1、附录 Bridge research in Europe A brief outline is given of the development of the European Union, together with the research platform in Europe. The special case of post-tensioned bridges in the UK is discussed. In order to illustrate the type of European research being undertaken, an example is given
2、 from the University of Edinburgh portfolio: relating to the identification of voids in post-tensioned concrete bridges using digital impulse radar. Introduction The challenge in any research arena is to harness the findings of different research groups to identify a coherent mass of data, which ena
3、bles research and practice to be better focused. A particular challenge exists with respect to Europe where language barriers are inevitably very significant. The European Community was formed in the 1960s based upon a political will within continental Europe to avoid the European civil wars, which
4、developed into World War 2 from 1939 to 1945. The strong political motivation formed the original community of which Britain was not a member. Many of the continental countries saw Britains interest as being purely economic. The 1970s saw Britain joining what was then the European Economic Community
5、 (EEC) and the 1990s has seen the widening of the community to a European Union, EU, with certain political goals together with the objective of a common European currency. Notwithstanding these financial and political developments, civil engineering and bridge engineering in particular have found g
6、reat difficulty in forming any kind of common thread. Indeed the educational systems for University training are quite different between Britain and the European continental countries. The formation of the EU funding schemes e.g. Socrates, Brite Euram and other programs have helped significantly. Th
7、e Socrates scheme is based upon the exchange of students between Universities in different member states. The Brite Euram scheme has involved technical research grants given to consortia of academics and industrial partners within a number of the states a Brite Euram bid would normally be led by an
8、industrialist. In terms of dissemination of knowledge, two quite different strands appear to have emerged. The UK and the USA have concentrated primarily upon disseminating basic research in refereed journal publications: ASCE, ICE and other journals. Whereas the continental Europeans have frequentl
9、y disseminated basic research at conferences where the circulation of the proceedings is restricted. Additionally, language barriers have proved to be very difficult to break down. In countries where English is a strong second language there has been enthusiastic participation in international confe
10、rences based within continental Europe e.g. Germany, Italy, Belgium, The Netherlands and Switzerland. However, countries where English is not a strong second language have been hesitant participants e.g. France. Post-tensionedconcreterailbridgeanalysis Ove Arup and Partners carried out an inspection
11、 and assessment of the superstructure of a 160 m long post-tensioned, segmental railway bridge in Manchester to determine its load-carrying capacity prior to a transfer of ownership, for use in the Metrolink light rail system. Particular attention was paid to the integrity of its post-tensioned stee
12、l elements. Physical inspection, non-destructive radar testing and other exploratory methods were used to investigate for possible weaknesses in the bridge. Since the sudden collapse of Ynys-y-GwasBridge in Wales, UK in 1985, there has been concern about the long-term integrity of segmental, post-te
13、nsioned concrete bridges which may be prone to brittle failure without warning. The corrosion protection of the post-tensioned steel cables, where they pass through joints between the segments, has been identified as a major factor affecting the long-term durability and consequent strength of this t
14、ype of bridge. The identification of voids in grouted tendon ducts at vulnerable positions is recognized as an important step in the detection of such corrosion. Description of bridge General arrangement Besses o th BarnBridge is a 160 m long, three span, segmental, post-tensioned concrete railway b
15、ridge built in 1969. The main span of 90 m crosses over both the M62 motorway and A665 Bury to Prestwick Road. Minimum headroom is 5.18 m from the A665 and the M62 is cleared by approx 12.5 m. The superstructure consists of a central hollow trapezoidal concrete box section 6.7 m high and 4 m wide. T
16、he majority of the south and central spans are constructed using 1.27 m long pre-cast concrete trapezoidal box units, post-tensioned together. This box section supports the in site concrete transverse cantilever slabs at bottom flange level, which carry the rail tracks and ballast. The center and so
17、uth span sections are of post-tensioned construction. These post-tensioned sections have five types of pre-stressing: 1. Longitudinal tendons in grouted ducts within the top and bottom flanges. 2. Longitudinal internal draped tendons located alongside the webs. These are deflected at internal diaphr
18、agm positions and are encased in in site concrete. 3. Longitudinal macalloy bars in the transverse cantilever slabs in the central span . 4. Vertical macalloy bars in the 229 mm wide webs to enhance shear capacity. 5. Transverse macalloy bars through the bottom flange to support the transverse canti
19、lever slabs. Segmental construction The pre-cast segmental system of construction used for the south and center span sections was an alternative method proposed by the contractor. Current thinking suggests that such a form of construction can lead to brittle failure of the entire structure without w
20、arning due to corrosion of tendons across a construction joint， The original design concept had been for in site concrete construction. Inspection and assessment Inspection Inspection work was undertaken in a number of phases and was linked with the testing required for the structure. The initial inspections recorded a number of visible problems including: 1、 Defective waterproofing on the exposed surface of the top flange. 2、 Water trapped in the internal space of the hollow box with depths up to 300 mm. 3、 Various drainage problems at joints and abutments.
