220 Reports Structural Engineering International 4/2005 Introduction The viaduct Crni Kal (Fig. 1) is the largest and highest bridge structure in Slovenia [1]. Two carriageways (each with three traffic lanes) are about 100 m above the ground level in cumu- lative length 1053,50 m (left carriage- way) and 1056,35 m (right carriage- way). The main span is 140 m. The Y- shaped piers vary in heights from 9,0 m up to 87,50 m. Since the viaduct is lo- cated near the Adriatic coast it is ex- posed to very strong north-east and south-west winds. They occur very of- ten especially during the weather changes, mostly in late autumn, winter and early spring-period of the year. The velocity of the wind called “Bora” can reach a speed up to 200 km/h. For viaduct Crni Kal the wind-structure in- teraction studies were performed from the very beginning of the project. In fact, two studies of wind influence have been performed. The first study discusses influence of wind on the unfinished structure dur- ing all planned construction phases; where important structure elements could reach critical oscillation ampli- tudes caused by the wind excitation. Results obtained from the first study have been used to design the structure during all planed construction phases as well as temporary anchoring cables used to reduce oscillation amplitudes. Wind Effect on Structures: An Introduction The design of structures for effects of wind pressures is rou- tinely performed by structural engineers. Being able to con- vert something as variable as wind pressures into simplified design procedures, is typical of how engineers are able to re- duce extremely complicated phenomena into practical proce- dures. However, simplified procedures are applicable only within certain parameters, and it is the responsibility of the structural engineer to distinguish between routine formulae and those cases for which more specialized expertise is re- quired. This issue of SEI presents a variety of wind engineering ap- plications and research which go well beyond the boundaries of simplified procedures. The papers range from project re- ports where measures were taken to reduce building vibra- tions, to a description of the state-of-the-art in long-span bridge dynamics in China, to the use of orthogonal decompo- sition tools in analysing the wind effect on structures. The aim of the series is not to comprehensively treat theoretical as- pects of wind engineering, but to expose the readers to the va- riety of problems which are being solved, and which can be addressed with current knowledge. I thank the authors for their contributions, and extend a spe- cial word of appreciation to the reviewers who offered their time to review the papers. Jan Wium Member of the SEI Editorial Board Professor, Department of Civil Engineering, University of Stellenbosch, South Africa Analysis of a Bridge Structure and its Wind Barrier under Wind Loads Andrej Strukelj, Dr.-Eng., Faculty of Civil Engineering, University of Maribor, Slovenia; Iztok Ciglaric, Dr.-Eng., Graz University of Technology,Vehicle Safety Institute,Austria; Marjan Pipenbaher, Chief Constructor, Eng., Ponting Ltd, Maribor, Slovenia Summary In this paper a study of wind barrier efficiency in terms of traffic safety is ana- lyzed. A novel approach to bridge structures design is represented, where rele- vant traffic safety issues are incorporated into an early stage of design proce- dures. The numerical procedure based on standard turbulence model is applied to calculate resulting wind forces on the vehicle of arbitrary geometry.The effect of wind barriers geometry placed on both sides of the viaduct on resulting vehi- cle wind forces is analyzed. Used numerical procedure has also been experimen- tally verified in a wind tunnel laboratory. Complex multibody models that could be used to analyze vehicle handling and riding dynamic are represented. Further, vehicle models are used to show how resulting wind forces could affect vehicle dynamic and traffic safety issues. Relevant traffic safety situations are considered and discussed for particular wind barrier. Peer-reviewed by international ex- perts and accepted for publication by SEI Editorial Board Paper received: May 31, 2005 Paper accepted: September 5, 2005