The present specifications define the criteria to be adopted for procurement testing and controls on workshop production of materials for metal girding, as well as all control checks to be performed during provisional acceptance and construction assembly and installation.

1.2 FIELD OF APPLICATION

The present specifications are applicable to all metal structures and mixed steel and concrete structures for the construction of railway bridges.

1.3 CORRELATED DOCUMENTS

The present specifications are correlated with European standards currently in force, and in particular the standards listed below:

Eurocod 1 or ENV 1991 sections 1 and 3 – Actions on the bridges.

Eurocod 3 or ENV 1993 section 6

ENV 1090 sections 1 and 5 – Steel constructions

EURONORM 10155 : Construction steel resistant to atmospheric corrosion. Quality standards.

EN 10025 : Non-alloy hot rolled steel products for structural use – technical supply conditions.

EN 22553-24063 : Technical drawings – Designation and schematic welding representation.

EN 10002 section 1 (Jan.1992) - Mechanical Testing.

EN 10045 section 1 (Dec.1991) – Welding

EN 10160 : Non destructive testing on metallic materials – ultrasound control checks on steel plate over 15 mm – pulse reflection methods.

EN10056 : Hot rolled steel products – equal wing and rounded edge angle bars – standard profile _ measurements and tolerance limits.

EN 10029 : Hot rolled general purpose steel plate –thickness equal or over 3 mm. Measurement, weight and shape tolerance limits.

EN 25817 : Arc welded steel seams – Imperfection quality level guide (N.B. for all welding, the imperfection tolerance will be B quality level, except for parapets and planking that may be C level).

EN 25520 : Imperfection classification in fusion welding, with explanatory comments.

EN 970 : Non-destructive control checks on fusion metals –Visual control checks applicable where not specified otherwise.

EN 287 : Welders qualification tests.

EN 288 : General regulations for 1st and 2nd part fusion welding .

EN 729-2-3 : Certified quality system by an accredited EWF and SINCERT organisation

EN 719 : Personnel in charge of welding activity coordination.

EN 473 : Personnel in charge of non-destructive control checks.

2 SECTION 2

2.1 GENERAL INFORMATION

For all metal structure construction the Railways must employ a suitable Construction company specialized on «Construction, assembly and installation of metal structural work» with an internal organisation capable of managing all construction and welding activities in the workshop and/or on site realisation of the contract work.

The constructor must demonstrate a quality system according to EN 729-2-3 and EN ISO 9001:2000 standards certified by an accredited EWF and SINCERT organisation.

The following requirements are necessary in particular:

· Welders certified by an accredited SINCERT organisation according to EN 287 standards;

· Welding procedure certified according to EN 288-3 standards;

· The constructor must have performed a railways steel bridge for one of Railways Company of one European Union Countries, in the same fields as those included in these specifications, in the last two years ( to be demonstrated with an appropriate declaration signed by the competent organisation)

· The constructor must possess his own accredited workshop according to EN CEI 45001 standards.;

· The constructor must possess an NDC sector (non-destructive control ) according to EN ISO 9001.2000 standards certified by an accredited SINCERT and EWF organisation and employ certificated level 2 personnel according to EN 473 standards;

The application of the present Technical specifications does not relieve the constructor of the drawing up of the Quality Plan and the Quality Control Plan, which are obligatory.

The aforesaid document must be presented to the Railways who reserve the right to make any necessary modifications. It remains understood that said document must be approved by the Project design engineer and the WS.

2.2 CONSTRUCTOR’S DUTIES AND LIABILITIES.

The constructor must present the Railways and Work Supervisor (WS) with two copies of the workshop plans as well as the lists of all materials necessary for girder construction.

Any eventual replacements or changes in either profiles or structures that the Constructor may decide to make compared to the indications included in the approved plans, must be requested prior to modification, explaining the reasons for any changes, and the WS will have the sole and unquestionable right to authorise said changes or not.

In cases where the Constructor is not able to procure rolling plates, these may be obtained from sheet metal cut with oxyacetylene flame, plasma, laser or by mechanical means, but in this case the various pieces must be cut so that the rolling direction of the plates coincides with the predominant stress direction of the plates.

2.3 QUALITY AND CHARACTERISTICS OF THE MATERIALS TO BE EMPLOYED.

2.3.1 MAIN STRUCTURES

2.3.1.1 Materials subject to protective surface treatment.

The steel used for all main structures such as load bearing beams, “I” beams, cross beams, bracing, joint covering, plates and node point squares plats, must comply with the following quality standards:

S275 C/D1 EN 10025/90 (now S275 JO /J2G3)

S355 C/D1/DD1/DD2 EN 10025/90 (now S355JO / S355J2G3 / S355K2G3 / S355K2G4)

Where more precise information is not available, the quality grade choice will be made according to the following table:

Temperature for performing Charpy V resilience tests (Minimum required value on an average of three standard tests: 27 J)
Steel thickness (mm)	Important elements subject mainly to traction or fatigue (even if compressed)	Important elements subject to static compression or secondary elements
s ≤ 25	T = Tm	T = Tm + 20
25 < s ≤ 40	T = Tm - 10	T = Tm + 10
40 > s ≤ 50	T = Tm - 20	T = Tm
s > 50	T = Tm - 20 T = Tm	T = Tm

T = Temperature for performing Charpy V tests (°C)

T_m= Minimum working temperature (°C) to be established in agreement with the WS.

All mechanical and chemical characteristics must comply with EN 10025 standards

For steel plate destined for composite profile construction with partial and complete penetration welding (except for composite profiles with butt welding), or in any case even with fillet welding, where the plate is subject to stress in the direction transversal to the rolling direction ( e.g. cross joint) ductility levels must be controlled through transversal traction tests according to EU 10164 standards with class 3 average pinching with Z35 rupture point for S275 (ex Fe 430) plates and Z25 rupture point for S355 (ex Fe 510) plates.

For structural elements not destined for welding, the instructions according to EN 10025standards for S275 C and S355 C steel apply. In this case silicon killing is permitted.

