Lisø PhD Dissertation Manuscript - NTNU

limited to details of the building’s identity, the building type, ownership and possibly the address. For
buildings erected after 1983, more information is available. A search based on selected building types
reduced the sample from the approximately 3.7 million buildings in the register to around 9,000
buildings in the municipalities in question. In the search results, 10 to 12 buildings have been chosen
from each of the 10 municipalities selected. In selecting the buildings, the time when the building was
registered or erected was used as an indicator of the building’s age. Where the buildings’ floor space
was stated, this has been used as an indicator for finding buildings comprising main load-bearing
structures with spans of more than 10 metres.
The selected municipalities were then asked to provide the following information for each of the
chosen buildings:
A copy of the building licence application form.
Copies of plan drawings and front elevations used in the building licence application.
Confirmation on whether the municipality had archived construction drawings and design
calculations or not.
The information has been used to select the buildings that will best suit the original priorities of the
investigation. To make the investigation practicable, buildings for which documentation existed was
given priority.
Selected buildings
Based on the assessments above, 20 buildings were selected (see Table 3, LAST PAGE). The table
lists the municipality in which the buildings were selected, the building type and the requirement that
currently applies to characteristic snow load on the ground and to the reference wind velocity. As
shown in the table, attempts have been made to keep the selected buildings as anonymous as possible.
Problems in obtaining the necessary documentation implied that an investigation of only one building
was conducted in two of the municipalities, while this was extended to three buildings in two other
municipalities.
Three of the buildings were constructed in the period before 1970, eight were built in the period
1970-79 and nine were built in the period after 1979. This implies that the loads are determined by
the 1949 building regulations for three of the buildings, by NS 3052 for eight of the buildings and by
NS 3479 for the latest nine buildings.
Project documentation investigation and field study
Calculation models, loads, forces and solutions used when the buildings were constructed have been
investigated. The forces in the structure were then determined in accordance with new load
requirements, and the capacities checked in accordance with new design rules. In the light of these
analyses, the structure’s utilization ratio has been determined in accordance with new calculation
rules, and the need for reinforcement assessed.
On site, it has been investigated whether the structures have defects or deficiencies that are not
apparent from the project documentation investigation. Special attention has been paid to the
investigation of whether the construction is in accordance with the documentation, and whether there
are weaknesses in the structure owing to reduced durability or due to reconstruction.
RESULTS
Geometry and material data
External dimensions, maximum spans and the material of the main load-bearing structures are shown
in Table 3. The building’s external dimensions are quoted as width, length, height and roof slope. The
height indicates the cornice height for buildings with approximately flat roofs and the roof ridge
height for buildings with other roof shapes. Additions or extensions that are not included in the
assessments have not been included in the dimensions.
Manuscript No. ST/2005/024694 8 of 13