Our team had been asked to plan and design a small residential building of Ground + 3 floors. The requirements were to plan atleast 4 medium size apartments per floor. The plot area available was 7565 square feet. It was not rectangular, and so apartments would be of differing builtup areas. Our main target were buyers looking for a medium size 2BHK apartment. There was an additional requirement for a separate Drawing Hall for guests wherever possible.
Plot Survey
A lot of options were proposed. Our goal was to maximize usable area for the residents. Front open margin was fixed at 12′. Side margins were fixed at 6′ 6″ on both sides. One plan was finalized after a few meetings with the developers.
Construction of buildings can be divided into three main categories:
Load bearing construction
Composite construction
Framed construction
But among the three types, framed construction is widely used for all kinds of constructions.
An engineering structure is an assembly of number of elements transferring the loads and providing a form space to serve the desired function.
Building Construction and Design
The structural design is a science and art of designing, with economy and elegance, a durable structure is that which can safely carry the forces and can serve the desired function satisfactorily during its expected service life span.
The entire process of structural planning and designing requires not only imagination and conceptual thinking but of practical aspects, such as relevant design codes and byelaws, backed up by aple experience, institution and judgement.
The process of design commences with planning of a structure, primarily to meet the functional equipment of the user or client. The functional requirements and the aspects of the aesthetics looked into normally by an architect while the aspect of safety, serviceability, durability and economy of the structure for its intended use over the life span.
What is a building?
A building can be defined as a structure consisting of walls, floors, education, business, manufacturing, storage, hospitalization, entertainment, worship etc.
Normally all building are constructed according to drawings and specifications prepared by architects. Each city has prescribed building bye-laws to which building must confirm. The building bye-laws lay down norms like minimum front, side and rear backs, minimum height and area of habitable rooms, kitchen, bath, minimum area of windows, width of staircase etc, apart from respecting the bye-laws the building design should ensure optimum utilization of built-up space, thermal comfort, proper ventilation, desirable illumination and acoustical characteristics and it should satisfy the functional requirements of people who live and work in the building.
A lesson for all the Civil Engineers and Designers to learn
I got a project of designing (Architectural Design) a Hostel in Lucknow, India. The Structural design that is, column positions and wall construction was already done. The client wanted me to design a Hostel keeping the column positions and exterior wall construction intact. I have written this article to address all the Civil engineering students as well as Civil Engineers to avoid making such blunders while they design. Please do read this article because understanding the intensity of the job of a Civil Engineer is must for every student and professional. I guess this realization has been washed away and forgotten in the wave of commercialism.
Hostel Design, Lucknow, India
The client mailed me the layout of the existing construction. After I studied the layout, I figured out that the Column layout was pathetic. I wonder what kind of Civil Engineer must have made the layout or if at all any Civil Engineer has done it.
Errors in Construction
Wrong size of the Columns
The size of the columns was 9”x9” and the building is supposed to be constructed upto G+2 floors which is really disastrous for the structure.
It could lead to structural failure and ultimately structural collapse.
(The duty of the Civil Engineer is to understand and not make such dramatic blunders. The consequences of this kind of structural design could be disastrous.)
Column layout and Exterior wall Construction
9”x9” size columns are only preferred if you were to construct only a ground floor structure using M15 grade concrete. If you are to construct another floor that is (G+1), the minimum size of the column should not be less than 9”x12” using M15 grade concrete.
If the client insists on using smaller columns (9”x9”); in that case, use of M20 grade concrete should be done mandatorily and the construction should not be initiated before the client agrees to do so.
Guidelines to be followed for making a column layout
In this article, we will go through the essential thumb rules to be followed for giving a column layout. Of-course columns have to be designed in accordance to the total forces acting on the structure, but apart from that, it is essential for every Civil engineer and Architect to remember a few thumb rules so that they are prevented from making mistakes.
You can hire me for your structural design need. Contact me.
Three thumb rules to be followed are as follows:
Size of the Columns
Distance between Columns
Alignment of columns
Minimum Size of RCC columns
The size of the columns depends on the total load on the columns. There are axial loads and lateral loads. Large beam spans induce bending moment not only in the beams, but also in columns which are pulled by the stresses in the beams. It is important to use advanced structural design software like ETabs or Staad pro. I highly recommend every structural designer learn these software. The thumb rules are for general designing in very small projects.
For this general thumb rule, we will assume a structure of G+1 floors high, using standard 6″ walls.
Minimum size of an RCC column should not be less than 9” x 12” (225mm x 300mm) with 4 bars of 12 MM Fe415 Steel.