2.3.1.2 Self-protecting materials

The use of materials that are self-protective against environmental corrosion is permitted: S355 C2KI now S355JOW, S355J2G1W, S355K2G1W, S355K2G2W.

The mechanical and chemical characteristics must comply with EN 10155 standards.

2.3.1.3 Secondary structures

S235JR EN 10025 may be used for secondary structures such as guard railings, plank support bars, foot-guards and any elements that are not part of the main structure .

S235JR EN 10025 is to be employed for striated or meshed plate for planking or foot-guards. This plate will have a thickness of 5 mm + 2mm striating.

Grate planking must be made from cell-structured hot galvanised grating with 30 x 30 mm mesh, bearing plate 30 x 3 mm, and secondary rod 20 x 3 mm, or some other type with equivalent characteristics in weight and capacity. The steel material used is show on EN 10025.

2.3.1.4 Tests on materials

All materials employed must be ordered with tests to be performed according to EN 10204 standards, item 3.2 of prospectus I and supplied so that they result unquestionably as qualified products. The supplier and/or foundry must identify all pieces with a nucleated punch showing the casting and plaque number. The certificate of origin issued by the manufacturer according to EN 10204 standards, must contain the chemical composition of the casting analysis prescribed in prospectus II of EN 10025 standards.

The following tests must be performed in relation to the aspects described above:

All profiles, plates, large sized plates and sheets must be subjected to mechanical and chemical tests on three samples taken from each 400 KN, or fraction thereof, of materials obtained from the same casting and with thicknesses that do not differ more than 4 mm ( for C, T and double-T shaped bars, reference will be made to the wing thickness);

Specimens will be taken from each sample for the following tests:

1 traction test

3 resilience tests

1 bending test (where specified)

1 chemical analysis (for each casting)

1 pinching test (where specified)

It must be remembered that in order to belong to the same 40t test unit, the plates must have been subject to the same processing cycle and heat treatment.

For plates, large-sized plates and sheets destined for welded profile construction, as well as the tests relative to mechanical characteristic control checks according to EN 10025 standards, other tests must be performed according to agreements established with the supplier on material order by the Constructor, relative to the additional limits described in the paragraph «Materials Subject to Protective Surface Treatment»;

Surface condition and dimensional characteristic tests must also be performed on all materials.

The aforesaid tests must be performed in foundries and the results of all tests must be included in the product quality certificates issued by the foundry in question.

2.3.2 NUTS AND BOLTS

Bolts will be exclusively «high resistance type».

Bolt types will be selected according to the type of joint necessary, and in particular:

for joints with slot bolts: EN 20898 1st part : class 8 nuts

For friction joints: class 10.9 screws EN 20898 1st part: class 10 nuts

In both types of connection the washers and plaques will be in C50 EN 10083, tempered drawn steel with hardness : HRC 32 ¸ 40.

Refer to prospectus II and III EN 20898 for mechanical and chemical characteristics.

All nuts, bolts, screws etc must be certified according to EN 20898 standards by the manufacturer.

2.3.3 CONNECTORS

All materials must comply with the following prescriptions:

Stake connectors

Steel suitable for stake connector manufacturing and compatible for welding with the material of the structural element in relation to the stakes; the product should be marked with the following mechanical characteristics and be included in the product certificates:

- fy ≥ 350 N/mm²

- fu ≥ 450 N/mm²

- Elongation: ≥ 15% - - -- Pinching: ≥ 50%

All welded stakes will be subjected to visual control checks to ensure that no discontinuity exists in the metal collar after welding.

No cracks are permitted in stake welding.

Bending tests will be performed on 5% of the stakes.

Connectors produced from profiles, plates etc.

A steel equivalent to that used for the structural element to which the connectors are welded.

2.3.4 SUPPORT EQUIPMENT

For instructions concerning support equipment, refer to the project drawings that must contain all fundamental equipment characteristics .

3.4 II.1 ADMISSIBLE STRESS

The admissible stress levels permitted for basic materials and welding are those indicated in the Standards adopted for the project.

3.4.1 RULES AND INSTRUCTIONS CONCERNING STRUCTURAL DETAILS AND WELDED JOINTS.

3.4.1.1 General indications : aspects of project design.

1 During the project design stage, priority must be given to easy assembly of the various structural elements, to make accessibility convenient for the welder.

2 When uniting structural elements through welding, the joint types must comply with the following:

· Full penetration butt joint;

· Full penetration T joint;

· Partial penetration T joint (with a bevel of at least 1/3 of the minimum thickness used and the seam side at the foot ³ ½ of the same thickness);

· T joint with corner seams;

· Lap joint with corner seams.

Full or partial penetration joints and the preparation of the edges that will be included in the drawings or on the edge tables for revision where necessary, will be defined by the Constructor after prior approval by the control organisation, and will be approved by the Railways.

For butt welding of two main elements of different thickness, the thicker element must be gradually tapered until it is equal to the thickness of the thinner element.

For full penetration T joints the welding must be gradually widened until the width is at least equal to 1.3 times the thickness S1 (minimum employed thickness) of the plate on which it will be attached (fig. 2.3) :

L ≥1.3 S₁

To guarantee an adequate joint between the core and the platband.

For partial penetration T joints, where no particular instructions are specified for edge preparation, assembly, and control of final measurement, the caulk opening angle must not be less than 45° and the height of the resistant section will be assumed as being equal to the depth of the caulk «gpp» (fig.2.5).

For joints with corner seams, the height of the theoretical groove «g» is calculated starting from the theoretical caulk vertex; in general the «g» grooves should be appropriately sized and in any case no less than 4 mm, or half the thickness of S1, if this is thicker than 8 mm.

In cases where different project instructions exist, the height of the groove «g» will be the height of the resistant section to be considered in calculations. (fig. 2.1).

The side of the corner seams «z» (fig. 2.2) that unite the two plates with thicknesses S1 and S2 (S1 < S2) must be sized adequately so that they satisfy the calculation conditions, and normally, also the following limit:

S₁/2 ≤ z ≤ S₁

For thicknesses S₂ >10 mm it is better to apply the rule z ≥ z₁, on condition that it is not in conflict with the previous limit.

