Physical and geometrical non-linear behavior of precast beams on elastomeric supports

The stability of long and slender precast beams has been associated with structural collapse during the transitory phase of construction. The inevitable deviations regarding the execution between the support cross-section and midspan aggravate the instability problem, thus causing the beams to become even more susceptible to its effects. The focal point of this study is the numerical and behavioral evaluation of concrete beams that present geometric imperfections on elastomeric supports and analyze the influence exerted by the variables of: strength characteristics of concrete, physical non-linearity of the concrete and the compression stiffness of the bearing pad. The numerical analyses were developed on a computer program based on the finite element method (FEM). Among the principle conclusions drawn from the study, one finds that the increase in the characteristic strength of the concrete provides the beam with a higher degree of stability, and the consideration of the physical non-linear behavior of the material did not allow the equilibrium point on the numerical model to be found in some of the cases that were evaluated. The rotational stiffness of the pad decreases as the skew angle increases. Therefore, one needs to remember that in very critical situations, it may not be possible to find the point of equilibrium, thus leading to collapse.