Impact sound insulation performance of floating floor assemblies on mass timber slabs

Mass timber buildings become increasingly popular in North America and worldwide. Mass timber panels are mainly used structural slabs in mass timber buildings. However, due to the lightweight and low-stiffness of mass timber panels, the human induced impact sound on floors has been identified as an issue to be solved. Floating concrete topping is a common solution adopted for insulating the impact sound transmission through the mass timber slabs. However, there is few guidance on designing floating concrete floor assemblies and high performance floating floor assemblies for mass timber slabs. In this study, the relationship between concrete topping thickness, dynamic stiffness of elastic interlayers and the impact sound insulation performance of continuous floating concrete assemblies was first investigated according to ASTM test standard. It was found that the floor assemblies with lower apparent dynamic stiffness of elastic interlayer and thicker concrete topping had higher apparent impact insulation class (AIIC) ratings, but limited under 53 dBA without additional floor finish. The empirical prediction equation overestimated the improvements of floating concrete toppings on mass timber slabs. Then, a series of discrete floor raised floor assemblies using elastic mounts were tested using the tapping machine. The results showed AIIC rating of the discrete raised floating floor reached up to 65 dBA. At last, the low frequency (50 to 630 Hz) impact sound insulation performance was conducted according to JIS standard using the ISO rubber ball. With the comparison of sound pressure level (SPL) spectra among ISO rubber ball, ISO tapping machine and real adult walking on both bare floor and different floating floor assemblies, the ISO rubber ball was found to be a suitable source simulating human foot fall noise. The raised discrete floating floor still demonstrated outstanding impact sound insulation performance. However, the correlation between corrected maximum sound pressure level (LFmax) index and apparent impact insulation class (AIIC) was very low. Overall, the floating floor assemblies had similar performance regardless of the type of mass timber slabs as long as the slabs had the same thickness and wood species

Sound transmission loss of cross-laminated timber walls: Comparison between measurements carried out in transmission suites and point mobility measurements

The transition from concrete-based to wood-based construction is drawing more attention to the use of cross-laminated timber elements, especially in the building sector. In this context, there is a need to assess the transmission loss performances of such elements already during the research and development phase, when making several tests in sound transmission suites would be overly expensive and time-consuming. The flexural behavior of a composite structure can be determined by point mobility tests. From this kind of measurements, it is possible to estimate the loss factor of the partition and its bending stiffness which, in turn, can be used to determine its sound transmission loss once some basic physical properties are known. In this paper, the sound transmission of cross-laminated timber partitions is obtained with this method. Results are validated by means of measurements in sound transmission suites

Vibration performance of in situ cross-laminated timber (CLT) floors in medium-rise buildings

