table of contents 1 rannila structural decks 2

Structural systems / Rannila Structural Decks5.4.2002

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TABLE OF CONTENTS

1 RANNILA STRUCTURAL DECKS.................................................................. 2

1.1 TOLERANCES............................................................................................................................ 2

1.2 RAW MATERIALS..................................................................................................................... 4

1.3 TYPES.......................................................................................................................................... 5

1.4 QUALITY CONTROL................................................................................................................ 7

1.5 DESIGNING ................................................................................................................................ 7

1.6 STRUCTURAL DETAILS .......................................................................................................... 71.6.1 Insulated roofs ...................................................................................................................... 71.6.2 Non-insulated roofs..............................................................................................................11

1.7 FASTENING FREQUENCY IN ACCORDANCE WITH B6 ( Finnish norm ) ........................15

1.8 STRUCTURAL MODELS .........................................................................................................161.8.1 Structures with 1, 2 or 3 spans and cantilevers ......................................................................161.8.2 Gerber system......................................................................................................................171.8.3 Extended end lapping...........................................................................................................181.8.4 Rannila-120 pre-curved structural deck ................................................................................181.8.5 Curved arch structures .........................................................................................................191.8.6 Use of stressed skin..............................................................................................................191.8.7 Anti-condensation coating....................................................................................................19

1.9 ACOUSTICS...............................................................................................................................211.9.1 Acoustic control in sports halls.............................................................................................211.9.2 Rannila structural decks with web perforation ......................................................................221.9.3 Example: case study of acoustics, power plants ....................................................................221.9.4 Absorption coefficients ........................................................................................................231.9.5 Measurement results concerning steel structures ...................................................................251.9.6 Economic aspects.................................................................................................................27

1.10 INSTALLATION ...................................................................................................................271.10.1 Installation details, insulated roofs........................................................................................271.10.2 Installation details, non-insulated roofs.................................................................................311.10.3 Fastening frequency in accordance with B6 ( Finnish norm ) ................................................361.10.4 Tools ...................................................................................................................................371.10.5 Storage ................................................................................................................................371.10.6 Notes for installation............................................................................................................37


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1 RANNILA STRUCTURAL DECKS

In recent years, the drive to develop lighter and more cost effective steel structures hasresulted in the use of cold-formed and thin steel components. There are many advantages tobe gained when structural decks are used:

• Wide range of profile options• Long spans without secondary framing, creating remarkable time and cost savings• Good corrosion resistance with zinc and other coatings• High quality, durable surface finish• Simple fastening methods• Perforated profiles provide excellent acoustic properties• Stressed skin effect eliminating wind bracing on the roof to reduce costs further

Rannila Structural Decks are load-bearing sheets specifically designed for roofs. They canbe also used as casting moulds for flooring. Structural decks can be used in both insulatedand non-insulated roofs. The designer selects the appropriate profile, depending onloadings, aesthetic considerations or the need for stressed skin performance.

Insulated roof:

a) Insulated roofs are typically used in industrial buildings, warehouses, supermarkets etc.The aim is to achieve spanning between main frames and to carry all related loads. Theroof construction consists of a structural deck, mineral wool thermal insulation and anexternal roof sheet or membrane.The wider flange on the upper side of the deck providesgood support for the insulation. Insulation will support the membrane. In twin skin roofconstructions, a spacer purlin will support the upper sheet. The under side of the deck iscoated to provide a finished surface.

b) In non-insulated roofs the structural deck act also as the external weather sheet. Theprofile is visible and the coating is factory-applied on the outer surface.This type of roof iscommon in shelters or in unheated buildings. An anti-condensation coating is generallyused as condensation protection in cold roof structures.

c) Structural decks can be used also as casting moulds for flooring on request.

1.1 TOLERANCES

The permitted dimensional and shape tolerances of structural decks are based on thestandard SFS-EN508-1. Although steel is a homogenous material, and profile sheets areroll formed, tolerance ranges for dimensions such as shape, length and curvature arerequired in thin steel sheet production. These tolerance ranges are a result of wear and tearof tools, inaccurate measurement and temperature changes. Quality control measuresduring production ensure that products comply with these ranges. Examples of producttolerances required by the standard. Further tolerances are given in the standard.


