Lisø PhD Dissertation Manuscript - NTNU

INCREASED SNOW LOADS AND WIND ACTIONS ON EXISTING
BUILDINGS: RELIABILITY OF THE NORWEGIAN BUILDING STOCK 1
By Vivian Meløysund 2,3 , Kim Robert Lisø 2,4 , Jan Siem 5 , Kristoffer Apeland 6
ABSTRACT: Results from an investigation of snow loads and wind actions on 20 existing buildings
in Norway are presented. The objective has been to investigate to what extent existing buildings meet
current regulatory requirements relating to safety against collapse owing to snow loads or wind
actions. 18 buildings have a utilization ratio of more than 1.0 under current regulations. The new
design rules have led to most of the buildings investigated having reduced safety against collapse
owing to snow loads and greater safety against collapse owing to wind actions than the regulations
now demand. The investigation indicates too low reliability for a considerable number of buildings
according to current building regulations, when evaluating the possible consequences of the
conclusions in a national perspective. Scenarios for future climate change indicate both increased
winter precipitation and increased temperatures, and thus changing the snow loads on roofs. Wind
scenarios for the decades to come indicate an increase in frequencies of strong winds in areas also
exposed today. Thus, the future reliability of the buildings in these areas could decrease.
CE Database subject headings: bearing capacity, buildings, climatic changes, Norway,
reliability, snow loads, structural design, structural safety, wind loads
INTRODUCTION
Background
Large snow loads on roofs during the winter of 1999/2000 led to the collapse of several buildings in
northern Norway. The accident at Bardufoss Community Centre, where the roof caved in and claimed
three lives, was the most serious of these accidents (Fig. 1). The most important causes of this
collapse were a faulty construction of the roof when the building was erected and larger snow loads
on the roof than it was designed for.
Earlier, many roof structures in Norway have not been designed to withstand sufficiently large
snow loads, from the viewpoint of current design rules. Several roof structures in parts of the country
have presumably a so low load carrying capacity in relation to the current design codes that they may
1
Preliminary results presented at the Fifth International Conference on Snow Engineering, Davos,
Switzerland, July 2004, (Meløysund et al. 2004).
2
PhD fellow, SINTEF Building and Infrastructure, P.O.Box 124 Blindern, NO-0314 Oslo, Norway. E-mail:
vivian.meloysund@sintef.no.
3
Norwegian University of Science and Technology (NTNU), Department of Structural Engineering, Richard
Birkelandsvei 1 A, NO-7491 Trondheim, Norway.
4
Norwegian University of Science and Technology (NTNU), Department of Civil and Transport
Engineering, Høgskoleringen 7 A, NO-7491 Trondheim, Norway.
5
Professor, Norwegian University of Science and Technology (NTNU), Department of Architectural Design,
History and Technology, Alfred Getz vei 3, NO-7491 Trondheim, Norway.
6
Dr.techn., Dr. techn. Kristoffer Apeland AS, P.O.Box 7029 Majorstuen, NO-0306 Oslo, Norway.
Manuscript No. ST/2005/024694 1 of 13