Rehabilitation and maintenance of buildings - 03

Karel Mikeš

Contents

           Properties of material Failures of steel structures Types of refurbishment Methods of reliability verification Basis of members design of steel structures

Basis of joint design

Assessment of steel structures Strengthening of members Strengthening and refurbishment of structures Refurbishment of masonry structures using steelwork Seismic upgrading using steel structure 2

Connections

   Bolted Welded Riveted (history) Realised:   In shop On site Calculation:  on resistance  on calculated internal forces 3

Connections Bolted connections Types:  According to static behaviour:   Normal (no preloading) Slip-resistant (controlled tightening)    According to loading: Shear Tension 4

Bolted connections Shear loading     Common bolts: shear bearing   Slip-resistant bolts: slip bearing 5

Bolted connections Shear resistance

F v .

Rd



i

0

,

5 g

A s M

2

f ub

for bolt grades 4.8, 5.8, 10.9

F v .

Rd



i

0

,

6 g

A s M

2

f ub

for other bolt grades

A s f ub i

g M2 =1,25 Core area of cross section of bolt Ultimate strength of bolt Number of shear planes 6

Bolted connections Bearing resistance t d d 0 f ub f u

F b .

Rd



k

1  g

b M d

2

t f u



b



min

  3

e

1

d

0 Effect of bolt pitches

; k

1  2

,

5

p

1 3

d

0  1

;

4

f ub f u ;

1   Minimum thickness in one direction Diameter of bolt Diameter of hole Strength of bolt Strength of material

e 1 d 0 d

7

F b.Sd

Bolted connections Resistance of slip-resistant bolts

A s f ub n

m Slip resistance  prestressing force

F s .

Rd



k s

g

n M

3 m

F p .

C F p .

C

 0

,

7

A s

Core area of cross section of bolt Ultimate strength of bolt Number of friction planes friction coefficient ... 0,2 to 0,5

f ub

g

M

3  1

,

25 8

Bolted connections Bolts loaded in tension  Resistance in tension

F t .

Rd

  0

,

9

f ub A s

 g

M

2  The same resistance for common and preloaded bolts 9

Welded connections

 Fillet welds  Butt welds  fully supply basic material Welds = rigid connections (no slip) 10

Welded connections Fillet welds a  ┴  ┴  ║  ║ effective throat thickness of the fillet weld direct stresses perpendicular to the throat shear stresses perpendicular to the axis of weld shear stresses parallel to the axis of weld direct stresses parallel to the axis of weld (neglected) 11

Welded connections Check of fillet weld  2   3   2    2

II

  

w f u

g

M

2    0

,

9 g

f u M

2 g

M

2  1

,

25  w correlation factor depends of steel grade 12

Welded connections Two fillet welds in parallel shear       0 

ll



F

2

a

 

ll

 

w f u

g

Mw

13

Welded connections Connection of cantilever V – 

ll

 transferred by web:

F

2

a

 M – transferred by whole weld cross-section: 

R



M W we

      

M

2

W we W we



I we z

Point 1:  II ,  ┴ ,  ┴ Point 2:  ┴ ,  ┴ 14

Welded connections Flange-to-web weld V Sd  Longitudinal shear flow V ℓ :

V

 

V I S [ kN / m ]



ll



V

 2

a



I V S

2

a

 

w f u

g

M

2 15 V 



Riveting

Assembly  Heated to white heat  Pneumatic hammer (clamping rivet’s length max. s = 4,5 d)  Function (after cooling)  Fully filled hole   Before riveting diameter is by 1 mm less then hole diameter Prestressing connected sheets   Material  Rivet from steel with lower strength than basic material (when they are exchanged can be cut off) Head  Half spherical  (Countersink) 16

Riveting

    Supply at the refurbishment: Additional rivets or bigger diameter Bolts – slip resistant connection, „ retro “ Bolts injected by epoxy heads of bolts   Riveting is history Exhibition on 3 rd floor of Eiffel's tower 17

Riveted connections - Resistance

  Shear Shear  Bearing

F v,Rd

 0

,

6 g ... as for bolts

f ur M

2

A

0  Tension

F t,Rd

 0

,

6 g

f ur M

2

A

0 18