|Title||Contribution to the extension of the lifetime of existing concrete structures trough an adequate structural evaluation and strengthening with advanced materials|
|Partners||TEC4, Pedelta, CTT Stronghold , DG Carreteras, Generalitat de Catalunya|
|Project Leader||Antonio Mari Bernat/Jesus Miguel Bairan Garcia|
|Contractor||Ministerio de Economia y Competitividad|
|Program||Proyectos de Investigacion Fundamental no orientada|
|Professor in charge||Antonio Mari Bernat/Jesus Miguel Bairan Garcia|
|Summary||Concrete bridges, which are key elements of the transportation infrastructures, must carry increasing loads and suffer deterioration along their service life. In addition, most current codes are oriented for designing new structures so that, in some aspects, precision is subordinated to simplicity of use and they use partial safety coefficients which are not adequate for existing structures. Consequently, many bridges currently in service could become theoretically obsolete in case of being evaluated using design codes, resulting in an exorbitant cost of replacement. For this reason, it has been approved that the future Eurocode-2, part 1-1 will incorporate an adequate methodology for evaluation of existing bridges, allowing for keeping in operation many bridges that no longer meet the design criteria but are otherwise able to safely carry the design loads.
In this context, the main objective of the project is to contribute to the development of an adequate methodology for the structural evaluation and strengthening of bridge decks and other concrete structures, focusing on the rigorous determination of the shear and punching strengths, which are still poorly known. With this purpose, it is posed to consolidate, extend and experimentally verify a shear strength mechanical model recently developed by members of the research team, which has showed an excellent correlation with the results of a large international data base of shear tests. Such a model is currently being considered, among others, for being incorporated into the future Eurocode 2 and ACI structural concrete codes.
In some cases, a bridge must be strengthened to extend its life span. For this reason a strengthening technique using shape memory alloys (SMA) will be developed within the project. The model will be extended to incorporate the effects of shear strengthening techniques using SMA, FRP and external prestressing, and their performance will be compared through experimental tests. The influence of the proposed strengthening system on the failure mode and ductility will be also studied.
The proposed research project aims at solving some critical aspects which require further research, related to size effect, partial bond between concrete and steel, members composed by two different concretes, with T sections, plastic hinges, punching and shear in slabs, continuous post-tensioned bridges and effects of the proposed strengthening system on the failure mode and ductility.
The proposed model and their theoretical formulations will be experimentally verified through load tests at three scales: small (material and strengthening prototypes), medium (specimens representative of the different shear actions, focusing on the concrete compression chord) and large (punching and shear in bridge slabs, size effect in large reinforced and post-tensioned concrete continuous beams, with or without strengthening). The possibility of performing a “proof test” on an existing bridge, in cooperation with a Transportation Authority, is also open. Finally, the partial safety coefficients to be included in the model will be calibrated to reach a similar safety level than in new designed bridges, taking into account the uncertainties associated to existing bridges.