Det finnes begrenset med informasjon angående vibrasjonsegenskapene til CLT-gulvsystemer installert i konstruksjoner. Ingeniører som ønsker å anvende CLT sin utmerkede styrke til masse forhold støter ofte på et bruksgrensetilstand problem. På grunn av et relativt lavt forhold mellom masse og stivhet blir systemet lett satt i bevegelse og vibrasjoner blir et problem. Helt siden introduksjonen av CLT har det blitt arbeidet med å utforme retningslinjer som skiller mellom akseptabelt og ikke-akseptabelt design. De fleste av disse retningslinjene tar ikke hensyn til betydningen av ikke-bærende konstruksjoner. Denne avhandlingen anvender OMA for å belyse hvordan in-situ gulv blir påvirket av omkringliggende elementer. Et omfattende studie har blitt utført på syv ulike gulv ved Ås videregående skole i løpet av prosjektperioden. Totalt ble tretten forskjellige tester utført for å samle inn feltdata.Innhentede data ble analysert for å bestemme gulvenes vibrasjonsegenskaper og for grundig å dokumentere effekten av in-situ elementer. Overføring av bevegelse på tvers av ikke-bærende skillevegger er gitt spesiell oppmerksomhet for å forklare oppdaget modusformer. Fordelingen av bevegelse er dokumenter gjennom VDV og arms konturkart. En analytisk del er inkludert for å vurdere hvor nøyaktig oppdatert Eurokode 5 kan forutsi fundamental egenfrekvens og kvadratisk gjennomsnitt for akselerasjon. Den aksepterte antagelsen om at ikke-bærende skillevegger kan ignoreres i design fasen utfordres. Gjennom detaljerte in-situ eksperimenter er det demonstrert at de har innflytelse på modale egenskaper. Spesielt er modusformen til den fundamentale egenfrekvensen påvirket av omkringliggende skillevegger. Integrasjon av CLT-gulvsystemer i konstruksjoner øker raskt kompleksiteten, noe som redusere antall identifiserbare modusformer. Fordeling av bevegelse på gulvet er vist til å følge lav frekvens modusformer via VDV og arms. Konsekvensen av dette er at skillevegger spiller en viktig rolle i å bestemme kritiske aksjelerasjonspunkter. Den reviderte EC5 systematisk undervurder av gulvenes grunnfrekvenser, mens den overestimerer gulvenes akselerasjons egenskaper. En slik unøyaktigheten reduseres byggekodens egenskap til å skille mellom akseptabelt og ikke-akseptable design.There is limited information regarding the vibration characteristics of CLT floor systems within superstructures. As designers utilise the excellent strength-to-mass ratio of CLT, they are often faced with a serviceability problem. Due to the relatively low mass-to-stiffness ratio, the system is prone to oscillation, and vibration becomes a major issue. In recent years, there have been a lot of efforts to establish guidelines for distinguishing between acceptable and unacceptable design. However, many of these guidelines do not consider the importance of non-bearing structures. This thesis utilises OMA to highlight how in-situ floors are affected by surrounding elements. A comprehensive study was conducted on seven floors within Ås High School during the thesis project. In total thirteen distinct tests were carried out to gather field data, which was then analysed to determine modal characteristics. By determining modal characteristics, the effects of in-situ elements are thoroughly documented. Transfer of motion across non-bearing partitions is given special attention to explain detected mode shapes. The distribution of motion is documented through VDV and arms contour maps. An analytical component has been incorporated to assess the accuracy of the updatedEurocode 5 in calculating the fundamental natural frequency and root-mean-square acceleration. The standing assumption that non-bearing partition walls can be ignored during design is challenged. Through detailed in-situ experiments, it becomes clear that they play an essential role in determining the modal characteristics of the floors. It has been found that partition walls have a significant impact on all modal characteristics. The configuration of surrounding partition walls especially impacts the fundamental mode shape. As the CLT floor system is integrated into the superstructure, its complexity rapidly increases, decreasing the number of identifiable modes. Distribution of motion across floors documented with VDV and arms is shown to follow low-frequency mode shapes. The consequence is that partition walls play an important role in determining critical acceleration spots. The revised EC5 underestimates the fundamental frequencies performance of the floors while overestimating its arms performance. This inaccuracy reduces its effectiveness in discriminating between acceptable and unacceptable design

Sound radiation and sound insulation performances of maritime bulkheads

The research of materials matching low weight and high resistance has always been a key factor in the shipbuilding industry to increase performances and loading capacity. Nowadays, other issues add up to economical convenience, and building quiet ships is important not only for passengers and cabin crew, but also to make harbor areas more comfortable and to respect the aquatic environment. In this context, using sandwich or composite materials must be carefully evaluated and the sound insulation performances must be considered throughout all stages of the design process. This work presents some evaluations about the sound insulation performances of a ribbed fiberglass bulkhead and of a balsa-core sandwich bulkhead. In particular, the bending stiffness and the sound transmission loss obtained by sound transmission suites and mobility measurements are provided. From such measurements it has also been possible to determine the radiation efficiency of the structures, whose optimization is particularly important when a reduction of the noise pollution is required

