PSI - Issue 44

Fabio Mazza et al. / Procedia Structural Integrity 44 (2023) 147–154 Fabio Mazza et al. / Structural Integrity Procedia 00 (2022) 000–000

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(a) In-plane (IP) backbone.

(b) Out-of-plane (OOP) backbone.

Figure 3. IP and OOP backbones for Blind Contest slip-track partitions.

The two monitored piping system branches are placed below the third floor of the fixed-base structure (Figure 4a), suspended along their length. All piping ends are fixed to beams except for the top right one, that ends with an elbow, connecting it to the upper floor. VLP20 (longitudinal) and VLP40 (transversal) vinyl pipes are filled with jelly beads to simulate the presence of water. Piping branches are discretised through elastic beam elements, fixed at their ends to upper floor beams using rigid links. Two elevated tanks (2 m x 2 m x 2 m) filled with 50 kN of sand are placed on top floor of the fixed-base structure (Figures 1d and 4b). The supporting system is thus simplified into a single beam element, with different bending stiffnesses in the X and Y directions due to frame asymmetry. An equivalent concentrated mass (5910 kg) accounting for sand, tank and frame weights is placed at beam upper node, at a relative height of 2.0 m with respect to roof level.

(a) Piping system in-plan view (unit in cm).

(b) Elevated tank lateral view (unit in mm).

Figure 4. Piping system and elevated tanks details.

3.3. Medical equipment

A simplified modelling strategy for medical devices or shelving is based on the solution of free body equations of motion. Rocking and sliding time histories can be evaluated analytically by numerical integration of relevant equations, providing the acceleration time history ü f (t) of the closest structural node as input, thus considering the structural filtering effect on ground excitation.

Table 3. Geometrical properties for medical equipment.

Device

Level

b 1 [cm]

b 2 [cm]

h [cm] 160.0 178.0

h G [cm]

m [kg]

60.0

Dialysis machine

2 3

45.8

48.0 68.0

45.0 98.5

138.0

Incubator

105.0

A functional device can be associated to an equivalent rectangular rigid body (base b 1 × b 2 , height h ) with a known centre of gravity (height h G ). The rocking motion is activated when the overturning moment M ov = 0.5mhü j in direction j is higher than the restoring moment M res = 0.5mgb j , being m the equipment mass, ü j the horizontal absolute acceleration and g the gravity one. The sliding motion starts if the inertial force F i = mü j exceeds the break-away force F b = µ s (mg) . An incubator placed at the third level and a dialysis machine at the second one are analysed, postprocessing the respective nodal acceleration input time histories. Both are equipped with four casters for mobility and lie on foam-