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Civil Eng Formulas + Buildings Short > steel design > Flashcards

steel design Flashcards

1
Q

shape factors of sections

A

hollow circle - 1.27
circular plate - 1.7
diamond section- 2
triangular section- 2.34

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2
Q

Center of gravity of semi circles

A

semi circular line = 2R /pi
semi circular plate =4R/3pi
hemisphere = 3R/8

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3
Q

ultimate plastic load for propped cantiliver

A

11.656 Mp / L^2

hinge at x= 0.414 L

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4
Q

maximum permissible deflection in SSB

A

table 6 is 800:2007
elements succeptible to cracking = L/300
not succeptible to cracking = L /240
for cantiliver = L/150 and L/120

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5
Q

limiting grip length in lap joint

A

Lg < 5d
effect of bending stress can be ignored in above condition
8d >Lg > 5d , reduction factor required
Lg > 8d , redesign required

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6
Q

minimum pitch, guage , end distance

A

pitch/guage = 2.5 bolt
end = 1.5 hole
= 1.7 hole (for hand cut element)

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7
Q

maximum edge , pitch distance in welds and bolts

A

end distance = 12 t.e , e = sqrt(250/fy)
comp pitch distance = 12t or 200 mm
tension pitch distance = 16t or 200 mm
in case of staggered = 1.5* distances

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8
Q

maximum pitch of tack bolt

A

for plates, flats = 32 t or 300 mm
if exposed to weather 16t or 200 mm
for compression = 600mm or λ1 <40 , 0.6λ
for tension member = 1000 mm

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9
Q

bolt and bolt hole

A 
dia = 6.06 sqrt(t)      Unwins formula
nominal dia : hole clearence
12 ~ 14 mm : 1mm
16 ~ 24 mm : 2mm 
 > 24 mm   : 3mm
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10
Q

slot welding size limitation

A

width of slot > 25mm or 3.t

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11
Q

long joints, weld and bolt unbuttening effects

A

L > 150 throat

L > 15 bolt

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12
Q

slenderness ratio limits of steel members

A

λ < 180 , compression member
λ < 180 , tension member, but stress reverse due to
live load
λ < 250 , for wind earthquake loads
λ < 350 Tension member but reversal of stress due to wind load
λ < 400 , for tension members

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13
Q

net tearing area of staggered bolting

A

[ B -n.D +(S^2) /4g ] * t

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14
Q

lug angle design

A 
minimum bolts at lug > 2 bolt
number of bolts at locations 
n1 = Fconnect /Rv
n2= 1.4* Fout /Rv
n3= 1.2* Fout /Rv
n2 interconnecting bolt must start in advance
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15
Q

design of bolted connection

A
  1. find dia of bolt = 6.04 *sqrt(t)
  2. find rivit value
  3. find no of bolts required
  4. arrangement of bolts
  5. width and thickness of plates
  6. efficiency of joint (if asked)
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16
Q

design of lacing

A 
1. spacing of lacing
 C /r.min  <50 or 0.7*λ
2. dimension of lacing
 t > L1 /40, or L1 /60 
 λl = K.L1 /r < 145 (K=0.7 for double lacing or welded )
3. Forces in Lacing
 V= 2.5% of Pu
 F = V/ N*sin()
4. Forces < strength compressive and tensile
 T= 0.9fu Anet /1.25
 T= Ag * fy /1.2
 C= fcd* Ag (fcd depends on λl)
5. tie plate or batten plate 
 Dend > 2.B
           > centroidal distance between main members
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17
Q

width of lacing bars

A 
bolt dia mm - width of lacing bar
16 - 50
18  - 55
20- 60
22- 65
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18
Q

to prevent web crippling

A

A = a +2.5*h2

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19
Q

to prevent web buckling

A

find K.l /r =2.45d / tw
fcd *Ag > R
A= a + d (1:1 dispersion)

