E0055 Rev0 Bolted Steel Joints

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BOLTED STEEL JOINTSCode

E0055.0

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Effective Date: Page

1/13Power (in compliance with EN codes)

Revision Date Revision description

00 15/05/2008 First issue

Prepared by: Giancarlo Brunorisignature:

Verified by: Vincenzo Ruggierisignature:

Approved by:signature:

1. PURPOSE AND SPECIFIC APPLICABILITY2. DOCUMENTATION3. BOLTING CHARACTERISTICS

4. SURFACES CONDITIONING AND BORING

5. BOLTING PROCEDURE6. CHECK7. FINAL DOCUMENTATION


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1. PURPOSE AND SPECIFIC APPLICABILITY

This specification provides the API requirements for the manufacture of bolted joints,to be assembled in support structure and in frames supporting environmental plants.

The term bolted joints as used in this specification is intended to cover fabricatedjunctions, which are part of support structures and frameworks.

Particularly, the supply covers the following activities:

1. Supply of the component, able to be assembled or erected;

Manufacturing of the compound column or beam and relevant examinationand test, marking, cleaning an painting (covered by the procedure E0052);

2. Completion of the column/beam (welding of end plates, etc.),

Boring the holes for bolts,

Working of the contact surfaces;

3. Procurement of bolting;

4. Assembly the components.

1.1 Definition

The following definitions shall apply to the specification:

API (ECS SE): Alstom Power Italia S.p.A. Environment Control SystemSouth Europe or its designated representative.

Client: Final client or its designated representative.

Vendor, Manufacturer: Firm to which order is awarded.

Bidder: Firm invited to issue a proposal for the scope hereinspecified.

1.2 API documents

All documents and drawings furnished by API shall be treated as proprietaryinformation and shall not be used for others than their original purpose without writtenpermission by API

1.3 Applicability

This specification is applied to all contracts requiring application of EUROCODE 3(EN 1993).

This specification is an integral part of the order. Derogation from the order or fromthis specification shall be required in writing, with the adequate forewarning, and areonly admitted if accepted by API with written notification.

2. DOCUMENTATION

2.1 Reference documentation

The Constructor shall follow the requirements of Code and Standards below listedand that specified in contract documents.

EN 1990 Basis of structural design.


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EN 1993-1-1 Eurocode 3: Design of steel structures, Part 1-1: General rulesand rules for buildings.

EN 1993-1-8 Eurocode 3: Design of steel structures, Part 1-8: Design ofjoints.

EN 1090-1 Execution of Steel Structures General rules and rules forbuildings.

EN ISO 12944 Paints and varnishes Corrosion protection of steel structuresby protective paint systems.

EN 14399-1 to 6 High-strength structural bolting assemblies or preloading.

EN ISO 898-1 Mechanical properties of fasteners made of carbon steel andalloy steel

EN 20898-2 Mechanical properties of fasteners Nuts with specified proofload values Coarse thread

EN ISO 4014 Hexagon head bolts Product grades A and B EN ISO 4016 Hexagon head bolts Product grade C

EN ISO 4032 Hexagon nuts, type 1 Product grades A and B

EN ISO 4034 Hexagon nuts Product grade C

2.2 Rules quoted in this document

Moreover the above mentioned rules and codes, the following are quoted in thisdocument.

ISO 4759

ISO 7089

ISO 8501

If not diversely stated in relevant job documents, the last edition of Code andspecifications shall be used.

2.3 Alstom control procedures

1. API E0063.0 Final documentation check and inspection

2. API E0064.0 Identification and retrievability

2.4 Manufacturing documentation

The supplier shall submit to API, for information or approval, the followingdocuments:

1) Bolt materials certificate EN 10204 2.2, attesting their adherence to the specifiedrule.

2) Certificate of statistical tightening test, according to EN 14399-2, on high strength(8.8/8 and 10.9/10) bolt/nut/washers assemblies for checking the behavior of thefastener assemblies so to ensure the required preload. The result of test shall be:

a) Rotation/bolt force curve, with noted the angles pi, 1i, 2i;

b) Torque/bolt force curve with determination of the torque at the design preload

and the mean value km and its standard deviation sk;


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c) Elongation/bolt force curve with determination of the bolt force correspondingto the 0.2% of permanent bolt elongation.

