On Site Constraints
The onsite constraints involve the active Lewes Road which is present to large amounts of traffic and pedestrian activity; it is also a major bus route. Section 4.0 of The Design Manual for Roads and Bridges, requests that all construction activities near to an existing highway must not cause disruption to the traffic. However, in any case, this road is going to require closing in order to complete the connections to the underside of the bridge.
Proposed Solution
Many highways projects involving bridge construction make use of night time/holidays where traffic will be significantly reduced; a road closure would not affect the local residents as much as if it were to proceed within the day time.
The foundations and supports however have been designed as to be constructed far away from the road so that a closure may not be required. However the highways act 1980 requires suitable hoarding around any construction site near to an existing carriageway. Therefore, when the piers are constructed, suitable hoarding and provision for protection against the public realm must be enforced.
Foundations
The foundations will be cast pad foundations that protrude from the existing ground level. These will be cast in situ with suitable falsework and left to cure subject to engineer’s requirements (usually 48hrs). These will be cast in 3 locations as displayed. If possible, the ground should be graded as to incorporate the pad foundations to allow a flush presentation. Excavators and concrete trucks can access these areas through the existing Lewes road.
Supports
The supports will be made of stainless steel or a steel alloy as with the helical design of the bridge. These will use a very similar methodology to that of the M8 bridge whereas they will connect on a pivot to make up loss of tolerance. These will be prefabricated and fixed to the pad foundation using concrete anchors once the concrete has set.
Bridge Sections
The sections will be delivered in quarters, the first half will be fitted within the Mithras house end and the second will be suspended and attached underneath via platform on the Lewes road. It is at this point of the construction process that we will require a road closure. The sections will be delivered by flatbed wagon.
Ramps and StairsÂ
The ramps and stairs towards the Mithras house end will not require a great amount of engineering to install as the design intention was to use the majority of the topography before installing ramps ( as specified in the DMRB). Both stairs and ramp at this end will be prefabricated and fixed to the ground.
Towards the other end however there will be a greater height of which to comply which can lead to a requirement in great lengths of ramp. These will also be prefabricated but most likely bought in sections, again with a similar design process to the other side of the bridge, by fixing to relative foundations. The railings and buttresses will be made of similar bridge materials. And the ramp possibly of cast reinforced concrete with waterproofing membrane.