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Profile height

Profile height Tolerance

h = 50mm ± 1 mm50 mm < h = 100mm

± 1,5 mm

h > 100 mm ± 2 mm

Sheet flanges

Tolerances of sheet flanges are measured at a minimum distance of 200mm from theprofile ends.

Tolerances of top and base flangesmay be –1 < b1,2 < +2

b2

Effective cover width

The effective cover width is measured at a minimum distance of 200mm from the profileends. The effective cover widths of both ends are measured (b1, b2). The average of themeasurements b1+b2/2 is calculated and the result is compared with the effective width ofthe centre line of the sheet. The measurement margin may not be greater than the tolerance.

h

b1

200 mm

Effective width

200 mm

Middleline ofsheet

Tolerances:for sheets h = 50 mm ± 5 mmfor sheets h > 50 mm ±h/10, max.15mm


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Straightness of the sheet

The straightness of the sheet is checked along a theoretical line. The theoretical line isdrawn along at a 200mm distance from the sheet ends via the edge of the sheet’s top flange.The distance of the line on the profile’s centre line may not be greater than the tolerance.

The tolerance may be 2.0mm per metre, at a maximum 10mm; e.g., in a 5 m long sheet, thecurvature may be max. 10mm.

Sheet cross-measurement

S

Sheet length

The sheet length tolerance measured along the sheet middle line may be at a maximum:

Sheet length ToleranceL = 3 000 mm -5 = L = -10 mmL > 3 000 mm -5 = L = +20 mm

Sheet edge undulation

Sheet edge undulation may be D = + 2mm within a maximum of 500mm.

1.2 RAW MATERIALS

b

The sheet cross-measurement S may be at amaximum:S = 0,5 % of b

D


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Structural decks are manufactured by roll forming from cold rolled, hot-dipped galvanizedsteel coil. The material used is mainly of steel quality S350GD+Z manufactured inaccordance with the norm SFS-EN 10147. The material tolerances comply with the normSFS-EN 10143. The yield stress ReH of the most common steel material is 350 N/mm2 andthe breaking strain A80 is 16%.

Yield Breaking Breaking stress stress strainRe Rm A80N/mm2 N/mm2 %

S280GD+Z 280 360 18S320GD+Z 320 390 17S350GD+Z 350 420 16S550GD+Z 550 560 -

Structural decks for use on insulated roofs are usually either plain galvanized or polyestercoated. For decks used as external weather sheets, coatings are usually PVDF or PURAL..The material thickness varies between 0.6mm and 1.5mm. Sheets manufactured fromaluminium and stainless steel are also available to special order

1.3 TYPES

Rannila 45JA / 45JBFor span lengths up to 3.5mEffective width 915 mmTotal width 980 mmHeight 44 mmSheet thickness 0.60… 1.00 mmMax. length 15.0 mMin. length 0.40 m

Rannila 70A / 70B

For span length 2.5 to 4.5 mEffective width 850 mmTotal width 910 mmHeight 70 mmSheet thickness 0.60… 1.00 mmMax. length 15.0 mMin. length 1.0 m


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Rannila 113B

For span lengths 4.0 to 6.0 mEffective width 750 mmTotal width 782 mmHeight 113 mmSheet thickness 0.60… 1.20 mmMax. length 20.0 mMin. length 1.0 m

Rannila 120A / 120B

For span lengths… … … … … … … 5.0 to 6.5 mEffective width… … … … … … … .695mmTotal width… … … … … … … … … about 730mmHeight… … … … … … … … … … … 117mmSheet thickness… … … … … … … ..0.6 to 1.2mmMax. length… … … … … … … … … 25.0mMin. length… … … … … … … … … ..1.0m

Rannila 153A / 153B

For span lengths… … … … … … … over 5.5mEffective width… … … … … … … .560mmTotal width… … … … … … … … … about 600mmHeight… … … … … … … … … … … 153mmSheet thickness… … … … … … … ..0.75 to 1.5mmMax. length… … … … … … … … … 20.0mMin. length… … … … … … … … … ..1.0m


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1.4 QUALITY CONTROL

Rannila carries out permanent quality control to ensure high product quality. A qualitycontrol agreement has also been signed between Rannila and VTT (The TechnicalResearch Centre of Finland) concerning all structural decks and the Steelcomp deck sheetalong with other Rannila products. Raw materials and manufactured products are bothincluded in the quality control agreement.

