EVALUATING THE FLOOR IMPACT SOUND INSULATION ... - …...voided slab systems would be one of...

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International Journal of Civil Engineering and Technology (IJCIET)

Volume 9, Issue 5, May 2018, pp. 420–431, Article ID: IJCIET_09_05_047

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=5

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

EVALUATING THE FLOOR IMPACT SOUND

INSULATION PERFORMANCE OF THE

VOIDED SLAB SYSTEM APPLYING TO POST

TENSION METHOD

Seunguk Na

Architectural engineering department, College of architecture,

Dankook University, Yongin-si, Gyeonggi-do, South Korea

Inkwan Paik

Architectural engineering department, College of architecture,

Dankook University, Yongin-si, Gyeonggi-do, South Korea

Sung-ho Yun

Kwangjang Structure Company, Seoul, South Korea

ABSTRACT

The purpose of this study is to investigate the performance of sound insulation for

the newly developed voided slab system using post-tension. To verify the effectiveness

and applicability of the voided slab system, a mock up test was conducted to evaluate

its sound insulation performance against floor impact noises. Mock-up tests were

conducted to evaluate the floor impact sound insulation performance of the reinforced

concrete slab applying voided slab with post tension method. The mock-up test

specimen was built in compliance with the standard apartment housing floor plan in

South Korea. Two houses with standard floor area of 59m2 and 84m

2 were constructed

as mock up test houses to evaluate the sound insulation performance. Through this

method, it would be possible to materialize long-span voided slabs structures as well

as all the advantages of the both voided slab systems and post tension in concrete

structures. The test results showed that the average insulated noise level against heavy

impact sound was 46.8dB. Moreover, the mock-up test results of the lightweight floor

impact sound were over 58dB from all the tests. Since the floor finishing materials

were not installed in the mock up test specimen, the measured level of lightweight

impact sound was higher than 50dB.

Keywords: Floor impact sound; voided slab system; mock-up test; sound insulation

performance; apartment housing

Evaluating the Floor Impact Sound Insulation Performance of the Voided Slab System Applying to

Post Tension Method


Cite this Article: Seunguk Na, Inkwan Paik and Sung-ho Yun, Evaluating the Floor

Impact Sound Insulation Performance of the Voided Slab System Applying to Post

Tension Method, International Journal of Civil Engineering and Technology, 9(5),

2018, pp. 420–431.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=5

1. INTRODUCTION

As the scale of buildings has been getting larger in recent years, it has been required to

construct long-span structures. In order to improve the serviceability and usability of such

long-span structures, there are various approaches to enhance load distribution and reduce the

weight of slabs. One of the effective methods to reduce the weight of slabs is voided slab

systems or hollow-core slab systems [1-3]. A voided slab system or hollow core slab system

is one of the newly developed construction methods applied to enhance the load resistance by

effectively utilising the moment of inertia in a concrete slab [4-6]. There are several

advantages of a voided slab system such as economic efficiency, usability, environmental

friendliness and so forth [7-13]. On the other hand, it also has a number of disadvantages

which are difficulties in construction work on site compared to normal reinforced concrete

slabs despite the decrease in the quantity of concrete and reinforcing bars [14-16].

Furthermore, it would cause deterioration of economic efficiency since extra construction

costs are incurred when the voided parts would not be properly constructed. These problems

frequently occur in the early development of the voided slab systems. However, recently

developed voided slab systems which maximise the structural performance by using the

moment of inertia have been overcome such difficulties so the application of the voided slab

system is getting popular in the AEC industry [2, 4, 6, 17, 18].

The application of the voided slab systems to buildings has been more popular, and is

being continuously used in various countries including those in Europe, Asia, North America,

the Middle East, and Oceania [7, 19, 20]. In particular, it has been demonstrated that a voided

slab system would be beneficial to reduce the noise propagation and noise complaints

between floors in apartment dwellings in Japan. While voided slab systems with steel pipes

have been applied to Hyatt hotel and several different freezing warehouses in South Korea, it

was not widely applied due to difficulties in construction and economic efficiency. In spite of

such problems on the voided slabs, the voided slabs have since gradually applied to large

buildings and long-span structures such as underground parking, office buildings, factories,

cinemas, and religious facilities. Furthermore, it has been investigated that the application of

voided slab systems would be one of alternatives to solve social issues such as noise

complaints and floor impact noises caused by footsteps in apartment housings, which occupy

the majority of domestic dwelling types in South Korea.

