steel design Flashcards
shape factors of sections
hollow circle - 1.27
circular plate - 1.7
diamond section- 2
triangular section- 2.34
Center of gravity of semi circles
semi circular line = 2R /pi
semi circular plate =4R/3pi
hemisphere = 3R/8
ultimate plastic load for propped cantiliver
11.656 Mp / L^2
hinge at x= 0.414 L
maximum permissible deflection in SSB
table 6 is 800:2007
elements succeptible to cracking = L/300
not succeptible to cracking = L /240
for cantiliver = L/150 and L/120
limiting grip length in lap joint
Lg < 5d
effect of bending stress can be ignored in above condition
8d >Lg > 5d , reduction factor required
Lg > 8d , redesign required
minimum pitch, guage , end distance
pitch/guage = 2.5 bolt
end = 1.5 hole
= 1.7 hole (for hand cut element)
maximum edge , pitch distance in welds and bolts
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
maximum pitch of tack bolt
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
bolt and bolt hole
dia = 6.06 sqrt(t) Unwins formula nominal dia : hole clearence 12 ~ 14 mm : 1mm 16 ~ 24 mm : 2mm > 24 mm : 3mm
slot welding size limitation
width of slot > 25mm or 3.t
long joints, weld and bolt unbuttening effects
L > 150 throat
L > 15 bolt
slenderness ratio limits of steel members
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
net tearing area of staggered bolting
[ B -n.D +(S^2) /4g ] * t
lug angle design
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
design of bolted connection
- find dia of bolt = 6.04 *sqrt(t)
- find rivit value
- find no of bolts required
- arrangement of bolts
- width and thickness of plates
- efficiency of joint (if asked)
design of lacing
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
width of lacing bars
bolt dia mm - width of lacing bar 16 - 50 18 - 55 20- 60 22- 65
to prevent web crippling
A = a +2.5*h2