When setting up for shaker testing, the shaker must be aligned with the structure in order to excite the structure in the desired direction. Most times the shaker force levels used are very low in amplitude with no need to bolt the shaker to the floor or another mounting arrangement. However, there may still be some vibration that transmits back through the base to the floor. In these cases, friction against the floor alone may not be enough to stabilize the shaker and it should be firmly affixed to the floor. For low levels of force, hot glue around the base is typically adequate. In instances where hot glue is not sufficient the shaker may be attached with bolts or a clamping arrangement to the floor.
Another possibility when exciting at low force levels is to sit the shaker trunnion onto sand bags or rubber mats. This approach may be quicker/easier that applying hot glue, but does not always work well enough to maintain proper alignment since the shaker can still vibrate out of place. If shaker base vibration is observed, make sure that the shaker alignment is checked during the sequence of testing to assure that misalignment is not introduced. In addition, the driving point frequency response functions should be routinely checked to make sure that no significant change in the system has occurred.