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The latest demands in construction design towards slender structures with large spans, large open interiors, unconventional shapes and constructional solutions are leading to the extensive problems related to the serviceability limit state. Slender structures with large spans have lower natural frequencies and lower natural damping, considerably influencing the dynamic response of the structure. Annoying vibrations induced by human activities can significantly affect the structure's functionality, comfort of people and quality of life. Design recommendations for composite steel-concrete floor vibrations can be found in different standards. This paper presents a short overview of design procedures for vibrations of composite steel-concrete beams and design recommendations of floor vibrations induced by human activities, through two design criteria.

When applying high strength bolts in friction connections, a load-bearing capacity depends on pretension force in the bolts as well as on friction coefficient found on friction surfaces. It is important to get the reliable value of the pretension force, so friction connections often undergo experimental research. In order to use strain gauges, which are inserted into the bolt shank, bolts need to be calibrated before we even use them in experimental research. Research that has been conducted shows a great difference between nominal and experimental strain in bolts, therefore FEA calibration of the bolts had to be carried out. Good results matching were obtained, hence a use of strain gauges was justified even for bolts without a shank.