Tjänstbarhetsgränstillstånd

Tjänstbarhetsgränstillstånd is a Swedish term that translates to "limit state of serviceability" in English. It refers to a condition in structural engineering where a structure or component ceases to be suitable for its intended use due to excessive deformation, vibration, cracking, or other forms of damage that impair its functionality, even if it remains structurally sound and able to withstand applied loads without collapse.

In essence, a structure must not only be safe (i.e., not fail catastrophically) but also perform acceptably during its service life. Tjänstbarhetsgränstillstånd addresses these functional requirements. Examples include preventing excessive deflections that could cause discomfort to occupants, ensuring vibrations are within acceptable limits for machinery or human perception, and controlling crack widths to prevent aesthetic issues or ingress of corrosive substances.

Design codes and standards typically define specific criteria for different limit states of serviceability, which engineers must consider alongside ultimate limit states (e.g., collapse). These criteria are usually expressed in terms of maximum allowable deflections, vibration amplitudes, or crack widths under characteristic loads. Failure to meet these serviceability limits can lead to user dissatisfaction, costly repairs, or a reduced lifespan for the structure.