Wednesday, 30 November 2016

Beyond The Lines: Here's How To Interpret Structural Designs - Engr. Osaz’ ENOBAKHARE



Structural designs/drawings do not readily appeal to the eye as do architectural designs. This is quite so because its aim is not essentially to showcase the aesthetic value of a structure but to give it strength, stability and durability throughout its life span. 

The structural components of a building (e.g. Foundation, stanchions, beams, columns, floors, roof, etc) in practice are often seen as its skeleton and lifeline; hence so much attention is given to them. Inaccurate structural designs or the absence of same as well as poor interpretation or application has also been highlighted as major causes of building collapse across Nigeria. 

The need to strictly implement the provisions of a structural design during construction should be the ultimate goal of all stakeholders on a project especially the project owner. Don’t remain a novice, at least have an idea.



This picture above will help: The red lines stroked at ends carry the dimensions of the component which show the lengths from one point to another. 

Always read the dimension together with the scale; in this case the scale is 1:100 and the dimensions are in millimeters. 

Then let’s take one of the provisions which states R1003:150mmc/c -it means provide or use ‘R’ i.e. Mild steel bars (or iron rods) of ‘10’ i.e. size 10mm cross-sectional diameter with bar mark ‘03’ (the bark mark is an identification number) and placed them at ’150mm c/c’ i.e. the centre to centre distance from each other should not be more than 150mm. In the same way, let’s interpret another provision; Y1601:150mm c/cB –it states that use ‘Y’ i.e. High Yield tensile steel bars of ‘16’ i.e. size 16mm diameter with identification tag ‘01’ and place them at ‘150mm c/c’ from each other at B i.e. at the bottom. 

Note that while the former indicate the use of mild steel bars, the later specifies the use of high-yield tensile steel bars. R and Y are different types of Iron rods; they have different strength index. For instance, R is not as strong as Y. 

Also note that the centre to centre distance in the two provisions is deemed okay at 150 mm. For 4Y1602 and 2Y1204 –it simply means use ‘4’ numbers of ‘Y16’ and ‘2’ numbers of ‘Y12’ steel bars to form your column stand (otherwise called iron rods-in-pillar). ‘02’ and ‘04’ are just identification tags. You can also see the mix and quality of concrete specified and so on. Further drawings (called sections) are used to show how they would appear on ground eventually.


The sizes, arrangement and numbers of Rebars
in a structure are read directly
from Structural drawings 

Ignoring the provisions of a structural design is to the detriment of the life and properties of future occupants of the building. This callous act is condemned in its entirety and should not be encouraged by anyone.

Another worrisome trend is that some unsuspecting building owners are cajoled into paying an architect, a builder or a surveyor to prepare them a structural design; that’s absolutely crazy! It’s like paying a carpenter to stitch your cloth; it only comes back with more holes and ‘pummm’ off he goes. 

Due to the technical analysis and complexities associated with drawing up a structural design, only a Professional Structural Engineer is authorized to prepare one.  It is therefore pounds foolish to start your building project especially single or multi-storey without involving a Professional Structural Engineer.

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