Transient analysis - footfall loading
I am trying to simulate a single person walking along a floor which spans 9 m. I am modelling the human footstep force in the time domain. I have created nodes for each footstep based on the pace length of 0.76 m starting at 0.32 m up until 8.64 m. I am assuming the walker steps off the floor after the last footstep and also would like to observe the response of the floor after this point. The path is in the centreline of the floor:
To do this, I have made a transient analysis (MSUP method) with 14 load steps (1 load step before the footsteps start, 12 load steps for each footstep and the last load step to look at the free vibration response) – see below. Walking pace is 2 Hz so the length of each time step is 0.5 secs. I have output the acceleration response at certain node locations which were my accelerometer locations in my lab tests.
What I expect the response to be is that as the walker walks across the floor, the highest response would be at mid-span (as the first mode is the first bending mode). However, as shown below, when the walker is at mid-span is actually the lowest. Have I missed something here in the analysis settings that is causing this issue?
Any help or guidance would be much appreciated!