Rehabilitation and maintenance of buildings - 03

Karel Mikeš

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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

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Connections Bolted Welded Riveted (history)

Realised: In shop On site

Calculation: on resistance on calculated internal forces

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ConnectionsBolted connections

Types: According to static behaviour:

Normal (no preloading) Slip‑resistant (controlled tightening)

According to loading: Shear Tension

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Bolted connections Shear loading

Common bolts: shear bearing

Slip‑resistant bolts: slip bearing

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Bolted connections Shear resistance

for bolt grades 4.8, 5.8, 10.9

for other bolt grades

As Core area of cross section of bolt

fub Ultimate strength of bolt

i Number of shear planes

gM2 =1,25

2

60

M

ubsRd.v

fA,iF

2

50

M

ubsRd.v

fA,iF

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Bolted connections Bearing resistance

p 1e1

d

d

0

Fb.Sd

521 ,k

1

4

1

33 0

1

0

1 ;f

f;

d

p;

d

emin

u

ubb

Effect of bolt pitches

t Minimum thickness in one directiond Diameter of boltd0 Diameter of holefub Strength of boltfu Strength of material

2

1

M

ubRd.b

ftdkF

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Bolted connections Resistance of slip-resistant bolts

Slip resistance

prestressing force

As Core area of cross section of bolt

fub Ultimate strength of boltn Number of friction planesm friction coefficient ... 0,2 to 0,5

C.pM

sRd.s F

nkF

3

ubsC.p fA,F 70

2513 ,M

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Bolted connections Bolts loaded in tension

Resistance in tension

The same resistance for common and preloaded bolts

2 90 MsubRd.t Af,F

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Welded connections

Fillet welds

Butt welds fully supply basic material

Welds = rigid connections (no slip)

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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)

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Welded connections Check of fillet weld

2

222 3Mw

uII

f

2

90M

uf,

2512 ,M

bw correlation factor

depends of steel grade

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Welded connections Two fillet welds in parallel shear

0

Mww

ufll

aF

ll 2

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Welded connections Connection of cantilever

V – transferred by web:

M – transferred by whole weld cross-section:

Point 1: tII, t┴, s┴

Point 2: t┴, s┴

aF

ll 2

zI

W wewe

weR W

MweW

M2

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Welded connections Flange-to-web weld

Longitudinal shear flow Vℓ:

VSd

V

]m/kN[ISV

V

222 Mw

uf

aI

SV

a

Vll

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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)

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Riveting Supply at the refurbishment:

Additional rivets or bigger diameter Bolts – slip resistant connection, „retro“ heads of

bolts Bolts injected by epoxy

Riveting is history Exhibition on 3rd floor of Eiffel's tower

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Riveted connections - Resistance Shear

Shear

Bearing ... as for bolts

Tension2

060

M

urt,Rd

Af,F

2

060

M

urv,Rd

Af,F