The z1 limits are shown in the following prospectus:

S₂(mm)	10÷20	30	50	70	100
z₁(mm)	5 ÷ 6	8	11	13	14

The shape of the seam or the first pass in multiple pass joints, must respect the following relation indicated between the width (Lp) and the depth (g + p):

0.5 Lp ≤ g+p ≤ 1.1 Lp

where p = penetration depth;

Lp= the slanted side of the welded seam.

The control check of the correct seam form will be performed using production standards.

In the case of overlapping platbands (e.g. beams with uniform resistance) in the area of the end section of the overlapped platband, an adequate joint must be guaranteed between the double layer and the platband, however, a closing corner seam must be added in any case, with a groove height that is at least half the height of the thickness of the platband, and united to the side seams.

3 It is possible for beam core transversal stiffeners not to be welded to the stretched platbands; in this case they must be positioned at a distance more than 25 mm, and no more than 5 times the core thickness, from the platband level surface in order to permit the placing of the seam around the end of the stiffener. (fig. 2.7).

When welding the core stiffener to the platband, the foot of the seam must be smoothed using a grinder to make any variations in shape gradual and to eliminate any possible notching.

4 For the construction of elements composed of caissons, that are internally inaccessible, according to the project design requirements and compatible with the destination of the structural element, a ½ V must be prepared (cut into the plate with the lesser thickness) with a support plate or with corner seams as shown in figures 2.8a and b. Permanent metal supports are forbidden for elements subject to fatigue.

5 Particular care must be taken in the construction of elements in which the platbands meet at an angle that is fairly acute, such as those used to form «gussets» (fig. 2.9 ). The platband of the gusset is welded to the platband of the beam until the welding has penetrated the vertex deeply ,the opening of the angle α will depend on the beveling of the angle ω formed by the two elements to be united together; their relation will be that established by the UNI 11001 table, as follows:

	20° ≤ ω < 50°		α =	70°
	50°	≤ ω ≤ 70°	α =	60°
70°		< ω < 90°	α = 50°

The space at the vertex of the joint will be ≥ 3 mm.

6 The connecting joints between core and platband on the main beams (bridle bars of the reticulated girders or longitudinal girders for solid walls) will generally be executed with appropriately sized corner seams.

In cases where the rails are positioned near the core, the core- upper platband joints on the girders must normally be full penetration type, unless otherwise specified according to the instructions in item 5 section 3.4.1.2.

The core – upper platband joints of girders on mixed structure scaffolding will be executed in the same manner. The node points of the lower bridle bars on reticulated girders, the fixing gussets of the transversal beams or any other zones that are particularly important will normally be executed with strong penetration joints, except in the case of butt node points that require full penetration. In any case, when the beam is executed with corner seams outside the node point zone, the core edges must be changed gradually (from grooved edge to right angled edge) for a length no less than 300 mm (transition zone).

In the case of mixed structure bridges with ballast, for slab thickness generally greater than or equal to 40 cm, partial penetration will be permitted for welding between the core and the upper platband.

3.4.1.2 General indications: construction aspects.

1 Particular care must be taken to avoid sharp angled cuts or openings. All openings and cuts made using any method whatsoever must have well-rounded corners; alternatively but only subject to prior authorisation by the State Railways, these connections could be replaced by holes drilled at the vertex of each angle.

2 The vertex on the corner seams must be completely united.

3 When butt welding T or double T beam elements together, the platband and core joints will normally lie on the same section.

In certain cases, the core and platband joints can be staggered according to a Z formation, studied appropriately for the purpose.

When butt-welding the platbands an access opening must be arranged on the core to guarantee access to the welded joint from all sides during execution and control.

A normal semi-circular access opening with arc of a circle ends could be placed on the core for this purpose. Wherever there is severe stress or fatigue or where direct load is applied on the platband, an elongated grooved access opening will be applied so that it can be welded in closed position after the core and platband joints have been completed and the relative non- destructive control checks have been performed. ( figures. 2.11 a, b ).

In any case, for all core and/or platband butt welding , before beam composition, and after the prescribed non-destructive control checks, the welding area on the platband or the core in question must be smoothed before assembling the beam elements for corner welding.

4 In the case of a junction formed by three or more structural elements ( for example in a composite beam cross welded between core, platband and stiffening ribs) adequately sized access openings must be foreseen to permit correct joint welding and control checks. (figures 2.7 - 2.12).

The access openings must be arc of circle, or in any case in a conveniently shaped form . The welding seams that reach the access opening edge must be welded around it.

5 Wherever there may be any danger of lamella tearing, the constructive details must be designed so that they prevent or at least minimize the retraction tension in unfavorable directions, that is , in directions perpendicular to the rolled surface.

Several methods can be used to avoid these situations such as :

· plan the assembly sequence with great care so that welding is performed with the least restriction possible;

· modify the order of pass execution;

· perform buttering on any unfavorably orientated rolled surfaces;

· perform partial penetration seam welding with prepared edges .

In certain cases, rolled materials can be used with reduced microinclusion content or even forged elements instead of rolled materials.

With a view to minimizing the danger of lamella tearing, for full penetration T joints, the expression that provides the welding width at the foot ( L = 1.3 x S1 ) is considered valid for the values S1 ≤ 1/3 S2 (fig. 2.3).

Where these conditions are not satisfied and the thickness S2 is more than 40 mm, the value of L must be increased gradually until it reaches a value equal: L ≥ 2 x S1.

3.4.1.3 Advice concerning welded joint details :– edges

Automatic heat cutting ( flame-cutting or plasma) is recommended, or cutting using tool machines such as planes and cutters that are essential for U and J beveling etc. manual or automatic flame-cutting or other methods are permitted where surfaces are finished later with precision grinding to remove all traces of cutting grooves and other rough surfaces.

3.4.2 WELDING METHODS

3.4.2.1 General information

1 The welding methods taken into consideration are the electric arc welding methods described in item 3.4.2.3.

2 All welding will be performed using a specific heat input(HI), calculated according to the formula :

HI = 0.06 x I x V / v (kJ/mm)

where : I = welding current (A),

V = welding voltage (V),

v = translation speed from heat source (mm/min),

that does not diverge from the measured value by more than 20% during test trials for welding technique qualifications. Generally the maximum heat input will be 2.8 kJ/mm while the minimum should not result any lower than 0.8 kJ/mm.

3 All equipment necessary for performing welding operations must be in perfect working condition and their fundamental characteristics must be controllable by the State Railways.

3.4.2.2 Welding methods specifications

Welding method specifications must be calculated for every joint to be performed in production by the constructor company. Calculation methods for welding methods must comply with the instructions provided in EN 288 standards, part I.

All welding methods must result as qualified according to the instructions provided in the following chapter.

3.4.2.3 Applicable welding methods.

The welding methods in question in these technical specifications are as follows:

· Manual shielded electrode welding;

· Automatic submerged arc welding;

· Semiautomatic and automatic continuous arc core welding with gas protection

· Manual, semiautomatic or automatic welding for connectors;

• semiautomatic and automatic full continuous arc welding for civil and industrial structure welding; for bridges, this use is limited to secondary elements such as handrails and planking elements.

When using continuous arc methods, robot systems may be used . However, in general, automatic type welding is preferable.

Other methods may be authorised in special cases, after qualification tests, non destructive control checks, and approval by the WS.

For this purpose, the Contractor must present precise technical proposals concerning the qualification and control methods for the particular case in question.

1 Comments concerning weld material

The weld materials employed must be able to guarantee deposit mechanical characteristics as similar as possible to the basic materials. In particular, the difference between the minimum values in the specification tables between the yield stress of weld materials and those of the basic material must not exceed 100 N/mm2.

The tenacity of the basic material and the weld material deposit must be calculated using the same type of technological testing. The difference between the minimum values in the specification tables between the tenacity of weld materials at an established temperature must result as being at least equal to the basic material.

In general, the chemical composition of the deposit should be substantially equivalent to that of the basic material.

With steel possessing improved resistance to atmospheric corrosion, weld materials for normal C/Mn steel can be used, except for the last two finishing layers where, in any case, it is necessary to use weld materials with an adequate percentage of Cu-Cr-Ni at least equal to 10% more than that of the basic material, especially in the case of Ni, that must not result less than 1.5 %.

.2 Manual method using shielded electrode welding;

For S275 and S355 type steel, E44 and E52 series , quality class 4, basic electrodes must be used.

These electrodes must be marked with the symbols that provide a guaranteed Kv resilience value at least to the minimum temperature of the basic material tests (e.g. Kv 00 for JO type; Kv 20 for J2 type, etc.).

The Constructor is bound to indicate the commercial brand of the electrodes he intends using for welding operations.

The use of non-homologated electrodes is permitted only after method qualification tests as established in item 2 of 3.4.3.1.1.

3 Automatic submerged arc welding method

Automatic submerged arc welding could be used in the version with a single arc or twin arc welding head or with several welding heads, in the single head version or opposite head version.

The choice of the arc-flow combination must be made to guarantee that the deposit mechanical and composition characteristics are the same as those of the basic material.

As well as all the other general characteristics necessary for other methods, welding procedure for jointing using submerged arc welding must also include all aspects necessary for identifying the welding installation, number and arc layout, as well as the location of the welding heads compared to the joint.

4 Arc welding method with gas protection

The welding position must be indicated in the welding method specifications relative to this procedure.

The protection gas must be a blend such as Ar-CO2, Ar-CO2-O2, Ar-O2 with a dew point that must not be lower than -40°C. Pure CO2 can be used if recommended by the weld material manufacturer.

5 Connection welding procedure.

Connectors for adjacent slabs can be welded to the platband using semiautomatic core continuous arc welding (NOT to be used for stake welding). Stakes must be welded using shielded electrode or automatic methods.

For this case, the only welding method permitted is the use of a de-oxidizing capsule on the end of the stake and ceramic ferule.

The platband surface in the connector welding zone must be cleaned in the same manner as any other welding edge .

3.4.3 WELDING PROCEDURE SPECIFICATION QUALIFICATION

3.4.3.1 General information

All welding procedure specifications for structural construction must be qualified according to the instructions in the items listed below and accepted by the Railways before manufacturing start-up.

3.4.3.1.1 Welding Procedure Specification Approval

1 Welding procedure qualification tests.

In general, except for cases described in item 2 in 3.4.3.1.1, welding procedure specifications must be qualified and certified according to EN 288 part 3standard requirements..

Welding procedure certification must be issued by an Official Organisation.

2 Homologated materials

Welding procedure qualification tests do not need to be performed for manual welding with shielded electrodes homologated on steel with resistance class up to 510 N/mm² (S355).

3.4.4 QUALIFICATION OF PERSONNEL EMPLOYED IN WELDING ACTIVITIES.

3.4.4.1 Welders and welding operators.

Welders involved in production for manual and semi-automatic welding application must be qualified according to EN 287 Part 1 standards, for all work positions and procedure in use. Welders who will be working in the present contract context must pass a welding test including a T joint with corner seam to be evaluated according to the standards described above.

Personnel working on automatic and robot welding systems must possess EN 1418 certification.

Welder qualification must be endorsed with the demonstration of the appropriate qualification certificate issued by an accredited SINCERT and EWF organisation.

The Constructor’s welding coordinator must keep records in a special register for this purpose, of all qualified welders and operators, updating the records according to any qualification variation (class extension, renewal) .This register must also contain all periods of inactivity by all welders and/or operators in relation to specific methods.

Both the register and the qualification certificates must be available in the Constructor’s plant and presented to WS personnel on request.

Furthermore, the WS has the right to request new qualification testing whenever welding results show faults or defects that can be attributed to insufficient professional capacity.

3.4.5 WELDING EXECUTION METHODS

3.4.5.1 General information

1 Before beginning any welding operations, the edges of the parts to be united and the adjacent zones for a width of 100 mm must be subject to visual and instrument control checks to ascertain the absence of any cracks or flaking, and to ensure the correct preparation conditions. No welding repairs are permitted on edges and the aforesaid adjacent zones.

The main element edge surfaces to be welded must be examined previously using a magnetoscope.

In the case of full penetration cross joints specific ultrasound control checks (EU160 cl. B) must be performed on the intermediate plate area to be jointed to guarantee the absence of flaking or excessive segregation (at least 100 mm on each side of the joint). This ultrasound control can be omitted for steel plate with guaranteed striating in the direction of the thickness ( Z > 25% for material S355, and Z > 35% for material S275, according to EN 10164).

2 Electrode or arc switch-on must be performed on the appropriate auxiliary production test plate placed or tack-welded at both ends, or in groove.

The use of end production test plate is obligatory in any case, for all butt welding, for automatic welding, and for all details where welding must be sealed afterwards, as in arc stiffening on platbands.

3 The welders and the welding operators are responsible for controlling the surface of each pass to ensure the elimination of all scoria, profile defects and surface irregularity or roughness. If the results are not satisfactory, the area must be subject to grinding before performing the following pass.

4 On all butt and full penetration corner seams, as a general rule the reverse side grooving should be performed followed by a restart. Subordinately, a support plate or welding without grooving can be performed by welders with special class qualifications.

5 For automatic stake welding, each time a welding stage is begun on framework, each welder must submit the first two welded stakes for control checking; if the visual check is satisfactory, the stakes will be hammered to a 45° bend. After bending, they will be straightened and must not show any signs of cracking or lack of fusion.

If this control check shows negative results, the Constructor is bound to re-organise the welding technique on auxiliary plates and repeat the tests on the first two welded stakes on the same framework, a second time.

All stake welding in the workshop or on the work site must be performed exclusively by personnel with specific experience. The personnel in question must demonstrate their knowledge of machine setting parameters and welding specifications by performing a practical test before the Railway representatives or nominated control organisation.

6 Special care must be taken during piece assembly, providing for spot-welding to safeguard pieces from wrenching from base materials or from welding defects. In particular, wherever possible, assembly U-bolts must be used ; the U-bolts must be removed by grinding the relative welding seams.

Joints can be assembled with welding points (spots) as a rule, no shorter than 50 mm in length, removable during the execution of the welded joint.

In butt joints that are grooved back to front, spot welding is performed on the rewelding side.

Any points/spots to be incorporated in the welded joint must be ground at the edges and examined during welding operations; all cracked areas must be automatically eliminated.

In the case of welding on ceramic plate, as a rule, groove spot welding is not required.

3.4.5.2 Pre-heating and interpass temperatures.

Pre-heating application on a welded joint before welding execution, and maintaining the temperature during welding are some of the factors that determine the welding heat cycle, together with the thickness of all the structural elements that make up the welded joint (combined thickness in fig. 6.1) and the specific heat input. In turn the heat cycle produces different metallurgical structures in the molten area and in the thermally altered area of a joint according to the chemical composition of the base material and the weld material.

3.4.5.3 Special prescriptions.

1 It is strictly forbidden to perform welding using any method whatsoever when the environmental temperature is lower than –5C.

2 The Constructor’s workshop must be equipped with a depot for stocking welding material (electrodes, arcs, flux, etc) that is perfectly closed and with a relative humidity level no higher than 50%.

3 Once the original packing of the fluxes and electrodes have been opened, they must be dried at a temperature between 350° - 400° C for two hours and preserved in an oven at 150°C until the moment of use.

Non-melted flux can be recovered and reused if mixed with new flux (mixture of 30% of previously used flux with 70% of new flux). At the end of the work shift, any unused flux must be removed from the machines and stocked in a special container. It can be used again later after drying procedure as described above.

The efficiency of the electrode and flux drying and preservation for submerged arc welding may be controlled on Railway’s request, by checking the diffusible oxygen content conducted on the deposit, using the testing methods described in AWS A4.3, standards: mercury column technique (required value < 5 ml/100g).

4 When performing T joints or overlaid lap joints with corner seams, the surfaces that are in contact with each other must adhere well. In these joints the maximum tolerance distance is «d» (fig. 6.2), within the limits indicated below, and in any case with adequate seam increase:

· In the case of manual and semi-automatic welding: d = 1 mm for thicknesses less than or equal to 10 mm; d = 2 mm where the minimum thickness of the joint is greater than 10 mm;

· In the case of automatic submerged arc welding : d = 1 mm.

Inn the case where the separation distance is wider, surface buttering may be necessary to correct the distance, otherwise, a different edge preparation could be proposed as an alternative to the WS.

5 For the terminal section of the joint between the core and the platband on T beams and double T beams, executed with inter-penetrating seals , as a rule, no welding should be performed for a length of 150 mm before the execution of butt joints between the beams.

To permit correct butt joints on profiles, in the case where the core – platband joints result as complete, a section of about 150 mm of the core-platband welding must be eliminated from each side of the joint (unseaming).

As a rule with butt joint welding the operation sequence is as follows:

· Preparation of the edges to be welded and the elimination of the core ends;

· Assembly and spot welding of the structural elements (core joint space is larger than the platband space);

· Platband welding preferably at the same time, or through partial alternating filling on both platbands;

· Core welding;

· Core to platband welding in the unseamed areas..

On the other hand, in the case of beams welded with corner seams, a transition area of about 200 mm must be foreseen (figure 2.11).

6 As a rule, all elements united incorrectly must be cut and re-welded.

7 Any structures deformed as a result of welding must be straightened by localised heat application or heat straightening using mechanical means.

The welded joints of elements subjected to straightening must be examined using adequate non-destructive control methods after straightening according to the extension and the type of joint.

The temperature of the heated area (generally about 600°C) will be defined according to the base material supply status.

The parts heated during straightening must be substantially free of all stress and external force, except for those resulting from the mechanical means used during heat application.

3.4.6 WELDING DURING THE ASSEMBLY STAGE ON SITE.

1 Welding during assembly stages on the work site must comply with all prescriptions concerning structural details, welding procedure methods, preserving of base materials and weld material, execution methods, personnel employed in welding activities, as well as the welded joints and their testing as described in the items listed above.