It is a significant factor to improve the quality of life and comfort of residents to insulate

noises from indoor and outdoor-generated in apartment dwellings [21-24]. In South Korea,

one of the most commonly generated noise problems amongst residents in apartment housing

is noise complaints that occur between upstairs and downstairs neighbours. Since such noise

complaints have become a serious social issue, a number of technologies and strategies have

been suggested to resolve the problem. Interlayer noise is a type of floor impact noise which

is the most important aspect to evaluated the comfort and the level of indoor noise [21, 25-

27]. When it comes to reduction of interlayer noise problems, it is necessary to assess the

level of impact of sound insulation from slabs applied in a building structure. It has been

reported that the void former materials used in the hollow part of the voided slabs have a

remarkable capability in terms of sound insulation against floor impact sounds. In this study,

the authors developed a new voided slab system which uses post-tension to maximise the

Seunguk Na, Inkwan Paik and Sung-ho Yun


extension of span in a building. The purpose of this study is to investigate the performance of

sound insulation for the newly developed voided slab system using post-tension. To verify the

effectiveness and applicability of the voided slab system, a mock up test was conducted to

evaluate its sound insulation performance against floor impact noises.

2. EXPERIMENTAL PROGRAMME

2.1. Voided slab system

The voided slab system proposed in this study combines the post tension method with the

concrete casting in place voided slab system which uses paper tubes for void former materials

(see Figure 1). Through this method, it would be possible to materialize long-span voided

slabs structures as well as all the advantages of the both voided slab systems and post tension

in concrete structures.

Figure 1 Schematic vies of voided slab using post tension

There are a number of advantages using the suggested voided slab method is summarised

into two aspects. Firstly, one of the significant aspects for this method is the environmental

friendliness of the void formers. Since the void formers were made from papers, it would be

able to reduce environmental burdens compared to existing void formers. The existing

materials for the void former utilise plastics, Expanded Polystyrene (EPS), High-density

Polystyrene (HDPE) and so forth. These materials would cause great environmental impacts

such as emission of carbon dioxide, consumption of large volume of energy and so forth

during manufacturing void formers. Various studies have developed void former materials

and shapes in order to enhance adhesiveness and lower the weight. The proposed method of

this study would be an alternative method to overcome both environmental burden and the

weight of void former. Secondly, the application of post tension would make it possible to

reduce the depth of slab. The lowering the depth of slab would lead the usability of the slab

system such as minimisation of deflection on slabs, and the lightweight of the entire structure.

Moreover, the lightweight of the entire building would be beneficial for economic efficiency

by constructing more storeys compared to the ordinary reinforced concrete slabs.

2.2. Overview of the test

Mock-up tests were conducted to evaluate the floor impact sound insulation performance of

the reinforced concrete slab applying voided slab with post tension method. The mock-up test

specimen was built in compliance with the standard apartment housing floor plan in South

Korea. Two houses with standard floor area of 59m2 and 84m

2 were constructed as mock up

test houses to evaluate the sound insulation performance (see Figure 2 and Figure 3). The

concrete and reinforcing bars used for this specimen had a compressive strength of 24MPa,

and tensile strength of 400MPa for D16 and 500MPa for D19 (see Table 1).


Post Tension Method


The floor of the mock up specimen was finished with lightweight porous concrete, side

insulation, and finishing mortar, as popularly applied in apartment housing in South Korea

(see Table 2). The properties of the materials used in the mock up test specimen are

summarised in Table 3.

Table 1 Properties of the materials

Materials Strength

Concrete fck=24MPa

Re-bars fy=400MPa (for lower than D16)

fy=500MPa (for over D19)

Table 2 Details of the floor finishing

Area Materials Depth

Rooftop Voided slab 250mm

2nd floor

(with floor finishing)

Mortar 40mm

Lightweight porous concrete 40mm

Voided slab 250mm

2nd floor

(without floor finishing) Voided slab 250mm

(a) 1st floor



(b) 2nd floor

(c) Rooftop

Figure 2 The floor plans of the mock up specimen

Table 3 Details of the concrete mix design

Design

strength

(MPa)

W/C

(%)

S/a

(%)

Unit content (kg/m3) Air

content

(%) Water Cement Fine

aggregate

Coarse

aggregate Admixture

24 49.4 47.5 162 328 882 993 1.64 3.5


Post Tension Method


Figure 3 The cross-sectional plan of the mock up test specimen

2.2.1. Floor impact test

Equipment used for the floor impact sound generation and measurement is shown in the

Figure and Table. In this test, two types of sound generator for light and heavy impact sounds

were used for generation of the floor impact sounds. In the case of the heavy impact sound

generator (i.e. A bang machine), the tests were carried out at a tyre air pressure of (2.4 0.1)

105, which is the air pressure for a bang machine as regulated by the Korea Standard (KS).

