This document presents the design of a three-span precast pre-stressed concrete girder bridge with spans of 12.0015m, 24.140m, and 12.0015m. The objectives are to develop a cost-effective bridge design using LRFD methods that meets NMDOT standards. The design includes AASHTO Type III girders, a reinforced concrete deck, bearing pads, pier columns, drilled shaft foundations, and considers loads, reinforcement, and strength requirements. Analysis and design software such as CONSPAN and RC-PIER are used to optimize the superstructure and substructure elements.

1. Precast Pre-stressed
Concrete Girder Bridge
Dissertation Presented in Partial fulfillment
for the Bachelor of Science
in
Department of Civil Engineering
Jiangsu University

2. Dissertation Defense by
Nkosiyabo Isaac Mafu
Dissertation Committee
Assoc. Prof: Dr.Jie Yin
Assoc. Prof: Dr. Bo Su
Assoc. Prof: Dr. Hai-Xia XU
Lecturer Dr. Hai QIAN (Secretary)

3. Contents
• Overview of the bridge
• Objectives
• Design steps
• Superstructure design
• Bridge layout
• Beams
• Shear reinforcement
• Substructure and foundation

4. Overview of the bridge
• This project Site location is assumed to be near Socorro, New Mexico, with the
bridge crossing a waterway on a normal (perpendicular) alignment.
• We illustrates New Mexico Department of Transportation (NMDOT) design
procedures for a three-span pre-stressed concrete girder bridge. The bridge
consists of the following spans respectively12.0015 m, 24.140 m and 12.0015 m.
spans, with a 15.240m wide bridge.
• The superstructure is supported by AASHTO Type III girders, which are continuous
for live load. The substructure consists of three-column piers and abutment bents
supported directly by drilled shafts. The abutment is of the semi-integral (floating)
type.

5. Transverse section

6. Elevation of the bridge

7. Objectives of this research
• The objectives of this research project are three-fold:
• 1) Develop a cost-effective and aesthetically acceptable concrete
Girder with 3 spans in excess of 45 meters.
• 2) Revise the New Mexico Department of Transportation (NMDOT)
with the need to build a simple girder bridge across a river, in
accordance with the research and recommendations.
• 3) Develop approximate formulas to estimated Load and Resistance
Factor Design (LRFD) methods.

8. What is LRFD & AASHTO
• Load uncertainties incorporated by load factors.
• Resistance factors account for the uncertainties associated with
material properties.
• Load and Resistance Factor Design (LRFD).
• Provides more consistent design and level of safety in th superstructure
and substructure design.
• LRFD methods are used throughout this whole research project, except
where a suitable LRFD does not exist.
• AASHTO is the American Association of State Highway and
Transportation Officials( Test Protocols and guidelines for highway
construction and design throughout the USA)

9. Design steps included in the project
The following design steps are included in
this example:
• Concrete deck design
• AASHTO Type III girder design
• Bearing pad design
• Pier and abutment cap design
• Pier column design
• Drilled shaft design
• Seismic design

10. Superstructure Design
• .
• The superstructure design includes the following elements: deck design, pre-
stressed girder design, and bearing pad design. Deck design follows the NMDOT
standard deck
• Girder analysis and design is performed using the computer program CONSPAN,
Version 09.00.03.01. Input data and design loads needed for the computer
analysis are developed and listed.
• From the resulting output, a final girder design is developed and finally the
NMDOT standard beam sheet is completed.
• Reinforced elastomeric bearing pad design is also illustrated.

