Designing a Bridge Deck Flyover: Civil Engineering Project

This project provides a detailed design for a bridge flyover, addressing traffic congestion issues in an expanding city. It explores two primary construction options: a continuous beam bridge and a cable-stayed bridge, comparing their advantages and disadvantages. The project includes a general design description, key issues, scheme comparisons, and recommendations, ultimately favoring the continuous beam option due to its economic efficiency and adaptability. The design incorporates detailed considerations for construction methods, procedures, environmental sustainability, and cost estimation. Calculations for load paths, overall stability, load analysis, and steel analysis are presented. The project also covers ultimate and serviceability limit states, including shear force and moment computations, providing a comprehensive overview of the design and construction process. The project uses C50 concrete and motorway standards for the continuous beam option, dividing the road span into four spans. It also considers the aesthetic and functional aspects, along with the impact on the local environment and community. The student has included a cost estimate, detailed calculations, and a discussion of environmental sustainability measures, making it a thorough analysis of the bridge flyover design.

Designing a Bridge Deck Flyover 1
Bridge Engineering: Designing a Bridge Flyover
By
(Student’s Name)
Course Name:
Professor Name:
University Name:
Date of Submission:

Designing a Bridge Deck Flyover 2
Contents
GENERAL DESIGN DESCRIPTION..................................................................................................................3
OPTION 1: CONTINUOUS BEAM BRIDGE FLYOVER..................................................................................4
OPTION 2: CABLE STAYED FLYOVER BRIDGE SYSTEM..............................................................................4
KEY ISSUES...............................................................................................................................................4
SCHEME COMPARISON FOR OPTION-1 AND OPTION -2..........................................................................5
RECOMMENDATIONS FOR PICKING OPTION 1........................................................................................5
CONSTRUCTION METHOD.......................................................................................................................5
CONSTRUCTION PROCEDURE..................................................................................................................6
ENVIRONMENTAL SUSTAINABLITY..........................................................................................................6
COST ESTIMATE.......................................................................................................................................6
CALCULATIONS............................................................................................................................................7
LOAD PATH ABD OVERALL STABILITY.......................................................................................................7
LOAD ANALYSIS.......................................................................................................................................7
STEEL ANALYSIS.......................................................................................................................................9
ULTIMATE LIMIT STATE IN CABLE..........................................................................................................10
Computation of the Design Strength..................................................................................................10
Computation of the Design Load.......................................................................................................10
SERVICEABILITY LIMIT STATE.................................................................................................................10
SHEAR FORCE AND MOMENTS COMPUTATION....................................................................................11
BIBLIOGRAPHY...........................................................................................................................................13

Designing a Bridge Deck Flyover 3
GENERAL DESIGN DESCRIPTION
There is increasing traffic congestion within the Midlands and the problem is imminently
reported on a daily due the expansion of the city. This problem has raised an alarm and therefore, there is
a proposal which requires that a flyover be constructed to ease the traffic flow at the junction of the major
road which intersects all the major roads in the town. However, the major concerned is that this flyover
should not interrupt the already existing primary roads within the area. Also, it is clear that the only
traffic controlling point with the town is the major roundabout within the area. In early 50’s, there were
trams along the major roads and they were used to serve the city however; these trams are currently not in
use and serve as central reservations within the city. In fact, the trams now offer an opportunity of
building a dual flyover carriage without necessarily adjusting the existing roads (Schacht and Marx, 2015
p.70).
Additionally, it is important to take into consideration the fact that the proposed flyover should be
economical in terms of its elegant and its functionality as well. Obviously, the local environment and the
apparent appearance of the town is also a major concerned which need to taken into consideration under
the design aspect of this parameter. Some of the elements to be considered in the process include offices,
premises, small businesses as well as local shops which are adjacent to the proposed carriage way.
Therefore, the efficiency and minimum disruption during the construction is a key priority in the
designing and the implementation of this project. This should even include stakeholders and the overall
community as a whole (Zhu and Law, 2015 p.1983).
OPTION 1: CONTINUOUS BEAM BRIDGE FLYOVER
In the construction of a flyover continuous beam bridge can be a type of the design to be used in
the construction. This entails having two or even more beams which are jointed on the support edges. The
continuous beams are of the two types based on the material science and these two categories include
concrete continuous as well as the pre-stressed continuous beams. Moreover, for this flyover construction
the continuous beams tends to have a number of advantages which ranges from few movements along the

