Design of Connections

7/29/2019 Design of Connections

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DESIGN OF CONNECTIONS FOR STEEL

ELEMENTS ACCORDING TO ENV 1993-1-8


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WEB PANEL

IN SHEAR

CONNECTED

PARTS

Parts of a beam-to-column connection

Major axis joint configurationJoint configuration


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PARTIAL SAFETY FACTORS

Valorile numerice ale coeficientilor de siguranta pot fi impusi la nivelul normelor nationale de calcul.

Valorile recomandate sunt: M2=1,25; M3=1,25; M3,ser=1,1; M4=1,0; M5=1,0;M6,ser=1,0; M7=1,1


4/24

JOINTS RESISTANCE

DESIGN HYPOTHESES

The design resistance of the connection is determined through the individual design resistance of

its principal component parts.

The design of the connections may consider either a linear elastic analysis of a elasto-plasticanalysis.

Generally, when in a connection subjected to shear meet fasteners with different stiffness, the

fasteners with the a greater stiffness will take this force (exceptions are presented in this code)

Connection design is based on a realistic evaluation of the distribution of forces and moments

inside a joint. This evaluation calls on the hypotheses:

-Internal forces and moments are the result of joint resolution under external efforts;

- Every element as component of the connection is able to cope with these external efforts;

-After the distribution of internal forces and moments, the deformations resulted will not exceedthe capacity of deformation of bolts or welding between component parts of the connection;

-The distribution of the efforts to the component parts of the joint must be realistic evaluated

based on the relative stiffness of the elements of the connection;

-Deformations associated with any design model based on elasto -plastic analysis take into

account the rotation of the rigid body and/or any possible in plane deformations; the same case is

considered when the model is a physical one, tested in laboratory (according to ENV 1990)


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CONNECTIONS SUBJECTED TO SHOCK,

VIBRATIONS AND ALTERNANT SOLICITATIONS

METHODS FOR CONNECTING

WELDING

BOLTS WITH

LOCKING DEVICES

PRELOADED

BOLTS

INJECTED

FASTENERS

OTHER TYPES

OF FASTENERS

RIVETS

Anytime when the connection must be prevented from slipping, preloaded bolts will be

used, category B or C, as well as fit bolts, rivets or welding.

Parts of bracing system that take wind action or are used for insuring the general

stability will use fasteners in category A.


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ECCENTRICITY AT INTERSECTIONS

In joints where components will be eccentrically connected, bending moments along with axial

forces will be considered, excepting when this is not a relevant case, according to pt. 5.15,ENV 1993-1-8 and Annex BB 1.2, ENV 1993-1-1

Setting out lines in a chord-to-internal member connection


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BOLTED OR RIVETED CONNECTIONS

BOLTS, NUTS AND WASHERS

Reference standards: group 4, 7 and 6, ENV 1993-1-8

Classes of the bolts, according to ENV 1993-1-8;

Yield strength fyb and ultimate tensile strength fub for bolts in classes 4.6, 5.6, 6.6, 6.8, 8.8 si

10.9 presented in the table below will be adopted as characteristic values during the proces of

design and verifications.

Nominal values of limit yield strength fyb and of ultimate tensile strength

fub for different classes of bolts

ANCHOR (HOLD DOWN) BOLTS

Grades in reference standards, groups 1 and 4, concrete reinforcing bars

according to EN 10080 only if:

Bolts subjected to shear will have the nominal yield strength under 640

N/mm2 and those subjected to other kinds of stresses under 900 N/mm2


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CATEGORIES OF BOLTED CONNECTIONS

I. Connections subjected to shear:

Category A: Bearing type; classes 4.6 up to 10.9, no supplementary conditions imposed to

the faces in contact and no preloading of the bolt are required. Design ultimate shear force in

the bolt must not be exceeded by the design shear resistance, according to table and nor design

bearing resistance according to tables also.

