To the contents of Vol. 49, issue 2

Ton Vrouwenvelder

This is a special issue to acknowledge the outstanding contribution of former editorial board member and editor-in-chief Ton Vrouwenvelder to the Journal Heron. He joined the editorial board of Heron in 1976 when F.K. Ligtenberg was acting as editor-in-chief. By that time Heron was the joint effort of the Stevin Laboratory of Delft University of Technology and the IBBC Institute of TNO. In 1990 Ton Vrouwenvelder succeeded Jelle Witteveen and became the new editor-in-chief of the Journal. Nine years plus one issue later, which was the last Heron issue in the previous century, Ton resigned as editor-in-chief of Heron and Jan van Mier, already in the editorial board as a secretary, took over his position. In this period of nearly a decade Heron changed scope which was significantly influenced by the fact that Heron became the joint publication of activities of TNO Building and Construction Research and the Netherlands School for Advanced Studies in Construction. The latter is an inter-university research institute in which, by that time, also the universities of Eindhoven and Twente were participating. It contained research groups in civil engineering, architecture and management in construction.

In the period Ton Vrouwenvelder was in the board as member and later as editor-in-chief he was a very dedicated and enthousiastic contributor to the Journal. He motivated colleagues to write papers for the Journal and was a very stimulating factor in the editing process. He wrote, and still writes, many articles himself in the Journal or through his PhD-students or co-workers at TNO. His joint affiliation as a TU Delft professor and TNO employee was a great help for this. Ton Vrouwenvelder has the reputation of a leading scientist in the field of reliability analysis and probabilistic design of civil engineering structures. Also Ton is a well-respected member of national (NNI, CUR) and international (Eurocode, CIB, JCSS) committees in this area. His joint affiliation also positioned him in the overlapping area of theoretical and applied research which fits with Heron in which research-oriented and application-oriented papers are published.

The four papers collected in this special issue reflect topics of Ton's research interests and expertise. The first paper is authored by Paul Waarts, who finished his PhD in 2000 with Ton as a supervisor. They are long-time colleagues at TNO as well as at the Delft University of Technology. The paper entitled "More sophisticated modelling reduces model uncertainty, a case study on vibration predictions" is a typical topic inspired by the research interests of Ton. It deals with the pratical application of the reliability theory on vibration predictions from traffic or building activities. The second paper is authored by professor Rackwitz who worked together with Ton for the Eurocodes, partly within the Joint Committee of Structural Safety (JCSS). Rackwitz and Vrouwenvelder are both active promotors of the use of probabilistic methods in civil engineering. The paper of professor Rackwitz is entitled "Discounting for optimal and acceptable technical facilities involving risks". The third paper is co-authored by Chris Geurts, Piet van Staalduinen and Sten de Wit. All authors were guided by Ton during their PhD or MSc thesis works and are now colleagues of him at TNO. The paper entitled "Towards a reliable design of facade and roof elements against wind loading", describes certain cases of wind loading on structural elements where codification is still needed. This paper has been inspired by the coding preparation work Ton has been involved in since the late 1980's. Finally, the fourth paper is co-authored by van Noortwijk, Kalk and Chbab and is entitled "Bayesian estimation of design loads". The first author Jan van Noortwijk cooperated with Ton in several projects on probabilistic analysis of dike failure and flooding performed by TNO, HKV Consultants and Delft University of Technology.

On behalf of the editorial board members, I like to take the opportunity to express my sincere gratitude to Ton Vrouwenvelder for the extremely valuable contributions he made to the Journal for such a long period of time. Due to his activities the Journal further established its national and international reputation in the field of structural mechanics, construction and building materials. L.J. Sluys