Design considerations and assumptions made in this design.
1. Design method used is Working stress Method for all components. 2. Grade of concrete is M20 and for steel it is Fe415. The material used shall confirm with relevant related codes with latest editions. 3. Structural steel shall be mild steel with yield stress 250 N/mm2 4.Load combination combination as per IS 1893 - 2002 Imposed load as per IS 875 Live load = 0.5 kN/m2 on bridge floor area. Dead load : Self wt of members and weight of checker plate on floor. Wind load : Intensity of wind considered = 39 m/s m/s k1 = 1.00 k2 = 1.06 and k3 = 1.00 Design speed = 41.34 m/s Design wind pressure = 1025 N/m2
5. References I.S. 800 I.S. 456 I.S. 875 - Part III Design of steel Structures - S. Ramamruthm.
Kasheef and Associates Consulting and Structural Engineer Aurangabad.
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1. Load due to Wind : Bridge Height = 2.25 m Max. size of member TUBE 89 89 4.5 Exposed area of wind = Area of all members per bay of 1.875 m length = ( 2.25 x 3 + 2.93 ) x 0.089 = 0.862 m2 For both sides = 2 x 0.862 = 1.724 m2 Wind Velocity = 39 m/s Probability or risk factor = k1 = 1.00 Terrain height and structure size factor = k2 = 1.06 Topography factor = k3 = 1.0 Design wind speed = Vd = k1 k2 k3 Vb = 1 x 1 x 1.06 x 39 = 41.34 m/s Design wind pressure = 0.6 Vd x Vd = 0.6 x 37 x 37 = 1025 N/m2 Effective area of pipe = 0.67 x 0.7 x 1.875 = 0.88 m2 Total area exposed to wind = 0.88+ 1.724 = 2.604 m2 Total Total wind wind force force = 1.025 1.025 x 2.604 2.604 = 2.66 2.669 9 kN ( On each each bay bay of of 2.1 m lengt length) h) Increase for gusset plates and any other obstruction by 15 % = 1.15 x 2.669 = 3.07 kN Load per panel point = 3.07 / 4 = 0.77 say 0.80 kN. For end points = 0.4 kN This is to be applied in both the directions ( + and - ) 2. Live Loads due to Maintanence etc. Live load intensity considered is 0.5 kN/m2 on bridge floor area. 3.0 Dead loads of bridge : Weight of checker plates and other arrangement for walk way = 80 kg/m2 = 0.8 kN/m2 Weight of 8 mm tk 700 mm dia pipe = 140 kg/m = 1.4 kN/m Weight of water = 3.85 kN/m Total weight = 5.25 kN/m Weight on each horizontal member = 1.875 x 5.25 = 9.85 kN Weight of supporting arrangament of pipe = 0.5 kN Total weight = 10.35 kN say 10.5 kN on inner inner and 5.25 kN on outer member. All these loads are applied on the STAADpro model in which self weight factor is given as 1.1 to accommodate weight gusset plates. T and the CODE CHECK commond is used f or IS 800.
Seismic force calculations Total seismic weight of Bridge = 203 kN ( Sum of Reactions for DL+LL ) Earthquake Zone Considered = Zone II Seismic base Shear Wh = ( Z/2 ) x ( I / R ) ( Sa / g ) Time period = 0.085 H
0.75
W
= 0.404 s ( Using H = 8.0 m )
Seismic coefficient Z = 0.10 I = 1.0 R = 4 , Sa/g = 2.5 Wh = 6.35 kN
( Seismic force )
This load is much less than wind loads ( 0.8 x 4 x16 = 51.20 kN ) Hence wind will gov ern the design.