Particular care must be taken in protecting groove edges against rusting and in providing appropriate protective shelter during welding operations, with the use of suitable equipment. This is especially important when different methods are used other than shielded electrode welding; in this case the Constructor will provide for adequate procedure that must describe all the protection means against atmospheric agents in the area where welding is performed.

2 Maximum care must be taken the study and assembly of the joints and edge preparation to ensure correct execution of all joint welding. Precise instructions must be furnished by the metal structure constructor for these aspects.

3 The welding procedure envisaged for assembly welding will generally be manual welding with basic homologated shielded electrodes, and similar to the base material for mechanical and chemical characteristics.

Other procedure is permitted on condition that the instructions in item 1 are observed after obtaining Railway authorisation.

4 Welders working in on site welding positions must be qualified. Tests proving welders’ capacity may be requested on site especially in the case of particularly important joints or joints to be welded in positions with difficult access, with the execution of pre-production test plates.

5 Joints performed on site will be controlled using similar methods to those applied in the workshop; the same criteria for extended controls apply in the case of negative joint welding results. In any case, butt joints on main structures executed on site must be subjected to magnetoscope and ultrasound control checks.

6 On resistance class S355 steel joints, or those of higher classes, and with Sc combined thickness greater than 100 mm, non-destructive control checks must be performed no earlier than 48 hours after welding operation completion.

3.4.7 NON-DESTRUCTIVE CONTROL CHECK METHODS

3.4.7.1 General prescriptions

All welded joints will be visually controlled, and also controlled using the equipment appropriate to the joint type, the kind of fault or defect that may be present, and the work location, according to the present instructions.

As a rule, instrumental control checks include magnetoscopic, X-ray and ultrasound tests on the finished joint, and a control check with penetrating liquids only on surfaces with grooving on the reverse side of full penetration joints. Final instrumental control checks are performed after satisfactory visual checks as a rule.

Generally ultrasound controls on full penetration butt joints will be performed on thicknesses over 30 mm. For thicknesses up to 30 mm , normally testing will be performed using X-rays, and where necessary integrated with ultrasound controls for elements subject to particular stress.

1 Non-destructive control test personnel qualifications

The personnel charged with non-destructive testing of welded joints must possess at least level 2 certification according to EN 473 standards. Alternatively, at least level 2 ASNT or CICPND certification could be accepted.

3.4.7.2 Execution methods

1 Visual control check

Visual control checks will be performed according to EN 970 standards.

2 Magnetoscopic control checks

Magnetoscopic control checks will be performed .

3 Penetrating liquid control checks

Penetrating liquid control checks will be performed.

4 Ultrasound tests

4.1 Sensitivity setting

Sensitivity grading for tests will be performed by tracing a reference curve at “constant amplification” using the methods.

4.2 Sample block

The reference block for sensitivity setting must have the same thickness, (with a tolerance of ± 10%), as the greatest thickness of all the elements that compose the joint to be tested.

4.3 Execution methods

Normally ultrasound testing on welded joints will be performed by the WS or the authorised organisation. The execution methods are generally those of best class. In any case, for assembly and construction stages it must be kept in mind that it will be necessary to perform control tests when the majority of the joint surfaces are not accessible (for example in full penetration cross joints and T joints, the main joint must be controlled before the welding of the second core, to permit access to the platband of the part opposite the core that was welded first).

The examination methods must be specified clearly in the control report.

4.4 Reflector registration.

All the reflectors that produce a response with an amplitude greater than or equal to 20% of the reference curve for control sensitivity, must be carefully analysed to define the geometrical characteristics of any faults or defects, to form a supposition on its nature and to evaluate it in terms of acceptability.

All the non-geometrical indications with an amplitude over 20% of the reference curve must be registered in the test report

Registration of the test report must be performed so that the zones where response variations were registered are easily identifiable, for example, using a coordinate system with origins based on a punched reference mark.

3.4.8 INSTRUMENTAL CONTROL CHECK RANGE

3.4.8.1 Visual control checks

Normally all welding must be visually controlled 100%.

3.4.8.2 Instrumental control checks.

The Constructor is bound to describe in an appropriate document the complete range of non-destructive instrumental control checks he intends applying on production jointing, with explicit reference to an established railway bridge; alternatively, the indications describing the range of control checks may also be included on the construction technical drawings.

The control check range program must be approved by the Railway after approval by the organisation charged with control procedure.

Normally the program to be followed is that described in the points below.

1 Corner seal or partial penetration joints.

Magnetoscopic control checks will be performed by the Constructor on 100% of the joints on all the more important bridge structures, and recorded in the test report.

The WS or another authorised organisation will perform control checks in a testing plant, limited to 30% of the length of every seal of each joint, whether corner seals or partial penetration; this procedure may be increased according to the type of welding method used and the results of the tests performed.

2 Full penetration joints.

The magnetoscopic control checks will be performed by the Constructor on 100% of the full penetration butt or T joints, and recorded in the test report. The Constructor will also perform ultrasound tests on at least 50% of the length of each joint.

Different procedure may be approved by the WS as established in item 3.4.8.2. for particularly important joints because of structural statics or because of particular stress, in other words, wherever control checks must be extended to 100% because of the nature and entity of the stress.

The WS or another authorised organisation will perform magnetoscopic control checks in a testing plant, on 30% of the length of all seals, and ultrasound control checks on 100% of the established percentage. Intensification of control checks after negative results

3.4.8.3 Intensification of controlcheck after negativ results

Whenever any faults are revealed through instrument control checks on samples, all controls are intensified. Normally a welding section on each side of the faulty area is examined for a distance of at least 100 mm, but keeping in mind the type of fault and the importance of the structural element. Further control checks will be performed using at least the same method that revealed the defect.

All repairs executed with or without welding must be recontrolled using the same method that revealed the defect; the zones where the unacceptable defects were found using ultrasound control, must also obviously be recontrolled using the same method that revealed the defect; furthermore at least two other sections must be controlled for each repaired section, these sections will be chosen by the testing personnel.

In cases where repairs are numerous, or where unacceptable systematic faults are discovered, the structural elements or the joints in question will be eliminated.

