Civil Engineering/how to analyze

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Question
A two storey building,say 12m by 15 m, already exists; and it is to be proposed that an extension  of a like similar structure(also a two storey) be attached by connecting the integral parts(so that it looks unified).  How do i analyze the said extension? Do i analyze it as an independent structure, also 15m by 12m,because the previous sructure already existed long its lifespan? Or do i consider when designing the new extension the previous structure since it might "react" and be a loading to the new structure. please clarify this for me. In that case the dimensions might be bigger in the new structure(although their floor plan is the same), correct?


Also,what is the unit wt. of reinforced concrete?

How do i usually determine the magnitude of seismic loading? many tnx

Answer
Dear Nords

You may need a professional to give you services in this subject. But for your information.
If old part and new one are interconnected together you must model the 2 sections simultaneously. But the design should be performed on the new extension, naturally, unless extra loading is loaded on the old section due to the new structure action which may need some local modifications. May be new extension may need greater or smaller size of structural members. But actually if the old structure is designed according to codes of practice , some modification made in standards may require greater sizes.

unit weight of reinforced concrete is considred to be  :2400 to 2500 kg / m3 depending on concrete admixture and amount of reinforcement.


The seismic loading is defined as percent of the building weight (7% to 30 % normally) loaded horizontally based on a trapezoidal pattern along the height of the structure ( the greater base is located on the top story). Seismic loading is related to the seismic zonation of your country and the region your project is located in.  You will need to consult your local standards to get more informed.


Regards
BEH

Civil Engineering

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