Design of Bolts at Support : Using 20 mm dia Bolts and 12 mm tk Base plate Strength of Bolt in Shear = ( 3.14 / 4 ) x 20 x 20 x 100 = 31.41 kN Strength in Bearing = 20 x 12 x 300 = 72.0 kN Safe load = 31.41 kN No of Bolts required = 149.075 / 31.41 = 4.75 Say 8.0 Nos Use length of bolt = 40 x 20 = 800 mm embeded in concrete. ( No tension hence nominal bolt length as 40 x dia )
DESIGN OF PIER PILE AND PILE CAP Design of Pier : Loads on itermidiate pier : Load from Bridge Vertical = Horizontal Fz = Horizontal Fx =
232.84 10 252
kN kN kN
( 4 x 58.21 kN See reactions )
Wind on Pier: Wind load = 1.025 x 6.0 x 0.6 = 3.69 kN considered 1/3 on top Considering Ht. Of Pier 6.0 m above River Bed. Pressure due to water current on pier = Water pressure = wh2/3 = 10 x 5 x 5 / 3 = 83.33 kN Considering dynamic dynamic effects = 2 x 83.33 = 166.67 acting at 1.67 m from base. Weight of Pier = 6 x 3.7 x 0.6 x 25 = 333 kN Design force at base of pier Axial Force Force = 233 + 333 = 566 566 Say 570 kN Moment Mz = 252 x 6 = 1512 say 1550 kN-m Moment Mx = 10 x 6 + ( 3.69 / 3 ) X 6 + 166.67 x 1.67 = 345.72 kN-m say = 350 kN-m Concrete Grade M20 Permissible stresses
6ac = 6bc =
Area of cross section for pier = M.I. For pier section Iz = Ix =
DESIGN OF PILE CAP : Pile Pile cap cap = Rect Rectan angu gula lar r C/c of Piles = 1800 mm Projection Beyond pile face = 400 mm Depth = 750 mm Eq. Length of Beam=
1800
mm
Load on each beam= Direct load on on beam ( P/4 ) = 570 / 4 = 143 kN Load due to Mz = Mz/ L = 1550 / 2.7 = 575 kN kN Moment due to Mz = M = ( Mx/3)/4 Mx/3)/4 = (350/4 (350/4 ) / 4 = 22 kN-m Load on each beam= M= Max. Total B.M =
718 22
kN kN-m
183.55
kN-m
Concrete Grade = 6bc = 6st = m= j = k=
M20 7 150 13.33 0.872 0.384
Steel Required for Beam =
2005
mm2
Used steel Bar dia = Nos= Ast =
20 7.00 2199
mm say 8 nos mm2 Safe
Loop R/f 20 % of Ast = Bar dia = No of Rings =
401 10 6
N/mm2 N/mm2
mm2 mm Nos
DESIGN OF PILE : Overall size of Pile oad on on pile pile cap from pier pier ( P/6 ) = 570/5 = 130 k kN Load due to Mz =( M/L )/2 = ( 1550 / 2.7 ) /2 = 287 kN Load due to Mx =( M/L )/2 = ( 350 / 1.8 ) /2 = 97.50 kN W t of Pile Cap = 254 kN Load on Each pile = Length of Pile = Eff. Length = Dia of Pile = Steel used Dia = No of Bars required = say = Slenderness Ratio = Strength one Pile =
565 5 5 500 16 12.206 12 10 1154.09
Height = W idth = Depth =
kN
4.1 3.1 0.8
m m m
m ( Approx ) m mm mm Min steel 1.25 % 2454 Nos kN
Capacity of pile Group : Bearing capacity at end of pile = Shear modulus of soli( c ) = Eq. Plan Area = Eq. Perimeter = Length of pile = Capacity in Direct Bearing = Capacity in Shear = Total Capacity = Capacity of Single pile : Dia = Length = friction factor = Capacity in friction = Capacity in end bearing = total capacity = Capacity of al all pi piles in in gr group =
120 20 12.71 14.4 5 1525.2 1440 2965.2
0.5 5 0.35 370.91 23.56 394.47 1972.35
kN/m2 kN/m2 m2 m
Assumed
kN kN kN
m m kN kN kN kN
unit wt of soil w = 18 kN/m3 Angle of repose = 30 Deg. kp = ( 1 + sin0 / 1- sin0) kp = 3 2 Capacity = kp x ( wl /2 ) Mu x perimeter