Certificates of substances with information on tested properties of raw materials andcoatings are available on request for all raw materials used for Rannila structural decks andSteelcomp deck sheets. The raw materials used can be traced on the basis of the coilnumber. Manufactured products are controlled in accordance with special instructions andprocedures required by the quality control agreements to ensure high quality products. Thecontrol documentation is filed in accordance with separate instructions and it is possible tocheck data of each manufactured lot, if required. VTT carries out inspections andmeasurement checks in accordance with the quality control agreement.

1.5 DESIGNING

When specifying structural decks, the following strength properties and conditions must beconsidered:

• Bending strength• Single load strength / shear strength• Combined effect of bending and single load / shear force• Deflection

For structures with one span, the deflection is often the critical factor. The dimensioningfactor for a continuous structure is usually the combined effect of the bending moment andthe single load at the support.

Structural decks can also be used in a stressed skin configuration. The conditions to beexamined depend on the norm used and they include:

• Buckling of plane field• Moving of top flange on gable support• Buckling of sheet field• Combined effect of bending moment and sheet force (in web and flange)

1.6 STRUCTURAL DETAILS

1.6.1 Insulated roofs

The structural deck is installed with the B side down, i.e., the narrow flange down (picture1). The edge flange of the sheet then comes down against the support, making installation


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easier (fixing of overlap screws). The wide flange is installed upwards, achieving moresupport width for mineral wool insulation. The bearing capacity of the structural deck isusually greater when installed in the above-mentioned way than when the sheet ispositioned the other way around. If the sheet is coated, the colour is applied to the B side.

Picture 1. Insulated roof structure

Side lapping

Structural decks are sidelapped with each other as shown in picture 2.. Sidelappingfasteners are usually special screws or rivets. The max distance between fasteners is 500mm.

Picture 2. Side lap

Additional side lapping

If the normal bearing capacity of the sheet is not sufficient, the capacity can be increasedby overlapping sheets. Snow drift areas can be strengthened by overlapping one or twosheet pans. In this case there is a double profile in the overlap area (picture 3).

Picture 3. Additional side lapping


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End lapping

In an end lap, sheets must be overlapped by a minimum of 150 mm (picture 4).

Picture 4. End lap

Extended end lap

In an extended end lap, sheets are placed one over the other at the support (see picture 5). Ifthe structure is designed to be continuous over the support, profiles must be fixed togetherfrom webs. The cantilevered part of the upper sheet must be fixed with screws to the lowersheet, as shown in picture 5. Screws are positioned in the upper part of the web followingB6 ( Finnish norms) edge and centre distances, see point 14.8. Numbers of required screwsare provided by the designer.

Picture 5. Extended end lap


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Gable

In the gable bay, the sheet extends to the edge of the the support (picture 6).The location of the fastening screw is shown in the picture no 7.

Picture 6. Gable Picture 7. Screw positionsB= width of non-stiffened flat section

Support piece

An additional support piece increases the capacity of the structural deck by improving thecapacity against the combination of support reaction and support moment. The supportpiece 320 mm long, manufactured from the same profile and installed under the structuraldeck at the support, see picture 8. The support piece is typically used in the middle supportof a 2-span structure i.e. when the support reaction with the support moment is the criticaldesign issue.

Picture 8. Support piece


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Gerber joint

In the Gerber joint, fasteners are positioned in the web of the structural sheet (see picture2.8). Screws must be positioned in the upper part of the web following the B6 edge andcentre dimensions, see point 14.6. Numbers of screws are determined by the designer.Sheets are overlapped by a minimum of 150 mm.

