Name of Book :– Structural Motion Engineering
Page Length :- 626
Source of Motion Problems
In general, a “designed” structure has to satisfy a set of requirements pertaining to safety and serviceability. Safety relates to extreme loadings that have a low probability of occurring during a structure’s life. The concerns here are the collapse of the structure, major damage to the structure and its contents, and loss of life. Serviceability pertains to moderate loadings that may occur several times during a structure’s lifetime. For service loadings, the structure should remain fully operational (i.e., the structure should suffer negligible damage and, furthermore, the motion experienced by the structure should not exceed specified comfort limits for humans and motion-sensitive equipment mounted on the structure). An example of a human comfort limit is the restriction on the acceleration; humans begin to feel uncomfortable when the acceleration reaches about 0.02 g. A comprehensive discussion of human comfort criteria is given by Bachmann and Ammann .
Safety concerns are satisfied by requiring the resistance (i.e., strength) of the individual structural elements to be greater than the demand associated with the extreme loading. The conventional structural design process proportions the structure based on strength requirements, establishes the corresponding stiffness properties, and then checks the various serviceability constraints such as elastic behavior. Iteration is usually necessary for convergence to an acceptable structural design. This approach is referred to as strength-based design since the elements are proportioned according to strength requirements