Lecture 3 s.s. iii Design of Steel Structures - Faculty of Civil Engineering Iaşi

Lecture 3

STEEL INDUSTRIAL BUILDINGS

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

1

1. Steel sheet roofing and cladding

Profiled steel sheet is commonly used as a cladding for roofs and sidewalls because of their qualities:

strength, lightweight, durability, ease-speed of erection and low cost

Recommended slopes of the roofing:

A) Long corrugated sheets with no end laps between ridge and eaves; long sheets in other profiles-

trough, tiles, with no end laps between ridge and eaves 50,

B) Unprotected profiled sheets where end laps are necessary 150,

C) Insulated decking:

The resistance of a cladding sheet to longitudinal bending is proportional with the depth of the

corrugation and the gauge thickness;

The strength of the sheet is proportional with the section modulus of the profile;

The stiffness of the sheet is proportional to the moment of inertia of the profile section.

The design of the appropriate thickness of the cladding sheet is based on the tables offered by the

producers, depending on the total weight on the roof and on the spans of the cover sheet.

The cladding may be sustained continuously by three, four or several supports or it may be simply

supported.

NON STRUCTURAL STEEL ELEMENTS

a b c

Different profile shapes of steel sheeting used for roofing: a)- corrugated; b)- with trough; c)- deck trough; d) – deck trough with tray; e) – build-up deck

a b c d e

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

2

Cladding shuts are formed from cold-reduced steel shut or coil covered by appropriate surface treatments: galvanized coating, aluminium and plastic coating, pre-painted sheet, built-up weather proofing. - may be one single sheeting or, - double sheeting panels in between insulating material like mineral wool or foam being placed at site The slope of the roofing is minimum 8%. Material-types and qualities - galvanized rolled steel stripes and coils with 0.5 - 0.75 mm thickness (EN 10142, 10147) and tolerance limits according to EN 10143. - pre-painted sheeting with polyester 25 m, according to EN 10169, NFP 34 - 301. Other organic layers are also used: Plastisol, PVC, etc, with different thickness and metallic coating: GALFAN, ALUSI, EZ. Other materials used for the panel decks: stainless steel and aluminum. Mounting at site Sheeting must be fixed in position by overlapping the panels such as the covering rib to be under the wind dominant direction. Marks like left (L) or right (R) show mounting the direction: from eave or from ridge. Cutting must be performed with electric saw in order to be clean and not overheating the material. Drilling for bolts or rivets must be performed with electric screwdrivers.

Profiled steel sheets for roofing or walling


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

3

Sheeting layout Some accessories are presented for fixing the sheeting to the purlins or sheeting rails: ridge caps, corner and eave closures and flashings which are usually made from flat, galvanized sheet and bent to whatever curve it needs.

Details of fixing the roof cladding: a) seam fastener with 6 mm diam. galvanized steel bolt; b) purlin fastener with 8 mm diam. galvanized hook bolt; c) seam fastener with self-tapping screw; d) purlin fastener with drive screw; e) seam fastener with

blind rivet; f) purlin fastener ith galvanized bolt and movable hook; g) purlin fastener with stud welded bolt; h) purlin fastener with a sheet clip; i) purlin fastener with fired stud; j) purlin and insulation fastener with curtain wall stud


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

4

L(m) --> 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00

t g k

0.50

5.0

1 260 191 146 116 94 77 65 55 43 42 37 32 29 26 23

2 260 191 146 116 94 77 60 47 38 31 26 22 19 16 14

3 260 191 146 106 78 60 46 37 30 25 20 17 15 12 11

4 239 153 104 75 55 42 33 26 21 17 14 12 10 9 8

0.63

6.3

1 388 285 218 172 140 115 97 83 71 62 55 48 43 39 35

2 388 285 218 172 137 105 82 65 53 43 36 30 26 22 19

3 388 285 204 145 107 82 64 51 41 34 28 24 20 17 15

4 327 210 143 102 76 58 45 36 29 24 20 17 14 12 10

0.75

7.5

1 508 373 286 226 183 151 127 108 93 81 71 63 56 51 46

2 508 373 286 226 174 133 104 82 67 55 45 39 32 28 24

3 508 373 258 184 136 104 81 64 52 43 36 30 25 22 19

4 415 266 182 130 96 73 57 45 37 30 25 21 18 15 13

1.00

1.0

1 800 588 450 355 288 238 200 170 147 128 112 100 89 80 72

2 800 588 450 355 257 195 152 121 98 80 67 56 48 41 35

3 800 586 379 271 200 153 119 95 77 63 52 44 37 32 28

4 609 392 267 191 141 107 84 67 45 44 37 31 26 22 19

1.25

12.5

1 110

5 812 621 491 398 329 276 235 203 177 155 138 123 110 99

2 110

5 812 621 466 345 262 205 163 132 108 90 75 64 55 47

3 110

5 747 510 364 269 205 160 127 102 84 70 59 50 42 36

4 818 526 359 256 189 144 112 88 71 58 47 40 33 28

Profiled steel sheets for roofing or walling

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

5

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

6

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

7

Structure of the roof and of the external walls


Side rails

Gable stanchions

Purlins

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

8


vertical

braces of the columns

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

9

PURLINS FOR INDUSTRIAL BUILDINGS

Purlins are beams that sustain the layers of a flat roof or the cladding of a sloping roof of the buildings • They may be simply supported or continuous beams. • Types of steel sections: hot rolled sections, cold formed sections, Castella

