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## Analysis and Design of Concrete Highway Bridge

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United Arab Emirates UniversityCollege of Engineering Graduation Project II

Analysis and Design of Concrete Highway Bridge

Done By:

Abeer Abdullah 970722811

Amal Al-Amiri 199903930

Ramla Kalantar 199904023

Advisor:Dr. Bilal El-Ariss

First Semester 2004/2005

The Objective of the project is to:

Learn structural analysis and design of concrete highway bridges.

Acquire the knowledge and experience of applying the needed codes, specifications and soft ware.

Abu Dhabi Municipality commissioned proposals for an Overpass Bridge over Abu Dhabi/Dubai highway at Al-Bahia residential area.

The bridge is 95 m long

(311.7 ft).

The analysis and design of this bridge was done for the superstructure elements.

There are two methods used in structural design:

- In 1900s, the method used in design was called the working-stress design (WSD) method. In this method service loads were used.
- Since 1963, the ultimate-strength design method was rapidly used. In this method the service dead and live loads are multiplied by some load factors.

The method used in our project is the ultimate-strength design method.

- In Ultimate-strength design method there are two approaches by which the structural safety can be obtained:
- Load Factors
- Strength Reduction Factors

Structural Safety

- Load Factors:
- The service loads are multiplied by some load factors that are larger than one.
- Strength Reduction Factors:The material strength are multiplied by a reduction factor less than one.

- Strength Reduction Factors:The Code provides Φ values for several situations:
- Flexure…………………………………………. Φ=0.9
- Shear…………………..………………………. Φ=0.85
- Axial compression with Sprials……………… Φ=0.75
- Ties………………………………………...…… Φ= 0.7
- Bearing on concrete………………………. …..Φ=0.7

(AASHTO 8.16.1.2.2)

Design Specification

AASHTO:

AASHTO stands for American Association of State Highway and Transportation Officials. we used the following sections of AASHTO specifications:

Section 3: Loads

Section 8: Reinforced Concrete

ACI Code:

ACI stands for American Concrete Institute. ACI was founded in 1904

Reinforced Concreteis a composite material ofsteelbarsembedded in a hardenedconcrete.It is strong durable material that can formed into many varied shapes and sizes.

- Cement:

OPC is the most common type in use.

The main chemical compounds in cement are calcium silicate and aluminates.

- Water:

when water is added to cement to form cement past chemical reaction occur and the mix becomes stiffer with time

(water cement ratio is an important factor affecting concrete strength)

- Aggregates :
- The bulk of concrete is aggregate in the form of sand and gravel which bounded together by cement.
- a. Coarse aggregate – gravel or crushed rock 5mm or larger in size.
- b. Fine aggregate – Sand less than 5 mm in size.
- Admixtures:
- as setting accelerators or retarders, etc.

Reinforcing bars can be plan or deformed, the bar sizes used in U.S customary units ranges from #3 thought #18. While in SI units the bar are numbered 10, 13, 16, 22 and 43. these numbers represents the bar diameters approximately.

In design we will use 420 MPa, the corresponding grade in U.S customary unit is 60,000 psi.

Steel

Strength in tension

Poor

good

Strength in compression

good

Good but slender bars will buckle

Strength in shear

Fair

good

Durability

good

Corrodes if unprotected

Fire resistance

good

poor

Comparing Properties

Advantages of reinforced concrete

- Has a high compressive strength.
- Resists fire actions.
- Low maintenance material, has a very long service life.
- An economical material and has an ability to be cast into a variety of shapes

Disadvantages of reinforced concrete

- Has very low tensile strength.
- Has a low strength per unit of weight of concrete which leads to heavy members.
- The properties of concrete vary due to its proportioning and mixing.

1.Reinforcement Requirements due to flexure

The main reinforcing ,it may not be spaced farther on center than 3 times the slab thickness, or 18 in.

One-fourth the positive moment reinforcement in continuous members shall extend along the same face of the members into the support in beams, at least 6 inches.

Types of needed reinforcement

Development length (ld):

The reinforcement bars must be extended some distance back into the support and out into the beam to anchor them or develop their strength.