3) Certificate of testing for conformity evaluation according to EN 14399-1, para. 5.

a) Testing for dangerous substances,

b) Testing of dimensional requirements of the components,

c) Testing of mechanical characteristics of components,

d) Testing of functional characteristics of assembly: Torque/bolt force curve forthe individual values of the bolt force at a specified value of the appliedtorque. The torque applied shall be that determined on basis of the testsperformed at point 2.b above; the obtained Fbm shall be the minimum preloadrequired for the bolt assembly tested.

e) Certificates must show the obtained test values, not a generic conformance.

4) Certificate of test, according to EN 1090-1 Appendix A, to determine the slipping

factor under pre-load bolts:a) Purpose of this test is determining the class of friction after a particular

surface treatment. Usually, it has to be verified the slipping of the coatingsurface under a friction load.

b) The test results shall be exposed as detailed in EN 1090-1 Appendix 2, A.2.6.

Manufacturer has to require above documentation at the purchasing. In case it wasnot available, he has to include tests in his activities before delivery material to site.

Manufacturing documentation will be produced according to the job MaterialRequisition (MR).

3. BOLTING CHARACTERISTICS

3.1 Bolts

In compliance with EN 1090-1 8.3:

The bolt shank must stick out from the nut after the tightening. Use of boltsnominal length in excess of about one thread pitch should be usual.

For not preloaded bolts, at least one whole thread pitch (more the sort outthreading) must remain free between the nut support surface and the part notthreaded of the shank. For preloaded bolts, at least four whole thread pitch (morethe sort out threading) must remain free.

Bolts must not be welded.

With pre-loaded bolts, washers are required under both bolt and nut. With notpreloaded bolts their use is not mandatory but recommended. Washers must bebevelled and the bevel must be toward the bolt head/nut.

Generally, for carpentry use, are used bolts with tolerance category C (bolts withlarge tolerances [grade C h14/15] on non threaded parts and rough manufacturingon the threaded parts [g8/H7]. Where a better coupling between bolts and bores isrequired, it must be used bolts of tolerance category AB, i.e. h12/13 fornon-threaded parts, g6/H6 for threaded parts. For more details see ISO 4759.


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3.1.1 Normal bolts (resistance classes 5.6/6)

Bolts (class 5.6) shall be in compliance with ISO 4014 for tolerance category A and Band ISO 4016 for tolerance category C (ISO 8765 for category A fine pitch bolts),material in compliance with EN ISO 898-1, nuts (class 6) shall be in compliance with

ISO 4032 category A and B and ISO 4034 for category C (or ISO 8673 for categoryA-B with fine pitch), material in compliance with EN 20898-2.

The resistant class and geometrical data are specified in contract drawings. Normalbolts used in API constructions, usually belong to the resistance class 5.6/6.

3.1.2 High resistance bolts (resistance classes 8.8 and 10.9)

There are in Europe two bolt systems, between them comparable, HR from France

and HV from Germany, codified in EN 14399 parts 16. Their primary differences are:

Height of nuts: nuts of HR system are slightly more height than HV system nuts

(0.90.85 bolt diameter of HR system versus 0.8330.8 bolt diameter of HV

system, in function of bolt diameter);

Length of threaded part of bolts: bolts of HR system have threaded length longer

than bolts of HV system (2.52.16 bolt diameter of HR system versus 1.91.45bolt diameter of HV system, in function of bolt diameter);

Mechanical property class: 8.8 or 10.9 for HR system bolts, 10.9 for HV systembolts.

In addition, there are a lot of other small differences that enforce the EN 14399 to codify:

This document on structural bolting reflects the situation in Europe where two technicalsolutions exist to achieve the necessary ductility of bolt/nut/washer assemblies. Thesesolutions utilize different systems (HR and HV) of bolt/nut/washer assemblies. Both systems

are well proved and it is up to the experts responsible for structuring bolting whether they usethe one or the other system.

It is, however, important for the performance of the assembly to avoid mixing up thecomponents of both systems. Therefore, the bolts and nuts for both systems are standardizedin one single part of this European Standard each and the marking of the components of thesame system is uniform.

Table 1 Systems of bolt/nut/washer assemblies

Bolt/nut/washer assemblySystem HR

Bolt/nut/washer assemblySystem HV

Generalrequirements

EN 14399-1

Bolt/nut assembly EN 14399-3 EN 14399-4

Marking HR HV

Property classes 8.8/8 10.9/10 10.9/10

Washer(s) EN 14399-5 or EN 14399-6 EN 14399-5 orEN 14399-6

Marking H H

Suitability test forpreloading

EN 14399-2 EN 14399-2

Preloaded bolted assemblies are very sensitive to differences in manufacture and lubrication.Therefore it is important that the assembly is supplied by one manufacturer who is alwaysresponsible for the function of the assembly.For the same reason it is important that coatings of the assembly is under the control of onemanufacturer.

