TWIN SAILS
OPEN LIFT BRIDGE
AGENDA
• Introduction
• Types of Bridges
• Open Lift Bridge
• Architecture of TWIN SAILS OPEN LIFT BRIDGE
• Details of TWIN SAILS
• Specialities and Advantages
• Problems and performance issues
Conclusion
•
The type of bridge is chosen by taking into consideration many
aspects like cost effectiveness, suitability, available technology,
maintenance cost, infrastructure available, technical expertise etc.
The concept of open lift bridges is generally implemented over the
water bodies wherein the boat traffic is to be regulated with a
greater accuracy in symbiosis with road traffic. These bridges shall
also be used as check points to control illegal operations in boat
traffic.
TYPES OF BRIDGES
• Girder Bridge
• Arch Bridge
• Truss Bridge
• Cable Stayed Bridge
• Rigid Frame Bridge
• Suspension Bridge
Girder Bridge
A girder bridge is perhaps the most common and most
basic bridge. A log across a creek is an example of a girder
bridge in its simplest form. In modern steel girder bridges,
the two most common girders are I-beam girders and boxgirders.
Arch Bridge
Arches are the second oldest bridge type and a classic
structure. Unlike simple girder bridges, arches are well suited
to the use of stone. Arches are good choices for crossing
valleys and rivers since the arch doesn't require piers in the
center. Arches can be one of the more beautiful bridge types.
Truss Bridge
The truss is a simple skeletal structure. In design theory,
the individual members of a simple truss are subjected to
tension and compression forces and not bending forces.
Cable Stayed Bridge
A typical cable stayed bridge is a continuous girder with
one or more towers erected above piers in the middle of the
span. From these towers, cables stretch down diagonally and
support the girder.
Rigid Frame Bridge
Rigid frame bridges are sometimes also known as
Rahmen bridges. In a standard girder bridge, the girder and
the piers are separate structures. However, a rigid frame
bridge is one in which the piers and girder is one solid
structure.
Suspension Bridge
Of all the bridge types in use today, the suspension
bridge allows for the longest spans. At first glance the
suspension and cable-stayed bridges may look similar, but
they are quite different.
Open Lift Bridge
The concept of open lift bridges is introduced to help
the passage of the boat traffic, wherein the vehicular traffic
is also operated over the same water body. This has become
possible with the invention of bridges and later on modified
as open lift bridges.
Architecture of “Twin Sails Open Lift Bridge”.
The unusual shape of the lift spans was chosen mainly for
aesthetic reasons. The most striking features of the structure
are its long lift spans which can be designed to a length of
over 35m, which are triangular, rather than rectangular, in
plan. Although the lift spans are longer than the conventional
rectangular ones, they are not significantly heavier; nor are
their area greater. Each leaf’s Center of Area is low compared
to that of a rectangular leaf, which will help the structure to
handle heavy wind loads. The Center of Mass is also low,
reducing the necessary length of the lever arms and hence the
amount of energy required to open the bridge.
 The Twin Sails Bridge (also known as The second harbour crossing) is
a double leaved bascule bridge in Poole, Dorset, England.
 The bridge provides a second road link from Poole town centre to Hamworthy. The
intention is that the bridge will allow development of four major sites,
two in the town centre and two in Hamworthy, including the old power
station which was closed in 1988.
Architect:
Wilkinson Eyre Architects
Structural Engineer:
Ramboll
Steelwork Contractor:
Cleveland Bridge UK Ltd
Main Contractor:
Hochtief (UK) Construction Ltd
 The new bridge is intended to operate alongside the existing Poole
Bridge with one of the bridges always open for vehicular traffic.
 The bridge comprises a 10.8-metre (35 ft) wide carriageway with two vehicular lanes
and two separate cycle lanes.
• two 2.5-metre (8 ft) wide footpaths are provided which cantilever from the bridge.
• The bridge is constructed in five spans, with a total length of roughly 139 metres (456
ft).
• The approaches comprise two 27-metre (89 ft) spans, the centre lifting span consists
of two triangular leaves that span 23.4 metres (77 ft) between the main bearings to
provide a clear channel of 19 metres (62 ft) when open.
 The bridge features two distinct structural forms:
the approach spans constructed as composite steeL boxes with curved soffits, and
the triangular lifting spans comprising fabricated steel boxes with orthotropic deck
plates, again with curved soffits.

The abutments and piers sit on top of 53 foundation piles, mostly 1.2m in diameter
and sunk 31m into the Channel bed.
 The deck and sails were made up of 41 sections of steel.
 The construction process itself was inventive. The most economical method of
constructing this bridge was to fabricate much of the steel superstructure offsite.
Modular sections were brought to the site, assembled to form individual deck spans
Welded together on the quayside adjacent to the Channel.Once assembled each span
of the superstructure was jacked up off temporary supports on
self-propelled modular transporters (SPMTs), driven onto a barge and
floated into position.
 an acknowledgement of the area’s maritime heritage.
The deck in the pivot zone contains observation windows allowing pedestrians and
vehicle occupants to see across the Channel to the opposing sail and enjoy dramatic
views of the structure’s operation.
 The project received the outstanding achievement award for exterior lighting at the
Architecture Lighting Design Awards 2012.
 It was also among the top four final bridges selected at International Institute of
Structural Engineers Awards 2012, as well as being selected under the
commendation category for its structural authenticity.
 After being opened in April 2012, the bridge failed to function three
times during the same year. The Poole council has demanded an
inquiry from Hochtief (UK) Construction who is responsible for repairs
during the first functional year.
 In addition, sections of the road surface fell off due to the use of
deficient binder material.
 Other problems have included reduced hydraulic pressure, software
issues and loss of power to the lifting system.
This ingenious design for an opening traffic bridge combines
elegance and functional efficiency. When closed, the slender deck blends
with the surrounding landscape, and when open the tapering arms create
a dramatic landmark, reflecting the masts and sails of passing boats. The
detailing and fabrication are of the highest standard, and ensure easy
maintenance.The client and the public are delighted with this iconic and
vital bridge.
Thank you