A Structural System from Structural Engineering perspective refers to a load resisting system which transfers the load to the foundation. This structural system is basically divided into two major parts:
The part of the structural system which is below ground level is called as Substructure which basically includes foundations, columns below ground level etc.
The part of the structural system which is above the ground level is called as superstructure which includes whole structure except the part of the structural system which is below ground level. It commonly includes column above ground level, slabs and beam, bridge deck, pier above ground, Trusses.
Also Know: Difference between Column and Shear Wall
Superstructure can also be called as an envelope which encloses and subdivides space in order to create a protected environment. It is that part of the structural system where wind load and snow loads are resisted. Superstructure serves the purpose for which the building is intended to be used so special care needs to be taken while designing the superstructure. The superstructure is the part of the system which is seen above the ground so its structural as well as architectural aspects are taken care while designing.
Loads imposed on a structural system are resisted by superstructure so proper care must be taken while selecting and designing the system. The superstructure consists of about 80% to 90% of the whole structural system. The superstructure is the part of the structural system which is seen above the ground so aesthetics of building are to be taken care. So Architects also have a key role in selecting the structural system.
Superstructure comes across different loads throughout its life some crucial and some minor. During these crucial loading of structures, stability is always under consideration. One of the methods to provide stability during these crucial times is by providing diagonal members called bracings. By providing bracings column and beam work together to carry lateral loads downward. Another method is to rigidly connect beams to columns to prevent a change in the angle between the beams and columns so they work together as a rigid frame. Still another method is to provide long walls called shear walls in two perpendicular directions which act as vertical beams (cantilevers) in transmitting forces to foundations.
So keeping in mind the importance of the structural system, the structural members are needed to be protected against any damage, especially from fire. So to protect members against the fire they are encased in fire resistant floors, roofs, walls etc. One another method is the use of fire resistant material on it.
Hence Superstructure plays an important role in Structural System and there are lots of points which need to be considered while planning and designing the structure.