Characterization of Acoustic, Vibration, and Creep Performance of Composite CLT-Concrete Floors
Research Team:
Chris Higgins – OSU, School of Civil and Construction Engineering
Arijit Sinha – OSU, Department of Wood Science and Engineering
Mariapaola Riggio – OSU, Department of Wood Science and Engineering
Bulent Tunc – OSU, School of Civil and Construction Engineering
Project Duration:
2022-2026
2022-2026
Facilities:
O.H. Hinsdale Wave Research Laboratory
Introduction
Beyond the basic structural performance, structural materials also need to meet standards regarding their serviceability in human-occupied buildings, to ensure the long-term comfort and safety of the human occupants. This study investigates the performance of CLT and CLT-concrete composite floor systems through the lenses of acoustic, vibration, and creep performance.
Research Methods
The primary variables tested included CLT with and without concrete toppers, CLT species, three different shear connector types, and span configuration including both simple and cantilevered spans.
To assess acoustic performance, the researchers built acoustic boxes underneath samples with tapping machines placed on the specimens to generate the sound. They measured impact sound, chamber modes, absorption, and flanking noise around the acoustic boxes. around full-scale specimens.
For vibration testing, they tested simple and cantilever span configurations and confirmed results using numerical model-based approaches, which allowed them to derive natural frequencies, damping ratios, and mode shapes for each specimen. To address creep performance, they conducted long term tests on both full-scale samples and individual shear connectors. The creep tests were continued for just over a year, in order to account for seasonal variations in behavior due to weather and moisture patterns.
Key Findings
Some key results from the study included:
- The concrete topping governed the short-term serviceability of the tested floors. It increased the fundamental frequency of every specimen and reduced the impact sound level in every one-third octave band.
- The CLT wood species and the shear connector type and spacing had no measurable influence on the vibration or impact sound response. At service-level amplitudes, the interface behaved as fully composite.
- A parametric study with the validated models produced design charts that relate the concrete topping thickness, the CLT layup and the span to the fundamental frequency. A thicker topping, more CLT plies and stiffer connectors extend the span at which a CLT-concrete floor satisfies the vibration criterion of the CLT Handbook.
- Under sustained shear, the connector slip developed rapidly during the first weeks and then continued at a decreasing rate, with no indication of instability over 652 days. Connections in all-Douglas-fir CLT accumulated more slip than those in the Douglas-fir and SPF hybrid layup.
- Adding a bearing plate to the vertical washer screw reduced the long-term slip; a 6 mm plate was not consistently better than a 3 mm plate.
- The higher sustained load increased the elastic slip but did not increase the long-term slip in proportion.
- Warmer intervals accumulated more creep slip; the creep rate followed the seasons.
- The long-term deflection of the full-length floor strips followed the seasonal humidity cycle. After two years under sustained load, the composite floors retained about half of their initial stiffness, whereas the bare CLT panels retained about 70 percent.
Future Work
Some additional testing will continue for these specimens. The sustained-load tests on the connectors and the full-length floor strips will continue for an additional year to extend the record over further seasonal cycles. Additionally, the specimen without shear connectors will be retested with an acoustic mat placed between the CLT panel and the concrete topping, to quantify the effect of different interlayers on impact sound transmission.
Publications & Presentations
Tunc, B. (2025, November 4). Characterization of Acoustic, Vibration, and Creep Performance of Composite CLT-Concrete Floors. 2025 Mass Timber Research & Design Innovation Symposium, Corvallis, OR. https://www.youtube.com/watch?v=nEEWSxjIUuo
Publications on this work are expected soon.
Funding & Acknowledgements
This research was supported by the USDA Agricultural Research Service Award No. 58-0204-2-143.
