Modelos para la interacción tendón-hormigón en estructuras de hormigón pretensado con tendones no adherentes

Models ofr the interaction tendon-concrete in unbonded prestressed concrete structures

In principle, this paper tries to answer to the question of what happens before the tendon begins a free sliding with friction, relatively to the duct, in unbonded prestressed concrete structures; for that, an 'elastic locking' mechanism can be proposed. Combining both mechanisms, elastick locking and simple friction, on the basis of a t-u (unit tangencial force - relative displacement) relationship, an elasto-plastic model is got, more suitable than the rigid plastic one (perfect bond and simple friction). Structural analysis with this model has been set; and also a simple beam example has been solved for having practical results and getting the zones in which this model is no more calid and simple friction model must be used; results for this last one and for perfect bond hypothesis are also shown. It is concluded that, in practice, structural analysis can be only based on the simple friction model; its results are just slightly modified in discontinuity zones. Then, a general basis for studying structures composed by other materials is reached; in particular those having such a interaction that elastic locking has already a wider incidence and must be explicitely considered. And even, changing the t-u law, bonded structures (including reinforced concrete ones) can also be studied in phases in which bond tends to fail; for instance, in cases of safety re-evaluation a bond fault and others concerning refined structural analysis.