Algunos ejemplos de análisis no lineal de estructuras de hormigón armado y pretensado

Several examples of nonlinear analysis of reinforced and prestressed concrete shell structures

Several examples of the usage of numeric simulation of the nonlinear analysis of concrete structures are presented to illustrate some of the capabilities of such modern techniques of analysis. Certain difficulties which arise in their practical use are commented as well. First, a numerical model for the nonlinear material, geometric and time dependent analysis of reinforced and prestressed concrete shell structures is described. Then, the use of this model to analyze four numerical examples is shown. The first example deals with a free-form reinforced concrete shell where a small geometric imperfection is introduced at crown. It is shown that such imperfection produces a strong reduction of the ultimate load of the structure. The second example illustrates a long-term inestability caused in the free-form of the former example by creep-buckling. The two remaining examples treat with prestressed concrete structures. The first one describes an approach to analytically reproduce the complete behaviour until failure which was actually observed in the test of experimental model of a prestressed cylindrical model is used to study the behaviour of a concrete slab prestressed in two ways with post-tensioned unbonded reinforcement. The described example shows the big influence that the non linar material effects (concrete cracking, yielding of steel) and the nonlinear geometrical effects (equilibrium on the deformed geometry), as well as the time-dependent effects (concrete creep and shrinkage), have on the behaviour and reliability of the concrete shell structures.