PSI - Issue 78

Michele Morici et al. / Procedia Structural Integrity 78 (2026) 1673–1680

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3. Results from Permanent Monitoring System and Validation Monitoring System

The permanent monitoring system was installed during the construction phase of the ChIP building. The monitored parameters include accelerations at various levels, differential displacements of isolated floor, and strains in the bracing devices. Figure 2 illustrates the sensor layout of the permanent monitoring system. The sensor network is distributed across three main levels and organized into two independent measurement chains. The system integrates triaxial digital accelerometers (AX), strain gauges (BX), and displacement transducers (DX) (Table 1). Both measurement chains are connected to a central control room, where data acquisition, synchronization, and storage are managed using digital data loggers and GPS receivers. The first measurement chain includes sensors located at Level 0 below isolation (sensors D1, D2, and A5), and Level 0 above isolation (sensors B1 and A4), as well as a triaxial accelerometer installed in a free-field (FF) station (sensor A6) outside the structure. The second measurement chain covers Level 0 below isolation (sensors D3 and D4), Level 0 above isolation (sensor A1), Level 1 (sensor B2), and Level 2 (sensors A2 and A3). Finally, a weather station has been installed at Level 2 since February 1st, 2025.

Figure 2. Permanent Monitoring System - Sensor layout in plan view and at different elevation levels.

Table 1. Permanent Monitoring System Sensors Sensor Type

Sensor Brand & Model GeoSIG Digital AC-73D-H

Sensor ID

Accelerometer (triaxial)

A1, A2, A3, A4, A5, A6

Strain Gauge

Hottinger Baldwin Messtechnik (HBM) 1-CXY31-6/350ZE B1, B2

Displacement Transducer

Gefran PC67-750

D1, D2, D3, D4

Given the elevation complexity of the building, which under ambient vibrations would behave as a fixed-base structure, a preliminary identification was carried out to evaluate the main frequencies and mode shapes to be tracked over time. This preliminary campaign employed a significantly higher number of sensors compared to the permanent setup, adopting two uniaxial accelerometers (Table 2) placed at each corner of the roof level (Figure 3a). The validation monitoring setup included eight accelerometers, providing high redundancy and improving the reliability of the modal identification. This extended configuration was adopted to: 1) verify the rigid diaphragm assumption for the floor slab, 2) analyse the structural response independently along the two principal directions (X and Y), addressing the lack of clearly defined mode shapes in the permanent monitoring data, and 3) establish a baseline for the building’s dynamic behaviour to support interpretation of the long-term monitoring results.

Table 2. Validation Monitoring System Sensors Sensor Type

Sensor Brand & Model PCB Piezotronics 393B31

Sensor ID

Accelerometer (uniaxial)

X1, X2, X3, X4, Y1, Y2, Y3, Y4

The subsequent results were obtained using ARTeMIS Modal Pro 8.0 commercial software and the SSI-UPCX estimator (Döhler and Mevel, 2013, Reynders et al., 2008, Mellinger et al., 2016). Figure 3 presents the stabilization diagrams obtained for both the permanent (Figure 3a) and validation monitoring systems (Figure 3b), focusing on the frequency range up to 5 Hz. Within this range, the first three stable modes are clearly identifiable and