Message from the President Jim Forbes, President of the fib
Jiri Strasky, Technical University of Brno, and Strasky Husty and Partners, Brno, Czech Republic
The idea of prestressing - a product of the twentieth century - has announced the single most significant new direction in structural engineering of any period in history. It put into the hands of the designer an ability to control structural behaviour and, at the same time, it enabled the designer - or forced the designer - to think more deeply about the construction. Moreover, the idea of prestressing opened up new possibilities for a form that influences the general culture. To focus on that fact, and to narrow the scope, the paper will consider bridges only, even though prestressing has broad applications to all kinds of buildings. However, the idea of prestressing arose out of bridge design, and its most impressive forms, from a purely engineering viewpoint, have appeared in bridges.
Rajaiah Selvaraj, Central Electrochemical Research Institute, Tamilnadu, India
Srinivasan Muralidharan, Central Electrochemical Research Institute, Tamilnadu, India
Seshadri Srinivasan, Central Electrochemical Research Institute, Tamilnadu, India
The effect of silica fume in concrete is reviewed from the point of view of chloride diffusion, carbonation, oxygen diffusion, the pH of the pore solution and electrical resistivity, as they are the main parameters influencing the corrosion phenomenon in concrete.
Niels C. Lind, University of Waterloo, Canada
Structural safety is a part of general safety in a society. Safety factors should conform to a general rationale for all life safety. Two rationales are presented here, using a principle of time economy and using social indicators. The common-sense time principle of risk management states that a `life-saving' alternative, if it is truly to save lives, should return to the community more years of life in good health than the years of work consumed to pay for its cost. Alternatively, a risk acceptability criterion can be derived from a compound social indicator that reflects general benefit to society and that is a function of gross domestic product and life expectancy. To be acceptable, alternatives should increase the social indicator. The two compound social indicators, the Life Quality Index and the Human Development Index, yield practically identical criteria for risk acceptance.
A. H. J. M. Vervuurt, TNO Building and Construction Research, the Netherlands
N. Kaptijn, Dutch Ministry of Transport and Public Works
W. B. Grundlehner, Spanstaal BV, the Netherlands
In mid-2001 the final two bridges over the River Dintelhaven in the harbour area of Rotterdam were put into use. Both bridges are concrete box girder bridges and have been erected using the balanced cantilever method. In the first bridge, with a main span of about 185 m, four (external) tendons each with 91 carbon fibre reinforced wires (5 mm diameter) have been applied next to conventional steel tendons. The project is the result of an initiative that was started in 1994 by the Civil Engineering Division of the Dutch Ministry of Transport and Public Works and the CUR (Dutch Centre for Civil Engineering Research and Codes). In order to guide the activities, with regard to the application of the carbon fibre reinforced plastic (CFRP) tendons in the Dintelhaven Bridge, experiments were carried out at TNO Building and Construction Research, focussing upon the long- and short-term behaviour of the CFRP wires and tendons. In this paper the results of these tests are presented. Moreover, in the paper, attention is paid to the manufacturing of the tendons, as well as the installation of the tendons in the bridge.