Picture 9. Gerber joint

1.6.2 Non-insulated roofs

Structural deck are designed so that temperature changes will not cause harmful stressesand deformations. Thermal movements across the sheet rarely cause any problems, becausethermal expansion by temperature changes causes only minor deformations to thecorrugation shape. Instead, constraint actions parallel to the corrugation may be, ifdeformations in the sheet length are not allowed to freely occur. The designer must takecare to ensure that there are expansion joints wide enough at the structural deck ends,fasteners are adequate and that structures joining with profile sheets are flexible enough sothat any harmful constraint actions cannot be generated.Special attention should be paid to the sealing of the intersection of edge and extensionoverlap joints. It is not possible to quote a definitive number of screws for structural decks,because the precise figure depends on loads, support distances and whether or not stressedskin properties are utilised.

Extended end lapping

The extension overlap point is positioned so that the base structure will support itsufficiently. Sheets are overlapped by 200 mm at a minimum (pictures 10 and 11). Thedistance of the fastener row should be 50 mm from the lower end of the sheet. When usingscrews, sheets are fastened in each trough. In extended end laps, a sealant strip of 3x10 mmmust always be used.


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Picture 10. Extended end lapping of corrugated sheet

Picture 11. Extended end lapping of corrugated sheet

Picture 12. Extended end lapping with expansion allowance

Sealant strip(next tofastening)


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Fastening near a support

For fixing structural decks to the purlin, it is recommended to use double the number offasteners in profile troughs nearest to the support, see picture 13.

Picture 13. Fastener near a support

Roof pitch

Side laps of structural decks are shown in table 2. The type of overlap depends on the roofpitch and the profile height. In long, gently sloping elevations, the water level can riseconsiderably during heavy rain. If the level rises over the profile of the sheet, it generateswater pressure with the potential for leaks to occure. For this reason it is recommended touse either deep profiles or when shallow profiles are used, additional overlapping or sealingin long elevations.

Table 2. Overlaps of structural decks for different roof pitches

Structural deck (height 30 < h < 50mm)Sheets with capillary groove, like Rannila 45R >> 0.5 profile overlap and sealRoof pitch steeper than 1:10.

Structural deck (height 30 < h < 50mm)Sheets without capillary groove, like Rannila 45>> 1.5 profile overlap and seal.Roof pitch steeper than 1:10

Structural deck (height 45 < h < 153mmLoad-bearing profiles, as Rannila 70, 113,120, 153.>> 0.5 profile overlap and seal.Roof pitch steeper than 1:10.


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Side lapping

In gentle sloping roofs, the watertightness of joints can be improved by using overlapslarger than recommended. Roofing sheets must be fastened to each batten at the side lapjoints. Screws with EPDM seals, sealant strip or bulb-tight concealed rivets are used forareas between battens. The distance between fastening points should not be more than500mm (See picture 15). For roofs where the stressed skin effect of the structural deck isutilised, the number of fasteners must be checked separately by designer.

Picture 14. Sealing and fixing of side lap of the structural deck.

Picture 15. Side lap fixing location


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1.7 FASTENING FREQUENCY IN ACCORDANCE WITH B6 ( Finnish norm )

The minimum values given in pictures 16 and 17 are followed when positioning thefasteners. The fastening frequency can be less than that given in picture 16. In that case, therate of inlet and perforation strength is reduced with the ratio of edge distances so that thefastening frequency given in picture 16 corresponds to the total rate. In any case, thefrequency must not be less than 25 mm.

The largest distance between fasteners is chosen so that sheets join together tight enough toprevent water entering the joint. The largest centre distance permissible for self-tapping andself-drilling screws is the rate 10d and for rivets 20d.

Picture 16. The smallest edge and centre distances for fasteners, when a tensile force, orsimultaneously shear and tensile forces are directed to the joint.


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Picture 17. The smallest edge and centre distances for fasteners, when a shear force isdirected to the joint

1.8 STRUCTURAL MODELS

1.8.1 Structures with 1, 2 or 3 spans and cantilevers

The maximum span length permitted in a single-span structure equates to the free spacebetween the supports and, in structures with two or more openings, the measurementbetween the supports from centre to centre. The width of the support affects the maximumspan length permitted mostly when the dimensioning factor is the combined effect of thesupport moment and the reaction of support. In projects where there are two or three spans,the combined effect condition is generally the critical design factor. If a Z or C profile issupporting the structural deck, the support width must be 2/3 of the width of the supportflange for structural models, see picture 18.

