Architects are the most crazy people in this world, they think a structure can stand on the plan made by them, even if its in shape which we never seen standing on there own.
A structural engineer is like a master mind behind the story who makes the dream come true for many peoples.
Architectural plans are tend to change and get changed even after someone occupies the house.
As a Structural engineer we should consider that the, columns should not come into the core area of any flat (this is not possible always but, should try to minimize the possibility of columns in those area)
The end user of structure we built is a public and they don't use their mind when they do changes.
Many times buildings get collapse due to stupid decisions made by interior designer by saying, broke that column it coming in middle of my design.
though a owner might say that it may cause a problem, but such shit person denies the possibility by saying.
this is not the my first work, i had removed more such columns in past and my clients are more satisfied with my design.
So, after handing over of structure to the end user, we can not assure anyone that, they will not make any changes in structure ( due to this many buildings collapsed in Mumbai, last month also i saw a news from Mumbai on same incident).
As a designer we should try to avoid the column location in core area of flat which end user think that they can change it dynamically as per their need.
When designing a structure, we should consider the thicknesses of wall suggested by the architect. and should design a columns and beams within it.
If due to some parameters, if it is not possible to keep it in that limit, it should be conveyed to the Architect.
A Structural engineers should make a superimpose copy of drawing where rcc member are placed on architectural plan. should highlight the area where, columns or beams goes out of dimension specified.
If there are some areas where 2 floor height slab is to be made by keeping void on 1 floor.
should intimate the architect about tie beam or the size of structure which will be seen in that area, so that he can do some architectural features around it. (This is rare and happens in the commercial buildings specially at entrance).
You should not put the columns on both faces of toilet walls at periphery or duct area, as it will cause a problem for routing inlet of water ( you need to create ledge wall to accommodate it, if not think before execution and it will result in waste of space + Money)
A designer is one who not only think about the capability of the structure but the serviceability of structure too
While designing one should think about the services (embedded/surface) and do design accordingly (This point is mainly related to architectural design)
First of all you should see that length of which side is more.
Generally the main beams and secondary beams are fixed on this basis only.
Then you have to decide where do you need coloums and of which siz
1.Deciding type of foundation - Depending on soil type and available area foundation type can be decided.
2.Position of Column - Column positions are decided on the basis of Loading. Reinforcement of column depends upon availability of steel bars and availability of concrete material. Around 0.8-1% of total area, steel is provided in column. Size of column may remain same in top floors but reinforcement can be decreased.