Floating Harbour Bridge-2

FLOATING HARBOUR BRIDGE
Department of Civil Engineering Sebastian Beck Vladimir Djuric Max James Leo Youngman

1
Executive Summary
This report has been commissioned by Bristol City Council to assess the feasibility and initial design
of a solution to Bristol’s growing commuter congestion issues. It also addresses the need for
sustainable transport infrastructure by introducing a new pedestrian and cycle crossing of the city’s
Floating Harbour. The design employs state of the art fibre reinforced polymer (FRP) materials to
provide a lightweight 44m twin bascule lifting section which can be raised using hydraulic cylinders
without the need for visually intrusive counterweights. An effective clear span of 31m satisfies the
stakeholder requirements by leaving space for rowing head races and similar events.
The bridge will create a 4 metre wide route across the Harbour. 3.4m of air draft permits 70% of the
Harbour’s users to pass under the bridge, whilst the central section will open for larger vessels up to
ten times daily at the height of summer. Aesthetically, bespoke FRP fabrication methods permit sleek
deck tapering to be specified, and as such, the structure is anticipated to become a tourist attraction
in its own right.
The chosen site lies between two tourist landmarks on the south embankment; Brunel’s ‘SS Great
Britain’ and the Bristol ‘M Shed’ museum, and crosses 75m over to Canon’s Marsh on the north
embankment. This caters for both tourist and commuter demands by connecting existing cycle routes
and providing links to the city’s central business district, whilst being a suitable location for
construction. The weak alluvial geology underlying the site, combined with the costs of construction
works in the water, lends to a design with just two piers in the water. These considerations, along
with the need for an opening span, dictate the decision to utilise FRP for the bridge’s central deck;
seeking to take advantage of its high strength to weight ratio.
Modest concrete abutments support the central structure. The foundations comprise of both driven
and bored piles extending to a depth of 25m in order to reach the underlying bedrock and minimise
settlements.
The proposals are environmentally considerate by both incorporating industrial waste materials into
the concrete design to reduce the project’s carbon footprint, and working towards the project objective
of promoting sustainable transport in Bristol.
The total cost of construction will be £2.8million, occurring over a single winter period of four months.
Estimation of operation and maintenance costs predict a whole life cycle cost in the region of
£9-12million over a 120 year design life.
Contents
Executive summary .......................................................................................................................... 1
Part 1: Introduction ........................................................................................................................ 2
Brief ............................................................................................................................................................ 2
Report scope .............................................................................................................................................. 2
Client’s vision.............................................................................................................................................. 2
Project objectives ....................................................................................................................................... 2
Historical context ........................................................................................................................................ 2
Demand Prediction..................................................................................................................................... 3
Stakeholder Analysis.................................................................................................................................. 4
Site Selection ............................................................................................................................................. 5
Site Geology............................................................................................................................................... 6
Part 2: Preliminary design.............................................................................................................. 7
Design Constraints ..................................................................................................................................... 7
Layout......................................................................................................................................................... 8
Option Appraisal......................................................................................................................................... 9
Selected Design ....................................................................................................................................... 11
Technical drawings................................................................................................................................... 12
Part 3: Superstructure.................................................................................................................. 13
Composite material specification ............................................................................................................. 13
FRP Deck ................................................................................................................................................. 13
Finite element modelling .......................................................................................................................... 13
Piers and abutments ................................................................................................................................ 16
Opening System Design........................................................................................................................... 17
Detailing.................................................................................................................................................... 18
Hydraulic Cylinder Connections ............................................................................................................... 19
Opening Procedure .................................................................................................................................. 19
Part 4: Substructure..................................................................................................................... 20
Geotechnical design................................................................................................................................. 20
Construction method selection................................................................................................................. 20
Pile specifications..................................................................................................................................... 20
Pile analysis.............................................................................................................................................. 21
Pile cap..................................................................................................................................................... 22
Soil sulphates ........................................................................................................................................... 22
Site investigation reccomendations.......................................................................................................... 22
Part 5: Project Management ........................................................................................................ 23
Project strategy & whole life performance................................................................................................ 23
Life cycle stages....................................................................................................................................... 23
Provision for future changes during operation ......................................................................................... 23
Risk assessment ...................................................................................................................................... 24
Maintenance of components .................................................................................................................... 25
Quantifying whole life cycle costs ............................................................................................................ 25
Construction Sequence ............................................................................................................................ 25
Environmental Impact & Sustainability..................................................................................................... 27
Project finance.......................................................................................................................................... 28
Evaluation................................................................................................................................................. 29
Conclusion...................................................................................................................................... 29
Concluding Statement .......................................................................................................................................... 29
Calculations.............................................................................................................................................. 30
References ............................................................................................................................................... 31
Figures...................................................................................................................................................... 35

Brief Part 1: Introduction
2
Part 1: Introduction
Brief
Design a new pedestrian and cycle bridge to cross Bristol’s Floating
Harbour at a point between the SS Great Britain and the M Shed, to
serve both tourists and commuters. Undertake an options appraisal
of different sites and structural forms before developing the selected
design. The bridge must not impede navigation for rowers, ferries
or other harbour users. The design must be safe, functional,
sustainable, aesthetically pleasing and above all, economically
feasible for the client; Bristol City Council (BCC).
Report scope
This report represents the feasibility study stage of the project.
Figure 1 displays the whole report roadmap and outlines the
requirements of the feasibility study that will allow the project to
progress onto detailed design, public consultation, tendering of
contracts and eventual construction then operation.
Client’s vision
The ‘Mayoral Visions’, published by BCC in 2015 sets out their
objectives for capital spending [1]. The relevant objectives to this
project are:
Keep Bristol Moving: Encouraging sustainable transport
Vibrant Bristol: Making of the city accessible to all
The project will move Bristol towards these goals by:
Promoting safe, functional and pleasant walking and
cycling routes as alternatives to vehicles thereby reducing
air pollution and congestion.
Bridging the banks of two wards, creating a more
accessible city and encouraging more uniform economic
development that benefits Spike Island in particular.
Ensuring that the creation of the bridge does not adversely
affect community events and celebrations such as the
annual Harbour Festival and regular rowing races.
Project objectives
Budgetary: An objective of £3-5 million is specified, based on the
client’s requirements and available budget.
Programme: Construction processes must be selected and
scheduled in an efficient manner in order to minimise cost and the
project’s impact on stakeholders.
Function: The bridge must provide a pedestrian and cycle crossing
whilst allowing water users to safely navigate the harbour.
Aesthetics: The client desires a modest and elegant design, which
takes into account and complements the surrounding architecture.
Ideally, the bridge will become a local landmark in itself - connecting
the SS Great Britain, M Shed and the Spike Island Gallery to
@Bristol and the Aquarium. See the map in Figure 3 for details.
Sustainability: Socially; the bridge should provide a service for
residents and commuters throughout its design life whilst
encouraging sustainable transport. Environmentally; the bridge
should be constructed from ecologically friendly and recyclable
materials where possible. Economically; the project should be a
redevelopment and a driver of economic activity.
Quality and Safety: Designed according to the Design Manual for
Roads and Bridges (DMRB) and Eurocodes (EC), employing
international standards where necessary, in order to develop a high
quality and safe design, with proper scope for maintenance.
Historical context
Since 2004, Bristol has seen an unprecedented population rise of
46,700, which is 3% higher than the national average [2]. However,
the most recent footbridge to be constructed over the New Cut or
Floating Harbour was the 1934 Gaol Ferry Bridge [3]. Additionally
there is a 1.5km uncrossed stretch of water between the
Cumberland Basin and Prince Street Bridge which remains a barrier
to travel between the south and north of Bristol (see Figure 3).
The Bristol docks closed commercially in 1975 and regeneration
began in the 1980’s (see Figure 2) [4]. The Floating Harbour is
currently used almost
exclusively for recreational
purposes.
The possibility of a bridge
over the Floating Harbour has
been under consideration for
decades [5]. A ferry has
operated since 1977 to meet
some of the demand, serving
180,000 passengers a year
and 11,000 over the
Harbourside Festival
Weekend [6].
Figure 2 Development in Canon’s
Marsh from 1950 (lower) to 2014
(upper) [121]
Figure 1 Report roadmap based on RIBA principles [126].

Demand Prediction Part 1:Introduction
3
Demand Prediction
In order to confirm the need, determine the optimum site and
establish design traffic flows, a demand analysis was undertaken.
The number of cyclists commuting in the city doubled from 2010 to
2011, whilst the city council have been pushing heavily to reduce
congestion by providing alternate means of transport [7]. Thus,
there is considerable demand for a crossing over the Harbour.
Estimating Flow
Figure 3 shows bridges local to the Floating Harbour, with their peak
hour flows. The Gaol Ferry Bridge is the busiest pedestrian/cycle
bridge in Bristol, with 7,000 movements a day [8]. Prince Street
Bridge is overcrowded, and with pedestrian/cycle traffic rising
Pero’s Bridge is becoming similarly busy. Various solutions have
been suggested to confront this issue including an ‘Arnolfini’ Bridge
100m South from Pero’s Bridge to redirect traffic from Prince Street
[9] and a ‘Camden Road’ Bridge to remove demand from Gaol Ferry
Bridge [10].
The distribution of business and residential districts on opposing
sides of Spike Island results in a commuter flow from Bedminster.
Figure 4 demonstrates the minimum reasonable value of daily
commuter demand to cross Spike Island based on the 2011 census;
the actual value is likely to be larger.
A distribution for the daily demand of the proposed bridge was
estimated using the Department for Transport (DfT) collected
pedestrian and cyclist hourly traffic flows. On average, the ratio of
cyclists to pedestrians was 1:3. Assuming weighted average
contributions from various routes based on distance from the
proposed crossing, the resulting hourly traffic flow was calculated;
shown in Figure 5. Note the combined morning peak flow of
approximately 1700. This prediction of a daily flow of 8800 could
make it one of the busiest footbridges in Bristol. The predicted
annual flow of 3 million is a capacity increase factor of 18 compared
with the ferry service [6]. This corresponds to £2.4m in revenue at
80p per crossing.
Level of Service
The level of service of the bridge was calculated based on the
predicted maximum daily traffic.
Mean area per person at peak hour is shown in Table 1 to be 5.1m2
per person. Assuming pedestrian-only and constant flow, this is
above the threshold for Dr. J.Fruin’s, level of service ‘A’ for walking
(3.3m2) [11] and infers an unrestricted maximum walking speed with
zero delay from congestion. Even allowing for cyclists, slow walkers
and for use of the bridge as a vantage point, a 3m effective deck
width is sufficient to provide the level of service required to ensure
that the bridge is not congested at the predicted demand level.
Peak
Hourly
Flow
PHF
15min
Flow
Time per
Crossing
(s)
Length
per
person
(m)
Effective
Width
(m)
Personal
Area
(m2)
Level
of
Service
1700 640 1.4 1.7 3 5.1 A
Table 1 Level of Service Calculation
22%
58%
1300 Total Daily
Commuters
Figure 4 Daily Commuters from Bedminster (blue lower), to Tyndalls Park
(blue upper) compared with other destinations. [92]
0
500
1000
1500
Pedestrians Cyclists
Figure 5 Demand Estimation per hour of a bridge in proposed zone
Figure 3 Bristol’s Floating Harbour [90]

Stakeholder Analysis Part 1: Introduction
4
Stakeholder Analysis
Stakeholder
Inter-
est
Influ-
ence
Source
What is important to
the stakeholder?
Information
How could the stakeholder block
the project?
Stakeholder Engagement
Harbourmaster Meeting
30/10/15
19/11/15
[12]
Safety of all Harbour
users
Minimal impact on
recreational activity
Fixed bridge must be 28m above waterline
Additional staff for bridge = £40k a year
Issue with removal of moorings which are in high
demand
The Harbour will be a leisure dock in the future
Could provide a public case
against construction based on
impact on Harbour activity
Consult carefully at all stages of
design and construction
Bristol Rowing
Club
Email
02/11/15
[13]
Zero impact on
navigation in the
Harbour
Access for head to
head races
There are head to head races roughly 3x a year
27m clear span is required for side by side races
Expressing dissatisfaction and
impact on safety of rowers due
to decrease in navigation
Inform about features of the design
that will accommodate for their
needs
Bristol Sailing
Clubs
Email
17/11/15
[14]
Ability to sail along
harbour
10m clearance excessive for dinghies in the Harbour
SS Great Britain is as far east as they would sail
Expressing dissatisfaction with
needing to wait for bridge to
open
Inform about features of the design
that will accommodate for their
needs
The Matthew,
and other boat
tours
Meeting
26/11/15
[15]
Ability to sail along
the Harbour
The Matthew sails a minimum of twice a day in the
summer, and less in winter
There is significant demand from tourists for a crossing
Arguing that opening of the
bridge will slow down tours
Monthly newsletter
Cross Harbour
Ferry
Meeting
26/11/15
[6]
Maintaining use of
its service
180k passengers a year
11k passengers during Harbourside Festival alone
Forcing possible legal action
over construction
Financial compensation
Local residents Survey Minimal impact from
construction works
Increase in access
Supportive feedback
Improved access outweighs disruption during
construction
Complaining about construction
noise and air pollution
Monthly newsletter and exclusive
online portal for queries
Commuters Survey Speed and access
to areas of work
Pedestrian count and published data demonstrate high
commuter demand from south to north
Suggesting that bridge will not
improve access or speed to
areas of work
Updates on Bristol City Council
website
Bristol City
Council
Email
17/11/15
[16]
Satisfying all
stakeholders
Investing in
infrastructure
£3m budge available – Camden Rd. exceeded this by
£4m
Residents in favour, harbour users against
Councillors, such as Mark
Wright, Chair of the Harbourside
forum, could try to block project
Weekly design briefings, and
reporting during construction
Environment
Agency
Email
[17]
Minimising
environmental
damage
Sustainability
Bridge should be above the 1 in 200 year flood level,
with an element of freeboard to allow for climate change
Express dissatisfaction with
environmental impact, and
possibly pursue legal action
Inform about design and
construction strategy
Prepare thorough Environmental
Impact Assessment
Sustrans/Bristol
Cycle Campaign
Email
02/11/15
[18]
Sustainable travel Quality of onward links important
Approve of location proposals
Suggesting the crossing is not
supportive enough for cyclists
Proposing alternate plans
Updates on Bristol City Council
website
Customers
Local residents and
commuters
Tourists
Businesses
Actors
Bristol City Council
Harbourmaster
Transformation
The construction of an
opening bridge in the
Floating Harbour
World View
Encouraging sustainable
development and
transportation
Owner
Bristol City Council
Role – investor and manager
Environmental Constraints
Long term sustainability; a
key project objective
High Medium Low

Site Selection Part 1:Introduction
5
Site Selection
In order to maximise the benefits delivered by the bridge it must
connect existing infrastructure, improve access, and integrate with
future Harbourside developments. To minimise project costs and
negative stakeholder impact, factors such as geology and
constructability were considered. Two potential sites were proposed
primarily based on current demand and access, shown in Figure 6.
SS Great Britain
Location: A prominent site that offers obvious benefits for tourism.
The historical significance of the SS Great Britain may suit an
understated bridge design. At the centre of the Harbour, a crossing
would provide a direct route across Spike Island.
Surrounding Links: Gas Ferry Road is an underused direct road
across Spike Island to the south, and there is a 2.5m wide
pedestrian path to the north leads directly towards Millennium
Square.
Access: Excellent access to the south with room for a crane. Poor
access to the north means that barges will be required to crane in
sections.
Disruption: Short landings will be required to ensure that the route
does not impact access to the SS Great Britain; which could reduce
the potential clearance underneath the bridge. It is likely that the
ferry company will need to be compensated as this crossing would
directly impede on their business. Residents in the apartment
complex to the north may oppose the project. No moorings will need
to be relocated permanently.
Span: The longer span of the two, at 85m. The available landing
points would require an asymmetrical profile, curved on plan. This
will incur some lateral forcing from moving pedestrians, and
increase cost by requiring unique sections.
Harbour Way Road
Location: The most useful location for commuting traffic as it
connects existing cycle routes to the south with direct access to
Bristol’s city centre (via Millennium Square) to the north. A bridge
here would make a strong case for the Camden Road Bridge project
to go ahead, which would provide a continuous route over the New
Cut and Floating Harbour. Objection from the heritage component
of planning is foreseeable due to building adjacent to the historic
dockland railway.
Surrounding Links: Existing roads to the north offer links to the
city, whilst cycle and pedestrian routes exist to the south. The
current cycle track will need to be refined to cross the historic railway
tracks and meet the bridge’s southern landing.
Access: The access on both sides make this site more favourable
in terms of constructability. There is space to crane bridge sections
to the centre of the span, assuming that the disused rail tracks can
be temporarily built over. Additionally, there is sufficient space for
site facilities.
Disruption: Minimal disruption, with more industrial surroundings
and less adjacent housing. Construction here poses a lower
temporary risk to tourist attractions, and the immediately local
businesses will likely benefit both during and after construction, as
they are predominantly cafés.
Span: A shorter span of 75m, with landing points that will allow a
straight crossing and room for longer landings. The site is ¼ of the
distance from Prince Street Bridge to the Cumberland Basin; giving
slightly less connectivity whilst being less restrictive to harbour
usage, which is a key consideration after costs.
The Harbour Way site is preferable primarily because:
a) It best serves commuters.
b) It directly connects existing infrastructure.
c) It has better access.
d) It permits a straight, symmetrical crossing.
e) It is not located on a bend.
M-Shed
Figure 6 – Site location options and site visit photos
Feature SS GB Harbour Way
Span 85m 73m
North Access Very Poor Good
South Access Good Very Good
Moorings Removed None 4 Large
Navigation
Visibility
Medium – on Corner Good
Disruption High Low
Table 2 Site Appraisal
Millennium
Square
Spike
Island
SS Great
Britain

Site Geology Part 1: Introduction
6
Site Geology
The site is located in the Harbourside area, with exposed quarzitic
sandstone to the north dipping at 30°. The Floating Harbour,
originally the path of the River Avon, runs through the flat valley floor
with alluvium overlying Redcliffe Sandstone and Mercia Mudstone.
Coal Seams and mining
The site is close to some abandoned shallow coal mines and coal
outcrops [19]. It is recommended that mining reports are obtained,
and further exploration may be required as there is some risk of
excavating into voids.
Contamination
The area was historically industrial and contained gas tanks, railway
sidings and timber yards. However, a nearby contamination
laboratory suite of tests found only two slightly elevated pollutants
in the soil; in one location. These were tri-butytin (TBT) from antifoul
paint and pentachlorophenol (SVOC) from timber treatment [20].
Laboratory testing of soil samples nearer the site should be
conducted due to the elevated risk of contaminants being present
on site, posing a risk to the health and safety of the construction
team and the general public.
Ground Profile
The geological profiles in Figure 98
were estimated from current and
historical boreholes around the
site. They give soil properties
estimated from soil descriptions and some laboratory test data.
Different profiles are detailed for the design of foundations in the
river and on land. This is due to the large variation in strata depths.
Below these depths there are unknown strata close to the site
however an estimation of the likely strength of the soil used in
calculations is done in Section 4.1.
Made Ground
Borehole records indicate that made ground can extend between
0.8 to 3.6m deep [20]. The made ground on the north river bank
consists of grey brown slightly sandy clayey gravel and cobbles of
various lithology 3m deep.
Alluvium
Borehole records from the surrounding area imply that there are
variable deposits of estuarine alluvium depending on the location in
relation to the river. Further boreholes will be required at the exact
site location as a result of this variability [20]. The alluvium consists
of firm to soft silty clay with organic matter.
Mercia Mudstone & Redcliffe Sandstone
Underlying the alluvial deposits is a Triassic period Mercia
Mudstone Formation of unknown depth with variable Redcliffe
Sandstone beds visible in Figure 9 [21]. In its un-weathered state
the Mercia Mudstone is a weak rock; weathered it becomes a soft
clay [21]. The Redcliffe Sandstone is “commonly decalcified” at
shallow depths becoming un-cemented sand [21].
Figure 8 abandoned shallow coal mines
(red crosses) and coal outcrops (purple
hatched regions) [19].
Redcliffe Sandstone
Made Ground
Alluvium
A
A
Figure 7 Site location and cross section on a geological map of Bristol [127].
Figure 9 Estimate vertical ground
profile at site from nearest boreholes
Figure 10 Section A-A Estimated geological cross section of the site and surroundings

Design Constraints Part 2: Preliminary design
7
Part 2: Preliminary design
Design Constraints
The selected design of the bridge must satisfy a wide variety of
constraints. These have been collated and are visually displayed in
Figure 11 and Figure 12. Public bodies have published various
design codes, with legal requirements which must be adhered to.
The most critical relate to width, loading and gradients. Stakeholder
engagement has brought to light further constraints which, although
not legally binding, are considered crucial to the project’s success.
These include pier spacing, opening section width and air draft.
Finally, there are constructability constraints that determine whether
a design is feasible to build. These include crane limitations, site
access, and retaining wall stability.
Figure 11 - Design constraints on section [108] [93] [67] [69] [100] [103]
Figure 12 – Design constraints on elevation [102] [12] [86] [94] [95] [96] [108] [97]

Layout Part 2: Preliminary design
8
Layout
Before deciding upon a structural form, the desired profile of the
bridge was determined, as defined by best practice [22]. In order to
balance the gradient requirements of cyclists and wheelchair users,
the air draft of boats, the visual symmetry and the interaction with
surrounding infrastructure, landing ramps are required.
Moving Section
A permanent bridge would require an air draft of 30.5m; matching
that of the downstream M5 motorway bridge [23]. A 22m air draft is
necessary to allow for the daily tours of the Matthew, a landmark
tourist ship. Consequently, a stationary bridge from an aesthetic and
cost perspective is impracticable and a moving section is
necessary.
Permenant Air Draft
Data of boat lengths, provided by the Harbourmaster, was
interpreted to determine heights using standard ratios based on
boat types, and is plotted in Figure 14.
From this conservative estimation of traffic heights, a minimum
permanent air draft for a moving section of 3.4m was agreed upon
with the Harbourmaster to permit 70% of traffic to pass unimpeded.
This includes all frequent essential traffic including official safety
boats and various ferries.
Landing Ramps
In order to achieve a smooth and symmetrical shape to the bridge,
avoiding significant gradient changes, the deck profile shown in
Figure 13 was selected. 5m landing ramps give the specified air
draft of 3.4m, assuming 0.5m deck thickness. The range of available
clearances is comprehensively analysed in Figure 16. See
calculations on page 30 for derivation.
The cost and impact of extending the ramps further to increase the
centre span air draft begin to outweigh the benefits, as pedestrian
flows become impeded. Thus, a landing prominence over land of
5m was decided upon with 1/20 gradient extending 15 over water.
Alignment
See calculations on page 30 for: Vertical Sight Stopping Distance,
Vertical Comfort: Horizontal Stopping Sight Distance checks
[DMRB 6.1.1]
Figure 15 – Plan schematic of bridge and dimensions
0
20
40
60
80
100
0
20
40
60
80
100
120
140
160
3 4 5 6 7 8 10 12 15 20
Cumulative%
FrequencyofBoat
Height of Boat (m)
Frequency Cumulative %
Figure 13- Histogram of estimated heights boats moored in the harbour
based on Harbourmaster data [86]
Figure 14 - Deck Surface Profile
3.00
3.20
3.40
3.60
3.80
4.00
4.20
0 5 10 15 20 25
AirDraft(m)
Extent of constant 1/20 Gradient (m) from bank
0 5 10 15 20
Landing Length (m)
Figure 16 – Range of attainable central span air drafts

Option Appraisal Part 2: Preliminary design
9
Option Appraisal
Asymetric Steel Cable Stayed (Swing)
A hollow welded trapezoidal steel box section runs the length of the deck.
The enclosed area provides torsional resistance; essential for such a long
structure. A central I-beam provides bending resistance. The deck is
formed from 7 prefabricated sections.
This option requires minimal modification of the harbour wall. Central
cables segregate the bridge into two lanes, and a single pier rotates on
plan. This solution provides the largest clear water space for river traffic.
Cost: Low material use due in the deck, but high quality steel is required. Skilled labourers would be
required for such a structure, which will drive up constructin costs along with the extensive works for
the pier foundations.
Upfront: £9-15m. Similar Bridges: Media City Footbridge, 2011, Salford, 80m swing section; £11m
(unajusted) [24]. Punta de La Mujer, Buenos Aires, 160m bank to bank, 100m swing section, $6m
(USD, unadjusted) [25].
Maintenance: Large bearings are required for the opening mechanism. There are many connections
to protect from corrosion, requiring frequent structural checks and painting to protect against failure.
Access to opening mechanism is limited. Extended periods of closure for maintenance.
Construction: Specialist contractor. No heavy crane or jack-up barge due to modular construction
Superstructure: 5. Erect steel tower. 6. Balanced cantilever deck construction (sections can be fitted
from an anchored floating barge loaded nearby at dry docks).
Demountable Floating Steel (Bascule)
Steel deck with 15m spans mounted over steel cylindrical pontoons
forcibly submerged and tensioned against buoyancy with cables
stayed to helical piles drilled into rock. Applied loads relieve tension
in cables.
Although displacements (lateral and rotational) are large due to
the low stiffness of the structure, the water dampens pedestrian
induced vibration. A central steel spine u-beam resists bending
and torsion. CHS struts further resist torsion, which can be an
issue with light floating bridges due to differential pontoon
movement. A hydraulic cylinder system lifts the bascule to open the
bridge. Short spans only allow rowers to pass in single file but the
bridge can be demounted and moored parallel to the bank for
events. The cables may present a hazard to boats and there is a
lower navigational clearance, which affects multiple stakeholders.
Cost: Upfront: £2-4m. Very low foundation costs and prefab
construction reduces potential for on-site delays. Similar Bridge:
West India Quay, London, 1996, 85m, costed £1.7m unadjusted [26].
Maintenance: High - the opening system is lightweight, low stress and easy to access, however the
steel structure is vulnerable to corrosion, especially the cables in the water. Periodical demounting up
to 5 times per year may prove expensive due to the complexity of connecting the 12 high tension cables
to the bottom of the bridge.
Construction: Almost entirely prefabricated in local dry dock (500m downstream) except for the drilled
tension piles and bored bank piles. No cranes are required.
Substructure: 1.Install helical piles to anchor pontoons to rivererbed whilst mooring piles are bored.
Superstructure: 2. Complete fabrication in of the two halves of bridge. 3. Float the structure into
position and align with an anchored barge. 4.Tension cables and moor ends.
Substructure: 1. Sizeable cofferdam (river closed for several months). 2. Piles bored through base of
cofferdam. 3. Pile cap and abutment cast within cofferdam. 4. Opening System installed.
Key Specifications
Conservative 7.5m Span
Max Deck Moment: 155kNm
Lat. Restraints: 10m
Use Beam: UB457x191x82
Mb,rd =167kNm
Steel Box Wall: 5mm
Rough Deck Weight: 2 kN/m
Prefab Section Mass: 2 ton
Cable Tension: 138kN
40m
5m Cable
Connections
Elevation
20m
Mooring
Mooring
Plan
Section
2m
0.5m
Cable
Deck
Connection
Brackets
7 x Prefab Steel Deck Sections
10m
Mass (ton)
Item Steel Conc
Deck 10 0
Cables 4 0
Tower 50 0
Abutment 25 150
12 Bored
Piles
100 480
TOTAL 189 63028°
Key Specifications
15m Spans, Lat. restraints 10m
Deck Moment: 415Nm, Use I
Beam (for sizing): UB:
610x229x125
Mc,rd = 417kNm
Rough Deck Weight 5 kN/m
Strut Load: 200kN
Required Displacement
per Cylinder: 12.5m3
Pile Uplift, Unloaded: 83kN
Mass (ton)
Item Steel Conc
Deck 40 0
40 Struts 10 0
8 Pontoons 25 0
12 Helical Piles 5 0
4 Bored Piles 10 40
TOTAL 90 40
15 m
25 m
Elevation
0.65m
2m ⌀
L=6m
Tie down
cables resist
lateral
movement
Steel
cylinder
75% submerged
Section

Option Appraisal Part 2: Preliminary design
10
Steel Spine Girder (Swing)
A conventional steel girder bridge with a permanent 28m main span
and a balanced cantilever steel swinging section. A steel spine runs
above the deck creating a pedestrain/cycle divide and increasing air
draft by minimising the thickness of the deck below the deck surface.
A large bearing abutment and two sets of driven piles will require
extensive foundation work in the water. Upfront Cost: £5-8m. High
volume of steel and foundations will drive cost. Deck made up of 3
prefab sections which require heavy cranes and a barge for fitting.
Cranes will require ground and retaining wall strengthening below
outriggers. The main benefit of this design however is its
conventionality. It is a simple, tried and tested design which will not
require specialist contractors. Similar Bridges: Bryggebroen,
Copenhagen, 2006, 47.6m DKK (~£5m).
Maintenance: Medium. Difficult access to opening system, bridge will
need to be closed to maintain its large bearing. Corrosion is a major
problem in steel over water. Repainting over time is necessary.
Construction:
Substructure: 1. Retaining wall strengthened. 2. Cofferdam formed
and piles bored through base from jack up barge. 3. Remaining piles
driven and cast. 4. Pile cap and abutment cast. 5. Deck support struts
fitted. 6. Opening mechanism fitted.
Superstructure: 7. Steel sections constructed off site and shipped.
8. Positioning of sections from cranes mounted on the bank.
FRP Fixed Trunnion (Bascule)
A symmetrical configuration with FRP cantilevered bascule
leaves and concrete arched abutments spanning to the bank. The
40m central span permits rowing events. The high strength to
weight ratio of GFRP results in a low mass of the moving sections.
Each deck leaf can be lifted, without counterweights, by a single
hydraulic cylinder. Because of the low weight of the superstructure and the securing of the abutment to
the bank, foundations can be reduced and the pile cap will be installed just below water level, removing
the requirement for a cofferdam.
Upfront Cost: £2-4m. The ability to mould large, light sections as one reduces on-site assembly.
Colour and finish can be achieved during manufacturing.
Maintenance Very Low - minimal deck maintenance due to corrosion resistance, which is beneficial
for an exposed bridge over water. Easy access to bearings and connections. Redundancy due to two
opening sections comes at the cost of higher maintenance.
Construction:
Substructure: 1. Piling Mat. 2. In-bank piles bored and pile cap set. 3. Piles driven in river from a jack-
up barge. 4. Piles bored out and cast. 5. Pile caps cast 0.5m below water surface.
Superstructure: 6. Abutment and back span cast in situ from formwork mounted on barge. 7. GFRP
Deck sections shipped in and positioned by cranes mounted on banks. 8. Hydraulic cylinder and
opening system connected.
0.75m 1m
2m
Section
30m20m 10m
Elevation
35m
Mass (ton)
Item Steel Conc
Main Deck 30 0
Swing
Section
40 0
4 Driven
Piles
25 150
Abutment 15 100
4 Bored
Piles
25 150
TOTAL 135 400
Key Specifications
Max Span: 30m
Max Deck Moment: 3200kNm
Lat. Restraints: 14m
Use I Beam for Estimations:
UB1016x305x407
Rough Deck weight: 9 kN/m
Prefab Deck Section Mass: 27t
COM 25m from bank
Crane Required: 350t
[e.g. TEREX AC 350/6:
with 116.7t Counterweight
Up to 26.6t @ 30m radius] [125]
Prefab Swing Section Mass: 40t
COM 22m from Bank
Crane Required:500t
[e.g. TEREX AC 500-2
with 160t Counterweight:
Up to 41.6t @ 26m] [125]
14m40m
22m
GFRPConcrete
Elevation
Mass (ton)
Item Steel Conc GFRP
FRP Deck 0 0 52
Abutments 25 220 220
8 Driven
Piles
50 300 0
4 Bored
Piles
25 120 0
TOTAL 100 640 52
Key Specifications
Max Cantilever Span: 22 m
Max Deck Moment: kNm
Specify FRP Girder for
Example
Rough Deck weight: 9 kN/m
Air Draft: 3.8m
Prefab Deck Section Mass: 21t
COM 25m from bank
Crane Required: 250t
[e.g. TEREX AC 250-1,
96.6t Counterweight:
Up to 23t @ 30m radius] [125]

Selected Design Part 2: Preliminary design
11
Selected Design
Appraisal
In order to satisfy all of the primary stakeholders, an appraisal was
conducted. Table 4 and Table 3 compare the relative merits of each
design.
Given the client’s budget, any design that can minimise
maintenance and rehabilitation is favourable. Based on the
stakeholders’ stated priorities and preferences, Figure 17
demonstrates that the FRP option is the most favourable.
Key benefits:
Wide central span crucial requirement for rowing clubs
Resistance to corrosion and low maintenance costs
High strength to weight ratio
No counterweights which are visually intrusive
Compromise between piers in water and deck thickness
Pier arrangement
Option A: Reclaim land from the river with granular fill to form the
foundations for the abutments. This method reduces the health and
safety concerns of working over water as all the piles can be bored
via plant on the land. However, there is little precedent for such a
long cantilever FRP span and stability of the FRP deck to vibration
would become an issue. There would also be disruption to traffic as
a result of transporting to the location up to 1000m3 of sand (80 x
25t capacity lorry load).
Option B: A pile group and pier over the water. This was calculated
to be approximately 25% more efficient design in terms of materials
used. This saving is expected to offset extra cost of piling and
casting concrete over water. The shorter moving span allows a
faster opening time. Another benefit is providing an additional 15m
of clear span under each abutment which allows boat mooring
locations to be retained.
Abutment Geometry
Due to the large size of the abutment, it is unlikely that a precast
system is feasible.
A balanced cantilever construction is not feasible because of the
high weight disparity between the light FRP deck and the abutment.
The angled column system was selected as a compromise between
optimising opening system geometry, structural efficiency and
aesthetics.
Deck Sections
A single girder deck was selected for
its increased torsional resistance due
to larger enclosed area. This design is
possible due to the use of angled
abutment, offsetting the hydraulic
cylinder connection so that the
cylinder does not contact with the
underside of the deck during lifting.
Vertical
Column
Angled
Column
Arch
Option A: Bank-Fill
Option B: Piled Over-Water
10m
20m
16m
28m
22m
Dual Girder
Single Girder
Clear
Span (m)
Opening
Section
Width
(m)
Span
>3.5m
Air Draft
(m)
Max
Prefab
Section
Wt. (t)
Opening
Time
(s)
Cable 37 37 22m 2 180s
Floating 20 15 0 35 <60s
Steel 28 20 38m 40 60s
FRP 40 40 18m 22 <60s
Table 4 Quantitative options appraisal
Event Use Foundations
Initial
Cost
Whole Life
Cost
Cable Very Good
Piling and
Cofferdam.
Jack.
Anchored
Barges
High Very High
Floating
De-
mountable
Helical Piling.
No Cranes
Medium High
Steel Poor
Piling and
Cofferdam.
500t Crane
Medium Medium
FRP Good
Piling and
250t Crane
Medium Low
Table 3 Qualitative options appraisal
6 8 8 7
2
6 7 88
2
4
88
4
7
7
8
4
5
7
0
5
10
15
20
25
30
35
40
Cable Floating Steel FRP
Primary Stakeholder Priorities
[Rated 1-10 based on predicted preferences]
Private Boats: Air Draft, Pier
Spacing, Opening Time,
Impact on Moorings
Ferries/Tours: Air Draft, Pier
Spacing
Rowing Club: Clear Span
BCC: Cost, Aesthetics
Harbour Master: Events,
Opening Time, Short
Opening Section,
Maintenance, Navigation
Figure 17 Ratings of options in relation to stakeholder priorities

Technical Drawings Part 2: Preliminary design
2.5 Technical Drawings
12
[Note: Bridge is symmetrical in both axes]

Composite material specification Part 3:Superstructure
13
Part 3: Superstructure
The design of superstructure elements has been achieved
iteratively using hand calculations and finite element modelling in
Midas®. Partial factors of 1.35 for unfavourable permanent actions
and 1.5 for unfavourable variable actions have been adopted
throughout.
Composite material specification
The engineering properties of fibre reinforced polymers can be
manipulated by altering the fibre material and orientation, the resin
utilised, and the manufacturing process. This project will employ a
bespoke composite material to cater for its specific requirements;
namely achieving a high strength to weight ratio and good weather
resistance at a reasonable cost.
E-glass fibres are selected for their cost effectiveness; a fibre
orientation that is multidirectional and somewhat random is
specified in order to achieve strength in all directions [27]. This is of
particular importance due to the complex deck geometry and the
range of load cases experienced.
Vinyl ester resin shall be used for the matrix. It is known to provide
high water resistance, whilst being stronger than the polyester
alternative, and more resilient than epoxy resin [27].
The GFRP fabrication can be achieved in the UK, with options
including Plymouth based firm ‘Pipex’ and the National Composites
Centre in Bristol. An advantage of using the NCC is the scope for
prototyping and testing in accordance with DMRB-1.3 at their
facilities; as with a recent bridge at Frampton Cotterell [28]. It should
be noted that refinement of the composite material will be required
around connections to avoid localised issues, details of which will
be confirmed through this testing. Vacuum resin infusion will allow
the large deck sections to be formed with a high reinforcement
content [27]; a content of 60% will be sought.
As a consequence of the above specifications, and data made
available by ( [27], [29], DMRB – 1.3), the material properties for
design are taken to be:
Modulus of elasticity – 25 GPa
Poission’s Ratio – 0.25
Thermal Coefficient – 7 x 10-6
°C
Density – 2200 kg/m3
Ultimate Tensile Strength – 1500 MPa
DMRB-1.3 states that a ULS material safety factor of 3 is required
for permanent loading on GFRP decks, thus a limiting stress of 500
MPa is adopted.
FRP Deck
Aesthetically, the FRP bascule bridge stands out as a structural
form that will complement the surrounding architecture and
contribute to the objective of creating a landmark bridge. A
lightweight central opening span is key to the design. A challenging
design problem was found in the optimisation of weight and stiffness
in order to satisfy performance requirements whilst minimising the
subsequent actions on the opening mechanism and foundations.
The exact geometry was arrived at by firstly assuming that user
experience will govern design, and thus considering EC-1 crowd
loading (3.2 kN/m2; reduced from 5 kN/m2 as per long span bridge
reduction formula) against DMRB-1.3 deflection criteria (<span/300)
to deduce a suitable deck form to then analyse and refine for criteria
such as material stress limits, buckling, and dynamic performance.
Simple beam theory, considering each opening leaf to be a fixed
cantilever beam, shows that a constant section with second moment
of area 1.05 x 10-4 m4 will deform acceptably under a UDL of 13.1
KN/m (crowd loading + superimposed dead load). This gives a
starting point from which more complex tapered deck designs were
developed utilising Midas® finite element modelling software. Note
that these analyses ignore deflections under dead loads, as these
will be mitigated by pre-cambering during manufacturing.
The solution is a deck that tapers from section A at its ends, to
section B at its centre (see Figure 20 Deck sections A (left), B (right).
Units m.), comprising of two halves each weighing 21.5 tonnes (see
Figure 19). The deck has a cross fall of 1/50 at its edges to allow
drainage, thus preventing loading or pedestrian hazards by water
pooling.
Finite element modelling
Two finite element models were constructed; a simple beam model
of the entire central span to design a geometry for global
performance issues such as deflections and dynamics, then a
meshed plate model of half the span acting as a cantilever. The
latter considered localised issues such as buckling and stress
distribution into the bridge piers.
Figure 20 Deck sections A (left), B (right). Units m.
Figure 19 Deck form
Figure 18 Superstructure in Perspective
End
Centre

Finite element modelling Part 3:Superstructure
14
The deck is designed to perform acceptably with no force transfer
through the hydraulic jacks in service, such that they may be
removed or replaced during maintenance without the need to prop
the deck. The two halves will be connected by shear keys when in
the closed position, and this is modelled by a planar rigid link in the
beam model, whilst the plate model considers the worst case of zero
force transfer across this connection. The plate model also
considers the connection where the deck rests on the concrete pier
more realistically with fixed position boundary conditions across the
depth of the deck giving forces with lever arms rather than nodal
moment transfer. This model was initially constructed using a
coarse mesh for simplicity, and was then refined in areas deemed
critical by the first iteration of analysis. Comparison of the beam
model, plate models of several levels of mesh density, and basic
hand calculations permitted confident results to be obtained.
Figure 21 shows the applied forces to the central deck, the
consequent bending moments under EC-1 crowd loading and self
weight, and the properties of the critical section in bending.
Further to the simple case of full crowd loading, a number of load
combinations are presented in Table 5, alongside the resultant
deflections and stresses. This table highlights only the most adverse
load combinations found during analysis. Lateral deflections were
found to be below 1mm under every load case and so are not
presented.
Wind Loading
It is intuitive that wind loading must be considered for a lightweight,
slender structure. A wind pressure of 0.51 kN/m2 is obtained from
the following EC-1 formula, with orography assumed to be
insignificant at the site:
𝑉𝑏 = 𝑐 𝑑𝑖𝑟 𝑐𝑠𝑒𝑎𝑠 𝑐 𝑎𝑙𝑡 𝑐 𝑝𝑟𝑜𝑏 𝑉𝑏,𝑚𝑎𝑝 𝑞𝑝 (𝑧) = 𝑐𝑒, 𝑇 ∙ 𝑐𝑒(𝑧) ∙
1
2
∙ 𝜌 ∙ 𝑉𝑏
2
The susceptibility of the bridge to aerodynamic effects is indicated
by the ‘aerodynamic susceptibility parameter’, Pb. This is given by
the following formula (DMRB-1.3):
𝑃𝑏 = (
𝜌𝑏2
𝑚
) (
16𝑉𝑟
2
𝑏𝐿𝑓𝐵
2)
A Pb of 0.08 is found; which classifies the bridge as susceptible to
excitation, though not highly susceptible. It is recommended that
further testing, either in a wind tunnel or by use of computational
fluid dynamics software is conducted to fully assess this risk.
Table 5 shows that under the most adverse in service loading
conditions, maximum deflection is 0.12m. Yield checks show the
material to be safely within its stress limits; local buckling is
assessed and in the worst case a critical buckling load factor of 7.5
concluded. Figure 22 shows stress distribution under this
arrangement. It can be seen that the most critical situation for both
stress and buckling is at the point of initial jacking, where the forces
acting on the deck are that from the hydraulic jack (1000KN inclined
at 32°) and its self weight.
Several forms of connection were considered, and the optimal
solution was found to be a 2 m2 plate connection to spread the
jacking forces across this area of the deck’s underside. This keeps
13.1 kN/m + self weight
Cross sectional area, A = 0.494 m2
Second moment of area, I = 0.703 m4
Elastic section modulus, S = I/y = 0.622 m3
Moment capacity, My = S x σy
= 311,000 KNm
Figure 21 Bending moments under crowd load
Table 5 Load combinations. L = Longitudinal, V = Vertical, T = Tensile, C = Compressive
No. Load
Combination
Magnitude Arrangement Max.
Deflection
(span/300 =
0.15m)
Max. Stress Critical
Buckling
Factor
(1st
mode)
1a Crowd (V)
+
Crowd (L)
+
Wind
Vertical: 3.2 kN/m2
Longitudinal: 0.32 kN/m2
Wind: 0.51 kN/m2
Plan view of crowd arrangement
Abutment Centre Abutment
(-)0.120m (V) 64.1 MPa (C) 7.5
1b (-)0.061m (V) 46.1 MPa (C) 10.4
1c (-)0.061m (V) 46.2 MPa (C) 10.4
2 Thermal -10 to 30 °C Longitudinal expansion 0.007m (L) 30.4 MPa (T) 10.1
3 Opening Initial jacking force (1000KN) Closed – 0° n/a 278 MPa (C) 2.2
4a
Opening
Self weight + wind on raised
section
Half open – 42° (-)0.046m (V) 25.4 MPa (C) 31.2
4b Fully open – 84° (-)0.009m (V) 8.14 MPa (C) 58.8

