Transmission of Vibrations in Precast Concrete Slabs

Sammanfattning: Dynamic loads have historically not been a troubled area for concrete floors, foremostbecause of the high self-weight compared to the dynamic load. With new technical andcalculation achievements during the last decades concrete floors have become longerand more slender. This have led to more open plan structures with longer spans thatmake concrete floors more sensitive to vibrations.This thesis studies the dynamic effects of hollow concrete core elements induced by co-ordinated jumping and the vibration levels that spread to the floor above. The thesisinvestigates different standards and guides on how to perform a dynamic analysis andevaluate it. In the thesis an experiment was conducted on WSP Sweden headquar-ters in Stockholm. The fifth and sixth floor of the building was investigated in thisthesis. The floors are made of hollow concrete core elements of the type HD/F 120/27.First a so-called heel drop test was done on the fifth floor to evaluate the naturalfrequency of the floor. The floors were monitored while 12 people performed coordi-nated jumping. Three accelerometers were placed on the fifth floor where the load wasapplied and one on the floor above.The results from the experiment and simulation were evaluated with three methodsISO 10137, National Building Code of Canada and Design Guide - Floor VibrationsDue to Human Activity. The data from the experiment shows that the upper floor isunsuitable for office use for 2 standards. The lower floor is viewed as acceptable formore carefree setting such as shopping malls.A finite element analysis of the building was done in the program Brigade. The modelconsists of one wing of the building and the fifth and sixth floor. The remaining floorsare modelled as equivalent mass. The columns were modeled down to the fourth floorand the beams for the fifth and six floors were included. A stairwell between the fifthand sixth floor was also modelledEvaluation of the finite element results was done in the same fashion as the experi-ment. Here the upper floor was performing satisfactory for office use and the lowerfloor was similarly as the experiment above accepted for settings where more acceler-ation is considered acceptable such as for restaurants and shopping malls.The maximum transient vibration value (MTVV) results from the experiment andsimulation was compared and the lower floor was conforming pretty well with a dif-ference smaller than 1 % to around 30 % depending on the accelerometer. However,the results for the upper floor differs significantly, as the difference is about 770 %between the experiment and simulation. The finite element model is not able to ac-curately represent the real building for the acceleration of the upper floor. This couldbe explained by the the absence of partition walls for meeting rooms, copying room,toilets and the facade. Since this could limit the acceleration that is transmitted fromthe lower floor to the upper floor.