Dear sir/mam, In the preliminary design stage, in SAP or in ETABS how can we start with most appropriate size of column and shear wall ? I am a young structural engineer.
Is there any specific relation between column spacing vs column size, similarly aspect ratio of building vs initial size of column and shear wall. I have a question in my mind, please can anyone help me?
In my opinion for initial design process size of column and shear wall, dead load and live loads are the main factors that should be considered and one Earthquake load that is also very much important.
How can we prioritize the effecting factors during initial stage
Any good suggestion would help me improve.
Dear Mr. Khatiwada,
I can suggest you to read/overlook
1. "Limit state theory and design of reinforced concrete" by respected prof. Shah and prof. Karve. Structures publication.
or
2. Wright and MacGregor's Reinforced Concrete
I am sure you will find answers to many of your questions in mind.
Thank you.
You can do following approach:
1. Carry out preliminary gravity load analysis using moment distribution (consider as substructure consisting of beams over a floor along with columns one storey above and one storey below)
2. Carry out lateral load analysis using approximate method, portal or cantilever approach.
3. Do preliminary design of beams and columns based on the forces obtained by appropriate load combination above.
4. Now you are ready to do a full fledged analysis.
Alternately, consult an experienced senior, he will tell you what sizes to begin with based on his experience. Best is to develop your own database by the above approach.
Best wishes
As a C&S consultant, u need;
1) To understand the architecture intent in designing the building. From here u will know the loadings need to apply in the analysis.
2) The important load u need to apply live load (LL), superimpose dead load (SIDL), wind load (WL) and earthquake load. The selfweight u dont need to apply because SAP2000 and Etabs already count for u base on the the properties and the member sizes that u assign.
3) U can start the column with architect required. Sometime they don't like the bigger sizes. If the sizes that they request insufficient, u can recommend suitable sizes to architect or maybe u need to design it as steel or composite structure.
4) The ideal spacing of the column is 5m with the column sizes 200mm x 200mm and maximum spacing can go to 10m.
5) The shear wall u can design it at lift or fire staircase. U can start it with 200mm thk but u need to check the shear stress to make sure not more than allowable.
6) After u finish model the structures, please check the model before u run the analysis and the design code that u need to use. the checking of model to avoid u to face with error during run the analysis.
Hope this give u some idea to start in design
To build a model using either SAP, ETABS or any other software, there is a need to identify preliminary dimensions or cross sections of all main members mainly the columns. Off course that include also the other members like the beams and slabs that require to be given dimensions using the code.
For columns, building on the fact that the simplest formula for load column is the product of a stress by the area and another reduction factor.
You can simply use the tributary area to find the expected normal load on the column including the live and dead loads and applying the simple formula mentioned above which will give the area of the column and then you can assign the dimensions.
After building the model and making the analysis using the software, you can check if the dimensions are safe or not and change if needed.
As for the column spacing, in most cases it is connected to operation and function of the building, the more the spacing is, the bigger the column sections as well as the slabs and the beams.
Please check reference below.. hope it will be helpful for you… Regards…
http://www.roseschool.it/files/get/id/14753
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