- self-tapping or self-drillingscrew, rivet or nut screwe1,e3, and e4 >=3de2 >=1.5d

- nail e1, e2, e3 and e4 >=4.5d


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Picture 18. Structures with 1, 2 or 3 spans and cantilevers.

1.8.2 Gerber system

In the Gerber joint (picture 19), the junction of the profile is positioned at the zero point ofthe moment. Advantages are gained by using thinner material thicknesses and shorter sheetlengths (logistical advance). See picture 9.

Picture 19. Gerber system


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1.8.3 Extended end lapping

An extended end lap is often practical, when the field number is uneven. In this case, a one-sided end lap is made in the last gable field. End lapping can also be used in centre areas,achieving thinner sheet material thickness. Testing has shown that the optimum overlaplength is 10 percent of the length of the overlapped spans. A lengthwise overlappedstructure made in accordance with this principle can be dimensioned continuously. Thestrength of fasteners in the end-to-end overlapping should be checked in the webs(fastening the sheets to each other); the max. amount is 4 pieces/pan, i.e., the number offasteners increases. A high snow load (snow drift) in the gable field won’t create problems.In extended end laps, sheets are placed one on the other at the support, (see picture 5). Ifthe structure is dimensioned continuously, it must be ensured that profiles are fastenedfrom the web to each other. The cantilevered part of the upper sheet must be fixed withscrews to the sheet underneath as shown in picture 5. Screws must be positioned in theupper part of the web following the B6 edge and centre distances, (see point 14.8). Screwnumbers are provided by the designer. Structural model examples can be seen in picture 20.

Picture 20. Structural model examples, overlapped systems.

1.8.4 Rannila-120 pre-curved structural deck

The Rannila 120 pre-curved structural deck is primarily designed for insulated roofs, butpossesses several advantages that make it suitable for non-insulated roof structures. Thepre-curving helps to make span lengths longer. The pre-stressed Rannila 120 profile is usedonly as a single-span structure. With normal frame sizes, thinner material than is used intraditional structure solutions can often be employed. The single span structure also allowsnarrower support widths, and so it is possible to design a lighter steel structure.Transporting shorter sheets is less expensive than longer ones and they are light to handle.Installation is considerably easier. For pre-curved roofing structures, only flexiblemembrane is suitable. It is recommended that the lower membrane is initially fastened inthe joints; the upper membrane is then thoroughly welded to the lower one. Because of thepotential movements, special attention should be paid to eaves details, mitres and extensionof roofing material up the walls.


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Picture 21. Rannila-120 pre-curved structural deck.

1.8.5 Curved arch structures

Rannila-120 or -45J profiles can also be used for manufacturing single and double archtwin-skin structures where end supports are bound together with tension bars. In a twin-skin construction, profiles are bound together with top hat profiles. Separate instructionsand a computer programme are available for design calculations.

1.8.6 Use of stressed skin

Stressed skin means the stiffness of the profile sheet field in the sheet plane. Whenstructural decks are fixed tightly enough to each other and to the framework, the sheetplane can transfer forces along its own plane. When the stressed skin effect of the profilesheets is utilised for stiffening the building, wind braces or trusses can be either wholly orpartly replaced. The Poimu software programme can also be used to calculate the stressedskin capacity of profiled sheets.

1.8.7 Anti-condensation coating

Anti-condensation coating is an effective solution for condensation in facilities such as un-insulated halls and open shelters. The coating is compound sprayed onto the profiled sheetsurface. It collects water vapour and prevents it from dripping. Condensation absorbed inthe coating evaporates very quickly. (Adequate ventilation is required to facilitateevaporation).

The anti-condensation coating is a highly absorbent volcanic mineral called perlite. Thanksto their porous structure, small perlite grains can absorb as much as 1.5 litres of water persquare metre (1.000g coating). Due to the structure of perlite, water doesn’t build up asdroplets in the coating, but is absorbed through capillary action over a wide area. To testthe absorbing capacity of the coating, a British method is used where a copper funnel iscoated with anti-condensation compound and filled with ice water. Condensed water ismeasured with a graduated glass.


