PSI - Issue 44

Devis Sonda et al. / Procedia Structural Integrity 44 (2023) 115–122 Devis Sonda et al. / Structural Integrity Procedia 00 (2022) 000–000

119

5

3. Quantification of seismic vulnerability In order to develop a rapid methodology for the evaluation of the seismic vulnerability of a structure, it is necessary to define the parameters that will affect the capability of the structure to absorb energy (elastic and dissipated). The definition of these main parameters, able to, globally and synthetically, describe the dynamic behavior of the structure, must be related to requirements of building codes and the experience acquired by observing the effects of earthquakes on precast RC industrial buildings. The total energy, as highlighted above, is made up of elastic deformation capacity and dissipative capacity. Elastic deformation, in this specific case, is substantially related to the capability of columns to develop deformations in the elastic range. This capacity depends on the dimensions of the column and is severely limited by the presence of structural irregularities or by interfering elements such as infills. The capability to dissipate energy is substantially dependent on the structural ductility, which is concentrated at the base of the columns. Dissipative capacity mainly relies on the possibility of attaining this ductility due to the presence of adequate connections between the horizontal and vertical elements. The lack of connections between beams and columns, or their under sizing, generates structural collapses without developing ductility. The four parameters that can be assumed as the basis of seismic vulnerability evaluation of the structure in terms of its capability to absorb and dissipate energy, are shown in Table 1. It is possible to represent the total energy that the structure can absorb and dissipate through a graph which is, in a dimensionless energy plane, a 45° rotated square. The main axes are no longer force and displacement (in relative terms) but are the four parameters identified in Table 1, quantified in terms of the relationship between existing and new equivalent structure. The graph (Fig. 3) can be used to represent the relationship between the area, and therefore the total energy, of the new structure and an existing structure. If the existing structure has the same characteristics of the new one, they will have the same area. Since existing structures have generally characteristics of regularity and ductility that are less than or equal to the new structure, the area that describes the total energy of the existing structure will be smaller or equal to that of the new equivalent structure. To define the area that represents the total energy of the existing structure, we can quantify the parameters that we have identified as significant for the definition of the capacity to absorb and dissipate energy, in percentage terms respect to the new equivalent structure. The total energy that the existing structure can absorb is represented by the red area and compared to the energy that the new equivalent structure could absorb (green area). A ratio in energy terms can be made between areas representative of energy of the new equivalent structure (green area) and the existing one (red area). In the following a percentage quantification of the four parameters that we assume to be the basis of the energy area is proposed. The percentage assumes the value of 100% when the existing building has the same characteristics of the new equivalent one and a lower percentage value for situations of partial conformity. Each parameter has been divided into 4 steps describing the degree of conformity to the ideal situation to ensure simplicity to the procedure. Table 1. Parameters used to define the seismic vulnerability Energy Axis (45° rotated graph) Structural parameter Elastic Deformability ( y ) Structural regularity Interference with non-structural elements Column ductility Effective beam-column connections Dissipative Ductility ( x )