Vertical deflection varies from maximum at the free end of a cantilever to near zero at the support end of a cantilever. I was nearer the support end, so could see the differential vertical movement between my location and the free end. It was visibly obvious and concerning. People can feel very very small vibrations, much smaller than can be seen. When the differential movement is visibly obvious and more than several inches it gets my attention. I understand that any loading produces some deflection because no structure is infinitely stiff (no boner jokes here please). Swaying is not the type of forcing function of concern here.
Two straight forward questions that should be answered in my opinion are these:
What are the acceptable maximum amplitudes of vertical motion at the free end of the south end second deck cantilever for the range of potential vertical forcing functions? I expect that the frequency for people bouncing to music would be around 2 cycles per second, but say a range of 1 to 3 cps for starters. Two parameters here, amplitude and frequency of the vertical dynamic force.
What are the amplitudes of motion at that location that are actually occurring? Should be obtainable from video analysis. If less than the amplitudes in the above question, wala, we be scrong den.
