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Design of Concrete Girder Bridge

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Design of Concrete Girder Bridge

UNITED ARAB EMIRATES UNIVERSITY

College of Engineering

Civil & Environmental Engineering Department

Graduation Project II

Team Member:

Ahmed Al-Shehhi200000069

Waleed Al-Alawi200101647

Abdullah Al-Neyadi 200101637

Hassan Al-Hassani 200005052

Project’s advisor : Bilal El-Ariss

Presentation outline

- Executive Summary
- Introduction
- Background theory
- Methods and Techniques :
- Analysis of pier cap
- Design of bridge deck ,girders and pier cap

- Results and discussions
- Conclusions and recommendations

- Analysis and design of a concrete girder bridge
- Graduation project I
- Graduation project II
- Pier cap analysis
- Design of bridge deck , girders and pier cap

- Software used :
- SAP2000
- Analysis and determine bending moments and shear forces

- PROKON
- Compute the reinforcement areas needed for the shear and moments, and the dimensions of the different components of the bridge

Introduction

- Project description
- Bridge location

- Project description :
- Continuous girder bridges .
- Two lanes in each direction and two shoulders and carries the traffic in two directions .
- Two span girders .

- Bridge Dimensions

- AASHTO specifications
- American Concrete Institute (ACI) code

- Bridge location :
- Abu Samra Bridge is located on the high way between Abu Dhabi and Al-Ain .

Background Theory

- Reinforcement requirements:
- Design method
- Reinforcement requirements due to flexure
- Reinforcement requirements due to Shear
- T-Girder

- The method which will be used in our project is the ultimate-strength design method.
- It's called now ultimate strength design.
- The working dead and live loads are multiplied by certain load factors and the resulting values are called factored loads.

- The reinforcing bars will be distributed as follows:
- This reinforcing may not be spaced farther on center than 3 times the slab thickness.
- A percentage of the main positive moment reinforcement which is perpendicular to the traffic 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 that 1.5 bar diameter.
- Not less than1.5 times the maximum size of the coarse aggregate or 1.5 inches.

- Positive Moment Reinforcement:
- At least one-third the positive moment reinforcement in simple members and one-fourth the positive moment reinforcement in continuous members shall extend along the same face of the members into the support in beams, such reinforcement shall extend into the support at least 6 inches.

- The development length :
- 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 failure of reinforced concrete beams in shear are quite different form their failures in bending.
- Shear failures occur suddenly with little or no advance warning.
- If pure shear is produced in a member, a principal tensile stress of equal magnitude will be produced on another plane.

- Stirrups perpendicular to the axis of the member or making an angle of the member or making and angle of 45 degrees or more with the longitudinal tension reinforcement.
- Welded wire fabric with wires located perpendicular to the axis of the member.
- Longitudinal reinforcement with a bent portion making an angle of 30 degrees or more with longitudinal tension reinforcement.
- Combinations of stirrups and bent longitudinal reinforcement.
- Spirals.

- Design of cross section subject to shear shall be based on:
- Where Vn = nominal shear strength
- Vu= factored shear force at the section considered

- For members subjected to shear and flexure only (Vc) is computed by:
Where bw = the width of web

d = the distance from the extreme compression fiber to the centroid of the longitudinal tension reinforcement.

- When shear reinforcement perpendicular to the axis of the member is used:
- Where Av= the area of shear reinforcement with in distance s.
- S= Spacing between stirrups
- Shear Strength Vs shall not be taken greater than

- A minimum area of shear reinforcement shall be provided in all flexural members expect slab and footing where the factored shear force Vu exceeds one-half the shear strength provided by concrete 1/2.
- The area provided shall not be less than:
- Where b and s are in inches.

- Spacing of Shear Reinforcement
- Spacing of shear reinforcement placed perpendicular to the axis of the member shall not exceed d/2 of 24 inches.

