Chapter 11Chapter 11

Flange splice

Introduction

In shop, flanges shall be joined by complete penetration but welds, where possible. These welds shall develop the full strength of the plates. The flange plate can be obtained in length up to 15 m and thus in plate girder over 15 m span we have to arrange field splice at which the web plate and the flange plates are cut.

Flange joints should not be preferably located at points of maximum stresses. Where splice plates are used, their area shall be not less than 5 % in excess of the flange plate. There shall be enough bolts on each side of the splice to develop the maximum strength of the flange plate.

One splice plate covers the joint of the flange or splice plates on both sides of the flange plate may be used. For example if we have flange plate 32020 mm we can use one splice plate 320(20 – 22) mm.

-   Net area of flange plate = (32 - 42.4) 2 = 44.80 cm2.

-         Number of bolts (for one side), (single shear field bolts, M22, Q8.8)

n =

qb = 0.25 Fub = 0.258 = 2 t/cm2

Rs. sh = qb As n = 23.031= 6.06 t (n = No. of shear

planes)

y = 3.6 t/cm2 (St 52)

n =

Use 20 bolts (45)

bolts17.751.15

6.06

6.358.044.80

1.15 R

44.80

s.s

t

Or we can use One splice plate 32012 mm from the outside and two splice plate 12012 mm from the inside of the flange plate

-         Net area of splice plates

-         = (321.2 + 2121.2) 2 - 221.22.4

= 67.20 – 11.52 = 55.68 cm2.

-         Number of bolts (double shear or bearing field bolts, M22, Q8.8) = n

n = 1.15 RorR

8.44

d.sd.s

t

qb = 0.25 Fub = 0.258 = 2 t/cm2

Rd. sh = qb As n = 223.031= 12.12 t (n = No. of

shear planes)

Rb = Fb d min t

Fb = Fub

depends on end distance (S), (Table 6.2)

 

End distance in direction of force

1.2 1.0 0.8 0.6

3d 2.5d 2 d 1.5d

Edge distance = 2.5 = 1.0

Fb = 1.0 Fub = 8.00 t/ cm2

Rb = 8.0 2.2 2.0 = 35 tBack

y = 3.6 t/cm2 (St 52)

n =

Use 10 bolts (25)

bolts8.91.15

12.12

6.358.044.80