Guide-EN13155-A1-Rev000 - Altervista...Title Microsoft Word - Guide-EN13155-A1-Rev000.doc Author...

EN 13155-A1 Suite - User's Guide Date 2014/11/01 Rev. 0

1 Informative

Spreadsheets are protected but without password. End user can freely modify the spreadsheets to adapt them to your own necessity. For this fact spreadsheets are provided without warranty of any kind. The price that end user pay “one time” for the spreadsheet it’s only due to cover a little part of the cost of the time dedicated to build it. The author has made all possible effort during the compilation of the spreadsheets but there is no warranty about presence of compilation errors. Any error that end user will find on the spreadsheet will be corrected without supplementary cost. The author is not English mother tongue. So it's possible to find, in the guide and into the spreadsheets, phrases that are not correctly translated. For any correction or explanation contact: [email protected] For using correctly the spreadsheets it's necessary a good knowledge of the following matters: strength of material mechanical engineering material science theory of machine

and at least of the following standards: EN 13155: 2009 ENV 1993-1-1: 1992 FEM 1.001 EN 13001-3-1: 2013 and related parts of EN 13001 Machine Directive 2006/42/CE IIW: Recommendations for fatigue design of welded joints and components

1.1 Guide contents

1 Informative 1 2 Why EN 13155 Annex A.1 2 3 Spreadsheet for verification to the elastic limit 3 4 Spreadsheet for verification against buckling for axial compression and bending 3 5 Spreadsheet for verification of web buckling by shearing 7 6 Spreadsheet for buckling verification of unstiffened plates 8 7 Spreadsheet for bolt connection 10 8 Spreadsheet for welded joints verification 11 9 Spreadsheet for lifting lug verification 12 10 Spreadsheet for checking against brittle fracture 13 11 Spreadsheet for calculation of section properties - Classification 14 12 Remarks 16

12.1 Overall safety factor using EN 13155............................................................................. 16 12.2 Heavy loads................................................................................................................... 17 12.3 Fatigue strength............................................................................................................. 17 12.4 Lifting accessories and Finite elements method............................................................. 18


2 Why EN 13155 Annex A.1

The standard EN 13155 is an harmonized standard to the Machine Directive 2006/42/CE and it is a C-type standard. So we have that: -Application of the specifications of a C-type standard on the basis of the manufacturer's risk assessment confers a presumption of conformity with the essential health and safety requirements of the Machinery Directive covered by the standard- From EN13155 for this kinds of lifting accessories: Lifting beams C-hooks Lifting forks

mechanical resistance of load bearings parts could be assessed without static tests. Besides EN 13155 Annex A.1 avoids fatigue assessment limiting the accessory's life to 20000 cycles. For this scope we have to check the lifting accessory under the following load case:

DL WLLX S 2S where SDL is the "accessory self weight" and SWLL is the "working load limit", in other words the maximum load which can be lifted in working condition.


3 Spreadsheet for verification to the elastic limit

The spreadsheet perform the verification to the elastic limit typing the calculated stresses. We have only to choose the steel grade and the part thickness. The admissible normal and shear stresses are the same defined in EN 13001-3-1 which regards design of cranes.

fig. 1

EN 13155 use the von Mises criterion for plane stress.

4 Spreadsheet for verification against buckling for axial compression and bending

In this case EN 13155 doesn't cover the procedure for performing this kind of verifications but it prescribes to use ENV 1993-1-1: 1992. Why ENV 1993-1-1: 1992? Because for dated standards only reference cited applies (see EN 13155:2009 Chapter 2: Normative references). The choice of the standard (ENV 1993: 1992) for performing this kind of verifications maybe is not the best because in the bibliography of EN 13155 there is FEM 1.001 - Rules for the design of hoisting appliances - which prescribes "classical methods" which are fastest and simpler than ENV 1993-1-1: 1992 methods. For example FEM 1.001 refers to the historical standard "DIN 4114" and for what I know the first edition is dated 1939. DIN 4114 has been replaced by DIN 18800. But it's only my opinion. The spreadsheet performs the verification for combined axial compression and bending moment. In the first part we have to insert actions and section properties. In the "EN 13155-A1-Suite" there is a spreadsheet for calculating plastic section modulus for common rolled or welded sections (see Chapter 11). If plastic section modulus is not known for a conservative results we can put the elastic section modulus. The verification is applicable to sections of Class 1,2 and 3. The differences among this classes are defined as follow:

Class 1 cross-sections are those which can form a plastic hinge with the rotation capacity

required for plastic analysis


Class 2 cross-sections are those which can develop their plastic moment resistance, but have limited rotation capacity

Class 3 cross-sections are those in which the calculated stress in the extreme compression fibre of the steel member can reach its yield strength, but local buckling is liable to prevent development of the plastic moment resistance

Class 4 cross-sections are those in which it is necessary to make explicit allowances for the effects of local buckling when determining their moment resistance or compression resistance

Verification of Class 4 section is not simple because it involves an iterative procedure for defining the reduced resisting section area.

fig. 2

In the second part of the spreadsheet we have to choose the "imperfection coefficients".

fig. 3

This coefficient could assume four values: 0.21 - 0.34 -.0.49 - 0.76 depending from the buckling curve. The following tables helps to choose the coefficient and the buckling curve.

Buckling curve a b c d Imperfection coefficient 0.21 0.34 0.49 0.76


Cross section Limits Buckling about axis

Buckling curve

h/b > 1,2 and tf 40 y-y z-z

a b

h/b > 1,2 and 40 <tf 100

y-y z-z

b c

h/b 1,2 and tf 100 y-y z-z

b c

Rolled I or H sections

h/b 1,2 and tf > 100 y-y

z-z d d

tf 40 y-y z-z

b c Welded I or H sections (also with

flange reinforcements) tf > 100 y-y z-z

c d

Hot rolled hollow sections / any a

In general any b Welded box sections

Thick welds and b/tf < 30 - b/tw < 30 any c

U, L, T and solid sections any c

After that we have to define the "Equivalent uniform moment factor", the section class and the partial safety factor.

fig. 4

"Equivalent uniform moment factor" must be calculated from the following table.


Moment diagram Equivalent uniform moment factor βM Ends moments

1 1

M, 1.8 0.7

Moments due to in-plane lateral loads

M,Q 1.4

M,Q 1.3

ENV 1993-1-1 covers other moment diagrams. The table above resume the frequent cases for lifting beams, C-hooks and lifting forks. Once inserted the "Equivalent uniform moment factor" we have to define the section class. Class 4 sections are excluded. The partial safety factor is defined from National Annex. Frequent values are 1.05 and 1.1. After that we have the result of verification for combined axial compression and bending moment. Consider that if axial compression or bending moment is not present, the verification is still valid. Finally the spreadsheet performs verification for Lateral torsional buckling. This verification is necessary above all for I section beams which have low torsional moment of inertia. The worst case is when loads are applied above the section shear centre and it always happens for C-hooks but it could happen also for lifting beams. Generally hollow sections and box sections doesn't give problems for LT buckling.

fig. 5

For this scope we have to insert the coefficient M,LT from previous table and referred to y axis. After there is a problem regarding the elastic critical moment. The calculus, based on ENV 1993-1-1, is generally not simple and takes a lot of time. So the fastest way is to use LT-Beam free software downloadable from this website: https://www.cticm.com/content/ltbeam-version-1011


Finally the imperfection coefficient for LT buckling could assume only two values: 0.21 for rolled sections and 0.49 for welded sections.

5 Spreadsheet for verification of web buckling by shearing

EN 13155 prescribes to perform this verification under certain conditions. Generally this verification is not necessary.

fig. 6

The method used is the "simplified post-critical method" that's valid also for stiffened web. For further information refer to ENV 1993-1-1.


6 Spreadsheet for buckling verification of unstiffened plates

This verification is not mentioned on EN 13155 but it could be necessary for welded box lifting beams. I choose the procedure from EN 13001-3-1. Why EN 13001-3-1? Because it's mentioned on EN 13155 Annex H, because EN 13001-3-1 is harmonized to Machine Directive 2006/42/CE and is C-type standard. The method is a simplified approach based on DIN 18800-2 and is fast but for low a/b ratio could be too conservative. A similar approach is followed by FEM 1.001 which is derived from DIN 4114. In the first part of spreadsheet we have to insert the plate dimensions, stress actions (derived from classic theory of beams) and we have to define if "a" edges are both restrained or one of the two is free. Case A and B stress distribution are defined on the following figure.

fig. 7

fig. 8

After that we have to define manually the safety factors for normal and shear stresses.


fig. 9


7 Spreadsheet for bolt connection

Bolt connections are not mentioned on EN 13155. I choose the procedure from EN 13001-3-1. Why EN 13001-3-1? Because it's mentioned on EN 13155 Annex H, because EN 13001-3-1 is harmonized to Machine Directive 2006/42/CE and is C-type standard. The spreadsheet performs verification for shear resistance and bearing resistance of the bolted plates. Shear force is relative to one bolt.

fig. 10


8 Spreadsheet for welded joints verification

EN 13155 Annex A1 follows the same procedure of EN 13001-3-1. Correction coefficients depend from type of weld, stress direction is relative to welding axis and weld quality is defined as per EN ISO 5817 (which replaces EN 25817). Types of weld are described below.