The tests were conducted in accordance with KS F 2810-1:2001 (Field measurement of

impact sound insulation of floors – Part 1: Method using standard light impact source) [28]

and KS F 2810 – 2: 2012 (Field measurement of impact sound insulation of floors – Part 2:

Method using standard heavy impact source) [29]. The frequency range of the lightweight

impact sound was 125, 250, 500, 1000, and 2000 Hz, and the heavy impact sound frequency

range was measured using a 1/1 octave band of 63, 125, 250, and 500 Hz, respectively.

(a) Bang machine (Floor impact noise) (b) Impact ball (Heavy impact noise)

(c) Lightweight impact noise (d) Non-directional microphone

Figure 4 Floor impact noise source and measurement devices



To calibrate the effect of the background noise, the background noise was measured for

each frequency level before obtaining the noise data. When the level difference between the

background and measured noise was 6 to 15 dB, the acquired data were compensated through

the following expression.

⁄

Here, is the compensated maximum sound pressure level (dB),

indicates the

measured maximum sound pressure level including the background, and represents the

sound pressure level of the background noise.

The floor impact noise level L of the sound receiving room, which indicates the floor

impact sound isolation performance of the floor structure to be measured, was obtained

according to the formula for each measured frequency.

∑

Here, is the maximum sound pressure level measured at point j, and m represents

the number of measurement points. In the case of a lightweight impact sound level, the sound

absorption area of the receiver room was corrected through the following equation after the

level of the normalised floor impact sound was measured.

Here, is 10 m2, A is equal to

, A is the area of absorption (m

2), V is the volume of

the receiver room, and T is the reverberation time.

2.2.2. Floor structures and measurement location of the sound

The structures of the floor were composed of finishing mortar, void formers, and light weight

porous concrete. The floor impact sound was measured 0.75 m away from the wall, and four

points including the centre of the floor were selected as the measurement location in the

mock-up specimen. Microphones were used to obtain the impact sound data at a distance of

0.75 m from the wall, and at a height of 1.2 m from the floor. Error! Reference source not

found. shows the floor plan of the specimen, and the sound source and reception points of the

test (See Figure 5).

Sound source Receiver points

Rooftop


Post Tension Method


2nd floor

2nd floor

point 1, 2,

and 3

Figure 5 Sound source and receiver points

3.2.3. Evaluation method of insulation performance for standard lightweight impact sound

The data were analysed based on KS F 2863-1:2002 (Rating of floor impact sound insulation

for impact source in buildings and building element-Part 1: Floor impact sound insulation

against standard light impact source) and KS F 2810-2:2012 (Field measurement of floor

impact insulation of buildings – Part 2: Method using standard heavy impact sources).

The insulation performance rating criteria for light and heavy impact sounds are shown in

Table 4. As shown in Table 4, at least 58 and 50 dB are required for light and heavy impact

sound sources for a basis for the insulation performance of the floor impact sound of an

interlayer floor.

Table 4 Standard level of floor impact sound insulation (unit: dB)

Grade

Inverse A normalised floor impact

sound level (Lightweight floor impact

noise)

Inverse A normalised floor impact

sound level (Floor impact noise)

1

2

3

4

3. TEST RESULTS AND DISCUSSIONS

Table 5 show the result of standard lightweight impact sources based on KS F 2863-1: 2002

(Rating of floor impact sound insulation for impact source in buildings and building element–

Part 1: Floor impact sound insulation against standard light impact source) and KS F 2810-

2:2012 (Field measurement of floor impact insulation of buildings – Part 2: Method using

standard heavy impact sources).



