PSI - Issue 62

Carlo Pettorruso et al. / Procedia Structural Integrity 62 (2024) 677–684 Carlo Pettorruso/ Structural Integrity Procedia 00 (2019) 000 – 000

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The first task is related to the collection of input data, which concern the seismic scenario and the characteristics of the bridge. Starting from the identification of the seismic scenario, by referring to the provision of the Italian Building Code IBC §3.2.3, then it is necessary to collect the geometrical and material characteristics of the bridge, which can be taken from the bridge documentation or from an on-site investigation. Characteristics of interest include the mass of the deck, and the mass of the piers. The material and geometric properties are referred to the pier and the deck for the subsequent stiffness evaluation; for reinforced concrete piers it is also necessary to know the rebar design. The assessment of suitability is performed by considering a simplified model, which represents a single pier of the bridge, supporting the pier cap and a part of the deck defined through the load tributary area of the pier itself. From this simplified physical model, an equivalent single degree of freedom model of the elementary bridge unit is formulated. From the definition of IBC, §7.9.4.1, the effective mass, equation 1, of the equivalent SDOF model is defined as the sum of the masses of deck, pier cap and top third section of the pier. m eff = m deck + m piercap + m pier /3 (1)

Figure 2 Flow chart

The mass of the deck, Equation (2), is given by the sum of the self-weight of structural components (m g1 ), the permanent load of non-structural elements (m g2 ) and 20% of the variable load (m 0,2q ), according to the code provisions (IBC §2.5.3 and §5.1.3.12). m deck =m g1 +m g2 + m 0,2q (2) It goes on to define the resources of the pier in terms of first yielding moment, M y , and maximum shear, V RD . In the calculation of the moment at first yield, the axial loads induced at the base of the pier by the weight of the structural elements and part of the variable loads is considered and assumed constant. According to the resistances of the pier, for the equivalent SDOF model the accelerations related to the first yielding moment and resistant shear are defined as: