Author(s): Morten Bjerkas; Torodd S. Nord
Keywords: No Keywords
Abstract: This paper presents some of the experience with Swedish lighthouses constructed in the time period 1930-1974 with regards to design ice loads. Sweden erected altogether 59 caisson-type lighthouses in the time period 1930 to 1992. Most of the structures have sustained well the annual ice drift whereas few of the structures have been displaced and/or damaged. This study presents design ice load philosophy from the first structures designed in 1930s in southern Sweden to the lighthouses located farthest North in the Gulf of Bothnia. Some of the damaged structures are studied in more detail. The time development of ice loads is followed from the first papers reporting basis of design for ice loads in 1941 until a summary study was presented in1985. We can see a remarkable increase in recommended ice loads in the actual time period: The first structures were designed to sustain an ice load level of 0.75 MN/m at the water line, whereas the most recent lighthouses can sustain loads as high as 4 MN/m. Finally, new design load recommendations are discussed in the perspective of the experiences with Swedish lighthouses.