Type T1 Type T2 Type T3 Weld with full penetration or Back-welded

Butt welded Double semi V-weld,

semi V-weld for T joint

Weld with full penetration or Back-welded

Weld with small web Double semi Y-weld,

semi Y-weld for T joint

Weld without full penetration

Double semi Y-weld, semi Y-weld for T joint

Double fillet weld Fillet weld

The figure below shows an example of determination of stresses for a fillet weld where normal stress is perpendicular to the welding axis and the shear stress is parallel.

wr

wr

F2alF

2al

r wl l 2a

1 2a 0.7 min(t , t )

fig. 11


9 Spreadsheet for lifting lug verification

This kind of elements are not mentioned by EN 13155 but they are frequently used especially for lifting beams. The procedure adopted from the verification has been derived from: Germanischer LLOYD - Rules IV for the Certification and Construction Industrial services – Part 7: Offshore substation – Chapter 2: Structural design – Edition 2013 I chose this procedure for the classical approach for calculating stresses which follows a verification to the elastic limit. The only difference with GL procedure are the partial safety factors which for EN 13155 Annex A1 depend from SDL/WLL ratio (see table below)

Germanischer LLOYD procedure: adopted safety factors EN13155-A1 safety factors Partial safety factors: Total loads: 1,35 Normal stress: 1,45 Shear stress: 2,16 Combined stress: 1,25

Total safety factors for stresses: Normal stress: 1,96 Shear stress: 2,92 Combined stress: 1,69

Note to EN 13155-A1 safety factor a) 0% corresponds to lifting lug which carries working load only b) For pure shear stress the safety factor it's √3 times safety factor for normal stress

Depends from the ratio SDL/WLL SDL/WLL

(%) Total safety factor for

normal stress 0% 2 5% 1,95 10% 1,91 15% 1,87 20% 1,83 25% 1,8 30% 1,77 35% 1,74 40% 1,71 45% 1,69

fig. 12


On the first part of spreadsheet we have only to choose the steel grade and the lifting lug geometry. Germanischer LLOYD procedure considers a minimum transverse force Fy equals to 5% of Ps. If lateral reinforcing plates are not present relative dimensions must be 0. In the second part there is a verifications to the elastic limit for A.1 load case.

fig. 13

Germanischer LLOYD procedure is valid for pin shackle diameter at least 0.95 times lug hole diameter:

pind0.95

d

Which means that lifting lug design is based on pin shackle's diameter.

10 Spreadsheet for checking against brittle fracture

For EN 13155 A.1.4 must be carried out a verification against brittle fracture as per ENV 1993-1-1 - Annex C or within the table A.3. For this purpose Table A.3 could be too conservative and so the spreadsheet carries out the verification with ENV 1993-1-1 Annex C. In fact Table A.3 limits the thickness to 40 mm and considers loading rate corresponding to R2: R2 loading rate: Impact loading - Applicable to high strain rate, explosive or crash conditions Another advantage is that using Annex C it's possible to obtain intermediate temperatures and less restrictive verification for non critical members. Spreadsheet restricts temperature range until to -20°C. Some discrepancies could be found with Table 3.2 of ENV 1993-1-1 for large thickness (150-250 mm). Reduced value of steel yield strength is valid only within Annex C of ENV 1993-1-1. Table A.3 of EN 13155 restricts plate thickness to 40 mm. This thickness limit could be taken as a prescription. Same conclusion could be deduced from Table A1 of EN 13155.


fig. 14

11 Spreadsheet for calculation of section properties - Classification

The spreadsheet calculates the more important section properties for: I o H sections Circular hollow sections Rectangular hollow sections Box welded sections

Properties calculated are: Area moment of inertia Elastic modulus Plastic modulus Classification of section

Classification of section is based on ENV 1993-1-1: 1992 and it's slightly different from classification made with more recent version of EN 1993. For web and flange classification under combine axial and bending refers to ENV 1993-1-1: 1992.


fig. 15


12 Remarks

12.1 Overall safety factor using EN 13155

Overall safety factor changes from a member to another. Remembering equation A.1:

DL LLX S 2W and considering as an example a C-Hook we have a slightly difference between safety factor for bolted connection and pin respect to the bottom of the C-beam.

fig. 16

It's only an example: if SDL equals 7% of SWLL we obtain:

1

2

1,932

In general the safety factor varies between the following two extreme values:

DL

WLL

DL

WLL

S2SmaxS.F. 2; minS.F. S1S

For an extreme case for which is SDL = SWLL minimum value of safety factor equals 1,5.


