Assessment of the shear and punching strength of concrete structures using mechanical models, to extend their lifetime
Total activity: 24
Type of activity
MIN DE ECONOMIA Y COMPETITIVIDAD
Funding entity code
Accurate assessment of existing bridges and other transportation infrastructures requires a realistic evaluation of the internal forces and of the structure strength, as well as an adequate formulation of the structural safety to account for the uncertainties associated to already existing structures. Among these aspects, the present research project focuses on the evaluation of the shear and punching strengths of concrete structures, since their internal resisting mechanisms are not yet clearly understood. In addition, current design codes provide conservative formulations for shear strength, not adequate for structural evaluation purposes. The project aims to develop and calibrate a robust mechanical model for the accurate prediction of the shear and punching strengths of reinforced and pretested concrete structures. In addition, the model should be easy to apply, low cost, adaptable to future needs and adequate both for structural assessment and, after some simplifications, for design of new structures. With this purpose, an existing shear mechanical model previously developed by the UPC and UIB research teams will be improved and extended to predict punching strength in slabs and to members composed by different concretes. The excellent correlation of the previous model predictions with experimental results of a large international data base has favored its consideration as a possible shear model to be included on the future EC2 and ACI codes. The project aims to solve some theoretical aspects affecting the shear strength, such as the effect of the member size, the partial bond, yielding of the longitudinal reinforcement, and 3D phenomena. To reach these objectives, theoretical formulations based on fracture mechanics or other theories and on numerical models will be developed. Load test will be carried out on substructures representing the different parts of a beam contributing to the shear strength (compression chord, web and tie). He safety factors to be used in the model will be calibarated to account for the uncertainties associated to existing bridges. The mechanical shear model will be also extended to predict the shear and punching strengths of bridge top RC slabs and to capture the shear strength enhancement due to loads near supports. For this purpose, first the differences between the shear and punching failures and between the behavior of B and D regions will be identified and their governing parameters introduced in the formulation of the model. Secondly, the model will be experimentally verified though large scale tests on a specimen representing a portion of a box girder bridge. Several point loads will be successively applied over the slab at the cantilevers and between the webs at different distances from the webs axes. Conclusions about the topics studied will be drawn and recommendations for shear and punching strengths assessment of existing bridges using the developed model will be written. The UPC research team will cooperate with the other research groups of this coordinated project in the extension of the model to strengthened structures, in the definition of their tests through the prediction of their experimental results and in the use of such results for the validation of the extended model. The models developed will be implemented in spreadsheets accessible through an on line platform created for the project.
Fernández, I.; Herrador , M.; Mari, A.; Bairan, J.M. International journal of concrete structures and materials Vol. 12, num. 1, p. 1-23 DOI: 10.1186/s40069-018-0297-9 Date of publication: 2018-12 Journal article
Celada, U.; Duarte, N.; Bairan, J.M.; Oller, E.; Mari, A. Congreso de la Asociación Científico-Técnica del Hormigón Estructural p. 1-10 Presentation's date: 2017-06-21 Presentation of work at congresses