In this paper, a unified procedure for assessing the effectiveness of modelling strategies for existing buildings is proposed. The procedure is applied to unreinforced masonry and reinforced concrete real buildings struck by recent earthquakes. A matching index (MI) suitable to be adopted across different structural types is proposed. It aims to synthetically compare numerical outcomes with the evidence of the damage experienced by the selected case-study buildings.Results confirmed a good reliability and effectiveness of the developed numerical models (mean MI value higher than 0.70 for all the investigated case-study buildings) as well as the capability of the models in reproducing the same performance states that occurred in the real cases.

The loss of support of beam elements in Italian precast buildings is one of the main vulnerabilities recorded in past earthquakes. The reason for beam falling is due to the absence of adequate structural details in the beam-column joints, which were typically relying on friction for buildings located in regions previously classified as non-seismic prone. To guarantee the structural safety of the whole existing building stock, this collapse mechanism must be further investigated; in this regard, it could be interesting to evaluate the level of safety achieved by simple beam-column friction connections to allow, for instance, the prioritization of the retrofit interventions to guarantee a minimum level of safety in a wide range of structures. The paper investigates the influence of the parameters governing the beam-column relative displacements in the case of friction connections to establish criteria for evaluating the seismic loss of support probability in existing precast buildings. A simplified analytical model is introduced to describe single and double portal frames with and without the presence of stiff masonry infills. The influence of the epicentral distance on the results obtained is also preliminary addressed. Nonlinear time history analyses are carried out on a 2D finite element model to validate the effectiveness of the simplified model taking as reference a building that experienced the loss of support of a main beam during a past earthquake.

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.