TWIN SAILS OPEN LIFT BRIDGE

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 AGENDA

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 box- girders.

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 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 tra ffi c.  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 so ffi ts, and the triangular lifting spans comprising fabricated steel boxes with orthotropic deck plates, again with curved so ffi ts.  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 o ff site. 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 o ff 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 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 o ff 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 tra ffi c bridge combines elegance and functional e ffi ciency. 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.

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