Finite element modelling Part 3:Superstructure
15
stresses safely below the limit of 500 MPa and maintains a factor of
safety >2 against buckling. Figure 24 and Figure 23 show the stress
distribution and the first buckling mode shape in this situation.
It is clear that the area of greatest stress concentration and of most
critical buckling is the top of the web at the point where it meets the
bridge pier. Viewing the deck model on elevation (see Figure 25
Elevation of deck model at connection to abutment) reveals the
reason for such localised failures being predicted.
The exact detailing of this end connection point where the deck
rests upon the abutments in the closed position must be refined
further after testing, as per DMRB-1.3. Though, the current
configuration has a safety factor of 7.5 against buckling as it is. Note
that a critical factor of 14.5 was found against global failure of the
deck’s underside.
Dynamics
Analysis does give rise to potential dynamic issues as the bridge
has a vertical natural frequency of 2.6Hz. Although this is above the
2.3 Hz threshold for a ‘lively’ bridge excited by the first harmonic of
pedestrian loading [30], it is susceptible to the less powerful second
harmonic by being below 5 Hz. Increasing the natural frequency
above this threshold would require considerable weight to be added
to the structure, which would nullify many of its advantages.
Consequently, viscous dampers will be utilised at the connection
between the deck and hydraulic jack in order to dissipate energy
and reduce resonance. Lateral dynamic issues are not likely to
arise, as the lateral natural frequency was found to be 4.4Hz; safely
above the recommended threshold of 1.5Hz [30]. Dissipating
energy is of particular importance in FRP bridges as cyclic dynamic
loading may cause material bonds to deteriorate over time (DMRB-
1.3).
Central connection
The maximum shear force across the central connection is 80kN.
Figure 26 Detail of shear key illustrates this connection, including a
30mm expansion joint; selected based on a 42°C temperature
range (EC-1.5) in both the deck and bridge abutments. A continuity
step is detailed to prevent misalignment of the bridge leaves, with
one closing marginally earlier than the other. With two steel shear
keys of cross sectional area 240mm2, the maximum shear stress
will be 167 MPa; providing a factor of safety of 3.
Figure 22 Stress Distribution under
load combination 1a (crowd + wind)
Deck underside
Deck interior
Figure 23 Stress distribution under
load combination 3 (initial jacking)
Figure 24 First buckling mode under load combination 3 (initial jacking)
Figure 25 Elevation of deck model at connection to abutment
Figure 26 Detail of shear key

Piers and abutments Part 3:Superstructure
16
Piers and abutments
Figure 29 summarises the worst case loads imposed on the
abutments. Substantial longitudinal tensile forces are exerted
through the deck hinge in service. A reinforced concrete design is
optimised in such a way that this force is transferred by rebar in
tension back onto foundations on land, safely beyond the Harbour
wall (see 4.4.7), where the cost of works is lower. These bars are
set within a flanged deck beam composed of two T sections
spanning 2m centre to centre (Figure 27), which also acts as the
end spans of the bridge, and therefore is designed for EC-1 crowd
loading, as well as to EC-2 concrete standards. This is then
supported by a column section which must also take the
compressive forces exerted by the FRP deck in service and support
the hydraulic jacks when the bridge is opening. This concrete pier
and abutment will be one integral section, designed to withstand
thermal stresses rather than to expand over bearings. Table 7
shows performance under these loads in combination with wind and
thermal loading; resulting from a temperature change of -9 to 33 °C,
as per EC-1.5 and DMRB-1.3.14.
The longitudinal reinforcement detailing was achieved using
Midas® design tools to EC-2, whilst transverse reinforcement
detailing for the deck was achieved using an iterative Excel®
spreadsheet to design for EC-2. To be sure of the software output
the moment capacity of the column was checked; ignoring steel in
compression it was found to be 8,082 kNm. This is within 1% of the
Midas® output and is seen to be justification that the output is valid.
The solution is a modest concrete form (Figure 29), of total weight
150 tonnes. Mid-High strength C45/55 concrete shall be used to
avoid failure under thermal and working stress and to reduce the
structural class; increasing corrosion resistance.
More substantial solutions were analysed, which transferred smaller
loads onto the foundations, however this required a much greater
volume of concrete. One such solution used a 1m deep solid
rectangular beam, giving a total weight of 230 tonnes per abutment,
whilst load reduction to the foundations on land was only in the order
of 20%.
GGBS (Ground Granulated Blastfurnace Slag) will be incorporated
into the concrete mix. This is an alternative to cement, with almost
identical properties. It is a waste product from the iron and steel
industry [31], and hence has negligible embodied CO2. Additionally,
GGBS has been proven to be more resistant to cracking, chemical
attacks and more durable than traditional Portland cement [32].
13.1 kN/m
UDL: 30 kN/m (-z)
418 kN/m (-x)
3000 kN
z
x
215 kN
800 kN
530 kN
Case 1: In-service
Case 2: Opening
Figure 29 Imposed loads
Figure 29 Concrete Abutment (24m span)
Load Combination Magnitude Max. Stress Max. Deflection Max.
Bending
Max. Shear
1 Temperature
Crowd
Wind
42°C range
See Figure 29
0.51 kN/m2
15 Mpa (C)
(column)
5mm (L)
(beam)
5944 kNm
(column)
2264 kN
(column)
2 Bridge opening
(+ Temp., Wind, as
above)
See Figure 29 13 MPa (C)
(column)
5mm (L)
(beam)
5068 kNm
(column)
2456 kN
(column)
Table 7 Load Combinations L = Longitudinal, V = Vertical, T = Tensile, C = Compressive
Table 6 RC properties
Reinforcement Beam Column
Longitudinal 20xϕ40 44xϕ40
Shear Stirrups:
ϕ10@1040mm
Ties:
ϕ10@200mm
Transverse 9xϕ8 /m n/a
Cover
(XC3, class 3 as
per EN206-1)
50mm,
Cdev=10mm
50mm,
Cdev=10mm
Moment
Capacity
9000 kNm 8012 kNm
Shear Capacity 1314 kN 3560 kN
Figure 27 Concrete section details units m

Opening System Design Part 3:Superstructure
17
Opening System Design
One hydraulic cylinder will be used to lift each 21t leaf of the bridge.
Cylinder design is to AASHTO [33] specification. Hydraulic
mechanisms are a ubiquitous and reliable modern design with
minimal moving parts, low maintenance, high (95%) efficiency [33]
7.6.3] and suited to the tight geometric constraints of this bridge
compared with geared systems. Redundancy can be achieved by
employing auxiliary power systems [34].
The absence of counterweights and the fact that wind effects do not
overturn the deck during opening mean that single rather than
double sided cylinders may be used.
Geometry
Allowing maximum possible
cylinder stroke, the following
optimum geometry was
determined in Figure 30. See
calculation sheet, page 30.
Cylinder Design
Forces in the cylinder
resulting from static loading
can be found using basic
geometry. Kinematic theory
was used to establish
deceleration forces. It was
assumed that peak wind load and abrupt deceleration was an
unlikely load combination.
The cylinder fluid will resist a higher load during deceleration by
using backpressure and a dashpot mechanism, where fluid flows
out through an orifice.
Axial and radial piston motors have an efficiency of 85% and
AASHTO recommends a maximum working pressure of 31MPa
[33]. These would be mounted within the abutment and connected
to separate power supplies on each bank.
A cushion is to be fitted to the ends to reduce the speed, while
tamper proof covers and locking devices must be specified.
Failure Criterion
The following load cases and failure criteria (Figure 33 - Design
loads and resistances of the hydraulic cylinder) govern design.
Buckling Resistance: The buckling of a Shell and Rod cylinder
system can be estimated using a reduction factor for the Euler
critical load.
𝑷 𝑬 =
𝝅 𝟑
𝑬 𝑫 𝑹𝒐𝒅
𝟒
𝟔𝟒 (𝑳 𝒎𝒐𝒅) 𝟐
, 𝑳 𝒎𝒐𝒅 = 𝑿 𝟏 𝑲𝑳 𝑻𝒐𝒕𝒂𝒍
𝑿 𝟏 =
𝟏
𝑳 𝑻𝒐𝒕𝒂𝒍
𝑳 𝑺𝒉𝒆𝒍𝒍
∗√
𝑰 𝑺𝒉𝒆𝒍𝒍
𝑰 𝑺𝒉𝒆𝒍𝒍
+
𝟏
𝑳 𝑻𝒐𝒕𝒂𝒍
𝑳 𝑹𝒐𝒅
𝟕. 𝟓. 𝟏𝟐. 𝟑 [33]
Material Failure: Calculated using the Rankine Formula with
imperfection factor ‘a’ equal to 0.9 and factored yield stress of
Duplex Stainless Steel: fy = 460 N/mm2 [35].
Load Cases
Abrupt Deceleration: In order to achieve an opening time of 60s,
a peak angular velocity (ω) of 0.02 rad/s is required (assuming the
first 10s are acceleration). Discussion with the Harbourmaster
concluded that an emergency stopping time of (t) = 3s was desirable
for safety [12]. The deceleration forces are calculated from mass
(m) = 21t, moment of inertia (I) = 54880 kg/m2 [From 3D CAD Model]
and the radius (R) = 10.46m of centre of mass (COM). The lever
arms of COM about the trunnion LV & LH are geometrical functions
of the opening angle. See calculations, page 30.
𝑀 𝑇𝑜𝑡𝑎𝑙 = 𝑀𝑆𝑡𝑎𝑡𝑖𝑐 + 𝑀∝ + 𝑀𝐿𝑖𝑛.𝐷𝑒𝑐𝑒𝑙. = 𝑚 ∗ 𝑔 ∗ 𝐿 𝐻 +
𝝎∗𝑰
𝒕
+
𝝎∗𝑹∗𝒎
𝒕
∗ 𝑹
Applied Motor Force: The maximum allowable working pressure
(p) within a standard bridge cylinder is 20.7MPa [7.5.14 [33]]
resulting in a hydraulic force (F) of 860kN. To ensure piston force is
significantly larger than the static force, the bore was increased,
thus the section fails in crushing before buckling, 𝐹 = 𝑃. 𝐴.
Wind Load: Figure 31, shows the peak wind loads for the raised
section [EC1.4]. Using the peak deck axis force of 49kN (0.61kN/m2)
acting at the centroid of frontal area, the resultant moment remains
through to closure even at maximum angle of 50 degrees opening
by 952kNm.
Figure 30 Geometry of opening section
Figure 32 Cylinder Schematic
0
500
1000
1500
2000
2500
0 10 20 30 40 50
ResultanForcewithinHydraulicCylinder(kN)
Opening Angle of Deck (°)
Unfactored Design Loads and Resistances of
Hydraulic Cylinder
Buckling
Resistance
Adjusted for
Changing Stroke
Material Failure
Load (Rankine
Pinned-Pinned)
Abrupt
Decelleration +
Static
Maximum Working
Motor Force
Wind Force +
Static
Static Forces
Figure 33 - Design loads and resistances of the hydraulic cylinder
0
10
20
30
40
50
60
0 50 100 150 200 250 300
Wind Direction Bearing (°N): Deck Axis 25°N
Deck Fully Raised: Total Horizontal Wind Forces Per
Deck Section (kN) Total
Force
Perpendic
ular to
Deck Axis
Deck Axis
Figure 31 Wind Forces on raised deck section

