framed steel member conection

5/19/2018 Framed steel member Conection

1/20

Raju Sharma

Assistant Professor

Chandigarh University


2/20

Seat connection

Two types of seat connection are used

Un-stiffened seat connection

Stiffened seat connection

UNSTIFFENED SEAT CONNECTION

Angle is provided below the beam flange and is designed to transfer the

end reactions of beam to the column through connections.

The seat angle also provides a surface on which the beam flange may rest

during erection, eliminating erection bolts.


3/20

Generally the outstanding (seating) leg is taken as 100 mm

which is sufficient to check the web crippling of the beam Minimum two rivets required for the connection of seat angle

to beam flange

10-15 mm clearance should be made between the beam and

column. Seat is assumed to be flexible

Angle is provided at the upper flange of the beam and this is

called cleat or clip angle. provide later support

to the compression flange of the beam at this point only and

is assumed to carry no load.


4/20

Clit Angle

Conventional design assumed

Does not restrain the rotation at the beam end in the

vertical plane and the end reaction is the only force to be

considered

When the beam tends to rotate ,the cleat angle bends away

from the column as well as the beam Flexible beam seats

are the simplest and most desirable because the thickness

of the seat angle provides the only resistance against

bending in the outstanding leg.


5/20

Stiffened Seat Connections

The outstanding leg is stiffened by angles thus the seat

does not remain flexible.

Why stiffened Seat Connections are required ?


6/20

The outstanding leg of seat angle must be stiffened when the

reaction to be transferred to the column is too large

When the seating leg of 100 mm cannot provide the required

bearing area

Due to large reaction the number of rivets required to join the

connecting leg with the column may be large

The rivets can be accommodated on an additional angle called

a stiffener angle. packing equal to the thickness of the seat

angle are used between the column flange and the stiffener

angle.


7/20

The rivets connecting the column flange to the

outstanding legs are not tack riveted two stiffener angles,

bending moment (R act independentally .in this case the

rivets connecting the stiffener angle with the column

flange are designed for shear, bending moment (Rexx) and

twisting moment(Reyy), where exx, eyy are the eccentricities of

the reaction parallel to the outstanding legs and connected legs

respectively


8/20

Design of Unstiffened seat Connection

A seat angle is chosen suitably on the following

consideration:

The seat angle is assumed to have a length B, equal to thewidth of the beam flange.

On the basis of web crippling of the beam length of the

outstanding leg of the seat angle may be calculated. The

seat length is kept more than the calculated bearing length.

b = (R/p x t) - 3h2


9/20

Above equation can give negative value of b for a large

beam with a small reaction. Therefore minimum bearing

length is

b < .5 (R/p x t)

R = end reaction in N

p =permissible bearing stress in Mpa (.75fy)

t = thickness of the web of the beam in mm

h2 =depth of the root of fillet from extreme fibre of

flange for the beam in mm.


10/20

The connected leg is so chosen that at least three horizontal

rows of rivets can be accommodated. It can be assumed to

be 150 mm or more as desirable.

The thickness of seat angle is chosen such that the

outstanding leg does not fail in bending on a section at the

toe of the fillet. Let


11/20

e1

=the distance from the critical section to the reaction

acting at the center of the bearing length (Fig 1)

= 10 + b/2 -t- radius of root of fillet

M= moment at the critical section (Re1)

B = length of seat angle (equal to the width of beam

flange)

bc =bending stress in compression assumed to be

equal to the bending stress in slab basei.e 185 N/mm


12/20

T= 6Re1/(B bc )

The angle thickness is assumed and theM.O.R is

computed, which should be more than the moment at

the critical section.

Two or more horizontal rows of rivets are provided to

connect the seat angle with the column flange


13/20

These are subjected to direct shear forces. rivets dia is

assumed and number of rivets required to connect the seat

angle with the flange of column are determined. The

outstanding leg of the seat angle is connected to the beam

flange with two rivets of the same dia as provided on the

connected leg

N= (end reaction/rivet value) n is number of rivets

A cleat angle of normal size is provided on the top flange of

beam and is connected by two rivets.


14/20

Design of stiffened seat connections

Size of seat angle is assumed on the basis of the bearing length

calculated

b = (R/

p x t) -3h2

Suitable stiffener angles are selected. Outstanding leg of the

stiffener angle must provided the bearing area stiffening leg.

the outstanding leg of the stiffener angle must provided the

bearing area. Also, it should not exceed 16 times its thickness

to avoid local buckling.


15/20

Bearing area required= (R/p )

R= end reaction

p= permissible bearing in Mpa (.75 fy)

Thickness of the stiffner angle should not be less than

the thickness of the web of the beam supported.

seat is rigid so the reaction is assumed to have a greater

eccentricity.


16/20

Rivets in connecting leg are subjected to

Direct Shear

Moment

Connection behaves as a bracket connection TYPE II.

Bending moment about the face of the column flange is

determined.

The number of rivets are computed and check similar to

the bracket connection TYPE II is done.


17/20

(vf, cal/ vf ) + (tf,cal/ tf) 1.4

A cleat angle of nominal size is provided and is connected

with rivets of same dia as on the seat angle.Two rivets are

provided on each leg of the cleat angle.


18/20

Framed connection

1. The end reaction which the beam has to transfer is

computed.

2. CONNECTION OF FRAMING ANGLE WITH BEAM

WEB

Assumed dia

Find rivet value in double shear and bearing

The number of rivets n, can be computed by

N= (end reaction/rivet value)


19/20

3. Connection of outstanding leg of the angle with the

web of the girder.

Assume dia

Rivet value is computed in single shear and bearing.

Number of rivets required n to connect the

outstanding leg with the flange of the beam

n = (end reaction/ rivet value)


20/20

4. The size of the framing angle is governed by the

number and row of rivets on connecting and outstanding

leg.

5. The thickness of the angle can be computed as follows

Limited shear stress,.4fy=(end reaction/ 2x h x t)

Or t= end reaction/ 2hx .4fy

framed steel member conection

Documents

outstanding leg of seat

flexible angle

stiffened seat connections

beam end

beam flexible beam seatsare

clip angle

beam minimum

beam andcolumn