Abstract
The presented paper deals with strengthening and rehabilitation of U-shaped reinforced concrete bridges from the period of 1905–1930 using post-tensioning, which is a suitable, reliable, and durable method. These bridges have two main beams pulled over the bridge deck, which is supported by cross girders. The cross girders connect the two main beams forming a half-frame in the transverse direction, which provides spatial rigidity to the structure. The spans of these bridges are usually between 15 and 25 m. The high efficiency of post-tensioning can be seen on many implemented applications for bridge reconstructions worldwide. However, in this paper, the post-tensioning method is extended by a unique structural system of substitute cable ducts that allows for significantly expanding applicability of this method on existing concrete bridges. This method is highly recommended due to minimization of interventions into the constructions, unseen method of cable arrangement, and hence the absence of impact on appearance, which is appreciated not only in case of valuable historical structures but in general as well. In conclusion, the post-tensioning by monostrands in substitute cable ducts is a highly efficient method for strengthening of existing bridges in order to increase their load-bearing capacities in terms of current traffic load and to extend their service life. This method was also verified by monitoring the behavior of rehabilitated bridges before and after strengthening.
Highlights
Reinforced concrete beam bridges have been built since the very beginnings of reinforced concrete
A strengthening system using post-tensioning effects has been discussed in previous studies and applications; for example, Recupero et al [6, 7] presented an application of external prestressing technique for strengthening a single-span concrete railway bridge in Italy. e effect of strengthening was researched with the help of numerical simulations
Nilimaa et al [8] focused on Advances in Materials Science and Engineering strengthening of concrete railway bridges in the transverse direction using prestressed bars installed in drilled holes in the existing concrete
Summary
Reinforced concrete beam bridges have been built since the very beginnings of reinforced concrete. E essential requirement of this method is a favourable distribution of the original main load-bearing reinforcement, which provides abundant space for suitable drilling of substitute ducts in the available spaces between the original reinforcements without its interruption, or with just a small decrease in strength, which can be included in the strengthening design calculations and which can be compensated by the post-tensioning effects. (3) e prestressing reinforcement (cables composed of monostrands) is completely protected against mechanical damage after subsequent filling of ducts with injection If this protection is further complemented with anchored cable sheathing in a straight section between saddles on the bottom surface of beams, the entire prestressing set is hidden in the original concrete and in the newly constructed cover. Both simple and continuous reinforced concrete beam structures can be strengthened using cables in substitute ducts. It shows that suitable space could always have been found and that the substitute ducts could have been prepared without or with minimum damage to the original profiles of the main load-bearing reinforcement
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