Economical Span Combination and Section for A Three Span Continuous Post-Tensioned Concrete Railway Bridge
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Date
2015-05
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Addis Ababa University
Abstract
Significant traffic and congestion across urban areas, as well as waterways, create a demand for long-span bridges. The construction of these longer spans plays a critical role in the development of modern infrastructure due to safety, environmental, and economic reasons. A variety of bridge construction practices have been observed over the years. Planning, design and construction techniques are revised and refined to satisfy several parameters including feasibility, ease of construction, safety, maintainability, and economy. In Ethiopia, Reinforced Concrete bridges are commonly used for highways because of their ease of construction, availability of construction materials, low construction cost, etc. The bridges being built using reinforced concrete are most commonly used for full length, simply supported spans. However, there has been a growing need in the transportation sector to build bridges with longer spans, for instance, to construct elevated carriageways (for railways) in congested urban areas due to limited spaces and right of way. The ordinary reinforced concrete bridges for extending span ranges with incremental variations in the materials and conventional design procedures often result in relatively small increases in span range due to limited strengths and excessive deflections. These challenges would dictate to search for alternative materials and design philosophy, i.e. the Prestressed Concrete. Consequently, prestressed post-tensioned concrete continuous girder bridges will be discussed in detail in this research using different sections.
This thesis has assessed the cost-effectiveness (economic feasibility) of a three span continuous post-tensioned concrete railway bridge superstructure using Box and T-Girder sections for different span combinations. Summary of the results has showed that the economical span combination of a three span continuous post-tensioned railway bridge with a span of 100.00m is found to be 32.00 – 36.00 – 32.00m (L – 1.13L - L) for Box Girder, and 29.00 – 42.00 – 29.00m (L – 1.45L – L) for T–Girder. The study has also revealed that box girder sections are economical than the T-girder sections for a three span continuous post-tensioned railway bridge with a span of 100.00m.
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Keywords
Post-Tensioned Concrete, Economical Span Combination, Railway Bridge