When the presence of systematic defects cannot be attributed to unsatisfactory execution methods or lack of capacity on behalf of the welder or the machine operator, the constructor must repeat his qualification procedure.

In any case, the constructor must provide for the replacement of the eliminated joints; the new joints must be recontrolled using the same method that revealed the defect, on twice the quantity as that prescribed initially.

3.4.9 WELDING QUALITY

3.4.9.1 General prescriptions

All welding seams must be regular, smoothly attached to the base material and without excess metal. The defect acceptability criteria are described in detail below.

1 Visual control checks

The quality of the welding seams controlled visually must comply with the acceptability criteria established in EN 25817 standards, group B, for first class joints and group C for second class joints.

2 Magnetoscopic Control checks

The quality of the welding seams controlled using a magnetoscope must comply with the acceptability criteria established in EN 25817 standards, group B, for first class joints and group C for second class joints.

3 Ultrasound control checks

The acceptability criteria for application to defects detected by ultrasound control checks must comply with the following prescriptions:

a) – reflectors which according to the echo position and characteristics are interpreted as cracks, lamella tearing, lack of complete penetration, lack of correct fusion with edges, will not be accepted, regardless of the response amplitude.; elongated discontinuity localised at the vertex of welded seams and at a distance equal to the thickness of the platband, compared to the external face of the platband, will be considered as lacking in penetration if these cannot be classified by US control as scoria;

b) – elongated reflectors with echo amplitude greater than or equal to 150% of the reference curve will not be accepted;

c) – elongated reflectors with response echo amplitude between 80% and 150% of the reference curve will not be accepted if;

• their length results greater than ½ S, where S is the minimum thickness among those connected to the joint in question with a maximum of 8 mm, for S lower than or equal to 25 mm;

their length results greater than 1/3 S, with a maximum of 15 mm, for S greater than 25 mm;

• the total length of the reflectors in the welded section of 400 mm, with the greatest proportion of defects results as being longer than 20 mm;

• Two adjacent reflectors with respective lengths L1 and L2, at a distance “d” will be considered as a single length defect of length (L1 + L2 + d), if d ≤ (L1 + L2) and if the response amplitude of at least one of the two defects is greater than or equal to 80% of the reference curve.

3.4.10 REPAIR PROCEDURE.

3.4.10.1 Repairs without new welding operations.

Surface and profile defects may be eliminated, even without having to perform new welding operations if the depth of the defects does not exceed 10% of the thickness in question ( or the least of the thicknesses in question, when the defect is in the molten joint zone), but in any case the depth must not exceed 2 mm.

The defect can be eliminated through grinding; this must be controlled visually with great care, and in the case of doubt, with a magnetoscope; the hollowed surface must be well smoothed with the adjacent material.

3.4.10.2 Welded repairs

The Constructor must draw up one or more repair procedures for welded joints for approval in the same manner as the welding execution procedure.

This procedure must include at least the means and methods to be adopted for gouges or hollows, the pre-heating temperature, and all aspects concerning the envisaged welding procedure.

3.4.10.3 Hollow repair execution

Hollows must be ground with a grindstone or carbon electrode and compressed air blast (arc-air) followed by leveling grinding. The surface of the hollow must comply with all previously described requisites.

3.4.10.4 Execution methods

As for spot welding, the pre-heating and interpass temperature will be 25°C higher than the established temperature for joint welding, according to approved welding procedure.

The welding procedure to be adopted is normally basic homologated manual shielded electrode welding, with chemical and mechanical characteristics similar to those of the base material.

Continuous arc welding could be used to repair welded joints with hollows longer than 250 mm.

For weld material preserving and welding techniques, refer to the indications provided for production welding.

Tightly drawn seams are not permitted (specific HI < 0.8 KJ/mm) to fill hollows or scratches in order to prevent excessive local hardness.

Repairs must provide smooth surfaces well attached to the adjacent material; where necessary added seams or repairs should be smoothes using a grindstone or button mill cutter.

3.4.11 CONTROL CHECKS ON PRODUCTION TEST PLATES

Appropriate extensions in the same material as the beams, must be included on 30% of the beams welded in the workshop (production test end plates) . The WS also reserve the right to request the application of production test plates on joints executed on site.

The production test plates will be used to measure the hardness in molten areas, in thermally altered areas, and in the basic metal, as well as evaluation of correct welding penetration.

The methods and extent of macrographic control checks on production test end plates will be defined by the Constructor through appropriate procedure that will be presented and approved by the WS after approval by the appointed control organisation. Normally these control checks are performed on samples according to a percentage to be defined in the procedure described above. For the joints executed in the workshop this percentage cannot be less than 5% of the welded joints; for joints executed on site, the number of tests will be established each time according to the type of joint, the thickness, and the welding method applied.

Normally the procedure should provide for the execution of macrographic controls on suitable production test plates, including in the following cases:

• welding procedure application by the Constructor for areas where there is no consolidated applicative experience;

· During initial stages of automatic or robot method application.

Hardness tests will be performed in at least three points in the same area (basic material, molten area, thermally altered area) and it must be proved that the Vickers hardness test ( HV10) does not exceed the limits established in the certification procedure in any point.

3.4.12 WELDING ACTIVITY REPORT.

Records containing all welding work must be kept by the Constructor according to EN 729 standards, describing all details and circumstances concerning the work performed .

These records must contain a list of all the welding activities performed, all repairs, the names of each welder, the welding methods used (parameters, materials, pre-heaters, etc) any intermediate control checks, and any other aspects that may be considered useful for the contract work.

These records must be shown to the control personnel on work completion: copies of the records will be delivered to the Railways representatives for start-up tests and to be kept in the contract work files.

4.2.3 JOINTS WITH FRICTION BOLTS.

Misaligned holes that do not permit the passage of the appropriate bolt are forbidden. Oval drilling of holes is not permitted and in the case of difficulty, the hole diameter must be increased and a larger bolt inserted.

For the perpendicularity between the bolt axis and the bolted surface, a deviation of ≤ 3° is permitted.

