Precast concrete bridges (PDF)
(Note: An Italian translation of Bulletin 29 is also available; contact us for further detail
fib Bulletin No. 29
Title: Precast concrete bridges
Category: State-of-art report
Format approx. DIN A4 (210X297 mm)
Prefabrication presents many advantages over traditional construction for bridges. They have resulted from the industrial approach and favourable working environment, protected from adverse weather conditions. For many years, the profession has been familiar with the principles and methods aiming at mastering the quality of the precast products. Each plant has a self-control system, defining the working procedures and modules for internal inspection and control. Among the many advantages, the following are of particular interest to bridge construction:
- Quality and regularity of the concrete strength.
- Elements with elaborated shapes designed to get a maximum benefit from the materials and the prefabrication. They require the use of relatively complex moulds, but at the same time enable high quality surfaces with respect to shape, texture, dimensional tolerances, etc., to be achieved.
- Absence of laborious and hindering scaffolding.
- Shorter construction time due to the fact that precast elements are made at the plant independent from the foundations and other preparatory works on site.
Precast bridges are not without criticism:
- The perceived opinion from some instances, that precast bridges are monotonous and ugly.
- The larger number of transversal joints in older realisations, especially in viaducts, causing discomfort and maintenance problems.
- Certain specific technical issues, such as earlier doubts with regard to the transfer length of prestressing strands, particularly for large diameters subjected to fatigue stresses in railroad bridges. Another question concerned the effectiveness of the shear transfer at the interface between cast-in-situ concrete and prefabricated elements, especially in relation to fatigue stresses.
The aim of this State-of-the-Art report is to give a detailed overview of the existing solutions and applications world-wide and recent developments in the domain of precast bridges. They should enable the authorities and designers to form a realistic opinion about the possibilities and advantages of this technique, and get away from some still existing prejudices.
This Bulletin No. 29 was approved as an fib state-of-art report in April 2004 by fib Commission 6, Prefabrication.