beams, laced sections. • The connection between the parts of a continuous purlin may be welded at site or

bolted or combinations between these two.

Current rolled sections used for purlins

Spliced continuity connection: a- welded; b- bolted Splices for connections of continuous beams: a-part welded in workshop and bolted at site; b- bolted entirely; c- position of

connections; d- rigid connections

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

10

Purlins supports on rafters

Supports of simply supported purlins on top chord of the trusses;


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

11

Castella beams sections used as purlins have a greater moment capacity (about 50% more) than the hot rolled sections; purlins made of trusses (lattice girders) reduce the steel consumption with about 40%.

Different types of sections for purlins placed on wider bays: a)- Castellated sections; b)- lattice girders; c)- knee braced purlins; d)- knee braced lattice girders; e)-purlins with hangers; f)- purlins placed alternatively


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

12

Actions. Groups of actions in combinations

Crt. nr.

Actions for design Nominal Value

Safety factor

Design Value

1. (Gk,1): Self-weight - gp,k [daN/m2]·a*[m]; [daN/m] ** 0,9-1,35 *

gp,d

2. (Gk,2): Weight of roof sheeting (decking) – gsh,k/cosα [daN/m2]·a[m]

gsh,k·a gsh,k·a

3. (Gk,3): Weight of building service equipment (electric cables) – ge,k

[daN/m2]·a[m] ge,k·a ge,k·a

4. (Qk,1): Snow deposit on the roof- Sk [daN/m2]·a[m] gid,k·a 1,5 gid,k·a

5. (Qk,2): Weight of industrial dust deposit- gid,k [daN/m2]·a[m]

pzn·a 1,05 Sk·a

6. (Qk,3): Wind pressure****- pvnn [daN/m2]·a[m] pvn

n·a 1,05 pvnn·a

U.L.S. : ΣG,jGk,j +Q,1Qk,1+ΣQ,i0,i Qk,i S.L.S. : ΣGk,j +Qk,1+Σ0,i Qk,i

qk

[daN/m] qd

[daN/m]


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

13

Simply supported purlin

The purlins are members subjected to skew bending. The two components of these loads projected in the plane of the cross section on the axes of the profile are:

sin;cos )()(,)()()(, dkdkzdkdkdky qqwqq

Simply supported purlins with sag-rods Sag-rods are used in the cases of heavier loading, greater slopes or bigger normal stresses (>500daN/m2). They will be used only in the case when they clearly determine an economy in the steel consumption, that is if the section of the purlin simply supported without a rod is the result if the strength or slenderness condition.


Sag rod

Sag rods

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

14

PURLINS FOR INDUSTRIAL BUILDINGS Sag rods

Sag-rods take a part of the loads acting in the plane of the roof (qz) being internal supports of the purlins in this plane. Both ends of the rod are threaded in order to be screwed between two running purlins and fixed with nuts at the building site.

Purlins fixed with one sag rod on the bay: N1, Nn -number of sag rods per bay and half of the span

Purlins fixed with two sag rods on the bay: N1, Nn -number of sag rods per bay and half of the span

Details of fixing the purlins with sag-rods

nn NNN ,max 1max

2.12

lq25.1V

cos2

lV5.0n

cos2

lVN

;V5.1nVN

z

n

1i

in

n

1i

i1n

tR

Nd

max

0

4

3

1.1;cos

5.0max

lqV

VnNN yn

3.13

lq1.1V z

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

15

Relationships for simply supported purlins without or with one (two) sag rod

Sizing and verifications of members in skew bending

0My

EdzEd,ynec

y/f

,MkMW

0My

z,el

Ed,z

y,el

Ed,y/f

W

M

W

M

0My

z,pl

Ed,z

y,pl

Ed,y/f

W

M

W

M

0M

y

y

yw

Ed,ymax,

max3

fS

It

V

)

IE

3l3.1M

48

5f;

IE

2l2.1M

48

5f(

IE

lM

48

5f;

IE

lM

48

5f

gross,z

2

Ek,z

z

gross,z

2

Ek,z

z

gross,z

2

Ek,z

z

gross,y

2

Ek,y

y

32

l2.1qM;