All bolts must be carefully tightened to 100% of the official value. Careful control checks must be performed on bolt tightening and appropriate certification must be issued. The prescriptions in relation to this aspect are provided below:

Bolts can be tightened using pneumatic spanners on condition that said spanners are equipped with torque limit devices;

Tightening control checks must be performed using a dynamometric spanner, or some other suitable instrument that guarantees precision to ± 10%. This control must be made on 20% of the bolts, selected so that it covers all joints in question. Even if only one single bolt does not comply with tightening standards, control checks must be made on 100% of the joint bolts.

Any bolts that result tightened with a torque greater that 5% over the prescribed value will be eliminated and replaced.

Bolt tightening operations will be performed as follows:

a) The joint must be placed in the final position using an appropriate number of “plugs” able to stiffen the joint suitably and to ensure that holes are in correct alignment;

b) Bolts will be tightened with a torque equal to 60% of the prescribed value beginning with the bolts inside the joint and proceeding towards the external bolts;

c) Tightening to 100% torque in the same order as that described above.

Bolt tightening control checks will be performed as follows:

a) Marking of the nut, screws and plate to identify the relative positions;

b) Loosening of the nut with a 60° rotation taking great care not to rotate the screw. The screw head must be held securely from the opposite side;

c) Nut tightening with the prescribed torque and a control check to ensure that it returns to its original position.

4.2.4 TOLERANCE

For tolerance and processing quality providing for H11 tolerance for screw diameter. (See previous item)

4.2.5 BOLT PROTECTION

All bolts complete with washers must be immersed in a suitable protective substance compatible with the proposed painting cycle.

4.2.6 PIECE ASSEMBLY

For pieces to be curved, curving operations must be performed hot (bright red) and pieces must be left to cool slowly.

It is forbidden to continue curving operations on pieces that are no longer bright red.

Lastly, when plates and wide plates (or the strips cut from sheet metal) are united to form composite structures (such as T beams) these must be appropriately finished with suitable machining action to respect the dimensioning in the drawings and the prescribed tolerance levels.

4.2.7 DIMENSIONING TESTS ON SINGLE PIECES.

The WS will also control the dimensions of the single pieces to ensure that they correspond with project dimensions, taking prescribed tolerance levels into consideration.

4.2.8 TOLERANCE LEVELS FOR WELDED BEAMS AND ASSEMBLED ELEMENTS.

The tolerance levels described in the table in Fig. 2 are applicable to all welding and welded element dimensions .

Tolerance levels for assembled elements.

The following tolerance levels are applicable to assembled elements:

stiffener straightness:

+/- 4 mm for h less than or equal to 2000 mm;

+/- 8 mm for h greater than 2000 mm

-bolted joints:

+/- 1 mm of level difference between the parts to be joined and planarity difference between the adjacent parts in contact; - reverse deflection

-0, +15% of the theoretical reverse deflection

As well as pieces that present production defects, the WS reserve the right to also refuse pieces on which even one single dimension is less than that prescribed , although keeping in mind the admitted tolerance level, and the Constructor will be responsible for all charges and obligations as a result of faulty pieces.

It is clearly understood that all material used to replace refused pieces must be previously tested using the same methods as the accepted pieces, already described in this article, and the Constructor will be solely responsible for any delay in respecting contract terms.

4.2.9 PAINTING AND PROTECTIVE COATINGS.

Structures must be painted with two coats of rust-proof, non-polluting paint with a zinc phosphate base (C.T. 101) and two coats of synthetic paint (C.T. 111), or cooked linseed oil based paint, as decided by the WS. Each coat must have a thickness no less than 4 micron when dry.

The rust-proof paint must be applied in the workshop once the metal surfaces have been sanded to almost white level. The RAL colour for the various coats will be decided by the Principal.

All paint must be mixed frequently to ensure that the pigment does not settle in the bottom of the container.

Once they have been sanded, the surfaces in contact with the friction joints must be protected with a suitable adhesive film or with a special paint approved by the WS, until they are assembled on site. These preparations must be specified in the work plans.

Any chipping or damage to paint during assembly work will be touched up on the work site.

5 SECTION 5

5.1 ON SITE ASSEMBLY

The Constructor must issue the Railways with a detailed project plan and program, outlining the procedure he intends following for metal structure assembly and installation. Another safety construction must be provided under the structure for operator’s safety and for convenient control check operations on the assembled structure.

As well as all the control checks to be performed according to instructions in the previous section, during the assembly stage all assembly work must be controlled to prevent any defects that can occur frequently, as listed below:

· inversion or change of element position;

· shape correction using flame equipment, resulting in element forcing;

· failure to provide the packing foreseen in the project design;

· dirty or soiled joint cover surfaces;

· bolts that are not tightened correctly;

• bolting sequences that are not followed in correct order (for example: from interior to exterior for joint covers);

· elements assembled out of square ( horizontal and vertical);

· non-corresponding holes;

· unstable temporary girder supports;

· element assembly using spot welding;

· on site welding that is not foreseen or that is performed incorrectly;

• welding performed on rusty, painted, or galvanised surfaces, or surfaces that are not adequately prepared;

• insertion of inadequately dimensioned packing ( for example- only between external parts or visible surfaces) ;

· failure to repaint surfaces under staking areas;

• connector welding without adequate material pre-heating and without surface preparation;

· insertion of bolts with size and length not in compliance with project specifications;

• replacement of deformed, un-usable or missing elements, with others with uncertain mechanical and chemical characteristics;

· repairs on elements using operations that will compromise element integrity;

· non-authorised on-site welding;

· incomplete welding on connectors ( collars);

· paint that does not adhere to the support;

· painting performed on site outside the approved cycle;

· welding procedure not suitable for the assemble stage in question;

· Failure to clean the water draining holes;

• spot welding for reinforced concrete rods on connectors or platbands on mixed steel – concrete structures;

· Final supports not perfectly plane;

· material handling using devices that risk material deformation and/or cutting (e.g: cutting by scarfing clippers);

• failure to clean (sanding) the upper platband surfaces on mixed steel –concrete structures;

· defects as a result of incorrect material transport procedure on site;

• defects and distortion in certain structural elements as a result of incorrect structure installation, especially in sundry items;