Category B: Slip resistance in serviceability limit state: preloaded bolts for which the

slipping under shear efforts must prevented from during the serviceability limit state; slip

resistances are determined according to table and also, shear and bearing resistance forcesmust exceed the design shear force.

Category C: Slip resistance in ultimate limit state: the conditions are identical with those

imposed to B category but also, connections subjected to tension will be verified for the design

plastic resistance of the net cross section in ultimate limit state , according to ENV 1993-1-1

II. Connections subjected to tension:

Category D: tensioned bolts not preloaded:classes 4.6 up to 10.9, often subjected toversatile tensile efforts (braces).

Category E: preloaded bolts in tension: classes 8.8 and 10.9 of bolts for which the preloaded

stress is checked according standard group 7.


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CATEGORIES OF BOLTED CONNECTIONS

Category-verifications Criteria Observations

Connections subjected to shear

Type A

Bearing resitance

Fv,Ed Fv,Rd

Fv,Ed Fb,Rd

Bolts in classes 4.610.9 may be used,preloading is not necessary

Type B

Slip resitance under serviceabilitylimit state forces

Fv,Ed, ser Fs,Rd, ser

Fv,Ed Fv,Rd

Fv,Ed Fb,Rd

Bolts in classes 8.8 and 10.9 may be used,verifications for slip under limit state ofserviceability forces being necessary.

Type CSlip resistance under ultimate

limit state forces

Fv,Ed Fs,Rd

Fv,Ed Fb,Rd

Fv,Ed Nnet,Rd

Preloaded bolts in classes 8.8 or10.9, verificationsunder limit state of strength and stability beingapplied.

Connections subjected to tension

Type D

Resistance under tensile forcesof non preloaded bolts

Ft,Ed Ft,Rd

Ft,Ed Bp,Rd

Bolts in classes 4.610.9 may be used, they donot have to be preloaded; for the determination ofBp,Rd, see table.

Type E

Resistance under tensile forcesof preloaded bolts

Ft,Ed Ft,Rd

Ft,Ed Bp,Rd

Classes 8.8. or 10.9 are used and for Bp,Rd the use

of table is imposed

Design tension force, Ft, Rd includes any force due to prying. For bolts in shear and tension see also tables.


10/24

POSITIONING OF HOLES FOR BOLT AND RIVETS

Distances and spacing Minimum Maximum

Structures made from steels according to EN 10025with the exception of those made from steels

according to EN 10025-5

Structures made from steels accordingto EN 10025-5

Steels exposed to weatheror other corrososive

consitions

Steels not exposed toweather or other

corrososive consitions

Steels used unprotected

End distances e1 1,2d0 4t+40 mm max (8t ; 125 mm)

Edge distances e2

1,2d0

4t+40 mm max (8t ; 125 mm)

Distance e3

in slotted holes 1,5d0

4)

Distance e4

in slotted holes 1,5d0

4)

Spacing p1 2,2d0 min (14t ; 200 mm) min (14t ; 200 mm) min (14tmin ; 175 mm)

Spacing p1,0

min (14t ; 200 mm)

Spacing p1,i

min (28t ; 400 mm)

Spacing P2

5) 2,4d0

min (14t ; 200 mm) min (14t ; 200 mm) min (14tmin

; 175 mm)


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1) Maximum values fore1, e2, p1, p2 are unlimited , excepting:

-elements in compression, in order to avoid the loss of stabilityand corrosion;-elements exposed to tension in order to avoid corrosion.

