In some countries durability problems with post-tensioning tendons have in the past led to fairly restrictive regulations. Improvements to execution procedures have been developed since, and new or improved prestressing systems have been proposed, too. This development was, of course, subject of discussions in fib Commission 9 Reinforcing and Prestressing Materials and Sytems and in IABSE Working Commission 3 Concrete Structures. It was decided to organise a workshop with the aim to review the different aspects of the problems encountered and to discuss solutions available today. Keynote speakers from various countries were invited to contribute. Their papers are published in this bulletin, grouped together under the following themes: Inventory and condition (6 papers) Investigation and repair (5 papers) Technical progress (4 papers) Strategies for improvement (6 papers) Supported by the international federation for structural concrete fib, and the international association for bridge and structural engineering IABSE, the workshop took place on 15-16 November 2001 at Ghent University, celebrating the 75th anniversary of the Magnel Laboratory for Concrete Research, whose director also chaired the Scientific Committee and edited the bulletin. It needs to be emphasised that in the bulletin invited experts present their individual views. Although not yet discussed in any of the association's working bodies, the highly topical contents of the bulletin is believed to be of general interest to fib's members and to document a starting point for future work in this field. Therefore, the Council of fib agreed to exceptionally publish these papers within fib's series of Bulletins.

Prepared by the Highway Innovative Technology Evaluation Center, a CERF Service Center. This report presents the findings of a HITEC evaluation of the Channel Bridge System, manufactured by J. Muller International, which is a precase segmental overpass bridge system intended for use in bridge replacement projects or new construction. This report contains the first component of the evaluation plan, the technical analyses and evaluation of design attributes and performance history, with emphasis on the unique aspects of this technology.

Global warming, caused by a significant increase in the concentration of greenhouse gases (GHGs) such as CO2, has become a concern all over the world. The whole process carbon emissions of the civil engineering industry account for nearly 40% of global energy and process-related CO2 emissions, more than half of which come from the process of producing, using, constructing and dismantling in civil engineering materials and structures, resulting in the embodied carbon emissions. With the acceleration of global warming, warmer and uncertain climates will make engineering materials and structures subject to more severe environmental conditions. A series of durability issues will occur more frequently, such as the significant variations of humidity in air, the chloride-induced corrosion caused by the severe chloride ingress, concrete cracking caused by the expansion of rusts, and more severe carbonation of concrete structures due to the increase in CO2 concentration. The adoption of positive measures to address climate change has become a global consensus, as global warming has led to serious threats and challenges to the survival and development of humankind.