12.2 Heavy loads

In general more heavy is the load and less are the accelerations. Referring to Norsok R002 - 2012 the test load decreases for WLL over 25 tonnes. For example for a 25 tonnes WLL the test load equals 2WLL, for a 50 tonnes load the test load equals 1.8WLL (90 tonnes). As per Machine Directive 2006/42/CE: Machinery and lifting accessories must be designed and constructed in such a way as to withstand the overload in the static tests without permanent deformation or patent defect. Strength calculations must take account of the value of the static test coefficient chosen to guarantee an adequate level of safety. That coefficient has, as a general rule, the following values: (a) manually-operated machinery and lifting accessories: 1,5; (b) other machinery: 1,25. As per EN 13155 individual verification must be carried out with A.1 or A.3 method. Type verification must be carried out with A.1 or A.2 method. Individual verification: verification carried out on every item produced Type verification: verification carried out on one or more samples representative of a particular design and size of product before it is first placed on the market

Equipment Type verification Individual verification Lifting beams A.1 or A.2 A1 or A3 C-Hooks A.1 or A.2 A1 or A3 Lifting forks A.1 or A.2 A1 or A3

A.2 method defines a test load equals to 3WLL and the accessory must withstand the to the test load without collapse - permanent deformation are admitted. A.3 method defines a test load equals to 2WLL and the accessory must withstand to the the test load without permanent deformation. In both cases after the force has been removed the accessory shall be examined for deformation, cracks and other defects. EN 13155 doesn't establish a difference based on WLL. So heavy accessories must be verified in the same way of light accessories. Obviously for a single heavy unit A.3 method could be expensive.

12.3 Fatigue strength

From EN 13155: This standard does not cover the hazards related to mechanical strength of structural elements of attachments designed for more than 20000 lifting cycles. EN 13155 doesn't take on consideration the load spectrum. So it's like that if the accessory always lifts the WLL. Considering a welded detail with a FAT of 40 MPa and subjected to a variation of nominal stress from 0 to 177.5 MPa in correspondence of the WLL (so for 2WLL maximum stress reach the limit of 355 MPa) the fatigue life is:

3

c

Mf

11720 cycles

For FAT 180 MPa (non welded component - for more detail see EN 13001-3-1) the fatigue life is:


5

c

Mf

700000 cycles

Calculus above doesn't take in consideration dynamic factors; spectrum factor equals 1 and safety factors 1.25. (Another consideration to be made is that for 11720 cycles detail is located in low cycles fatigue and nominal stress method is not the right approach) The purpose of calculations above is to make attention on low FAT welded details if they are subjected to high variations of nominal stress.

12.4 Lifting accessories and Finite Elements Method

FEM method for evaluation of a mechanical resistance of a lifting accessory could lead to wrong results in presence of singular point where the stress (e.g. the first principal) doesn't converge by reducing mesh size. Considering the case of figure below, the first principal stress doesn't converge and reaches a value that's more than the yield strength of the material. Decreasing the mesh size the discrepancy becomes more large. In this case could be difficult also to obtain nominal stress

fig. 17

In this case it's important to identify the peak stress and evaluate if it can be a factor of hazard for mechanical resistance taking into account that structural steel are very ductile and peak stress, in the most of cases, leads only to a local and restricted plastic deformation. This is valid if the component works above the transition temperature. For low working temperatures brittle fracture can occur also for ductile steels, above all in presence of welded detail and high values of the first principal stress. Fatigue strength could be evaluate with local stress approach methods (e.g Hot Spot method).

Guide-EN13155-A1-Rev000 - Altervista...Title Microsoft Word - Guide-EN13155-A1-Rev000.doc Author...

Documents

Transcript of Guide-EN13155-A1-Rev000 - Altervista...Title Microsoft Word - Guide-EN13155-A1-Rev000.doc Author...