2) Buckling resistance of the steel plate between two holes isdetermined according to ENV 1993-1-1, using a buckling lengthequal with 0,6 pt; in the case whenpt/t


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a) Holes in parallel rows b) Staggered rows

Holes in stagger : a)- members in compression; b)-members in tension. 1-end (edge) row; 2-

internal row

ab

End (edge) distances for a slotted hole


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REZISTENTA DE CALCUL A DISPOZITIVELOR DE FIXARE INDIVIDUALE

For fasteners subjected to shear and/or tension, see table ;

For preloaded bolts, the design preload is determined with:

Design resistance for shear is used for holes with nominal diameters having nominal tolerances in reference

standards group 7;

Bolts may be used in holes with tolerance up to 2 mm providing that Fb,Rd to be greater than Fv,Rd, and in

addition for the classes 4.8, 5.8, 6.8, 8.8 and 10.9, Fv,Rd determined with the relationship in the table will be

multiplied with 0,85;

For fit bolts threaded part is not cut by the shear plane; the length of the threaded part including the bearing

length should not exceed 1/3 of the thickness of the plate (see figure);

Connections with one shear plane (lap joints) will be provided with washers under the head of the bolt and also

under the nut and the design resistance in bearing will be limited to:

Bolts in classes 8.8, 10.9 will be used with hardened nuts forlap joints with a single bolt or with a single row.

Connections subjected to shear having compensation plates, according to figure, for which tp>1/3dnominal , Fv,Rd

obtained from table will be amplified with:

7

7,0,

M

SubCdp

AfF

=

2

/5,1, MuRdb tdfF

0,1:,38

9

+= p

p

p buttd

d


14/24

Threaded portion of the shank in

bearing lengths of fit bolts

Lap joints with one single shear plane and one

single row

Fasteners through packings

Packingplate


15/24

Failure mode Bolts Rivets

Design resistance for shear plane

When shear plane cuts the threaded part of the shank (A is the crosssection):

classes 4.6, 5.6 si 8.8.v=0,6

classes 4.8, 5.8, 6.8 10.9v=0,5

When shear plane cuts the part of the shank which is not threaded (A isthe gross cross section): v=0,6

Bearing resistance

ab=min (

d; f

ub/f

u;1,0)

In the direction of the load transfer, dwill be adopted as:

-e1/3d

0for the end row;

-e1/3d

0-1/4 for the internal row

Normal to the direction of the load transfer k1 will be adopted as :

-2,8e2/d

0-1,7 ;2,5 for edge rows ;

-1,4p2/d

0-1,7 ;2,5 for internal rows

Tension resistance

For contersunk bolts k2

=0,63

Other cases k2=0,9

Punching shear resistance

Combined shear and tension resistance Any kind of verification is notnecessary

2

,

M

ubvRdv

AfF

=

2

1

,

M

udRdb

tdfkF

=

2

2

,

M

subRdt

AfkF

=

2

0

,

6,0

M

ur

Rdt

AfF

=

2

0

,

6,0

M

ur

Rdv

AfF

=

2

6,0,

M

up

Rdp

fdtB

=

0,14,1

,

,

,

,+

Rdt

Edt

Rdv

Edv

F

F

F

F

DESIGN RESISTANCES FOR INDIIDUAL FASTENERS SUBJECTED TO SHEAR OR/AND TENSION


16/24

DESIGN RESISTANCES FOR INDIIDUAL FASTENERS SUBJECTED TO

SHEAR OR/AND TENSION- SPECIFICATIONS

1)- For oversized holesbearing resistance is 0,8 Fb,Rd from the one for normal sized holes; for slotted holes with the

longitudinal slotted hole normal to the direction of the effort, the design bearing resistance is Rb,Rd.

2)- Countersunk bolts :

- Rb,Rd is determined based on the thickness of the plate, t , from which a deduction is made, equal with depth of the

sunk;

- Ft,Rd will be determined based on the angle and the depth of the sunk according to reference standars group 4;

alternatively, Ft,Rd will be adjusted with the detail of the design;

3)- When the effort in the bolt is no longer paralel with the edge, resistance for bearing will be determinedseparatelly for all the components paralel and normal to the edge.


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RESISTANCE OF GROUPS OF FASTENERS

The total resistance of a group of bolts may be taken as an average between the resistances in bearing, Fb,Rd

only if each of the individual resistances is greater than ,Fv,Rd. If not, the resitence of the whole gropu will be

the sum of the individual resistances.

