosion affects uniformly the structure whereas the lowest index of robustness appears when the corrosion affects the first three tendons. This is due to the distribution of loads on the structure that has a clear two dimensional behaviour: the highest loads are applied at the edge of the structure therefore a loss of prestress area at this location has more effect on the robustness of the structure. However, the robustness indicator of each case is closed to each other _less than 1.5% difference. It can be deduced that the robustness aspect of this type of bridge is not really affected by the corrosion and its reaction is little. The corrosion is an environmental factor that affects the most the robustness aspect of a structure under high loadings rather than an uniform corrosion on the entire structure; but corrosion does not reduce considerably the robustness of a post tensioned slab bridge with massive cross-section.
In some countries durability problems with post-tensioning tendons have in the past led to fairly restrictive regulations. Improvements to execution procedures have been developed since, and new or improved prestressing systems have been proposed, too. This development was, of course, subject of discussions in fib Commission 9 Reinforcing and Prestressing Materials and Sytems and in IABSE Working Commission 3 Concrete Structures. It was decided to organise a workshop with the aim to review the different aspects of the problems encountered and to discuss solutions available today. Keynote speakers from various countries were invited to contribute. Their papers are published in this bulletin, grouped together under the following themes: Inventory and condition (6 papers) Investigation and repair (5 papers) Technical progress (4 papers) Strategies for improvement (6 papers) Supported by the international federation for structural concrete fib, and the international association for bridge and structural engineering IABSE, the workshop took place on 15-16 November 2001 at Ghent University, celebrating the 75th anniversary of the Magnel Laboratory for Concrete Research, whose director also chaired the Scientific Committee and edited the bulletin. It needs to be emphasised that in the bulletin invited experts present their individual views. Although not yet discussed in any of the association's working bodies, the highly topical contents of the bulletin is believed to be of general interest to fib's members and to document a starting point for future work in this field. Therefore, the Council of fib agreed to exceptionally publish these papers within fib's series of Bulletins.
Describes several bridging concepts, which were developed and successfully applied during the author's forty years of close involvement with UK and international bridge design, construction, maintenance and research. The concepts mainly apply to the small/medium span range of bridges and viaducts.
Provides a review of the repair, maintenance and protection of concrete bridges. This book summarizes information from conference papers, research and technical reports, and others. It aims to increase the expertise of structural engineers and safeguard the investment. It presents solutions to the problems and pitfalls that engineers encounter.
This synthesis will be of interest to bridge designers, materials engineers, maintenance engineers, and others concerned with the durability of prestressed concrete bridges. Information is presented on the factors affecting the durability of prestressed concrete. Prestressed concrete bridges require special attention because the capacity of the structure is strongly dependent on the prestressing force. This report of the Transportation Research Board reviews the factors affecting the durability of prestressed bridge components and describes methods of detecting and assessing deterioration, preventive maintenance, repair, and methods of improving durability in new structures.
Corrosion of steel reinforcement in concrete is a major problem, with serious implications for structural integrity and durability particularly for bridges and marine structures. This new book provides a thorough overview of recent developments and applications in this area. It examines the durability, strength and suitability of alternative materials.