Table 5 Test results of heavy impact and lightweight impact source(Unite: dB)

Test

Frequency (Hz) Single

number

quantity

(

Location 63 125 250 500 1000 2000

Heavy

impact

source

Bang

machine

Rooftop 71.0 55.2 48.5 40.6 - - 42

2nd floor 79.4 63.4 54.1 45.7 - - 50

2nd – 1 77.3 61.7 53.9 45.7 - - 48

2nd -2 76.4 61.4 53.8 48.2 - - 48

2nd -3 74.2 62.9 54.3 45.5 - - 48

Impact

ball

Rooftop 61.8 57.6 52.8 43.3 - - 43

2nd floor 66.3 58.6 52.4 44.5 - - 43

2nd -1 67.4 63.1 55.1 47.9 - - 47

2nd-2 66.5 63.0 58.1 49.2 - - 48

2nd -3 67.2 62.9 59.9 49.5 - - 49

Lightweight

impact

source

Rooftop - 58.5 60.2 63.4 65.2 69.3 66

2nd floor - 60.2 62.2 66.0 71.6 76.5 73

2nd -1 - 58.5 61.3 64.0 65.7 69.0 66

2nd -2 - 59.0 61.3 63.6 66.3 69.3 67

2nd -3 - 59.1 62.2 63.5 65.6 67.9 66

(a) Results of heavy impact source: bang machine

(b) Results of heavy impact source: impact ball


Post Tension Method


(c) Results of lightweight impact source

Figure 5 The test results of heavy and lightweight impact source

The sound insulation performance standard regulates that at least 50dB and 58dB in the

case of the heavy impact sound source and the lightweight impact sound source respectively

for the sound insulation of apartment housings in South Korea. Table 5 and Figure 6

summarise the test results of the heavy impact sound source in the mock-up specimen. The

sound insulation performance against the heavy floor impact sound indicated the grade 1 and

2 for the sound insulation performance in the single numerical quantity (i.e. Grade 1 indicates

better performance of sound insulation over Grade 2 and 3). The test results for lightweight

floor impact sounds are shown in Table 5 and Figure 6. The results of the lightweight floor

impact sounds were exceeded 50dB.

As a result of the floor impact sound from the mock up test house, the test results of the

voided slab using post tension indicated that the measured values of the noise level were not

exceeded 50dB which is the insulation performance standard of heavy impact source for the

apartment housings in South Korea. These results are due to the existence of hollow parts

which would make it possible for the voided slab would isolate the noises from the upstairs.

For the lightweight impact sound, all the test results exceeded the standard noise

insulation performance for lightweight impact source (the value is 58dB). These results were

considered that the flooring materials such as carpets, floor boards and so forth were not

installed in the mock up test house. Despite the test results of the lightweight impact sound

insulation were over 50 dB, it would be allowed to apply to apartment housings in South

Korea. The noise complaints issued in South Korean apartment housings are normally heavy

impact sound rather than lightweight floor impact sound.

In summary, the test results showed that the heavy floor impact sound insulation

performance of the voided slab system applied post tension method showed less than 50dB

with satisfying the domestic standards. On the other hand, the test results of lightweight

impact sound insulation were indicated over 50dB. The reason for exceeding 50dB for the

lightweight impact sound insulation might be the floor finishing materials such as flooring,

carpets and so forth were not installed in the mock-up specimen. If the floor finishing would

be applied to the voided slab system with post tension method, the lightweight impact sound

insulation performance would be enhanced.

In addition, the floor impact noise complaints in apartment housings are frequently

happened due to the occurrence of heavy impact sound. It is considered that the adoption of

the proposed voided slab system using post tension in this study would be useful for solving

such social issues in the apartment dwelling in South Korea.



4. CONCLUSIONS

The purpose of this study was to evaluate the floor impact sound insulation performance of

the voided slab system with post tension method. Based on the evaluated data, the

applicability of the voided slab system to apartment housings was also examined. The test

results showed that the average insulated noise level against heavy impact sound was 46.8dB.

Moreover, the mock-up test results of the lightweight floor impact sound were over 58dB

from all the tests. Since the floor finishing materials were not installed in the mock up test

specimen, the measured level of lightweight impact sound was higher than 50dB. In addition,

the use of the voided slab systems proposed in this study would be beneficial to the apartment

housing in South Korea, because the floor impact sound noise complaints between neighbours

in South Korea are arisen by the heavy impact sound rather than the light impact sound.

ACKNOWLEDGEMENT

This work was supported by the Technology Development Program (C0513195) funded by

the Ministry of SMEs and Startups (MSS, Korea).

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