TEST RESULTS Dvij FOR CROSS-LAMINATED TIMBER (CLT) IN BURDEAUX, FRANCE

INTRODUCTION

AMC together with FCBA tested different configurations of walls and floors which included smart joints, aiming to decrease coupling at structural junctions. The aim of this project is to develop acoustically optimized innovative constructive solutions, the tests are based on CLT panels which fulfil acoustic, thermal, environmental quality and cost performance objectives.

In 2021, FCBA, CSTB and CERQUAL with the Wood Acoustic Committee, a committee of 48 members, created a CLT in-situ testing facility in France (Bordeaux) called the “Maquette Acoustique”, this comprises of 3 levels with 4 rooms per level.

This facility is used in this study to measure in-situ sound transmission loss and vibroacoustic transmission to qualify the flanking transmissions of junctions.

This report is presenting the measurements of Vibration Transmission Levels between subsystems of rooms and characterizing each transmission channel.

For a traditional masonry building the flanking transmission is known to be responsible for disturbing up to 50% of the acoustic insulation. This matter has often been studied and several calculation approaches have been developed. The more common model is based on a simplified SEA (Statistical Energy Analysis) application. For uniform walls which are perfectly assembled at a T junction, an SEA model is created consisting of 5 subsystems: 2 cavities (rooms) and 3 walls forming the junction.

The model used must be different for cases of light weight CLT constructions, In the year 2000 EN12354 was published to analyse the vibration transmission via the walls, the calculation model uses the following equation:

OBJECTIVES

One of the parameters for characterization of the flanking transmissions is the sound attenuations of the junctions, these are quantified by the vibration parameter (Dvij: velocity level difference). This quantity is the input data for the predictive calculations of the acoustic sound insulation between two rooms.

The Dvij value of a flanking path is obtained from direct measurements in junctions by accelerometers. The objective of this task is to measure the vibration level difference in different types of junctions.

TEST PROTOCOL

Measurements were conducted between two rooms. The cross junction is composed of a continuous floor on a CLT partition wall (ground floor) and a lightweight partition wall on first floor.

For each building system tested we adopted the following sub-structuration and subsystem names.

Meaurement process

• On each subsystem (entire floor decking or wall) one sensor is fixed at a random position.
• Energy is introduced with a hammer at random locations over the entire surface, a total of 20 impacts.
• Reciprocity principle allows us to consider the mean values as the mean of 20 random positions of accelerometer/hammer.
• The vibration level is extracted with 20 points of excitations on each subsystem (1 to 4).

Room´s Location

TEST RESULTS

In order to demonstrate the acoustic advantages of using Akustik EP 500 + Sylomer S35 supports and Akustik + Sylomer® Floor mounts in a Cross-Laminated Timber structure, vibration tests were conducted.

The acoustic test results for each configuration are shown below:

HORIZONTAL MEASUREMENTS

System A

System B

System C

OVERVIEW

These results clearly show the effectiveness of using Akustik Floor mounts + Sylomer® to improve the acoustic insulation of CLT structures.

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