Bolt system required, geometrical data and resistance class (only for HR system) arespecified in contract drawings.


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3.2 Coupling surfaces conditions before assembling

Columns and beams must arrive in shop/yard finished in every their part, includedend plates and T-squares. In case the coupling surfaces are ready for bolted joint,they must have been protected with corrosion preserving paper or equivalent; in case

they have been painted, or non protected or eventually the preservation is failed, theymust be conditioned as specified on the following.

3.2.1 Conditioning of coupling surfaces

The connections carried out with bolts are differentiated in not pre-loaded and pre-loaded. In the not pre-loaded joints, bolts work nearly exclusively by shear; in thepre-loaded connections the coupling is guaranteed by friction between the surfacesunder pre-loaded bolts working in tension (may also work under shear if someyielding happens).

3.2.1.1 Not pre-loaded shear-connections

The contact surfaces must be cleaned, free of grease, dirtiness, foreign materials,etc. They may be painted or shop primer preserved.

3.2.1.2 Pre-loaded shear-connections

The contact surfaces in the sliding resistant connection must be prepared accordingto the requirements of the following par. 4.1. If not immediately assembled (not withinthe next 12 hours after the sandblasting) and the bolts tightened, on the contactsurfaces may be applied a painting product with suitable friction coefficient. Thisproduct must have the friction coefficient qualified by test performed by a qualifiedtest institute and certified by a third party (Notified body); see para. 2.4.

4. SURFACES CONDITIONING AND BORING

4.1 Contact surfaces

The contact surfaces shall arrive in shop/yard prepared as defined in the aboveparagraphs; in any case they must be according to the contract drawings. If notprepared and in lack of specification the following instruction shall be applied.

1) Shear connection Bearing type. No special provision for the contact surfaces isrequired. Surface must be plane, machine worked, and must be cleaned by wirebrushing or flame with removal of all the free rust.

2) Shear connection Slip-resistant. If not otherwise required by contract drawings,surfaces shall be in accordance with EN 1993-1-8 3.9.1 Table 3.7 and EN 1090-1

8.8 Prospect 7: class of friction surfaces C (for a design slip factor =0.3). Thesurfaces of the contact joints shall be accepted when, at the workshop pre-assembling test, the contact effective surface shall be, at least, 80% of the total

joint surface. The check shall be made by thickness gauges.

For convenience we show the table and prospect before mentioned. From EN 1993-1-8 3.9.1:


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From EN 1090-1 8.8:

Prospect 7: Friction surfaces classification

Class Treatment

A Sandblasted surfaces, with removed any free rust, not painted; Sandblasted surfaces, spray metallized with aluminum; Sandblasted surfaces, metallized with a zinc based product and subjected to friction

factor test to have a friction factor not lesser than 0,5.B Zinc-alkali silicate paint 5080m, applied on sandblasted surfaces.

C Surfaces cleaned with wire brushing or with flame cleaning, with all free rust removed.

D Not treated surfaces.

4.1.1 Contact surfaces protection over painting

1) Contact surfaces for slip-resistant connections shall be preserved, during theelement painting, by covering it with suitable adhesive papers treated withantirust products or painting it with a stripping or cereous antirust film.Alternatively they can be painted with a, suitable for friction factor, primer.

2) After assembly the contact surfaces shall be protected against infiltration ofwater, oil and other contaminants. This may be made by:

a) Application of silicon rubber along all the junction perimeter;

b) When specified in contract documents, bolting the contact surfaces withinterposed fresh paint and, then, painting the junction perimeter to close anypossible opening.

4.2 Boring

All the drills shall be made by drilling machine, being excluded the punching machine use.

After drilling and/or boring the holes edges must be free of burr (beveled).

When it is possible, holes should be drilled with a diameter suitably reduced (at least2 mm) and successively they should be bored (or reamed) to the final diameter. After


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that the pre-assembled elements shall be assembled finished in every part, with theaid of suitable assembling pins and bolts (as under mentioned for Bolts in precisionbores).

In any case, misalignments of holes that not permit the bolt passing are not allowed.

In such cases it is necessary to bore the hole at a greater diameter with a suitablesubstitution of the interested bolts. The use of over sizing or slotting of holes must beauthorized in writing by API.

Drilling/boring diameter/distances shall be in accordance with contract drawings; inlack of specifications the following instructions shall be applied.

