FOUR STEPS TO DESIGNING THE STRUCTURAL LAYOUT OF A BUILDING

How to design a building’s structural layout – General Arrangement for a Building

The general arrangement (GA) of a building is a document that states patently  the nature of the structural elements in a building. you can also call the General Arrangement (GA), the Structural layout. The document shows components of the building like columns, beams, floor slab paneling etc. these components form the design of the building. Having a glance at the GA helps engineers ascertain the model of a building, and also the shape and types of structural elements in the building.

For a proper design, a design engineer should satisfactorily give a theoretical idea of what the structure should look like and also contain. That is there should be a standard and well articulated architectural design of the building. This will help to prepare the ‘General Arrangement’ or the ‘Structural Layout’ of the building. The GA also contains the labeling of the axes and members, unique grid lines, building structural levels, etc.

When the GA is complete, the engineer then makes an initial sizing of the different structural elements. This preliminary sizing may be guided by past experience or by requirements of the code of practice. After the sizing, the engineer then starts loading the structure.

Now let us first have a look at how to prepare the General arrangement.

Some General Ideas on Preparing General Arrangement (GA)

There are no standard rules on how to prepare a suitable general arrangement of a structure. Adequately presenting a general arrangement has to more with years of design and the construction experience.

However there are some important guidelines which are very vital:

  1. Respecting the architect’s original layout:

    When preparing a GA, always make sure you respect the architect’s design. The Architectural drawing determines the structural drawing for a building project. For example you do not place columns where the architect has meant to be a free space.  Also no structural element should disrupt the interaction of spaces. Do not project columns and beams in areas where the architect have stated as plain walls or sections etc. The GA should be consistent with the original form of the structure as designed by the architect.

  2. Selecting a stable model:

    It is very important that the model or General Arrangement (GA) you are presenting be stable statically. It should fully represent the behaviour of the structure, without any stability or equilibrium problem at joints and other locations in the building.

  3. Consider Buildability and construction implications:

    Any model that is being presented should be buildable. This can be achieved by first considering the technical capability of the local contractors executing the design model. For instance, in regions where there is non-availability of reinforcement bending machines and cranes, then the model will require high yield 32mm bars, or recommend the use of precast or prestressed elements. Also the design should reflect the budget of the project.

  4. Compare economy and structural requirements:

    While trying to decide on the best process for construction, also consider which process will be more economical. For Instance ask yourself between more steel and more concrete, which do you think is more economical in the region?
    A typical example according to Structville is: “consider an external beam that should have been 8m long under simply supported assumptions. If there are no openings at the wall panels under the mid span of the beam, you can comfortably hide an intermediate column there, thereby having two spans 4m each. The original 8m beam would have required more steel reinforcements, or deeper sections, or both to satisfy ultimate and serviceability limit state requirements. However, if you introduce a column at the mid-span, there will be redistribution of stresses, with a hogging moment at the propped mid-span, and hence, generally lesser reinforcements, concrete section, and deflection. However, you should note that you are now going to construct a new column and new isolated base (requiring concrete, reinforcement, and additional excavation cost). Between the two options, which one gave you the most economical solution? Is the cost of constructing foundation in that area cheap or expensive? These are all influencing factors, and years of design experience also counts“.

 

For case study examples on General Arrangement and GA thinking process visit structville.com

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