Project 2

Aim: To calculate the loads acting on the bridge as per IRC 6 and apply them on the given bridge

Procedure:

Given Data

• Span of the bridge is 10 m.
• Width of deck slab is 10.5m
• Width of carriage way is 9 m.
• Width of footpath is 1.5m
• The size of the Pier is 1.2 x 1.2 m.
• Radius of curvature in the bridge is 2 m.
• No of girders = 4
• I girder is 1.6m height
• Width of flanges is 2m
• Thickness of flange and web is 0.3m
• Thickness of deck slab is 0.225 m.
• Deck of bridge is flat with B <30 degree.
• Design speed of the vehicles is 50 km/hr.
• High flood level is 4 m above the Bottom of foundation level.
• The depth of accumulation of snow is 1250 mm
• The mean velocity of the river is 2.5 m/s
• The maximum crest elevation for the wave is 3 m
• The storm elevation is 8.5m
• Constant r as 5
• C_va as 3.
• C_r as 0.4

The dead load of the structure is done by the staad it-self

1. Thickness of Foundation = 1.5 m
2. High Flood level = 4 m from foundation
3. Storm elevation is at 8.5m
4. Height of girder = 1.6m
5. Thickness of deckslab = 0.225 m
6. Height of Pier from GL = 8.5-1.6-0.1 = 6.8m
7. Total heigh from the GL = 6.8+1.6+0.225 = 8.625m (FRL)

Water Current load

The height of pier subjected to water current,

H = HFL- Thickness of foundation = 4 – 1.5 = 2.5 m

Maximum velocity, V = √2 x V_mean= √2 x 2.5= 3.53m/sec

P = 52 K V^2= 52 x 0.66 x 3.53² = 427.65 kN/m²

pressure in terms of UDL = 427.65 * 1.2 = 513.18 KN/m

Centrifugal Load

Centrifugal force = (W x V²)/(127 R)

W = 70 T /4.570 m = 15.317 T/m

V= 50 Km/hr

R=2m

Centrifugal force = 15.317*50*50/(127*2) = 150.76 T

Water wave load

Storm water Elevation deck = 8.5 m

Maximum crest ɳ _max = 3 m

Centroid of I Girder = (1.6+0.225)/ 2= 0.9125 m

Maximum crest ɳ _max = 3 m

Δz_h = ɳ _max – Centroid of I girder = 3 – 0.9125 = 2.0875 m

Δz_v = ɳ _max – Elevation of bottom deck = 3 - 1.6 = 1.4 m

Fv* = 10 * 1.4 * 10.5 *10 = 1470 KN

Fh* = 10 * 2.0875 *10 *1.6 = 333.6 KN

Fv max = 3 * 1470 = 4410 KN = 441.0 KN/m = 441.0/10.5 =42 KN/m^2

Fh max = (1+0.3*(4-1)))3*333.6 = 1901.52 KN = 190.152 KN/m = 104.394 KN/m^2

Snow load

Assume wind packed snow

Density = 3.5KN/m3

Snow load, S_o = 3.5 x 1.25 = 4.375 kN/m^2

S = μ x S_o = 0.8 x 4.375 = 3.5 kN/m^2

Temperature Load

Maximum temperature in the location as per IRC 6 Isotherm at the location = 47.5 degrees

Minimum temperature in the location as per IRC 6 Isotherm at the location = -2.5 degrees

Effective temperature difference= (47.5 – 2.5)/2 +10 = 32.5 degrees

Stress due to temperature = α x ΔT x E= 12 x 10^-6 x 32.5 x 5000(40)^½= 12.322 kN/m²

Positive temperature difference

Temperature at top = 47.5 degrees

Temperature at bottom = (2.1/17.8) x 47.5 = 5.60 degrees

Calculation of barge impact

KE = 500 ｘC_H ｘ W ｘ V² = 500 ｘ1.25 ｘ 25000 ｘ 60² = 56.125 x 10⁹ Nm

a_B = 3100 ｘ ([1 + 1.3 ｘ 10^-7 x 56.125 x 10⁹ ]^0.5 - 1)= 261714 mm

P_B = 6.0 x 10⁶ + 1600 x (a_B)= 6.0 x 10⁶ + 1600 x (261714)= 9000 kN

Generation of Staad file

A STAAD file is generated as given below

Dead load of the structure is assigned using the self weight module

Water current load is acted upon the 4m of the column where HFL is present

Centrifugal force is assigned as per the vehicle definitions

Snow load is applied as pressure on the deck slab

temperature load is given as per the temperature definitions

Barge impact is calculated for different spans and applied as shown

Water currents are loaded as shown

The final analysis is done after application of loads and error free output is shown

The post processing is done after analysis and the following stresses are observed in the plates

Th eisplacement in columns is shown as below