Designing a Bridge Deck Flyover 4
joints, smooth deck, good rigidity of the structure, span capability, reduced maintenance cost, resistance
to wave and earthquake as well as strong applicability. Taking the span of the flyover to be 80.5m and the
width of the flyover to be 20m, then this option will ensure that the deformations and rigidity structure are
well organized in the round and have no adverse effects and are economical in the long run. Furthermore,
the substructures will be made of the abutments and the piers. On the other hand the superstructure will
mainly compose of the continuous beams along with the panels which prove safety parapet and walking
surface. Moreover, the road span can be divided into four spans with each span measuring 20m.
Moreover, the C50 concrete and motorway can be used in this option to build the continuous bridge.
OPTION 2: CABLE STAYED FLYOVER BRIDGE SYSTEM
Another construction method which can be used in this flyover bridge construction is the cable
stayed technique. The method is also suitable based on the span of the proposed flyover that is 80m by a
width of 20m. Some of the components of the cable stayed technique include cable, tower, pier, deck as
well as the superstructure foundation. The choice of the technique will be based on the appearance and
the behavior of the structure therefore enhancing the efficiency and increase discontinuity of the structural
behavior. In the construction, the cable stays will be arranged in accordance with the pure fan system
along with the radiating pair of stays. The stays are often referred to as pylon and the contractor have to
use two of them at the top. In essence, this pylon will be used to support the vertical deck at the edges of
the bridge deck. Additional cable planes can be used to allow for the makeable and invisible anchoring of
the remaining plate grinders.
KEY ISSUES
The maintenance cost for the cable bridges is economical, for instance one can easily repair the
damaged cables at anytime. In addition, the cable bridges are durable even if the ground conditions are
not good. In this aspect, the cable bridge design is the best choice for this but the engineer must
recognized the both the deteriorating time as well as the service life time span. Das (1999, p.45), depicts
on the two primary maintenance mechanism which can be employed in this design work. The first

Designing a Bridge Deck Flyover 5
method is the preventative maintenance and this technique demarcates on the elements which must be
considered as critical at earlier stage to avoid additional costs in the later days. The second bit is on
essential maintenance and this focuses on keeping the bridge safer at all time. Therefore, if the two
techniques are adopted and employed decisively then they will increase service life and safety of the
flyover bridge. This design work will also require that carrying weight capacity and load limits to be
subjected to the flyover be considered in the design work. However, the as the designer, it is important to
consider the durability of the road at the expense of the state conditions in the meantime.
SCHEME COMPARISON FOR OPTION-1 AND OPTION -2
The table below show the comparison between the two options picked
Parameter Being Compared Continuous Beam Bridge Cable Stayed Bridge
The length of the span of the
flyover
15.25m + 30m + 15.25 m 78m
Main materials to be used in the
process
C50 concrete materials Steel, Prestressed concrete, cable,
tower, pier and deck
The support to be used in the
construction
Box Beams 2 pier tower
Aesthetic Not much appealing and simple Appealing, more attractive and
beautiful
Cost Economical and cheap Expensive and economical in the
long run
Construction method Scaffold as well as cast in-situ Balanced cantilever
Construction period The time frame required for the
project is Shorter
Longer period is required in line
with construction as far the
method is concerned

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RECOMMENDATIONS FOR PICKING OPTION 1
From the two options provided for the analysis, the flyover bridge can be build above the
highway using the set pier and three continuous span beams. Although the second option of using cable-
stayed bridge is appealing and beautiful, the span of the flyover which is 80m makes it economically
expensive in the long run. Therefore, in the comparison the first option of using continuous becomes
more efficient and economical thus, overrides the second option. In essence, the continuous beam bridge
method offers an adoptable mechanism which can be ascertain with a short period of time and the one
which have low difficulty in terms of the overall work. Therefore, in this design construction and with all
specifications the best option to be used in this process is the continuous beam bridge construction
mechanism (Harris, 2018).
CONSTRUCTION METHOD
A flyover bridge deck is defined as a bridge which goes over the section of another roadway and
this is basically done to ease traffic. Over the past decades, the only technique which has been used in the
construction of the bridges is the cable-stayed method. The cable-stayed method is a technique which is
based on either steel or concrete however; these elements can be combined with other materials (Zhu et
al., 2015 p.2000). The bridge deck flyover can be made from three elements and such elements include
truss deck, steel box as well as the concrete prestressed box deck. In this design work, the consultant
engineer picks on the prestressed concrete box and this is supported by the cables at the support edges of
the flyover. The advantage of this method is that the technique does not rely on any bond as well as the
result self-weight deflections in the structure will just cancel out (Ai, 2017). Although, there are other
technical methods which the engineer could had opted for however; the choice on the method was based
on the below parameters
i. The scale of the entire bridge
ii. The overall problems which one can encounter during the design
iii. The span lengths regularity

