The Present Bridge
The present Whitchurch Bridge is the third to be constructed at the site. It was designed by Joseph Morris and built in 1902 by the Cleveland Bridge and Engineering Company Ltd.
Whitchurch Bridge carries the B471 over the River Thames between Pangbourne in West Berkshire, and Whitchurch-on-Thames in Oxfordshire. It lies within the civil parish of Whitchurch-on-Thames, which in turn lies within the district of South Oxfordshire and the county of Oxfordshire.
The Bridge is subject to a statutory weight limit of 7.5 tonnes mgw. Access to the Bridge is restricted by a low railway over-bridge on the Pangbourne (south) approach, and limiting road widths and a steep hill in Whitchurch-on-Thames. Carriageway width is 5.18m, and there is a single footway on the west (upstream) side of 1.3m width.
The Bridge is a four span continuous structure with cast iron trestle piers and brickwork abutments. There are two end spans, each 20.3m in length, and two inner spans of 20.75m. The north abutment has a fixed connection to the deck: the south abutment has elastometric rubber bearing pads. The main wrought iron plate girders are fixed to the cast iron column heads with bolted connections.
Each of the four spans is constructed of two main wrought iron longitudinal plate girders, with smaller section transverse wrought iron girders, supported on brick abutments and three river piers, each consisting of two piles with transverse cross-bracing. The carriageway is supported by wrought iron buckle plates between the transverse girders, overlaid with concrete. The parapet is of wrought iron latticework construction incorporated as part of the main longitudinal girders.
The Bridge has been subject to various strengthening improvements in the 1920's, 40's and 70's, including additional bracing around the column heads and between the pier columns.
Upstream fenders each consisting of three braced 300 X 300mm wooden piles at each pier have been in place for many years, and downstream fenders - to protect the Bridge piers from boat collisions - were added in 2005. The headroom for river traffic is 3.95m (summer river level), and the maximum depth of water under the Bridge is 4.4m, under the southern span.
Whitchurch Bridge lies within the Chilterns Area of Outstanding Natural Beauty and the Whitchurch-on-Thames Conservation Area, and is a Grade II listed structure for planning purposes. The local Planning authority is South Oxfordshire District Council (SODC).
The Whitchurch Bridge Company's professional adviser on Bridge engineering issues is Oxfordshire County Council (OCC).
Bridge Reconstruction (revised 13th April 2008)
Whitchurch Bridge is coming to the end of its useful life and major reconstruction is planned for 2013, by which time the existing Bridge will be 111 years old. The Company has already started planning for this work. Initial discussions on Planning issues have taken place with SODC as Planning authority, and, because the Bridge is a Grade II listed structure, the Conservation Officer is involved to ensure that the reconstruction plans, including both the design and the methods of reconstruction, conform to the listing requirements.
The nature of the work that needs to be carried out has been identified by the Company's Bridge engineering advisers at OCC, and preliminary drawings have been prepared. The works, being a major reconstruction of the Bridge, will have to comply with British Standard BS 5400, which specifies codes of practice for the design of steel, concrete and composite bridges. This Standard is onerous for the Whitchurch Bridge Company, and requires, for example, that the reconstructed Bridge be strong enough for 40/44 tonne vehicles, which the Company has no wish to see using the Bridge. BS 5400 may be superceded by a European Standard before 2013.
The Company is at one with local residents in wishing to retain a 7.5 tonne weight restriction on the Bridge after it has been reconstructed, and has agreed with OCC (as Highways authority) that an enforceable 7.5 tonnes mgw weight limit can be retained on the Bridge following its reconstruction.
The Company intends to retain the existing appearance of the Bridge. Our plans involve the installation of new piles supporting new, load-bearing longitudinal girders under the roadway, with the existing piles, pier caps and latticework side girders retained as key visual elements. The width of the Bridge will not be increased, and the headroom and width of the four river channels will not be reduced.
OCC is managing the Project on behalf of the Company in accordance with their best practice Project Management procedures, and a computer-based Project Plan has been drawn up. Architectural and detailed engineering design input is being procured from Jacobs. Tasks to be undertaken during winter 2007- 2008 include a topographical survey (to obtain accurate data on levels on and around the Bridge and approach roads), a geotechnical survey (to assess ground conditions under the Bridge for the new piles), and investigations of the abutments (to ascertain their depth and condition).
In accordance with the Construction (Design and Management) Regulations 2007 a "CDM Co-ordinator" has been appointed who will advise the Company (as Client) on all aspects of its responsibilities in respect of health and safety risk management matters.
The reconstruction costs are estimated at £2.45 million at April 2007 prices. These costs are reviewed annually by OCC and revised in accordance with construction industry cost indices. The cost may rise significantly if Planning, British Standards or European Directive requirements require design changes. In addition, the cost of labour and materials fluctuates and may not turn out to be as currently forecast.
Although reconstruction is not planned until 2013, the Company intends to submit a formal Planning Application for the reconstruction of the Bridge and to obtain Planning Approval by the end of 2008. This will help the Company to firm up on the costs of the works and enable it to plan with more certainty.
The Company already has substantial reserves set aside for Bridge reconstruction. However, the Company expects that an increase in Toll income will nevertheless be required each year from 2008 - 2013 to help build up sufficient funds for the planned works.
The works are likely to involve closure of the Bridge to all vehicles for not less than 3 months. A pedestrian crossing, by temporary bridge or ferry, will be provided for the duration of the works.
Click here for more details about future Toll increases.
Further information, including more details of the proposed works, will be posted here in due course.