Detailing Part 3:Superstructure
18
Detailing
Pier protection
Piles will be constructed around the
bridge piers to protect them from
accidental impact. Using an energy
transfer method [36] the protection piles
were modelled as steel circular hollow
section (CHS) cantilevers assumed to be
fully fixed in the soil 15m below the
waterline.
Correspondence with the Harbourmaster
identified the PS Waverley as the largest
and heaviest ship to use the Harbour. Its
mass (m) is 691,547kg, its beam (B) is 17.7m and its draft (D) 1.8m
[37]. The speed limit in the Floating Harbour is 2.68m/s [38], so an
accidental impact speed of 3m/s has been assumed in the
calculation (conservatively rounded). A CHS section with diameter
1.3m & thickness 0.425m was selected (see Figure 34)
See calculations, page 30.
Handrails
The handrail design is shown in Figure 35. It uses efficient LED
lighting with photoelectric controls installed to conform to DMRB-2
and subsequently British Standards (5489: Part 6). It is to be
fabricated from stainless steel for its corrosion resistance and
distinguishable colour for safety. Power will be supplied via cables
threaded within the main deck and through the handrail/deck
connection, see Figure 35.
Midas® was utilised to check performance against DMRB-2
requirements of a 0.7kN/m load imposed both vertically and
horizontally. This caused a maximum stress of (-)163MPa; safely
below the material yield limit of 250MPa. Critical load factor for
buckling was 38.6, which implies a high factor of safety against this
failure. Deflection checks show that maximum deflection is 24mm,
which is deemed to be acceptable. The resultant dead load on the
deck of this design is 0.3 KN at every stanchion.
Bearing Design
The specified bearing type is a bespoke Shaeffler Spherical Plane
type bearing of 400mm bore and 400mm axle. They are mounted to
the abutment via reinforced concrete anchorages to the web of the
concrete T-Beam.
Based on calculations, the maximum loads are shown in Table 8
assuming 5% normal contact area to the diameter measurement.
The capacity is based on similar examples [39].
Table 8 Bearing load cases
Load Type
Design
Force kN
Design
Stress
N/mm2
Resistance
N/mm2
Static
3000
[Section 3.2]
281.3 500 [1]
Peak
Deceleration
2000
[Section 3.2]
187.5 300 [1]
Cross Wind
1000
[Section 3.2]
93.8 300 [1]
Deck Hinge Plate
The axle of the bearing is connected to a steel plate that transfers
the load into the FRP. This is connected to the abutment with an
eye connection.
A steel plate is used to cover the deck surface at the intersection
between the FRP and the concrete sections in order to mitigate trip
hazards to pedestrians. It rotates on a hinge during the opening of
the bridge. This cover leads to great exposure of the bearing to
weather, however the benefit of this system is access for regular
maintenance of the bearings.
The FRP deck is attached at the central webs and upper flanges of
the deck via an array of 332x M32 bolts at 160mm c/c (see Figure
38). A minimum of 4x diameter spacing is allowable [40]. The
thickness of the FRP plates around the connection zone is
recommended to be detailed as 25mm thicker than the rest of the
FRP deck to deal with the higher local stress concentrations.
No threads should be cut into GFRP material, because of the risk of
delaminating fibres. High strength friction grip bolts cannot be used
as the creep relaxation is too great to ensure long term friction.
Resin injected bolts are recommended instead.
2m
1m1.4m
40mm ⌀
Figure 35 Handrail design
Figure 37 Cutaway of deck connection to abutment
Figure 36 Hinge connection; looking out from inside of sectionFigure 34 Pier protection

Opening Procedure Part 3:Superstructure
19
The Fibreline Design Manual (FDM) [40] was used to assess the
resistance to compression, tension and shear at the four steel to
FRP plates interfaces. These checks have been summarised in
Table 9. See calculations, page 30, for further detail.
Hydraulic Cylinder Connections
A clevis mount will be employed to keep the fulcrum as close to the
abutment as possible to reduce the moment of the cylinder force. A
bearingless well-greased pinned steel assembly is acceptable using
a high load bushing material such as ‘Nanovate’ with a tensile
ultimate strength of 2000 MPa and a high strength, corrosion
resistant steel pin such as Ferrium® S53® [41].
A steel clevis joint connects the hydraulic cylinder at both ends.
Geometry checks were performed on the clevis pin according to EC
3.13.2. The detail of the clevis connection is shown in Figure 39
Clevis pin dimensions for geometry checks.
Opening Procedure
The opening procedure for the bridge is outlined in a flowchart
(Figure 40 Bridge opening system. The system currently used for
opening bridges in the Floating Harbour is relatively slow. A
proposed system, to implement a remote CCTV system, could save
a significant amount of man-hours and OPEX for the client.
Failure
check
Resistance Design values
(see Figure 33)
Reference
Bearing in
Plate and
Pin
Fb,Rd 11630
kN
Fb,Ed 976 EC 3.13.2
Shear in
Pin Fv,Rd
6366
kN
Fb,Ed 976 EC 3.13.2
Bending in
Pin
MRd 201343
kNm
MEd 35,966
kNm
EC 3.13.2
Combined
bending
and Shear
in Pin
- (0.055) - 1 EC 3.13.2
Table 10 Clevis connection failure mechanism checks
Failure check Resist.
kN
Design
kN
FoS Reference
FRP
connection
to steel
plate
FRP tension in
direction of
pultrusion
1912 750 2.5 FDM 1.4.3
FRP shear
failure in
tension at 45°
2684 750 3.6 FDM 1.4.3
Steel plate
peak tensile
force
7830 750 10.4 BS5950
Local
bearing bolt
check. 25%
of bolts
active
Shear failure 184 40 4.6 FDM 1.4.6
Tearing of
laminate
(Condition 3)
240 40 6 FDM 1.4.6
Steel bolted
connections
Local bearing 276 40 - BS5950
Bolt shear 89.8 40 - BS5950
Table 9 Failure mechanism checks for local connection details
Figure 39 Clevis pin
dimensions for
geometry checks
Figure 38 Connection detail of FRP to concrete
An official operates
pedestrian warning lights
and then closes
pedestrian gates remotely
when it is safe to do so
The bridge is opened
remotely
The bridge closes. The
official is now ready to
return to other tasks at hand
An official monitors the
vessel’s movement and
pedestrians on the bridge
using closed circuit
television
~5 minutes
5 minutes
Bridge opens, vessel passes
through
Bridge closes, official opens
pedestrian gates
Official arrives back at the
Harbourmaster’s office
An official arrives to close
pedestrian gates and oversee
the bridge opening procedure
15 minutes
15 minutes
~5 minutes
Total time: 10-15 minutesTotal time: 35-40 minutes
Crew contact the
Harbourmaster’s office to
notify officials of their
intention to navigate the
Harbour
Crew contact the
Harbourmaster’s office to
notify officials of their
intention to navigate the
Harbour
Current System Proposed System
Figure 40 Bridge opening system

Geotechnical design Part 4:Substructure
20
Part 4: Substructure
Geotechnical design
The foundations selected at this location were heavily determined
by the geology and soil properties. The alluvial clays and silts
present are of low bearing capacity and susceptible to consolidation
(see Figure 41). Therefore the only feasible option to transfer the
load into the underlying strata is via piles.
Construction method selection
The method of construction has significant impact on the
cost of the structure. This section will assess the possible
options and select a design proposal. Option A is the
recommended construction method after consideration of
the potential strengths and weaknesses of all the options
and the levels of risk to the health and safety of the scheme.
Option A – Piling from a jack up barge
A pile driving barge would arrive via the River Avon. It would
drive steel circular hollow sections (CHS) through the
alluvium into the Mercia Mudstone. The centre of the CHS would
then be excavated with an auger and filled with concrete. They
would extend up to the water surface where a precast concrete
formwork would be craned over the pile heads and then sealed to
allow a RC pile cap to be cast around the driven piles (see Figure
43). The benefit of this option is the avoidance of large earth
movements or excavations suggested in option B or C. This is likely
to be significantly cheaper; however, it will require a jack up barge.
Option B – Piling in a cofferdam
An example of a cofferdam is shown in Figure 42. This option would
provide more stability to the bridge and less deflection of the pile
group than option A. However, the erection of a cofferdam is a
technical procedure which requires specialist equipment and is
generally expensive. It would also reduce river navigation for many
months. Furthermore, a number of serious safety hazards are
presented to construction workers when working in cofferdams [42].
Pile specifications
The substructure consists of eight piles supporting each pier, raked
at 22° across the river to resist the overturning moment of the
cantilever deck. The piles at the edges perpendicular to the bridge
deck are raked an additional 5° into the river to increase stability
against accidental lateral loading. This is within the standard rake
limit of 27° [43]. The piles extend 25m deep into the ground. The
piles are spaced at a minimum of 3 times the pile diameter in order
to avoid a reduction in strength due to interaction of the piles in the
group. High slump concrete is specified for the raking driven piles
in the water to ensure the concrete fills the CHS properly. Care is
required to ensure the tremie concrete pipe does not catch on the
rebar cage and lift it out of the pile as it is removed [43]. The water
in the Floating Harbour is brackish as it interacts with the tidal new
cut of the River Avon. The steel corrosion rate below water is
100μm/year, which equates to 12mm over the lifetime of the bridge.
In order to protect the steel against corrosion a new external
polyethylene coating is required every 20 years [44].
Calculations reveal that load spread of the concrete landing ramp
into the bank would apply a surcharge onto the gravity retaining
wall. This is an old masonry design, and it was decided that to
eliminate the risk of failure by negating these effects the piles over
land are constructed with a sleeve. This will mean that no resistance
is provided by the pile shaft until below the assumed depth of the
retaining wall where the sleeve would terminate.
Figure 41 Estimated Cu Profile at the site
Figure 43 Option A [43] Figure 42 Option B [43]
Figure 44 Borehole locations near to the site
Table 11 Midas output of worst cade loads from the concrete structure
Bored piles on
Land
Fx (KN) Fz (KN) My (KNm)
In Service 519 664 -2671
Opening 1170 543 -2195
Driven piles in Water Fx (KN) Fz (KN) My (KNm)
In Service -415 1234 1215
Opening 1170 543 -2195
-15
-10
-5
0
5
10
0 100 200 300 400 500
ReducedLevel(mAOD)
Cu (kPa)Estimated Cu Profile from SPT N values
BH01 BH02 BH03 BH04 BH05A
BH06 BH07 BH09 BH10 BH11
BH12 BH13 BH14 BH15 BH16
BH17 BH18 BH1 SSGB