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iv. Both the vertical and the horizontal bridge decks profiles
v. Material costs to be used in the construction
vi. Soil mechanics and its division nature
vii. The weather of the site
viii. The allocated and scheduled time and work frame for the project
In addition, different companies tend to sue different construction methods when erecting bridges
and some of the key constructions which they employ include
One, Staging also known as false- work; is used in developing temporary scaffolding and framing
which are used to support the various structural elements while carrying out the construction. Two, Span-
by-span method; is a method in which the fabrication is done to support the structural elements through a
creation of the sequential process span in situ (Kim et al., 2017 p.70).
CONSTRUCTION PROCEDURE
First, overall alignments are carried out and in the process the flyover laid out is located with the
respect to the abutment and piers. In addition, excavation is carried out to measured level which ensures
that the abutment and piers are correctly piled at the appropriate depth. Second, the concrete are placed at
the appropriate positions at the bottom section to form a firm foundation. This process is done within the
confinements of the ground and formworks. Thirdly, the constructors through the help and supervision of
the engineers in the field embark on placing the abutment concrete and the pier columns. Fourthly, the
process is successfully completed and meets the engineering and the BS criteria then, the workers embark
on building the pier caps. At the same time the more abutments are also built. Thereafter, the precast
grinders, steel and box grinders are then placed. Also, the works can build the deck using either the
concrete or the slabs. Finally, the workers complete the bridge flyover construction by building the
roadways, the guardrails as well as painting the pavement markings (Tollazzi et al., 2016 p.50).

Designing a Bridge Deck Flyover 8
ENVIRONMENTAL SUSTAINABLITY
The following are some of the safety and construction constraint mechanism which will put in
place during the flyover construction (Farooq and Akram, 2018). It is important fence the construction
site so as to protect human and animals from access the site to reduce accident instances occurring in the
site. Sprinkling of water to dusts generated and using of the dust and building nets to prevent falling rocks
from causing accidents and to control the resulting air pollution. Developing of the diversions and using
the flag persons to direct traffic during the construction process. Authorization of only permitted persons
to access the site and such persons include permitted workers, constructor, engineers and consultant
engineers (Domaneschi et al., 2015, February p.160).
COST ESTIMATE
The total budget for the bridge is mainly dived into two sub-classes that is the substructure and
the superstructure. On the portion of the superstructure, the mainly structure budget is for the deck
pavement, parapet and the beam. On the other hand, the substructure consists of the piers and the main
budget is on amount to be used to purchase the pier material pieces. C50 concrete is the main material
which is used in the construction of the main bridge and it is estimated at 109￡/m3. Moreover, the bridge
thickness cost is estimated at 43.55￡/m3 per 150mm footings. Other costs include 57.99￡/m3 for the
beam exceeding 1m2; the cost for the parapet 0.5m high with the dimension of 125mm by 125mm is
estimated 19.2￡/m. Finally, another cost to be considered in this process is the cost of columns along
with the piers which exceeds 1m2 and the amount is estimated at 57.99￡/m (Hameed et al., 2016).
RECOMMONDATIONS
Backfill and permanent loads may cause settlements along the bridge decks of the flyover. There
the variations for settlements is an important element which need to be taken into consideration when
design the flyover. There is a likelihood of a monotonically variable settlements formed as time goes.
Therefore, an imminent measure must be put in place to tackle the mess if need be in the long run. In
fact, the monotonically variable settlements may be in two forms either they may operate in the same

