Self-anchored suspension bridges with prestressed concrete deck : some historic examples

This paper deals with a challenging bridge type, which is not very well known i.e. self-anchored suspension bridges with prestressed concrete deck. Some of these bridges were built in the 1950's over a canal around the city of Ghent after a design by Prof. Daniel Vandepitte (1922-2016). Prof. Vandepitte, passed away at the age of 94 years and was a brilliant teacher in structural analysis. He was a successor of Prof. Gustave Magnel (1889-1955) in the field of structural analysis and he designed several remarkable bridges in the early 1950's before he was appointed at Ghent University

The introduction of EC2 in Belgium

The draft European Standard ENV 1992-1-1 has been published as Belgian Standard NBN B15-002 already in 1999 together with the National Application Document (NAD). Hence Belgian designers have acquainted an almost 10 year experience with the basic concepts and design guidelines which also appear in EN 1992-1- (Part 1 of Eurocode 2). In the national annex of NBN EN 1992-1- most of the recommended values of the NDP's have been adopted. In the following, a survey is given of the main clauses where specific choices have been made which deviate from the recommended values. Also some personal reflections on particular design approaches in EC2 are presented

Assessment techniques for the evaluation of concrete structures after fire

As concrete structures exposed to fire behave in most cases very well, it could be of economic interest to repair the fire damaged structure. For this purpose a damage assessment based on scientific research is required as first step. In this paper, the Schmidt Rebound Hammer and colorimetry are addressed as toos for this assessment. Firstly, the effect of booth methods is studies on heated siliceous concrete specimens under laboratory conditions. Secondly, the practical applicability of both methods is examined by evaluating the fire damage of a concrete girder exposed to a real fire. Both techniques show to be very useful in evaluating the fire damage of the girder

Damage assessment of concrete structures exposed to fire

During a fire, concrete structures behave in most cases very well. It could therefore be of economic interest to repair the damaged structures, as costs for demolition and rebuilding can be avoided and the building can be reused faster. To assess the remaining loadbearing capacity in a scientific based way, information is necessary about the temperature distribution inside the concrete element and the residual material properties of both concrete and steel. But, at least of equal importance is a fundamental insight in how a concrete structure could behave during a heating cycle, as indirect actions due to thermal restraints can occur and cause significant cracking. These effects should be noticed during a visual inspection of the structure, however, cracks introduced by internal thermal restraints are not visible from the concrete surface. In this paper, fundamental knowledge is given about the effect of heating and cooling on the compressive strength of concrete. Diagnosis tools are discussed to obtain the temperature distribution, especially in the neighborhood of the reinforcement. Those techniques are based on the physico-chemical transformations of the cement matrix and the aggregates that occur during heating. To determine the effect of thermal restraints on the structural behavior, a methodology based on finite element methods is illustrated

Combined effects on residual strength of a high performance concrete exposed to fire

Concrete structures exposed to fire suffer from damage, but can remain a certain degree of residual strength. International research has shown that the compressive strength of concrete decreases not only with temperature, but also by the way of cooling and the storage conditions after fire. Fast cooling introduces a thermal shock which, based on experiments by the authors, could result in a 30% additional strength loss with respect to the loss during heating. When storing the concrete after the fire in air or under water, additional strength losses of about 20-30 % are found within 14 days after the fire. In this paper it is investigated for a high performance concrete what the combined effect is of heating, cooling and storage. One of the conclusions – but with respect to the specific test conditions (e.g. slow heating, 550°C max, pre-dried samples) – is that superposing both expected strength losses of about 30% in case a fast cooling is followed by a period of post-cooling storage results in too conservative strength estimations. It is deemed that the cracks resulting from fast cooling, will act as expansion chambers for the newly produced portlandite, thus strongly reducing additional stresses, which results in expected lesser damage

Self-anchored suspension bridges with prestressed concrete deck : historic examples

Manfred and I have some common interests, among which the history of concrete structures and for this occasion I have chosen a topic in this field. On 18 February 2016, Manfred received the Sarton Medal at Ghent University as a recognition of his unique and pioneering research work on the historie aspects of concrete structures and the link with modern strengthening and renovation techniques. At that occasion he presented a lecture on "What European History, Legendary Bridges and the Design of the Euro Have in Common", dealing with the different bridges appearing on the Euro bank notes. This paper deals with a challenging bridge type, which is not very well known: self-anchored suspension bridges with prestressed concrete deck. Some of these bridges were built in the 1950's over a canal around the city of Ghent after a design by Prof. Daniël Vandepitte (1922-2016). This paper is also a modest personai tribute to Prof. Vandepitte, who recently passed away at the age of 94 years and who was a brilliant teacher in structural analysis. He was a successor of Prof. Gustave Magnel (1889-1955) in the field of structural analysis and he designed several remarkable bridges in the early 1950's before he was appointed at Ghent University