The experimental program carried out on the THERMASTEEL-type structure aimed to characterize the seismic behavior of the system according to the requirements of EAD 340287-00-0203 and Eurocode 8. The tests were organized in two phases, covering both artificial, spectrum-calibrated actions and representative real earthquakes.
STRUCTURAL BEHAVIOR – PHASE 1
The structure was subjected to artificial accelerograms in the 3–25 Hz frequency range and beat-type sinusoidal signals at 5 Hz.
The maximum base accelerations exceeded 0.9 g, while the top accelerations reached approximately 0.65 g, without excessive amplification.
The maximum relative displacements were low, up to about 3–4 mm, confirming the elastic behavior of the structure and the stability of the connections.
The fundamental frequency decreased slightly (from 5.04 Hz → 4.54 Hz), indicating a minor reduction in initial stiffness but remaining within normal limits.
STRUCTURAL BEHAVIOR – PHASE 2
The structure was subjected to real accelerograms (Vrancea 1977, Vrancea 1990, Turkey 2023, Imperial Valley 1979) and artificial accelerograms spectrally adjusted to EC8.
The maximum accelerations at the top exceeded 1.2 g, with relative displacements between 5 mm and 18 mm.
Most tests fell within the EC8 drift limit (0.5% h ≈ 13.5 mm for a height of 2.7 m). Only in test Artificial R2, the relative displacement of 18 mm exceeded this value (~33% above the limit), corresponding to the performance level DS3 – collapse prevention.
In all cases, the structure maintained its integrity, with no cracks, no joint separation, and no loss of stability.
EVOLUTION OF FUNDAMENTAL FREQUENCY
The natural frequency varied between 5.04 Hz and 4.54 Hz, with a temporary recovery to 4.70 Hz after concrete curing (28 days).
The final value of 4.63 Hz confirms retention of global stiffness and absence of plastic structural degradation.
COMPLIANCE WITH DESIGN SPECIFICATIONS
The artificial accelerograms complied with the requirements of Annex E of EAD 340287-00-0203 (frequency band, duration, ramp-up/down).
Comparison of spectra showed compatibility of applied actions with the EC8 target spectrum for PGA = 0.4 g, ground type B, importance class II.
Performance levels DS1, DS2, and DS3 were achieved and documented through the measured acceleration (ag) and drift values.
GENERAL CONCLUSION
The tested prefabricated structure demonstrated robust seismic performance, characterized by:
Stability and structural integrity under accelerations up to 1 g;
Relative displacements generally below the admissible limit, with a single intentional exceedance to verify DS3 level;
Preservation of overall stiffness and no visible degradation, even after the application of severe real and artificial earthquakes.
These test results confirm that the THERMASTEEL structural solution meets the requirements for technical certification and can be confidently used in high seismic hazard zones, providing an adequate safety level and performance consistent with EAD 340287-00-0203 and Eurocode 8.
About Seismic Testing
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