Pile analysis Part 4:Substructure
21
Pile analysis
Bearing capacity
Pile bearing capacities were determined using the alpha method
because of the availability of relevant undrained shear strength
data. Values for SPT N blows in nearby boreholes (see Figure 44)
were variable and unreliable due to the presence of hard quarzitic
sandstone gravel and cobbles. These were converted to Cu values
using the empirical relation Cu=4.5N [45]. This relation varies with
plasticity index, 4.5 was selected as the plasticity index of the soils
was approximately 30% [20]. Some unreliable quarzitic sandstone
values and other outliers were
excluded from the analysis and the
graphical 3-σ rule was used in Figure
41 to determine a cautious estimate of
the characteristic Cu profile. There are
some values of Cu near the surface
that are ignored as they are made
ground. The unfactored loading
requirements for the piles from the bridge are displayed in Table 11
on the previous page.
These loads were applied to a GSA model of the pile group
structure. It was analysed as a planar problem (see Figure 45 and
Figure 45) assuming that the pile groups would equally share the
loads between pairs of raked piles. As the bridge is loaded
symmetrically, the design is mirrored on both sides of the bridge.
The bearing capacity of the soil did not govern the design, as the
settlement of the piles was very significant. The full bearing capacity
calculations are displayed on page 30.
Settlement of the pile group
The settlement of the piles was calculated using single pile
calculations rather than as a group. This is because the structure is
not simply axially loaded, and therefore the piles act individually
under settlement, i.e. at different rates. It was assumed that under
working loads there is a linear relationship between settlement and
the base and shaft resistances. The full settlement calculations are
shown on page 30 and the results are displayed in Table 12. Further
boreholes and laboratory testing are recommended to calculate
settlement more accurately with closer sampling to the site.
Pile elastic shortening
Pile elastic shortening also contributes to the settlement. It was
assumed that the loads transferred from the pile cap distribute
evenly into the pairs of raked piles. The worst case scenario was
considered where the tension piles would elastically lengthen as the
compression piles elastically shorten. The worst case tension
causing pile elastic lengthening is described in Table 12 as a
negative value. This would cause the largest differential settlement
and rotation at the pile cap.
Negative skin friction (NSF)
NSF is not a significant issue because the imposed loads are not
transferred onto the compressible soil strata. The load transfer
paths load through pile caps, into the piles, and into the underlying
Mercia Mudstone strata intentionally to avoid the slightly organic
alluvium and made ground which would have caused NSF (adverse
downward forces due to friction during settlement).
Block failure
Block failure only applies to axially loaded piles. The raked piles in
this design act in a different manner and would not fail acting as a
block, they would fail individually as they are spaced far enough
apart so as to reduce interaction effects.
Buckling
Piles that extend above ground may be prone to buckling. This is
the case for the driven piles over the water. The driven piles
selected for this construction are concrete cased with tubular steel
CHS. The effects of local buckling on fully concreted cased tubular
steel piles with steel grades S235 may be neglected subject to a
maximum diameter to wall thickness ratio of 90. For the selected
CHS section D=508mm, t=6.3mm, D/t=80.6, therefore buckling can
be neglected (EC-4 6.7.1). The piles on the land have containment
from the surrounding soils and do not need to be considered for
buckling [43].
Pile Group A B C D
North South North South North South North South
Soil Settlement (mm) 0.34 0.19 0.07 0.18 0.18 0.07 0.19 0.34
Pile Elastic Shortening (mm) 3.96 -2.20 0.49 1.36 1.36 0.49 -2.20 3.96
Total Settlement (mm) 4.30 -2.01 0.56 1.54 1.54 0.56 -2.01 4.30
Differential Settlement relative to the
North Pile of Group A (mm)
0.00 -6.31 -3.75 -2.76 -2.76 -3.75 -6.31 0.00
Table 12 Settlement of the pile groups
Model of Pile Groups A and D
z
x
BridgeBank
Figure 45 GSA output of axial loads in piles on land
x
z
Model of Pile Groups B and C
Concrete FRP Deck
Figure 45 GSA output of axial loads in piles over water

Pile cap Part 4:Substructure
22
Harbour wall considerations
The Harbour walls are masonry gravity retaining walls. Further
investigation is required to determine their strength in resisting
surcharge loading as a result of site equipment and plant.
Positioning a crane nearby to the edge of the water may destabilise
them; although the walls are likely to have some capacity in their
design as railways previously ran along the harbour; implying some
design for heavy loading.
In order to avoid load spread onto the harbour walls, some
conservative estimates of the geometry were used to determine a
safe crane location. A 45° load spread of the crane surcharge was
assumed. The safe location of the crane is shown in Figure 46. It
may be possible to locate the crane closer with detailed
investigation of the existing harbour wall.
Pile cap
The structure requires 4 pile caps to spread loads into its
foundations; two in the water (type A), and two on land (type B).
These were modelled as reinforced concrete slabs, shown in Figure
47.
The design primarily focused on checking the section for flexural
moment capacity and mitigating punching shear issues. The
reinforcement specified in Table 13 is sufficient to deal with the
shear and the moments applied to the pile cap. Figure 48 shows the
Wood-Armer moment distribution in the type A pile caps.
Connections
For piles that have moments being transferred into them, as is the
case for this bridge, the piles must extend a significant depth into
the pile cap to allow the safe transfer of load [43].
These calculations demonstrate that the suggested substructure
design is feasible, but may be optimising pending further
investigation.
Soil sulphates
Nearby at the SS Great Britain, laboratory analysis of soil samples
found sulphate levels to be 0.01g/l with a pH level of 7.7 to 8.26 [20].
This classifies the site as Sulphate class DS-1 which requires the
specification of ACEC Class AC-1 concrete in order to reduce the
effect of the sulphate chemical reaction [46]. It is likely that this will
be required in the concrete piles and abutments; testing nearer to
the site is recommended to confirm this.
Site investigation reccomendations
1. Contamination, sulphates and pH level laboratory testing
2. Oedometer testing for detailed settlement analysis
3. Triaxial tests to verify estimated Cu profile
4. Rotary cores of Mercia Mudstone to determine strength and
depth of the strata for pile socketing
5. Sampling from site boreholes for density and Atterberg Limit
testing of soils at various depths to refine estimated properties
6. Piezometer to determine ground water level.
7. Calcite content laboratory testing on Mercia Mudstone at
various levels to determine depth of weathering
8. Trial pits to determine the depth of made ground and allow
U100 to access underlying soil strata through the made ground
Column connection
Pile connections Beam connections
Figure 47 Pile cap details: (Left is type A and Right is type B)
y
x
Figure 48 Wood Armer moment distribution
in pile cap type A
Table 13 Detailing of dimensions and required
reinforcement in the pile caps
A B
Slab thickness 0.5m 0.75m
Direction-x
(top and bottom)
56xϕ12
@100mm
31xϕ12
@100mm
Direction-y
(top and bottom)
26xϕ12
@100mm
26xϕ12
@100mm
Total rebar 576m x ϕ12 318m x ϕ12
Figure 46 Estimated safe location of crane
Figure 49 Substructure design

Project strategy & whole life performance Part 5:Project Management
23
Part 5: Project Management
Project strategy & whole life performance
In order to ensure that the project is as sustainable as possible, and
that it reaches its 120 year design life, acknowledgement of the
whole life performance of the bridge and the ability of the bridge to
fulfil its purpose throughout its life cycle is critical. The aim of this
section is to demonstrate the stages of the project from inception
through to decommissioning and the measures that should be taken
to enhance the performance of the project. Whole life performance
begins from the construction stage - “Each stage in the cycle should
be planned and managed in order to provide the best basis for all
the following stages” [47]. The life cycle stages for this project are
described in Figure 50.
Life cycle stages
9. Demand analysis
A demand analysis was conducted in order to confirm the initial
expected need for the bridge. This can be found in Section 2.1.
10. Initial proposal
Refer to the Project Brief in Section 1.1, as outlined by Bristol City
Council.
11. Feasibility study
This report is a feasibility study for the proposed design. It confirms
the need for the project, identifies the constraints, makes a critical
evaluation of design options and highlights the financial and
technical feasibility of the project.
12. Design
A design brief which clearly defines the scope, priorities, objectives
and design criteria is crucial to success of the project. The final
proposal is outlined in Section 3. The design adheres to
construction design and management regulations, and is designed
with construction risks in mind. At the detailed design stage, the
designer must indicate every risk on all documents and drawings.
13. Contracts
A design and build contract [47] will be employed for the project.
Several contractors are expected to bid for the project in a bidding
process.
14. Construction
The construction sequence, timeline and implementation issues are
described in section 5.7. An application must be made to the
Secretary of State as this project relates to “certain types of works
that interfere with rights of navigation in waters up to the limits of the
territorial sea” [48]. An approval must be received before
construction works can commence.
15. Testing and commissioning
Inspection and testing of the static components of the bridge during
and after construction is necessary, whilst dynamic components
(such as the hydraulic jack and bearings) must be tested and
commissioned, either by the contractor or specialist personnel [47].
All test data will be recorded and logged for safety and maintenance
purposes.
16. Operation and maintenance
The bridge can be divided into several physical components, as
shown in Section 5.5. This section summarises each component’s
maintainability and recyclability. It is expected that the running cost
of the entire bridge over its 120 year design life will be in the region
of 3-4 times construction costs (see section 5.6). The design also
allows for very easy maintenance of the components with minimal
impact on the users of the bridge and local residents.
In addition, all of the materials can easily be recycled post
decommissioning. In order to successfully operate, maintain and
manage the bridge, a whole life asset management strategy should
be developed in line with ISO 55000 to maximise the output of the
assets, reduce the life cycle cost of the bridge and maximise safety
for users. The strategy should be flexible, resilient to future
changes, and have an underlying sustainable framework so that
triple bottom line factors (economic, social and environmental) are
considered in every aspect of the projects life.
Provision for future changes during operation
Within the next 120 years, the Bristol Harbourside will change
significantly. It is probable that the population in the area will
increase, and that derelict structures will be replaced with apartment
blocks. As a result, demand across the bridge could increase.
Due to the implementation of Bristol’s integrated flood management
strategy, water levels in the Harbour are not expected to rise during
the bridge’s lifetime [49].
Changes in use may be accommodated, as safety factors have
given spare structural capacity, and the bridge components are
somewhat compartmentalised; e.g. the hydraulic cylinders could be
simply replaced.
Figure 50 Project Life Cycle [47]

