The design of structures viz. buildings, dams, flyovers, towers is an intellectually challenging job. While it is obvious that the construction begins from the bottom, with mother Earth bearing the entire load of the structure, the design of a structure begins from the top. For every structure, there are live loads (e.g. the humans) and the dead loads (the weight of the structure itself). For very tall structures, there are wind loads, and for seismically active areas, there is the seismic load.
Each of these load calculations for designing are done according to the IS CODES (Bureau of Indian Standards). And no, they are not trivial! Each of these IS codes goes through multiple rounds of discussions amongst experts, references to international practices, and updates on material properties. For example, the property of steel hardening after crossing the elastic limit has given rise to the limit state design, which is the recent practice of design.
Each combination of design process and the implementation process, is a project. Now one can say that projects have different modes of execution for example AGILE, KANBAN, SPRINT, SCRUM, etc. For Civil Engineering projects the CPM / PERT method has been found the best amongst practitioners of construction. CPM is the critical path method, and PERT is the Programme Evaluation and Review Technique. The difference between AGILE and PERT, for example is that while changing requirements can change the nature of the product which is handled by AGILE, PERT talks about the uncertainties, for example material or labour shortage, supply chain problem etc. Therefore, AGILE is suitable for software development, while PERT is suitable for construction methods. Of course this is based on the current studies.
Now the design process has a tremendous effect on the implementation process. Typically, in Civil Engineering, a drawing or plan is proposed with all dimensions, after which a design is proposed with strengths of materials (viz. concrete and steel), and the net material requirement, for those proposed dimensions, as well as the dimensions of the reinforcements. The design is done from the top to the bottom. First the top floor is designed, and then the next to the top, till we reach the ground floor and finally the foundation. In terms of construction, the slab rests on the beams, and transfers the load onto the beams. The beams then transfer the load to the columns. Finally, the columns transfer the load to the foundation.
Now let us consider some examples. Suppose that the design is given for a concrete strength of 25M, and during the implementation, it is decided that 20M will be used, with the same dimensions this can be dangerous for the safety of the structure, even though safety factors are considered in the design. On the other hand, if it is felt at a later stage that a large hall will be required to hold big events, and that hall should be without the columns, then the slab above the hall (its roof) should be pre-tensioned or it should be bracketed. If this is not done, then the particular slab can collapse, causing harm to the people underneath. But, if a building is already present with its slabs and columns, and one requires a bigger hall without the columns, can we chop off one or multiple columns?
As soon as one removes the columns (one or many), the load distribution physics will go haywire. It will obviously result in a part of or the entire building collapsing, owing to creating a HUGE moment of inertia. One can be surprised because this doesn’t happen in jenga, where the blocks are gradually removed to make a structure taller. In Civil Engineering, we aren’t playing jenga, we are dealing with the lives of hundreds and thousands of people. Therefore, utmost care should be taken regarding all decisions. While we keep on seeing those weirdly shaped houses on the internet, thinking that they could be real fun, a Civil engineer has to burn his midnight oil to ensure the safety of the people.
