Overview
Bridges without joints or bearings, termed integral bridges, are superior to conventional bridges in various aspects. Joints and bearings are always potential weak points, and eliminating them will thus have a beneficial effect on durability and maintenance costs. Moreover, in many cases the collapse load of the entire system is improved, which is important with regards to the redundancy against unforeseen loadings.
On the other hand, integral bridges are per definition statically indeterminate structures, and temperature variations, support deformations, prestressing and long term effects will thus generally result in undesired restraint actions – particularly axial forces – difficult to quantify. Therefore, joints and bearings have until recently been arranged without further considerations.
The research project aims at contributing to a better understanding of the behaviour of bridges without joints or bearings, termed integral bridges, and at developing a consistent basis for the conception of integral bridges.
In a first part, the national and international state of the art shall be summarised and presented in a state-of-the-art report.
In a second, planned phase, based on the state-of-the-art report, criteria for the optimal selection of the support and joint layout shall be defined.
Assessment Report (Phase 1):
- Literature review / survey 75%
- Modelling 25%
Possible 2nd phase:
- Modelling
- Theoretical study
Results
Though the advantages of integral and semi-integral bridges outweigh their disadvantages in many cases, this is of course not always true. In particular, when dealing with high capacity roads (motorways), it must be carefully studied whether the cracks in the pavement that are to be expected behind the abutments of longer integral and semi-integral bridges can be tolerated.
Furthermore, since the behaviour of integral bridges is complex and depends on several parameters that are subject to relatively wide scatter, the decision of whether or not to adopt an integral design for a specific bridge is not straightforward. In addition, in comparison with conventional bridges, the dimensioning of integral bridges is subject to more uncertainties.
Thus, the conceptual design and the dimensioning of integral bridges require good analytical skills of the engineers involved and are usually much more laborious than for similar conventional bridges. In many cases, semi-integral bridges might be the optimal solution. If detailed properly, such bridges exhibit almost all the advantages of integral structures whilst mainly avoiding or at least strongly reducing the disadvantages. Semi-integral solutions should be explicitly treated in the revision of the guidelines.
By giving a survey of the actual state-of-practice in the field of integral bridges, the present report contributes to the improvement of the basis for the conceptual design of integral bridges and identifies where further investigations are needed.