Loads are the forces that come on the structure during construction or during service period. It is very necessary to define all the loads that structure is going to support, once the dimensional requirements have been defined. It is so because in high-rise buildings it is essential to provide additional supports in term of shear walls or structure bracings. If structure lies in an area where it is going to face lateral loading that is caused by wind than in that case rigid frames and shear walls are best to select. While in case of earthquake prone areas ductile frames, connections and diagonal structural bracing are best to use.
After the determination of actual structural form, now begin the design with primary load carrying elements. Precede it further in sequence to the other load supporting members until the basement of structure is reached. Begin the design with floor slabs first, once knowing about all the loads coming on the ground. Carry on the design following load supporting columns, beams and at the end foundation footings. Hence, it is necessary to define all the loads first before go for the design of a structure.
In most of the codes the design loadings are already specified. Generally there are two types of codes that are used for the design of structure. One of them is the building code and the 2nd one is the design code. Building code defines the laws specified by government. It includes minimum design loads on structure and the minimum standards for construction. On the other hand Design codes provide complete technical standards details which are used in establishing the actual structural design requirements.