Analys av nyttig last vid dimensionering av kontorshus
Sammanfattning: Imposed load is a load used in the design of buildings, and includes the weight of people, vehicles and interior. The imposed load is usually divided into sustained load and intermittent load. The sustained load is the load a building is exposed to during normal circumstances. Minor changes of this load occur on a daily basis, but major changes of the load occur seldom and are often related to changes in the use of the building or change of owner. The intermittent load has a short duration and is caused by deviating events, such as stacking of furniture or gathering of people. In offices, no major physical imposed load survey has been made after the turn of the 21th century. The load value used in the Swedish structural design standard EKS 11 is 2,5 kN/m^2, but on which grounds this value has been set is unclear. This value should represent the characteristic imposed load, which means that the return period is 50 years. To determine this value, a probability analysis must be performed. The probability analysis requires knowledge about the size of the mean imposed load in the Swedish offices. Furthermore, knowledge about the extreme values is required. In this master thesis, a load survey of the mean sustained load was carried out at four offices in southern Sweden. The intermittent load was determined in a simplified investigation. After the load survey was performed, a probability model was made from which the characteristic load was specified. By varying the input data in the probability model, it was analyzed how the characteristic load was affected by different circumstances. The results show that the imposed load in modern offices is lower than what has emerged in previous studies. In addition, the result indicates that the type of office has a certain influence on the size of the imposed load. The type of use and area of the room also affects the size of the imposed load. In this study, the personal load accounted for 11 % of the total sustained load. The remaining part of the sustained load originated from furnishing. When it comes to the intermittent load, there were a number of uncertainties, which meant that some assumptions had to be made. These uncertainties and assumptions caused a relatively large margin of errors for the intermittent load. This master thesis indicates that the characteristic load used in the Swedish structural design standard is greater than necessary. The result obtained in this study is far from the value 2,5 kN/m^2. However, a larger-scale load study should be conducted to verify the result.
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