1. Diameters:

a) Nominal tolerances for hole-bolt assembly is required according to EN 1090-1 8.1 point Dimension and location of holes: normal holes (1 mm M12/14, 2mm M16-24, 3 mm M27 and larger).

b) In those joints in which the bolts work in shear with a precision coupling, the

hole-bolt tolerances must not exceed 0.3 mm, included the tolerances (inaccordance with EN 1090-1 8.10 the hole-bolt coupling may be h13-H11).

c) The orthogonality between the hole axes and the bolted surface must be

within 1. If it is greater for contingent reason (e.g. a joint interesting alaminated shape) it shall be made use of angulated washers.

2. Distances

Spacing and distances must respect the specification of EN 1993-1-8 3.5Positioning of holes for bolts and rivets.

4.2.1 Shear bolts joints

Where it is allowed a joint subsidence under load, the hole-bolt gap may be definedaccording to EN 1090-1 8.1 point Dimension and location of holes: normal holes.

We recall the 4.2points

4.2.2 Friction bolts joints

Misalignments of holes that not permit the bolt passing are not allowed in any case.See 4.2.

4.2.3 Bolts in precision bores

When the joint subsidence under load is not allowed, bolts shall work in shear with aprecision coupling, with gap between hole-bolt not exceeding 0.3 mm (see EN 1090-1 8.10 Bolts in precision bore and pins). This situation is typical for pinnedconnections.

Holes for this type of bolting/pinning must be drilled with a diameter suitably reduced(at least 2 mm) and successively they shall be bored (or reamed) to the finaldiameter after that the truss to build shall be assembled finished in every parts, withthe aid of suitable assembling pins and bolts.

5. BOLTING PROCEDURE

5.1 Determination of bolts lengthFigures represent the characteristic quantities of a bolt and its clamp length.


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Figure 1 - Bolt representationFigure 2 - Clamp length

5.1.1.1 Bolts according to EN 14399-3 (HR type) and EN 4014 EN 4016

(normal bolts)For joints bolted with bolts type HR according to EN 14399-3 the suitable bolt lengthin function of the tightening thickness may be defined with the following table.

Table 1 HR type bolt length in function of Clamp Length

nom min max min. max. min. max. min. max. min. max. min. max. min. max. min. max. min. max.

35 33,8 36,3 16 21

40 38,8 41,3 16 26 19 21

45 43,8 46,3 20 31 19 26 24 22

50 48,8 51,3 25 36 19 31 24 27 25 26

55 53,5 56,5 30 41 19 36 24 32 25 31 28 28

60 58,5 61,5 35 46 27 41 24 37 25 36 28 33 30 31

65 63,5 66,5 40 51 32 46 24 42 25 41 28 38 30 36

70 68,5 71,5 45 56 37 51 30 47 25 46 28 43 30 41 34 38

75 73,5 76,5 50 61 42 56 35 52 31 51 28 48 30 46 34 43

80 78,5 81,5 55 66 47 61 40 57 36 56 28 53 30 51 34 48

85 83,3 86,8 60 71 52 65 45 62 41 60 38 57,8 30 55 34 53 39 47

90 88,3 91,8 65 76 57 70 50 67 46 65 43 62,8 37 60 34 58 39 52

95 93,3 96,8 70 81 62 75 55 72 51 70 48 67,8 42 65 34 63 39 57

100 98,3 102 75 86 67 80 60 77 56 75 53 72,8 47 70 42 68 39 62

110 108 112 77 90 70 87 66 85 63 82,8 57 80 52 78 39 72

120 118 122 87 100 80 97 76 95 73 92,8 67 90 62 88 51 82

130 128 132 97 110 90 107 80 105 77 103 71 100 66 98 55 92

140 138 142 107 120 100 117 90 115 87 113 81 110 76 108 65 102

150 148 152 117 130 110 127 100 125 97 123 91 120 86 118 75 112

160 158 164 107 133 101 130 96 128 85 122

170 168 174 117 143 111 140 106 138 95 132

180 178 184 127 153 121 150 116 148 105 142

190 188 195 137 162 131 160 126 158 115 152

200 198 205 147 172 141 170 136 168 125 162

M30 M36

S t min and S t max

M20 M22 M24 M27Thread d

l

M12 M16

It must be put attention when the threaded part of the bolt has been required to notbe included in the shear plane; in such case, the bolt length must be chosenaccepting a greater length sticking out the nut. It must be selected the minimum boltlength for required clamped part.