Risk assessment Part 5:Project Management
24
Risk assessment
There are numerous risks incurred by this project. They have
been assessed in Table 14. The assessment of risk was
qualitatively assessed utilising a methodology recommended by
CIRIA [50]. 𝑅𝑖𝑠𝑘 𝑟𝑎𝑡𝑖𝑛𝑔 𝑅 = 𝐿𝑖𝑘𝑒𝑙𝑖ℎ𝑜𝑜𝑑 𝐿 𝑥 𝐶𝑜𝑛𝑠𝑒𝑞𝑢𝑒𝑛𝑐𝑒 𝐶.
The residual project risks are considered to be acceptable risks
if the control strategies suggested are implemented effectively
by the various stakeholders involved in the project.
Likelihood L Consequence C
Very Unlikely Minimal
Unlikely Minor
Possible Moderate
Likely Major
Very Likely Severe
Hazard Hazard Category Description
Period of
Duration
Initial Risk
Assessment Control strategy
Residual Risk
Assessment
Stakeholder
implementing
control strategyL C R L C R
Over Budget Economic
Failure to control costs or delays that increase
costs of project
Design and
Construction
3 4 12
Careful design of construction sequence, procurement,
scheduling. Communication and management
hierarchy between stakeholders
2 3 6
Investors, BCC &
Contractor
Reduction in
footfall
Economic
Loss of revenue for local businesses and tourist
attractions as a result of construction
Construction 2 2 4
Keep existing pathways open as much as possible,
clear signage that businesses are still open,
compensation if required as a last resort
1 1 1
Contractor &
Local Businesses
Lack of funding Economic
Budget limitations for the client, threshold of cost
benefit ratio for public project approval
Design and
Construction
4 4 16
Procure multiple funding sources, design the structure
to avoid risk of delays and extra costs
2 3 6 BCC
Land
Acquisition
Economic & Legal
Extra expenses/delays due to difficulty in
buying/approve use of required land
Design 2 3 6
Public outreach and media strategy to reduce
objections to project and design to satisfy stakeholders
1 2 2 BCC
Maintenance
Economic &
Technical
Failure of components of the bridge causing river
traffic disruption and extra costs
Operation 2 3 6
Regular inspection and maintenance, whole life
procurement strategy. CCTV deterring vandalism
1 2 2
Harbourmaster &
BCC
Pollution Environmental
Dust and air pollutants, toxic chemicals to
watercourse, wildlife and ecology, noise pollution
of plant on site
Construction 4 3 12
Waste disposal strategy and emergency plan for clean-
up of water pollutants, acoustic insulation, testing of dB
levels, restriction on operating hours
1 2 2 Contractor
Drowning Health & Safety
Possibility of drowning due to working over and
next to water for staff during construction and
demolition and general public during operation
Construction,
End of Life &
Operation
2 4 8
Provision of lifesaving training, life vests, good lighting
and access during construction. High parapets to
protect pedestrians and warnings lights and barriers
during bridge operation
1 2 2
Contractor &
Harbour Master
Regulations Legal/Political
Failing to meet requirements of various
governmental bodies in design and construction
Design 3 3 9
Involve stakeholders and create management
strategies to ensure meeting of requirements
1 2 2
Contractor and
BCC
Media Social
Representation of the project in the media,
negative implications for funding/success
Whole Life 3 4 12
Involve local community in outreach program and
explain benefits of design
1 2 2
Contractor &
BCC
Disrupting
Traffic
Social &
Economic
Causing pollution and traffic as a result of site
vehicles
Construction 3 3 9
Traffic management strategy to reduce impact of site
traffic and limit delivery times to off peak hours
1 1 1 Contractors
Disrupting River
Traffic
Social &
Economic
Causing blockages during construction and/or
disrupting existing harbour users
Construction &
Operation
5 3 15
Make harbour users aware of disruption times,
changes to channel and construct in winter where
possible
3 2 6
Contractor &
Harbour Master
Planning
Permission
Social & Political
Failure to get permission or delays due to
redesigns, risk from nearby listed buildings
Design 5 4 20
Work closely with planning department and be
prepared to alter design to satisfy stakeholders
2 2 4
Designers &
Contractors
Vibration
Technical,
Serviceability
Wind/pedestrian induced vibration of the bridge Operation 4 2 8
Testing and design to resist vibration and resonance
and fatigue of cyclic loading
2 1 2 Designers
Unexploded
Bomb/ Live
services
Technical and
Health & Safety
Hazard to life and health of staff and
damage/disruption to services
Construction 1 5 5
Work with local service providers to identify possible
interactions with services and design strategy to avoid
or reduce disruption
1 2 2
Designers &
Contractors
Non- standard
materials and
structure type
Technical
Unusual design, lack of design precedence means
uncertain whole life performance and limited
fabrication options
Whole Life 5 4 20
Procurement and tendering strategy to minimise cost
of specialist FRP fabrication, careful maintenance and
composite material testing
3 2 6 Designer
Table 14 Risk assessment for the project

Maintenance of components Part 5:Project Management
25
Maintenance of components
FRP deck
- FRP is “virtually maintenance free” [51], however connections
to the deck will create high local stress concentrations and
cause fatigue over time and possible material defects (DMRB-
1.3).
- Regular inspection and maintenance required as brittle failure
could occur, and for wear of deck/need for resurfacing.
- Replacement would require complete removal of deck.
- Can be recycled and is compliant with EU legislation. There
are currently three methods. Of the three, co-processing
would be the most favourable. The waste material from the
FRP deck could be used in the cement industry as
replacement for fossil fuels [52].
Hydraulic cylinders
- Stainless steel; not expected to corrode.
- Require frequent inspection and maintenance; they tend to fail
in the oil port connection zone from fatigue [53].
- Redundant deck design allows jacks to be safely removed.
Schaeffler Bearings
- Negligible maintenance cost “Our high performance
ELGOGLIDE® sliding layer ensures that each bearing is
maintenance-free for life” [54].
- Hatch within the GFRP deck will enable full access to
bearings from top of the bridge.
- Desired lifetime 1560 hours [55] - Bridge average opening 3
times a day for c. 5 minutes = 0.25 hours/day.
- Can therefore last roughly 17 years.
- Estimated end of life recycling ratio is 80-90% [56].
Shear keys
- Regular inspection and maintenance required.
- Accessible by lifting one half of the bridge slightly.
- Estimated end of life recycling ratio is 80-90% [56]
Reinforced Concrete Abutment and Pier
- Negligible maintenance cost, hydrostatic water conditions =
minimal risk from scouring and reduced cracking effects.
- Should be inspected annually.
- Steel rebar can be recovered from the element, recycled and
then reused again. The concrete can be crushed and reused
as aggregate for other construction works. Consequently the
entire element is 100% recyclable [57].
Handrail
- Negligible maintenance expected for the stainless steel.
- Handrail constructed as 2m wide sections. Sections could be
replaced in parts (allowing operation to continue) and are fully
accessible from the top of the deck.
- Estimated end of life recycling ratio is 80-90%. [56]
Handrail lights
- £172 per year to operate entire handrail (246 1W LED Bulbs-
12 hours per day assumed [58] [59])
- Handrail lights are simple to replace and accessible by foot.
- LED lights can be recycled safely with minimal environmental
impact [60].
Quantifying whole life cycle costs
During the bridge’s life cycle there will be some unforeseen
costs through maintenance or repair of components.
Consequently it is difficult to quantify the whole life costs with
accuracy.
A report [61] assessed the whole life cycle cost of 21 bascule
bridges in Chicago built from 1902 to 1936. It found that whole
life cycle costs accumulated linearly throughout the life of the
bridge. Additionally, bridges over 100 years old tended to be
less than five times that of the initial construction costs.
Based on this data, it can be assumed that the life cycle cost of
the project will fall slightly below this (3-4x) due to the very low
maintenance components that have been deliberately taken
advantage of, such as GFRP and stainless steel.
Construction Sequence
Pile foundations for pier
Details: Construction of pile
foundations for the pier by driving
piles at angles from a jack up
barge (8 piles/pier). Also
constructing pier protection by
driving pier piles vertically (4
piles/pier).
Issues: Accuracy of placing and
angling the piles in water, and
moving the jack up barge around
the Harbour safely. Deviation of piles from intended raking
angle.
Plant: Pile driver, Jack up barge, floating barge to transport both.
Pile cap for pier
Details: Construction of a pile
cap to distribute loads to
foundations.
Issues: Erecting the
formwork, preventing water
entry, draining water from
formwork and cutting back
piles to expose steel rebar.
Solutions: Formwork can be
precast and lifted in place, with
divers sealing off formwork with rubber to prevent water entry.
Water should then be pumped out and the formwork allowed to
dry. The top of the piles should be cut by skilled workers to
expose rebar and this should be connected to rebar cage for
Figure 51 Pile installation
method
Figure 52 Precast concrete
formwork around the driven piles
to cast the pile cap

Construction Sequence Part 5:Project Management
26
the pile cap. Concrete should then be poured by a concrete
pump from the embankment.
Plant: Concrete pump, 350t Crane.
Abutment foundation
Details: Excavating embankment and
boring four piles at angles on each
embankment for the abutment.
Issues: Avoiding contact with the
Harbour wall, and the stability of the
wall.
Solutions: Extensometers should be
installed to measure horizontal
deflection of the Harbour wall, and
piezometers to measure changes in
pore water pressure which may affect stability.
Plant: Pile boring machine, concrete pump, dumper for waste.
Pier and Abutment Element
Details: In-situ construction of the
pier and abutment element by
pouring concrete over a rebar
cage.
Issues: Erecting the formwork over
15m between the pile cap and
Harbour wall.
Solutions: A floating barge should
be placed in between the pile cap
and Harbour wall which will support a steel truss scaffolding
frame, which in turn will support the formwork. It must be of
sufficient strength to support the weight of the concrete.
Plant:350 tonne crane, concrete pump.
Lift FRP Deck
Details: Lifting a leaf of the deck from a rented barge using a 350
tonne crane located on the embankment.
Issues: Space for the crane
to swing over and lift the
deck from the barge and the
weight of the crane affecting
Harbour wall stability
Solutions: Trees should be
cut down on the north
embankment in order to provide space for crane to swing into
the Harbour and lift the deck. Calculations have been
conducted in order to assess a safe distance for a crane from
the embankment wall in terms of stability. Further details can be
found in Section 4.4.7.
Plant: 350 tonne crane, floating barge.
Hydraulic Jack and Other Finishes
Details: Hydraulic jack must be attached to the base of the deck
and the base of the pier. The deck surface must be sprayed with
epoxy resin, and the handrails bolted to the deck.
Issues: Difficulty of manually attaching hydraulic jack from below
the deck whilst working in the water.
Solutions: A barge should be firmly tie roped to the Harbour wall
for access beneath deck.
Table 15 Construction Gantt chart
Figure 53 Bored pile
installation on land
Figure 54 Temporary
scaffolding and formwork for
concrete pier/abutment
element
Figure 55 Crane lifting FRP deck
sections off delivery barge into place

Floating Harbour Bridge-2

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