32

l3qM

2

d,yEd,II,z

2

d,yEd,II,y

00 My

Ed,II,zEd,II,y

My

Ed,I,y

nec,y/f

kMM;

/f

MmaxW

00 M

y

z

Ed,II,z

y

Ed,II,y

M

y

y

Ed,I,y f

W

M

W

M;

f

W

M

aIIzIIyIIaIy ffffff 2

,

2

,, ;

3.1i3

l

i

l;2.1

i2

l

i

l;

i

l

i

l

250,max

zz

f

z

zz

f

z

yy

f

y

azymax

zzy

2

lqV yEd,ymax,

0M

y

vRd,plEdmax,3

fAVV

II. Stiffness

III. Slenderness

0M;8

lqM I,z

2

d,yEd,I,y

I. Strength

8

33.1;

8

2

,

2

,

lqM

lqM zIzyIy

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

16

Purlins as continuous beams

In elastic with redistribution of the bending moments on internal bays and supports. The static scheme of continuous beams is most rational especially in the case when there are more than 5 bays along the building and also, the bays have equal dimensions


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

17

0;1053.0

125.0;0724.0

12.0;0779.0

,

2

,

2

,

2

,

2

,

2

,

IIIzyIIIy

zIIzyIIy

zIzyIy

MlqM

lqMlqM

lqMlqM

R

M

R

kMM

R

kMMW

IIIyIIzIIyIzIy

necy

,,,,,

, ,1.1

,1.1

max

0

0

00

Myy

n,yw

Ed

My

n,y

Ed,III,y

My

n,z

Ed,II,z

n,y

Ed,II,y

My

n,z

Ed,I,z

n,y

Ed,I,y

3/fSIt

V

;/fW

M

;/fW

M

W

M;/f

W

M

W

M

a

2

z

2

y

gross,z

4

k,z

gross,z

4

k,z

z

gorss,y

2

k,s,q

gross,y

4

k,y

sM

gross,y

2

kmax,q

gross,y

2

kmax,q

gross,y

4

k,y

gross,y

4

k,y

q

gross,y

4

k,y

Mqy

ffff

;I

lq00621.0

IE

lq

384

5f

I

lM002976.0

I

lq00313.0f

I

lM00476.0

IE

lM

48

5

I

lq0062.0

IE

lq

384

5f

;I

lq00307.0fff

zz

f

z

yy

f

y

azy

i

l

i

l

i

l

i

lzy

;7.0

250,maxmax

Purlins as continuous beams

Relationships for sizing and verifications


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

18

Continuous purlins in plastic

Continuous purlin considering the plastic reserves of the sections: a)- moments for design; b) and c)- consolidation of the cross sections in the first span

0My

Ed,pl

nec,y/f

MW

Rd,plEdyEdMy

vz

EdMy

y,pl

Ed,plV5.0V;lq5.0V;3/f

A

V;/f

W

M

00

zz

f

z

yy

f

y

azy

i

l

i

l

i

l

i

lzy

;5.0

250,maxmax

2

k,ys

2

k,ymax,q

gross,y

4

k,y

gross,y

max,k,q

M

gross,y

4

k,y

gross,y

max,k,q

q

a

gross,y

4

k,y

Mq

lq0789.0M;lq125.0M

I

lq0047.0

I

M05952.0f

I

lq00621.0

I

M0496.0f

fI

lq00151.0fff

s

y

sy

y

1

nec,yorcinginfre

1

nec,y

1

nec,y

My

11

nec,y III;2

hWI;

/f

MW

0


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

19

Purlins made of Castella sections


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

20

Knee braced purlins

Knee-braced purlins

Purlins with hangers

Purlins made of lattice girders with braces: a- in compression; b-in tension


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

21

Purlins placed alternatively

Static scheme and detail


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

22

Purlins made of trusses

Lattice systems for trusses: sections of steel used for purlins

Steel trusses used as purlins for wide bays


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

23

Connections between purlins and truss

Different sections of purlins sustained on the top chord of the roof trusses: a- UPN; b- IPN; c- welded section

Purlins made of lattice beams supported by the top chord of truss

2-2

1-1

4 - 4 3-3

1 - 1


C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

24

THE STEEL STRUCTURE OF THE SIDEWALLS

Side and gable rails and stanchions sustaining the structure of the walls

Detail C

Detail A

Detail B

Detail C

C.T

ele

man

. Ste

l Str

uct

ure

s III

. Le

ctu

re 3

25

Lecture 3 s.s. iii Design of Steel Structures - Faculty of Civil Engineering Iaşi

Engineering

Transcript of Lecture 3 s.s. iii Design of Steel Structures - Faculty of Civil Engineering Iaşi