Acoustic performance of junctions in cross laminated timber constructions
Typ
Examensarbete för masterexamen
Program
Sound and vibration (MPSOV), MSc
Publicerad
2019
Författare
Hörnmark, Jesper
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
With the emergence of cross laminated timber (CLT) as a structural material on
the global market, the need to understand the acoustical behavior of buildings con-
structed with the material grows. CLT faces a set of challenges that concrete or
masonry do not; being low density, high in stiffness, sometimes isotropic and some-
times orthotropic depending on the composition. Flanking sound transmission often
becomes an issue in the acoustic performance of mass timber buildings. While di-
rect sound transmission can be treated with conventional methods e.g. additional
layers, the flanking paths are more complicated to treat since they need to transfer
loads over the length of the element. This master’s thesis aims to investigate the
flanking paths in cross laminated timber buildings by measuring the structure-borne
vibration reduction index (Kij ) in realized buildings. The in-field measurements are
compared to standardized estimation models and lab measurements published in
past research.
This thesis finds that standardized estimations underestimate the performance of
the examined junctions in low frequencies. The lab measurements are closer to the
in-field performance but exaggerate the influence of metal connections and mass-
spring behavior of junctions with elastic interlayers. Additionally the theory and
results indicates that external loads on the junction play a major role in the result-
ing performance. Elastic interlayers are not as effective in low levels as in the high
levels of any given building, presenting a challenge as mass timber structures are increasingly being built taller.
Beskrivning
Ämne/nyckelord
cross laminated timber, CLT, mass timber, , vibration reduction index, Kij, flanking transmission.