The basic development length shall be:

No. 11 bars and smaller………

But not less than………………

Types of needed reinforcement

2.Parallel reinforcements

In slabs, A percentage of the main positive moment reinforcement shall be distributed in the parallel direction of the traffic:

Spacing limits for reinforcement:

For cast-in-place concrete the clear distance between parallel bars in a layer shall not be less.

1.5 bar diameter,

1.5 times the maximum size of the coarse aggregate,

1.5 inches.

Types of needed reinforcement

3.Shrinkage Temperature Reinforcement:

The total area of reinforcement provided shall be at least 1/8 square inch per foot in each direction.

4. Skin Reinforcement:

skin reinforcement will be uniformly distributed along both side faces of the member for a distance d/2 nearest the flexural tension reinforcement.

The area of skin reinforcement Ask per foot of height on each side face shall be.

The maximum spacing of skin reinforcement shall not exceed d/6 and 12 inches.

Types of needed reinforcement

5.Shear Reinforcement

If the diagonal tension exceeds the limited tensile strength of the concrete then shear reinforcement must be provided.

Stirrups perpendicular to the axis of the member.

Welded wire fabric with wire located perpendicular to the axis of the member.

Types of Shear ReinforcementTypes of Shear Reinforcement

- Combinations of stirrups and bent longitudinal reinforcement.
- Spirals.

Slab Design

Slab is assumed to e a rectangular beam with a large ratio of width to depth. A 12-in wide piece of such a slab is designed as a rectangular beam.

I ft strip of the slab will be designed and considers as a continues beam.

- Live load Moment=

(AASHTO 3.24.3.1)

- Dead load Moment

Mu= 1.4 MD +1.7ML

h=10’’ , f’c=4000psi , fy=60,000psi

- spans Section (b-b):
- d =10’’-1’’-1/4’’ = 8.75’’ (in)
- MD = 1.1 k.ft
- ML = 4.94 k.ft
- Mu = 1.4 MD +1.7ML = 9.938 k.ft
- = 144.2psi
- (Use table A.14)
- ρ =0.0033
- As = ρbd = 0.3564 in2
- Use Bar #4 @ 6.5 in (As=0.36 in2)

Cover:

Top reinforcement…………….2 in.

Bottom reinforcement…………1 in.

Development length:

For No. 4 bars = 1 ft

For No. 5 bars = 1.25 ft

- Minimum depth for T-Girders (0.065S) (AASHTO table 8.9.2)
- Compute Z larger of 0.9d or d-(hf/2)
- Steel Area
- Checking minimum reinforcement

(larger of )

Girder Calculation

- h = 6.93 ft = 83.16 in
- d = 83.16-2-0.5-1.693/2 = 79.81 in = 6.65 ft
- b = d/2 = 39.91 in
- hf = 10 in

Interior Girder Reinforcement

Skin reinforcement calculation:

Bar #3 is used for all shear reinforcement (stirrups)

Girder Dimensions and Properties for Shear

Reinforcement Calculation

Bar #3 is used for all shear reinforcement (stirrups)

Pier Cap Dimensions and Properties for Shear

- The Proposal overpass bridge over the Abu Dhabi/ Dubai Highway at Al Bahiah area will ease the movement to and from Al Bahiah residential area toward Dubai and Abu Dhabi.
- Al Bahiah residential will reduce their trip time to and from it.

Advantage

1.Cement is composed of 75% limestone.

2.extracting the raw materials for concrete has a lower impact than that of other construction materials.

3.Almost all concrete contains fly ash, a byproduct of coal-burning electric plants.

4.Old concrete that has reached the end of its service life can be recycled and reused.

Environmental Impacts

Disadvantage

One tone of cement:

- Requires about 2 tones of raw material (limestone)
- Consumes about 4 GJ of energy in electricity, process heat, and transport.
- Produces approximately one tone of CO2.

Economical Impacts

- Concrete is a durable material that actually gains strength over time and conserves resources by reducing maintenance and the need for reconstruction.
- Steel and Concrete are widely available in the UAE.
- By reducing the trip time that will economize the fuel consumption.
- Both Steel and Concrete can be recycled and used in other applications.

Conclusion and Recommendation

- Through out working on this project we gain skills, knowledge and some experience in bridge analysis and designing by following the

AASHTOand the ACI code.

- It is recommended to have an original copy of AASHTO specifications rather than the not clear photocopies we had.

Any Questions?

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