Investigation of impact sound behaviour in light weight floor constructions - A market survey and finite element analysis

Abstract

In the last years, the interest in high-rise timber framed building has gone up resulting in an increased demand for good solutions regarding sound insulation.
Due to the worldwide growing interest in environmental issues, it has become of greater importance for companies to find ways to take care of their residue, instead of throwing it away. This can benefit both the environment, as less new material is used, and the economy, as less material goes to waste. Ecophon is presently developing a new type of lightweight aggregate (LWA) from glass wool residue that comes from their production of sound absorbing tiles. It will be investigated if these new LWA’s can be used as ballast in intermediate floors.

The aim of this thesis is to find intermediate floor constructions where the new materials can be used. A market survey will provide the basis and suggest a few specific floor constructions where the LWA’s could replace other insulation materials.

To further investigate the materials sound insulation properties in an actual floor, a FEM-calculation in Abaqus will be used. The FEM-modelling will be executed on a standard type floor to ease further comparison with other filling materials. The FEM-modelling will give the opportunity to compare the new materials with others that are commonly used in today’s market. The results from the FEM-calculation will also be compared to measurements done by the consulting company Akustikverkstan.

Analyzing accelerations in the bottom plate for frequencies up to 125 Hz showed no significant improvement when adding LWA 1 into the floor. The accelerations decreased for some frequencies but then again got worse for others. To motivate an improvement, the accelerations would have to be lowered for all calculated frequencies. The most likely reason for the LWA's acoustic performance is its lack of stiffness which otherwise is the main reason to add mass. In this case, the mass is added without providing the necessary amount of stiffness.

With the measurements of the laboratory room at Akustikverkstan, it was possible to recalculate the accelerations in the bottom plate of the Abaqus model into sound pressure levels. This made comparison possible and one could see a correlation between the measurements and the calculations.
Possible applications for the material should be investigated further as the manufacturing process is cheap and energy efficient in comparison to other recycling methods for mineral wool residue. This is of interest for Ecophon, not only from an environmental point of view but also from an economical perspective.

Abstract (Swedish)

Efter en lång period där många bränder härjade i Sveriges storstäder förbjöds höga trähus. Denna lag upphörde att gälla i mitten på 90-talet och sedan dess har intresset för höga trähus ökat. Detta har resulterat i att behovet av bra ljudisoleringslösningar har blivit större.

På grund av det växande intresset för miljöfrågor har det blivit viktigare för företag att hitta nya lösningar för att ta hand om sitt avfall. Den typen av resonemang gynnar både miljön då mindre jungfruligt material behövs och ekonomin eftersom mindre material går till spillo. Ecophon håller för närvarande på att utveckla en ny typ av lättballast från den glasull som blir över vid deras övriga produktion. I denna uppsats kommer det att undersökas om denna lättballast kan användas som ballast i mellanbjälklag.

Syftet med uppsatsen är att hitta mellanbjälklagskonstruktioner där den nya ballasten kan användas. En marknadsundersökning ger grunden för att kunna föreslå vilka material som används i dag samt vilka material som skulle kunna bytas ut mot den nya ballasten.

För att vidare undersöka de nya materialens prestanda i ett faktiskt golv har FEM-beräkningar utförts i Abaqus. FEM-modelleringen utförs på ett standardgolv för att underlätta vidare jämförelser med andra isoleringsmaterial. Resultaten från FEM-beräkningen kommer också jämföras mot mätningar som utförts av konsultbolaget Akustikverkstan.

Vid analys av accelerationer i bottenplattan för frekvenser upp till 125 Hz kunde man inte se någon signifikant förbättring då den nya ballasten lades in i golvet. Accelerationerna minskade vid vissa frekvenser men blev också högre vid andra. För att motivera en förbättring bör accelerationerna bli lägre vid alla frekvenser i det undersökta spektret. Den troligaste anledningen till den nya ballastens akustiska prestanda är dess brist på styvhet, vilket annars är huvudanledningen till att man adderar massa till en lätt konstruktion. I detta fall är massa adderad utan att få den nödvändiga styvheten.
Med måtten på labbet i Akustikverkstan blev det möjligt att räkna om accelerationerna från Abaqus till ljudtrycksnivåer. Detta gjorde jämförelse möjlig och man kunde se en korrelation mellan akustikverkstans mätningar och FEM-resultaten.

För framtida utveckling bör andra möjliga applikationer för materialet undersökas. Att hitta en användning för detta material bör ligga i Ecophons intresse eftersom tillverkningsprocessen är energieffektiv i jämförelse med andra återvinningsmetoder för glasull. Detta ka ge en vinst, inte bara ur miljösynpunkt utan också ur ekonomisk synvinkel.

Popular Abstract

The Swedish building industry stands for over 7 million tons of the country’s yearly waste production today. The worlds waste mountain is rapidly growing, and as the building industry stands for a large part of it, they bare a huge responsibility to do better when it comes to recycling waste materials. In the master thesis that this article is based on, it was investigated if a gravel-like material made from glass wool waste could be used to improve the sound insulation in floors of high-rise timber framed buildings.

The interest of building high rise timber framed buildings are increasing. It can be argued that building with timber is better for the environment in comparison with using concrete. This is because of the large amount of gravel, water, cement and energy that is needed to make concrete. Wood on the other hand, is a renewable source and stores carbon dioxide during its growth.

As of today, there are no good way of recycling glass wool waste but a new method has been tried out.

This new method is both cheap and energy effective. With the new method, glass wool waste becomes a gravel-like material. It has been investigated if the new material could be used as ballast in wooden floors of high rise buildings to improve sound insulation between floors. Today, there is a problem with insulating wooden floors from impact sound, meaning the type of sound that comes from walking on the floor. These types of sounds where further investigated with help from a calculation program called Abaqus.

From a market survey of intermediate floors, it was found that gravel, sand, concrete or glass wool can be materials used as addition to insulate or prevent vibrations in the floors of a high rise building. All these materials are unfortunately made from so called virgin materials which basically means they belong to an ending supply here on earth. If these materials could be replaced by a recycled material, the wooden house could be made even more eco-friendly and much waste material could be useful again.

From calculations it was found that there was no significant improvement for impact sound when using a ballast material as filling in an intermediate wooden floor. This probably has its explanation in the materials structure, meaning it being a “gravel-
like” material and not a “concrete-like” material. It is however of greatest interest to either continue developing the material to give it the right properties to functions as an insulation material, or find another application for it. This is partly because of the great environmental advantage the recycling of glass wool could give to the building industry but also because of the cheap, and energy effective recycling process that it actually is.

• author: Sandberg, Fanny
• supervisor: Delphine Bard; Emma Arvidsson; Erling Nilsson
• organization: Engineering Acoustics; Department of Construction Sciences
• alternative title: Undersökning av stegljud i lätta träkonstruktioner - En marknadsundersökning och FEM-analys
• course: VTA820 20161
• year: 2016
• type: H3 - Professional qualifications (4 Years - )
• subject: Technology and Engineering
• keywords: intermediate floor, acoustics, impact sound, höga trähus, bjälklag, akustik, Stegljud, Ljud, wood, wooden high rise building
• publication/series: TVBA-5000
• report number: TVBA-5049
• ISSN: 0281-8477
• language: English
• id: 8892077
• alternative location: http://www.akustik.lth.se/publikationer/tvba-5000-examensarbeten/
• date added to LUP: 2016-10-13 14:18:51
• date last changed: 2017-04-26 17:07:04