If a spliced connection needs to be longer than 15 x bolt diameter both faces of the splice, shear resistance

Fv,Rd of all the bolts will be reduced with a factor1,f:

The values of this factor are : 0,75.1,0;

The shear resistance Fv,Rd will not be reduced if the shear force is uniformly transferred along the

connection (e.g., welded connection between web and flanges for a build up I section)

Long spliced connection


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CONNECTIONS WITH HIGH STRENGTH BOLTS CLASSES 8.8. AND 10.9

SLIP RESISTANCE

For preloaded bolts in classes 8.8 and 10.9, slip resistance will be determined as it follows:

where:

ks- coefficient depending on the type of the hole, from table;

n number of friction surfaces;

- friction factor, experimentally determined, according to reference standards, group 7. Thepreloading force is controlled in group 4 of bolts; it is determined with the following relationship:


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Type (description) ks

Bolts in normal holes 1,0

Bolts in either oversized holes or short slotted holes with the axis ofthe slot perpendicular to the direction of load transfer

0,85

Bolts in long slotted holeswith the axis of the slot perpendicular tothe direction of load transfer

0,7

Bolts in short slotted holeswith the axis of the slot parallel to thedirection of load transfer

0,76

Bolts in short slotted holeswith the axis of the slot parallel to thedirection of load transfer

0,63

Values for the coefficent ks

Friction classes of the surfaces(standards in reference group 7)

A 0,5

B 0,4

C 0,3

D 0,2

NOTE: Testing and inspection of connections are presented in

reference standards, group 7 The same reference standards classify other types of

processing the surfaces of representative specimens Preparation of surfaces subjected to preloading consists

in panting in several layers; these layers may affect intime the preloading force in the bolt

Slip factor


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TENSION AND SHEAR OF PRELOADED BOLTS

A slip resistant connection subjected to tension in ultimate limit state or serviceability limit state, Ft,Ed or Ft, Ed,ser

and shear, Fv,Rd or Fv, Ed,ser, the resistance of the bolt will be diminished according to the relationship:

Connection in B category:

Connection in C category:

NOTE:

If in a connection subjected to bending moment the force of compression in contact area exceeds the tension force,

no reduction is applied to the slipping resistance.


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ANGLES CONNECTED BY ONE LEG, OTHER MEMBERS CONNECTED

UNSYMMETRICALLY SUBJECTED TO TENSION


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DEDUCTION OF FASTENERS HOLES

A. DESIGN OF BLOCK TEARING: failure in shear at the row of bolts+ tensile rupture along the line of bolt holes on

the tension face.

Symmetric bolt group subjected to concentric loading design block tearing resistanceVeff,1,Rd

where:

Ant - net area in tension;

Anv - net area in shear.

Bolt group subjected to eccentric loading design block shear tearing resistanceVeff,2, Rd

B. ANGLES CONNECTED BY ONE LEG, OTHER MEMBERS CONNECTED UNSYMMETRICALLY, SUBJECTED

TO TENSION: the design resistance of either unsymmetrical members or symmetrical members connected

unsymmetrical is affected by the distribution of spacing and end (edge) distances of bolts

Single angle in tension with one row of bolts=concentrically loaded net section for which the design ultimate

resistance is determined with:


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Block tearing of different types of connections subjected to shear and tension

Angles connected by one leg

Reduction factors depending on pitch p1;

between limit values, interpolation is applied


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STRESS DISTRIBUTION BETWEEN BOLTS IN THE

ULTIMATE STATE DESIGN

1. In the connections subjected to bending moment the distribution of the internal efforts may be

linear elastic or, plastic considering a status of equilibrium both with the resistance of thecomponents and with their ductility. Linear-elastic distribution is preferred in the case when:

- bolts are in a C category connection;

-blots are subjected to shear and for every bolt: F v,Rd

Design of Connections

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