All buildings must be designed to withstand forces that may act on them at any given time so that the public can be protected from any hazard. As it may not always be possible to know the net force, mass of an object, or direction in which the force is applied, it is important to design strong, stable structures. In the wake of the World Trade Center tragedy, it has become more necessary than ever to use new, advanced materials. In addition, designers should consider the purpose of the structure and its design and test and assess construction materials. Examples of the types of calculations used by engineers in the design process are provided.