Designing a Bridge Deck Flyover 9
direction or may make the structures to become statically indeterminate as time goes. Apparently,
settlements tend to interact with the concrete slabs and elements. This results into the creep development
where there is a livelihood of a differential settlement affecting the structure (Chandra et al., 2016). The
impact of the differential concrete elements and the settlements interactions may affect either a part or the
structure as a whole. Therefore, proper mechanisms need to be taken into account to handle this
paramount effect (Pino et al., 2017).
Both the controlled deformation and forces are the main causes of the permanent actions on the
structures. Prestressing is thus classified as pertinent and permanent action based on this basis as the two
actions makes it to impose an effect on the structure. Additionally, it is important for the structural
engineer to distinguish the actions imposed on the structure by the prestressing effects through classifying
them into various sub-classes in the meantime. The classification of the prestressing can be based on the
prestress by tendons and the prestress by forced deformation at carry (Salatoom and Taneerananon, 2015
p.7).
Another essential element to consider under traffic loads is the carriageway width denoted as w.
keen consideration is viable when it comes to measuring of the height kerbs and the parameter need to
measured as height not more than 100m. Also, the inner vehicle restraint limits systems should be
considered in the process (Bao et al., 2015). Some of the aspects which must not be included in the
process include the vehicle fixed distance, central reservation kerbs and the restraints systems as well as
the vehicle restraints system width. It should not include the distance between fixed vehicle restraint
systems or kerbs of a central reservation nor the widths of these vehicle restraint systems. The above
analysis for the carriageway can be represented as shown in the diagrams below

Designing a Bridge Deck Flyover 10
CALCULATIONS
LOAD PATH ABD OVERALL STABILITY
In this bridge design context, it is important to consider the bearings and relative movements
which are likely to occur at the support and superstructure. This is important to avoid shrinkage, creep,
thermal effects, wind loading as well as the foundation settlement. In the design all the bearings are
arranged at the respective edges of the piers bridge. The bearings are mainly used in the process as they
offer frictions with low polytetrafluoroethylene properties (Stroscio et al., 2015, June, p.185).
LOAD ANALYSIS
Self- loading calculation
Considerations are taken for the roadway and the box beam when computing the self-load. In analyzing
the box beam material concrete C50 is used.
In the analysis it is clear that box beam area is given as
3 x 3−2 x 2 ¿ x 2+1 x 4=14 m2
But for the same box beam to be used in the analysis gc=25 KN /m3
Therefore, the load box beam is computed as 14 x 25=350 KN / m2
Taking the thickness of the to be design to be 0.008m and the width of the flyover to be (3.65m +3.65m)
and using C30 concrete
Then, the area of the flyover is given as ( 3.65 m+ 3.65 m ) x 0.008 m = 0.0584 m2
Thus, the load of the flyover = 0.0584m2x 25 KN /m3 = 14.6 KN / m2

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The load of the road: max height of the flyover = 7m
Hence, maximum load for the design can be given as 7m x 4x 1000x100 = 2800kN
Structural Analysis
The structural analysis for the flyover in terms of the bending and shear forces can be depicted as shown
in the diagrams below
Centroid Calculation
The data used in the calculation and the determination of the centroids to be used in the flyover mainly
shown in the table below
object Area/m2 Ay2/m3 Ay n/m3
1 3 x 3 – 2 x 2 =5 3÷2 =1.5 7.5
2 3 x 3 – 2 x2 =5 3 ÷ 2=1.5 7.5
3 1 x 4 =4 1 ÷ 2 =0.5 2
Y = ∑ Ay
∑ A ¿ 7.5+7.5+2
5+5+ 4 =1.21 M I xx=∑ In +∑ Ay2
I 1=I2 =b h3
12 =3 x 33−2 x 22
12 =5.42m4

Designing a Bridge Deck Flyover 12
I3= b h3
12 = 4 x 13
12 =0.33 m4
Ixx 27.5 7.5 0.33 5.425.42=28.17 m4
STEEL ANALYSIS
The steel analysis demarcates on the durability and stability of the structure as time goes by with
reference the overall design. In this design there is assumption that the main members of the bridge can
either be concrete of appropriate grades within a characteristic strength range from 35 N/mm2 up to 50
N/mm2 or steel of S355 grade (Arya, 2015). However, before embarking on analysis using this
assumption, it is important to check on the impacts of the characteristics strengths of the steel bar with
reference to the BS 5950 as this will help in ascertaining the level of buckling as far as the slenderness
ratio is concerned. First, by using the BS 5950 chart for the S355 analysis with a range of 35N/mm2 to
50N/mm2, we obtain the follow values from the data
Steel grade and design strength py (N/mm2 )
Slenderness ratio λ Characteristic Strength of Steel pc (N/mm2 )
35 313
40 301
42 296
44 291
46 286
48 280
50 275