Preliminary considerations on the loss of support for precast beam elements

One of the main objectives to be achieved for the safety of industrial precast buildings with simple friction beam-to-column connections is the reduction of their relative displacement. This goal is generally achieved through a global strengthening of the building or by locally introducing mechanical connecting devices between the elements. However, for low seismicity areas, these interventions may not be required, and it could be interesting to evaluate the level of safety achieved by simple friction; such an information would allow for instance the prioritization of the retrofit interventions. This paper aims to establish criteria for evaluating the loss of support probability in existing precast buildings in the case of a seismic event. The behavior of the friction connection is evaluated through a simplified model that describes the behavior of a portal frame composed of two columns and one beam. The equations of motion are derived, and a parametric analysis is performed by investigating the influence of the geometry of the structural elements, the nonlinear behavior of the columns, and the friction coefficient used in the column-beam connections for varying horizontal and vertical seismic acceleration. The objective of the sensitivity analysis is to provide some preliminary considerations about the influence of the main parameters that characterize the existing precast structure on the loss of the support probability.