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Picture 22. Test method demonstrating absorption capacity of the anti-condensationcoating.

The findings from this six-hour long experiment show that, in the funnel coated withRannila Anti-Condensation Compound, there is no condensation at all. In the non-coatedfunnel, the first water droplets appeared after 35 minutes. In six hours, the amount ofcondensed water was 33 ml.

The coating is non-combustible and doesn’t emit any toxic gases. The compound is water-based and doesn’t include any substances hazardous to health. It can also be safely used infood hygiene facilities. The coating has a fire classification in Sweden BR4, class 1.

The anti-condensation coating also gives corrosion protection to the structure. Waterdroplets can’t reach surfaces or structures exposed to corrosion, because the water isabsorbed over a wide area. After condensation has ended, water evaporates very quicklyfrom the coating.

The anti-condensation coating also has sound-insulation properties. It effectively dampenssounds caused by rain and wind.

The standard colour for the anti-condensation coating is light grey. The grainy surfacegives a pleasant appearance.

Picture 23. Enlarged picture showing surface structure of anti-condensation coating.

Table 3.Technical properties of the coatings

Coating thickness 1,5 mm (1 000 g/m2)Water absorption capacity about 1-1.5 l / effective (1000 g/m2 coating)Coating amounts 600 or 1000 g/m2

Density app. 1 kg/l

Non-coated Anti-condensationcoated


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Coating method sprayingColour light greyDiluent waterCoating components perlite grains, cellulose fibres, water, binding

agents

Ordering

The order must include the following information: coating amount g/m2, sheet side to becoated and overlaps needed. Coating is not used in end or side laps. In side laps, the normaloverlap (usually ½ wave) remains non-coated. In end laps, the non-coated area is generally200 mm.

1.9 ACOUSTICS

1.9.1 Acoustic control in sports halls

In sports halls, acoustic control is required to reduce the general noise level, to decreasereverberation and to ensure the function of the sound system. A short reverberation time isnecessary to achieve understandable speech. To ensure the correct function of soundsystems, the aim is to achieve a reverberation time of 2.0 seconds in small halls; in largesports halls, the rate should be under 3.0 seconds, preferably about 2.5 seconds.

Hall 1.

If dimensions of a hall are about 36m * 54m, with the average height about 10m, andbottom parts of walls consist of tiles (h=2400), other wall parts are made from steel sheets,the floor from hard material and the ceiling from non-perforated corrugated sheet, thereverberation time in the space is over 8 seconds in the medium frequency band. If theceiling of the hall is made from perforated steel sheets with mineral wool insulationunderneath (see the picture below), the reverberation time becomes remarkably shorter.With a perforated ceiling achieving an absorption coefficient of about 0.4 with 125 Hz, 0.6with 250 Hz, 0.8 with 500 Hz, 0.6 with 1 kHz, 0.5 with 2 kHz, and 0.4 with 4 kHz, thereverberation time is between 2 to 3 seconds depending on the frequency band.

Hall 2.

If the dimensions of a hall are about 18m * 36m, and the average height is about 8m, withwalls made from gypsum boards or thin steel sheet profiles, the floor made from hardmaterial and the ceiling from perforated corrugated sheets, the reverberation time in thespace is over 5 seconds in the medium frequency band. If the ceiling is perforated asdescribed above, the reverberation time decreases to about 2 seconds.


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Picture 33. Model of structure

1.9.2 Rannila structural decks with web perforation

Various alternatives for structuresFor sound absorbing ceilings, Rannila structural decks can be manufactured and deliveredwith a web perforation. A standard web perforation is designed for each sheet type. Thehole size used is ∅ 3mm. The area of holes represents 15% of the perforated area. Theeffect of the perforation on the sheet load-bearing capacity is minor. It only decreases themoment capacity by 4 %. The support reaction capacity is decreased by about 10%.

1.9.3 Example: case study of acoustics, power plants

General

Calculations relate to the projects in question; results may not be generalised. Calculationsshow that the size of facilities has no profound effect on existing sound levels, when theamount of sound increases by the same proportion.