Adaptive comfort assessments in urban neighbourhoods: Simulations of a residential case study from London

A warming climate, increasing frequency and severity of extreme heat events, and the heat island effect are cumulatively expected to exacerbate climate thermal loading on urban buildings. This in turn could lead to increased summertime overheating risk, with any active means for addressing this likely to influence future energy consumption and CO2 emission patterns. This paper examines how the microclimatic loading presented by the heat island (UHI) effect influences summertime adaptive comfort in traditional urban residential buildings.Funding: this work was partly supported by the Cambridge Commonwealth, European and International Trust, University of Cambridge

Design of cross-laminated timber (CLT) floors for human-induced vibrations

Cross-laminated timber (CLT) is an innovative engineering wood product made by gluing layers of solid timber boards placed in an orthogonally alternating orientation to the neighbouring layers. CLT panels provide an efficient solution for floors in single- and multi-storey buildings. Due to their light weight and often long-span, the design of these floors is generally governed by serviceability limit state criteria, that is, deflection or vibration limits. Vibrations induced by dynamic actions, such as people walking and their everyday activities, cannot result in structural failure but may cause discomfort to occupants if vibrations are not properly controlled. This paper gives an overview of some available methods for the vibration serviceability design of residential CLT floors. Differences between these methods are discussed through the consideration of criteria and their limit values. Although some criteria are common to certain methods, it may happen that the same criteria take into account different factors. In order to get a better description of the actual behaviour of floor structure, certain classifications of floors based on vibration serviceability performance were introduced in design methods

A review of residential segregation and its consequences in Nigeria

Residential segregation, the spatial separation of population sub-groups within a given geographical area, is a phenomenon which is prevalent in both developed and developing countries like Nigeria. This paper is aimed at reviewing residential segregation in Nigeria with specific reference to Northern Nigeria. The objectives of the paper are to review residential segregation from the pre-colonial to post-colonial era, and review its consequences in Nigeria. Prior to the colonial administration in Nigeria there existed no residential segregation based on race, ethnic or religious lines. The divide and rule policy of the British colonial administrators in Nigeria brought about residential segregation through the creation of ‘Sabon Gari’ settlements, which are occupied by the non-natives of Northern Nigeria. Residential segregation in Nigeria was reviewed in phases, that is, during the pre-colonial, colonial and the post-colonial era. In the final section of the paper the consequences of residential segregation in Nigeria, such as the socio-spatial division of households by income (high, medium and low density), inaccessibility of the poor to affordable housing, inadequate provision of infrastructure in the high density residential areas, and most importantly the cause of ethno-religious conflicts in across Nigeria, was discussed

Sound absorbing and insulating low-cost panels from end-of-life household materials for the development of vulnerable contexts in circular economy perspective

From a construction point of view, neighborhoods with residents living at or below the poverty threshold are characterized by low energy efficiency buildings, in which people live in acoustic discomfort with no viable options for home improvements, as they usually can not afford the materials and labor costs associated. An alternative to this is to use low-cost insulating elements made of non-conventional materials with acceptable acoustic properties. Given that household materials at their end-of-life (EoLHM) are free of costs and available also to the more disadvantaged population, they can be used to build acoustic panels for such contexts. This approach embraces several benefits since it reduces the amount of waste produced, the footprint deriving from the extraction of new raw materials and, by highlighting the potential of the EoLHM, discourages the abandonment of waste. In this paper, the acoustic properties of EoLHM, such as cardboard, egg-cartons, clothes, metal elements and combinations of them, are investigated by means of the impedance tube technique. The measured sound absorption coefficient and transmission loss have shown that EoLHM can be used for the realization of acoustic panels. However, since none of the analyzed materials shows absorbing and insulating properties at the same time, EoLHM must be wisely selected. This innovative approach supports the circular economy and the improvement for the living condition of low-income households