11. Bridge layout
Overall width = 15 m.
Number of lanes = 3
Lane width = 3.60m.
Left and Right Curbs = 0.472 m.
Supplemental Layer = 0 m.
Deck Thickness = 0.2286m.
Haunch Thickness = 0 m.
Haunch Width = 0.4064m

12. Beams
Height=1143mm
Top flange=406mm
Bottom flange=559mm
mid part/web=178mm
flange thickness=178mm

13. End and Mid-span for span 1&3
• 2 draped for the ends with a
distance from the bottom
1066.8mm
• 12 straight strands at the bottom
flange
• 14 Strands for the mid-span

14. End and Mid-span for span 2
• 6 draped strands top flange for the
ends.
• 38 straight strands at the bottom of
the flange
• 44 strands for the mid-span at the
bottom flange

15. Loads on the beams
• Analysis factor on the
conspan software dead
loads distributed
equally.
• Loads on the beams
are computed and the
dead loads are as
shown

16. Shear reinforcement
• Computer Analysis results
for the shear reinforcement
and strand pattern are
shown.
• Span 1 beam 2

17. Horizontal and Vertical shear
reinforcement
Horizontal Shear Reinforcement
• The calculated reinforcement
requirement (per meter of length) for
horizontal shear is listed in the
program output. Since the same
reinforcement (pairs of #4 bars) will
be used to satisfy both vertical and
horizontal shear, the area provided is
again As = 258.064 mm2
• Vertical Shear Reinforcement The
computer output calculates the
required reinforcing area per meter
length and is listed. The computer
program also allows the engineer to
develop the vertical shear layout. The
following shear envelopes have been
developed with a pair of #4 bars for
stirrups.

18. Substructure & Foundation design
Substructure and foundation design includes design
of the piers and abutments. For this
example the program RC-PIER, Version 09.00.03.01,
will be used as the primary design
aide. Refer to the preliminary design sections of this
document for details of the
preliminary pier and abutment configurations.
The pier is a three-column bent with circular columns
that will frame directly into
supporting drilled shafts. Piers 1 and 2 bearings are
fixed against longitudinal movement.

19. Load Combinations • This computer computer software
has a list of all AASHTO LRFD
loads and loads combinations.
• They are also different strengths
associated with different piers.
• For Pier 1 in this example,
applicable loads are DC, DW, LL,
LLp, BR, PL, WA, WS, WL, and TU.
EQ will not be applied in this first
run.
• From the LRFD Specifications, it is
determined that load cases
applicable to this pier are Strength I,
Strength II, Strength III, Strength V,
and Service I. Extreme Event I for
the 500-year flood and Extreme
Event Seismic Group I will not be
used for this first run.

20. DC: Component and attachments/Precast DC
DW: Wearing surfaces and Utilities/Composite
LL: Vehicular Live Load
LLp: LL Permit/ Permit live
BR: Braking Force/ Braking
PL: Pedestrian Loads/ Pedestrian Live
WA: Water and stream pressure/ Water
WS: Wind and Load on structure/ Angle 0
WL; Wind Load on Live/ Angle 0
TU: Uniform Temperature/ Temperature
EQ: Earthquake Effect/ Seismic

21. Conclusion
• Satisfy all the requirements for all the loads and support requirements.
• Run for 500-Year Flood (Extreme Event Group II)
• Conclusion of Preliminary Design
• With the check of the 500-year flood, the preliminary design work for the pier is concluded, and we are
now ready to transmit shaft loads to the Geotechnical Section for final foundation recommendations.
These loads, acting at the top of shaft, are as follows (referring to the Load summary for each RC-PIER
run):
• Strength Groups
• • Axial Load = 3,331.71 KN
• • Horizontal load = 88.96 KN
• • Moment = 281.33 m
• Scour depth is 3.05m
• Extreme Event Seismic
• Transverse
• • Axial Load = 2,931.38 KN
• • Horizontal load = 618.30KN
• • Moment = 447.41994 KN.m
• Longitudinal
• • Axial Load = 2,362.01 KN
• • Horizontal load = 160.14 KN
• • Moment = 1,347.68KN.m
• Scour depth is 0m.
• Extreme Event II (500-yr flood)
• • Axial Load = 2,473.21 KN
• • Horizontal load = 31.14KN
• • Moment = 383.70KN.m

22. Thank You