Sound absorbent cladding materials are needed to reduce the reverberation and the noiselevel. The simplest and usually adequate solution is to use ceiling sheets with webperforation, and then a mineral wool layer between the sheet and the vapour barrier. If apart of the ceiling should remain solid, a part of the perforated cladding can be placed inthe walls.

Additional perforation on the walls improves the situation, but if effective absorption isalready taking place in the ceiling, there is little to be gained by additional absorption in thewalls.


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1.9.4 Absorption coefficients

Picture 34. Absorption coefficients.

Curve 1 Corrugated sheet without perforationCurve 2 Corrugated sheet, web perforation ∅ 3mm perforation 15%, behind vapour barrier before mineral wool insulationCurve 3 Corrugated sheet, web perforation ∅ 3mm perforation 15%, behind 20mm mineral wool before vapour barrier and thermal insulation materials.

Examples of sound absorption

Picture 35.

ABSORPTION COEFFICIENTS

0102030405060708090

100

63 125 250 500 1000 2000 4000

Hz

%

Curve 3

Curve 2

Curve 1


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Picture 36.

Picture 37a.

Picture 37b.


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1.9.5 Measurement results concerning steel structures(Turku District Occupational Health Institute)

The curves below show the picture of the steel structure measured and the result of theabsorption measurement. The corrugated sheet used is Rannila 113 with web perforation O3mm 15%. Mineral wool used was AKU acoustic sheet (sound absorbing sheet).

Picture 38. Rannila 113 sheet with web perforation, without mineral wool, and absorption coefficient of solid surfaced module.

Picture 39. Rannila 113 sheet with web perforation + 30mm mineral wool (AKU acoustic sheet).


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Picture 40. Rannila 113 sheet with web perforation + 15mm mineral wool (AKU acoustic sheet).

Picture 41. Rannila 113 sheet with web perforation + 3mm mineral wool (AKU acousticsheet).


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1.9.6 Economic aspects

To manage economic aspects of the building project, acoustic requirements should bedefined first: airborne sound and impact sound insulation index, reverberation times andsound levels inside and outside in the surrounding areas. Because acoustic measurementsare standardised and explicit, their compliance with the requirements should be generallyaccepted. In various countries, building approval currently also includes sound insulationproperties of structures and buildings. When approval inspections are carried out, soundspecialists are used to state the fixed sound requirements by measurements. It is extremelyexpensive, and often impossible, to repair deficiencies afterwards. Unscientific soundsolutions can become very expensive and end in total failure.

Nowadays there are useful calculating programmes available for estimating technical soundproperties of structures and buildings. Sound properties of products are needed for thecalculation. These properties are defined with laboratory measurements, and changes inproperties are revealed by calculation.

The size and geometry of the space are essential information, when complying withrequirements for reverberation time. The required quantities and positions of soundabsorbing materials can be established using calculation models. Absorption coefficients ofsound absorbing products are necessary for a correct end result. The effect of soundabsorbing material on reducing noise levels can also be calculated.

The calculation of a structure’s airborne and impact sound insulation index requiresinformation about various structural components concerning the laboratory tested soundinsulation properties. This helps to establish how sound conditions required in variousfacilities inside the building comply with the requirements. In order to manage the soundlevel spread to surrounding areas, sound insulation properties of exterior walls must beknown. Finally, sound output levels of all equipment, ventilation devices etc., must bereadily available when making specification decisions.

In addition to decibels, other disturbing factors concerning sounds should also be known.One of these is a narrow-band blasting noise that may disturb neighbouring inhabitants,even though the so-called official standard has been complied with.

1.10 INSTALLATION

1.10.1 Installation details, insulated roofs

The load-bearing sheet is installed B side down, i.e. the narrow flange down (picture 44).The edge flange of the sheet is then placed down against the support and installationbecomes easier (fixing of the overlap screw). The wide flange is installed face up, and sothere is more support width for mineral wool insulation. The loading capacity of thestructural deck is also greater, than when the profile is installed upside down. If the deck iscoated , the colour is applied to the B side.

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