20
Q

condition of plastic , compact and semi compact rolled I-section

A

b/tf < 9.4 e
d /tw < 84e

compact
b/tf < 10.5 e
d /tw < 105e

semi compact
b/tf < 15.7 e
d /tw < 126e

21
Q

bolt grade 4.6

A

400 mpa strength

22
Q

Kb in bearing of bolt

A

Kb =min [e/3d , p/3d -0.25, fub/fu, 1]

23
Q

rivit hole size

A 
d' = d+ 1.5     for d<25
d' = d + 2      for d>25
24
Q

carbon content in mild steel

A

0.23%

25
Q

characterstics of steel used as plasstic steel

A

fy < 450 Mpa
fu/fy > 1.2
εplastic > 1.15*εelastic

26
Q

what is stainless steel made of

A

iron and chromium

27
Q

minimum size of weld based on size of thicker plate

A 
thicker plate   min size of weld
     <10 mm      3mm
11 ~ 20 mm      5mm
21~32 mm       6mm
     >32mm      8mm
28
Q

maximum size of weld

A

T - 1.5mm

0.75 T

29
Q

reasons of flange buckling, web buckling, web crippling

A

Flange buckling - Bending compression
Web buckling - Diagonal compression
web crippling - Bearing stress

30
Q

permissible deflections in gantry girder

A

span/500 manual operated
span/750 electrically operated
span/1000 capacity > 50t

31
Q

use criteria of stiffners in Plate girders

A

d1/tw >90, verticle stiffners for web buckling
d1/tw > 200, horizontal stiffners at 0.2d from flange
d1/tw > 250, horizontal at N.A
d1/tw > 400, section redesign

32
Q

end bearing stiffners Leff, area

A

Leff = 0.7L1
A = 4Aoutstand + 40twtw
designed as columns
so tight bearing

33
Q

outstand Area of outstand leg

A

A2e= kA2
k = 3A1 /(3A1+A2)
Ae = A1 + k*A2 ,
0.875A in case of symmetric angle

34
Q

for field rivets , permissible stresses are reduced by what percentage?

A

10%

35
Q

The critical slope of a roof truss above which snow load need not be considered.

A

50 degree

36
Q

slenderness ratio of bracing for hangers

A

160

37
Q

if beams arent restrained by cleats at ends for torsion

A

Length increased by 20%

38
Q

design wind speed factors k1, k2, k3

A 
k1 = risk cofficient
k2 = terrain, height , size factor
k3 = topography factor
39
Q

The depth of web of a plate girder usually varies between

A

1/8 to 1/12 of the span.

40
Q

From serviceability requirement the web is considered to be unstiffened if the spacing of transverse stiffeners is greater than

A

3 times the web depth.

41
Q

batten design properties

A

Column is divided into a minimum of three bays (i.e. minimum 4 number of battens required).

  • Thickness of batten plate shall not be less than 1/50th the distance between outer most connecting line of rivets of welds.
- (i) Effective depth of intermediate battens
> 0.75 α
> 2 *b*g
{b = width of column component
α= spacing of C.G. of column}

(ii) Effective depth of end battens
> α
> 2*b

42
Q

approximate are of web and flange contributing in strength of plate girder

A

Aeff = Aflange + (1/6)*Aweb

43
Q

maximum spacing of purlins in asbestos roofing

A

1.4 m

44
Q

Max Moment in continuous members like purlin

A

w.L^2 /10

45
Q

Effective length of compression flanges depending on end conditions

A

Effective length of compression flanges depending on end conditions
ends of compression flange unrestrained = L
ends of compression flange partially restrained = 0.85L
ends of compression flange fully restrained = 0.7 L

cantilevers

-built in support, free at end = 0.85L
-built in support, restrained against torsion at end by continuous construction = 0.75L
-built in support, restrained against torsion at end by cross members over several beams = 0.5L
- continuous and unrestrained against torsion at support and free at end = 3L
- continuous and partially restrained against torsion at support and free at end = 2L
continuous and restrained against torsion at support and free at end = L

Civil Eng Formulas + Buildings Short (16 decks)

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