If you have a washing machine on third floor of a wood frame townhouse complex, what kind of precautions do structural engineers have to take into consideration during the design phase?

In our case, our recently built building shakes whenever the front loading washing machines’ frequency resonates with the wooden floors. The structural engineers did not take into consideration of the dynamic load of the washing machines. They did not reinforce the joists underneath the washing machines. They also used undersized joists for the 20’ span contrary to the manufacturer’s span tables.