BẢNG TÍNH CỐNG HỘP THEO AASHTO

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BOX CULVERT CALCULATION SHEET

1.General

Culvert section along traffice direction

- Station :

- Design standard: 22TCN-272-05

- Live load : 1 x HL93

2 Material property

2.1 Concrete

- Compresive strength of cylindrical at 28 days: f'c = 30 MPa

- Elastic modulus Ec= 0.043*gc^1.5*sqrt(f'c) = 28561.32 N/mm2

- Tensile strength of concrete: fr = 0.63*sqrt(f'c) = 3.45 N/mm2

2.2 Steel

2.2 Pavement and backfill

- Friction angle between soil and wall δ = 11 deg (table 3.11.5.3-1)

30 400 30 400

400 30

30

1750

30 400 30

30

Page: 76

3 Dimention of Box culvert

Exterior Wall thickness (5) 30.0 cm

Interior Wall thickness (6) 30.0 cm

Parameters Top Slab Bottom Slab Exterior wall Interior wall

As.min (cm2) :

As.max (cm2):

Top Renf Bottom Renf Top Renf Bottom Renf Top Renf Bottom Renf Top Renf Bottom Renf.

7Ф28/15

10Ф32/10

7Ф20/15 7Ф20/15

Ф14/15

Ф14/15

10Ф28/10

7Ф20/15

10Ф22/10

4 Loading

4.1 Dead load

4.1.1 Vertical earth pressure (EV) (A12.11.2.2)

• The factor of vertical earth pressure Fe = MIN(1+0.2*h3/W,1.15)

→ Vertical earth pressure on top slab of culvert EV = Fe.γs.h

(Kn/m3) (Kn/m)

4.1.2 Horizontal earth pressure (EH)

- Basic earth pressure shall be assumed to be linearly proportional to the depth of earth and taken as

In which:

Ph : horizontal earth pressure at the depth of Z (kN/m)

+ Lateral earth pressure applied on the plate as figure

Ph = Ka*γs*h3

Ph = Ka*γs*(H+h3)

in which:

- Ph : Horizontal earth pressure (kN/m)

- γs : Density of soil (kN/m3) γs = 18

- ϕ : Angle of internal friction ϕ = 30 deg

- h3 : filling height from top of box culvert (m) #REF!

- H : Total height of box culvert (m) 4.3

- Ka : active earth pressure coefficient (3.11.5.3 - 22TCN 272-05)

in which:

δ: Friction angle between soil and wall (deg) 11

θ: Angle between wall and vertical (deg) 90

φ Intenal friction angle of soil 30

4.1.3 Water effect

Horizontal Water Load, Top (7) : 0.00 kN/m

Horizontal Water Load, Bottom (7) : 0.00 kN/m

Covering (h3)

Covering

Ph H

Slab2

Ground level

h3

Ph

ev

eh eh

live load

ls

Ka sin2( θ φ ) Γsin2θ sin θ δ . ( )

θ φ

sin φ( β) sin φ. ( δ) sin θ( δ) sin θ. ( β)

2

Page: 76

4.2 Live load

- Where the depth of fill is less than 600mm, the effect of fill on the distribution of live load shall be neglected

• The uniformly distribution of wheel where covering depth >= 600 mm detemined follow A 3.6.1.2.6

• Impact load detemined follow A 3.6.2.2

• Where the depth of fill exceeds 600 mm, wheel loads may be consided to be uniformly distributed over rectangular area

with sides equal to the dimension of the tire contact area as A 3.6.1.2.5, and increased by either 1.15 times the depth

of the fill in select granular backfill, or the depth of the fill in all other cases

• For single span culverts, the effects of live load may be neglected where the depth of fill is >= 2400mm and exceeds

the span length

• For multiple span culverts, the effects of live load may be neglected where the depth of fill exceeds the distance

between faces of end walls

• Where such areas from several wheels overlap, the total load shall be uniformly distributed over the area

• The dynamic load allowance for culverts shall be taken as:

• Design truck:

- Estimate for impact factor and distributed area of wheel

Distribution of wheel load for 1 lane

Distribution of wheel load for 2 lane

→ Truck is consider as concentrated load

Wheel load of Truck : 01 lane (lane number, Lane factor & IM factor should be applied)

1800 1200 1800

Wheel load of Truck : 02 lane (lane number, Lane factor & IM factor should be applied)

Page: 77

• Tandem:

Distribution of wheel load of Tandem for 1 lane

Distribution of wheel load of Tandem for 2 lane

Distributed wheel load of Tandem

→ Consider as concentrated load

• Lane load

The equivalent strip widths for Liveload on box culvert (A4.6.2.3)

- For one Lane: E1lane = 250 + 0.42 (L1W1)0.5

In which:

- L1: Modified span length = 4300.00mm

- W1: Modified edge-to-edge width of culvert = 8000.00mm

→ E1lane = 2713.36mm

- For multi Lane: Emultilane = 2100 + 0.12 (L1W1)0.5≤ W/NL

- W: Physical edge-to-edge width ofculvert = 8000.00mm

- NL: Number of lanes = 2

→ Emultilane = 2803.82mm The width of interior equivalent strip Es = 2713.36mm

4.2.1 Surcharge load (LS)

-Where a surcharge load is present, a constant horizontal earth pressure shall be added to the basic earth pressure

This constant earth pressure may be taken as

Where:

k = active coefficient of earth pressure

γs = density of soil (kN/m3)

heq = height of soil equivalent to design truck (m) Determine from table 3.11.6.2-1, 22TCN 272-05

Depend on the height of wall: 4.300 m

1200

Wheel load of Tandem: 01 Lane (lane number, Lane factor & IM factor should be applied)

Wheel load of Tandem: 02 Lane (lane number, Lane factor & IM factor should be applied)

1800 1200 1800

Page: 78

4.3 Load combination

Load combination and load combination factor shall be taken as Table 3.4.1-1

Table of load combination factor State Mark Str I-A Str I-B Str I-C Str III-A Str III-B Str III-C Service I

Table of load combination on a unit length of culvert (kN/m) State Mark Str I-A Str I-B Str I-C Str III-A Str III-B Str III-C Service I