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5.1.1.2 Bolts according to EN 14399-4 (HV type)

For joints bolted with bolts type HV according to EN 14399-4 the suitable bolt lengthin function of the clamp length may be defined with the following table (extracted fromthe Appendix 1 of EN 14399-4

Table 2 - HV type bolt length in function of Clamp Length


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5.2 Boring test

The Manufacturer, after has made the temporary shop assembling and has made theboring, must perform (with the API witness as by QC) the following test:

Geometries and design correspondence check,

Boring check,

Working check,

Visual and dimensional check of the contact between the elements to join,

After the test, trusses or girders that shall be dismantled before erection in site, mustbe assembled by temporary bolts and pins for shipping.

The Manufacturer shall directly provide the bolts and nuts, and every other material,required for pre-assembling.

A dimensional check report shall be issued and send to API.

5.3 Presentation (shop pre-assembly)

When explicitly required by the contract and/or by the job material requisition, theplatforms of at least two elevations, chosen by API, shall be pre-assembled in theworkshop. Any reduced pre-assembling shall be agreed upon with API.

5.3.1 Support and fixing devices

The required material, the extensions and the modalities for carrying out the pre-assembling, when required, shall be discussed with API who will reserve the right toaccept or reject the Constructors proposals.

Tack welding use is forbidden for pieces assembling in preassembling or erectionphase.

5.3.2 Holes correspondence check and spinning

Any adaptation and/or adjustment activity of prefabricated elements during theassembling on site (due to misalignment of holes, cuts, addition of materials, overtolerances, etc.), if attributable to the responsibility of the Manufacturer, shall becharged to him.

5.4 Bolt tightening

Bolts must be tightened until the minimum specified preload. In lack of specificationin contract documents adopt (EN 1090-1 8.6):

Fp = 0.7fubAs where

Fp = minimum preload [N],

fub= bolt ultimate tensile strength [MPa]

As = tensile stress area [mm2].

Tightening shall be carried out using one of the following methods, if not otherwisespecified in contract documents:

1. Turning moment check method, according to EN 1090-1 8.7.2 (preferred),

2. Part-turn method, according to EN 1090-1 8.7.3,

3. Direct tension indicator method, according to EN 1090-1 8.7.4,

4. Combined method, according to EN 1090-1 8.7.5.


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The greater difficulty to verify the preload depends from the tightening moment which90% is need to win the friction resistance among the rubbing surfaces during thetightness. A simple formula is the following:

M = (kdFu)/1000 where:

M = Tightening moment [mN],d = nominal diameter of bolt [mm],Fu= preload [N],k = torsion coefficient depending from:

Dimensions and shape of the rubbing surfaces, Friction coefficient among the surfaces, Screwing up method.

In first approximation it may be taken: k = 0.21 0.17 the greater valuesfor small diameter bolts.

GENERAL NOTE: If a bolt set, tightened at minimum preload, is unscrewed, it mustbe removed and the whole set permanently discarded, if not diversely, and explicitly,

specified in contract documents.For convenience the following tables for bolting tests, could be used.

5.4.1 Shear bolting

Bolts only subject to shear: it is allowed a tightening reduction to the 80% of thedesign preload as quoted in EN 1090-1 8.6 on condition that the suitablemeasure against the auto- screwing off is specified. In any case vertical axis boltsmust be assembled with upwards head.

Bolts also subject to axial load (preloaded bolts): bolts must be tightened to 100%of the value quoted in EN 1090-1 8.6.

5.4.2 Friction bolts

All bolts must be tightened to 100% of the value quoted in EN 1090-1 8.6.

6. CHECK

6.1 Visual examination

Bolted joints shall be subjected to a visual examination; in this check shall be made

use of instruments and examined: Tightening of bolts, by a torque wrench;


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Tightening of bolted plates, by thickness gauge: surfaces between which the 0.1mm thickness gauge does not pass will be considered in contact.

6.2 Dimensional Examination

A dimensional check of bolting shall be performed according to contractual drawings.

7. FINAL DOCUMENTATION

The documentation that the Constructor shall send to API for approval or informationis listed in the relevant MR, defining also the times when the documents shall beissued (see 2.4). API reserves to send his comments within 21 days from the datewhen the documents have been received. API approval shall not hover theConstructor from his responsibility as regards the correct execution of the drawingssupplied to the effects of a good erection and assembling.

The supply shall not be deemed completed unless all the documents listed in the MR

relevant to this specification have been issued.The documents sent together with the material shall show the quantity, the marknumber of pieces dispatched and the relating construction drawing number. Anycharge due to wrong filling out of the shipping documents shall be at theConstructor's expenses.

Final documentation shall be inspected and checked by API for compliance to itsspecification E0063.0.

E0055 Rev0 Bolted Steel Joints

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