1

Design of a Reinforced Concrete Deck-Girder Bridge

to AASHTO & ACI Codes

2

Given Data:

Effective Span= 63 ft

Effective Width= 3o ft

Live Load= HS20

Concrete Strength (Cylindrical Test) f'c =5000 psi (35 MPa)

Steel a- Grade 40 for Deck Slab fy = 40,000 psi (330 MPa)

b- Grade 60 for Girders fy =60,000 psi (414 MPa)

Deck Slab Design:

b = 20 in = (50 cm)

h (slab) = 8in = (20 cm)

t (Asphalt concrete) = 4in = (10 cm)

Dead load :

Moment for Dead load :

Moment for Live load from HS20 :

0.80 : factor for continuity

3

I : Impact factor

Total Moments on deck slab:

Moment for dead load on side walk slab :

Moment for Live load on side walk slab : (live load=85psf)

Total Moments on side walk slab:

4

Design Deck slab according

l

5

d required for slab :

Decrease the strength of material :

Use steel ɸ 5/8 in and concrete cover 1 in and take top layer 1 in

Spacing between bars :

6

Design of Interior Girders :

Design as T section : assume h for web = 40 in (1.00m)

Dead load :

Moment for dead load :

Live load :

7

Load for back and middle wheel=1.40*16000=22400 lb

Load for front wheel=1.40*4000=5600 lb

Shear force calculations :

8

To calculation max. shear force due to live load, max. shear force

found under back wheel after enter the truck across bridge .The

back wheel without increase while the middle and front wheel

load multiply by factor 1.40

9

Determination of Girder Cross Section Dimensions :

According AASHTO specification nominal shear stress from service

loads (v) :

Total h = 48 in

11

Stress calculation :

11

Web Shear Reinforcement

Critical state at distance d from the support :d = 40.625 in = 3.40 ft

12

13

Max. space between stirrup = d/2 = 40.625/2 = 20 in

Use steel bar # 5

Vs =

V = 67+46 = 113 psi of the middle distance = 63-10*2=43 ft

Beside the support :

Distance between stirrup

14

15