- Shrinkage temperature reinforcement:
- Reinforcement for shrinkage and temperature stress shall be provided near exposed surfaces of walls and slabs not otherwise reinforced.
- The total area of reinforcement provided shall be at least 1/8 square inch per foot in each direction.
- The spacing of shrinkage and temperature reinforcement shall not exceed three times the wall or slab thickness, or 18 inches

- The Total width of slab effective as a T-girder flange shall not exceed one-fourth of the span length of the girder.
- The effective flange width overhanging on each side of the web shall not exceed six times the thickness of the slab or one-half the clear distance to the next web.

Analysis of Pier Cap

- Dead load of pier cap
- Live load of pier cap

6’

3’

- Estimate the thickness
- L = 50.54 ft
- Length of span = 25.27 ft
- Minimum thickness of the bridge cap piers
- Width (b) = 0.5 Depth = 3 ft

Dead load of pier cap

- Own weight of pier cap = Density of conc. * area * 1
= 150 Ib/ft 3 * (6* 3) * 1

= 2700 Ib/ft

- Uniform wheel load = wheel load * S/6 * Impact factor
= 26 kip

- Concentrated load from interior girder
= 490 Ib

- Concentrated load from interior girder
= 546 Ib

Dead load

B.M.D

Shear force diagram

- Use several cases by distributing the wheel trucks.
- Take the maximum wheel load = 18000 Ib
- Find the reactions in each supports for all cases.
- Take the maximum values of reaction.

- These are the following cases:
- Case 1: Full shift left
- Case 2: Full shift right
- Case 3: Centre to left
- Case 4: Centre to right
- Case 5: one truck centre to left
- Case 6: one truck to left
- Case 7: one truck centre to right
- Case 8: one truck to right

- Example of calculationsCase 3: Centre to left

Uniform wheel load

- ∑ M2 = 0
- R1 =( 26 * 2.95 ) / 7.22 = 10.6 k
- ∑ Fy = 0
- 10.6 + R2 – 26 = 0
- R2 = 15.4 k
- ∑ M3 = 0
- R2 =( 26 * 4.17 ) / 7.22 = 15 k
- ∑ Fy = 0
- 15 + R3 – 26 = 0
- R3 = 11 k

- Reactions for eight cases

- Found the maximum in the same position of maximum dead load

Maximum shear force in case 2

Maximum positive moment in case 2

Design Stage

- Design of slab by using Prokon software
- Design the girders using manual calculation method
- Design the pier cap by using Prokon software.

- Use PROKON for slab
- Inputs: Slab cross section

- Area of steel (As)

- Use Hand Calculations Method

- Positive section
- The following equations were used to compute Area of steel needed for the section (As):
Fy= 420 MPa

F’c= 21 MPa

Mu = 4745 KN-m

b= 2200.656 mm

d= 1601.4 mm

- The following equations were used to compute Area of steel needed for the section (As):

- Minimum Spacing of stirrups = Maximum of
- 600 mm
- .
- Use minimum Spacing (S) = 600mm

As required (mm2)

Required reinforcement

Main girder section

Positive

5733

Interior

Negative

5733

Positive

5733

Exterior

Negative

5733

- Using Prokon software to design
- Inputs:
- Parameters:
- Fcu,
- Fy,
- D.L and L.L factors
- density of concrete

- Length of each span = 7.7 m

- Parameters:

- Minimum spacing s = maximum of ~ (depth – cover)/2 = (1829- 50)/2 = 890 mm
~ 600 mm

- So minimum spacing (s) = 890 mm.
- Minimum number of bars = length of span / Spacing= 7700 / 890 = 8.6 = 9 bars
- Take 10mm Stirrups diameter for the pier cap

- Finish the analysis of pier cap.
- Finish the design of superstructure for a girder bridge
- Use SAP2000 and Prokon programs in design
- The objective of GPII is fulfilled
- Learn main concepts on structural analysis and design

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