These days the minimum I use in my projects is 9″ x 12″ (225 mm x 300mm) with 6 bars of 12 MM Fe500 steel. You can never go wrong with strong columns. I also recommend use of M20 grade concrete for the structure (ratio 1 part Cement : 1.5 parts Sand : 3 parts Aggregate with 0.5 parts water by volume). I recommend use of 8 MM stirrups at a distance of 150 MM center to center throughout the length of column.
This setup of 9″ x 12″ RCC columns is safe for G+1 Floors. There are a lot of other considerations, but this is just a thumb rule.
A building is composed of various structural components such as Foundations, Plinth beams, Columns, Beams, Slab, Staircase, Doors and Windows.
RCC Building Design
Design of Foundation | RCC Building Design
Foundation design is the structural component from where the RCC design is initiated. The foundation design guide discussed earlier includes in detail the design procedure for isolated column footing. Column footing is the most commonly used type of foundation. It serves a variety of different buildings.
Calculation of loads in Foundation Design Calculation of loads is very important for the purpose of structural design. This article outlines the thumb rules for the calculation of various loads in foundation design.
Types of Foundations This is a generic article on different types of foundations. It covers some commonly used shallow foundations and also explains pressure distribution under a foundation.
Singly reinforced beam
A series of articles have been written for the design of Singly reinforced sections. The articles include basic definitions and formulas, understanding stresses and modular ratios, assumptions for singly reinforced sections, Design method 1, Design method 2, Moment of resistance and a number of solved numerical examples.
The article discusses the classification criteria for a column, and design of different types of reinforcements for columns which include longitudinal, transverse and helical reinforcements.
How to calculate the total loads on a column and corresponding footing?
This article has been written on the request from my readers. Engineering students generally get confused when it comes to calculating loads for column and footings design. The manual process is simple.
Types of loads on column
Self weight of the column x Number of floors
Self weight of beams per running meter
Load of walls per running meter
Total Load of slab (Dead load + Live load + Self weight)
The columns are also subjected to bending moments which have to be considered in the final design. The best way to design a good structure is to use advanced structural design software like ETABS or STAAD Pro. These tools are leagues ahead of manual methodology for structural design, and highly recommended.
In professional practice, there are some basic assumptions we use for structural loading calculations.
You can hire me for your structural design need. Contact me.
For Columns
Self weight of Concrete is around 2400 kg per cubic meter, which is equivalent to 240 kN. Self weight of Steel is around 8000 kg per cubic meter. Even if we assume a large column size of 230 mm x 600 mm with 1% steel and 3 meters standard height, the self weight of column is around 1000 kg per floor, which is equivalent to 10 kN. So, in my calculations, I assume self weight of column to be between 10 to 15 kN per floor.
Structural Engineering and Architecture are two different sciences that are inter-related. Structural Designing deals with the study of design of steel in a structure i.e., the internal skeleton of the structure that helps to keep the structure durable, sound and stiff.
Whereas Architectural Design deals with design of spaces meant for a particular function. It helps to create ambient environment that is pleasing to eye. The Architect designs the building keeping all the functional aspects in mind that are to be incorporated into the design and then they are executed by a Civil or Structural Engineer.
Inter-relationship of Architectural Design and Structural Design
The structures and structural members are designed to meet the functional and structural aspects. Both the aspects are inter-related. The functional aspect takes into consideration the purpose for which the building or the structure is designed. The functional aspect includes the determination of the amount and arrangement of space necessary for the structure.
Structural design is the science of studying the Mechanics of a structure. Designing the skeleton of a building determines the real strength of the structure.
If the structure is externally beautiful and internally weak, it results into dramatic structural failure.
Structural Framework in a building
In this article, we are going to discuss in detail about the “Various Methods of Structural Design”.
All parts of a structural steel framework of a structure shall be capable of sustaining the most adverse combination of dead loads, the prescribed super imposed roof and floor loads, wind loads, seismic forces where applicable, and any other forces or loads to which the building maybe reasonably subjected without exceeding the permissible stresses.
The following methods may be employed for existing steel framework:
The practice of Civil Engineering is extremely diverse, involving technical, legal, business & practical skills. It consists of various specializations like Structural Engineering, Project Management, Geotechnical Engineering and Surveying. The ability to combine skills in all these areas will contribute significantly to the success of a civil engineer.
Akashi Kaikyo Bridge, Japan - World's Longest Suspension Bridge
To provide an overview of factors which are relevant to the successful practice of structural engineering, we have to look at the role of a structural engineer, understanding the needs and objectives of a client, the difficulties and conditions faced on site and the constraints put down by the Architect. A structural designer is capable of calculating different loads and stresses acting on a structure and designing the structure to resist there forces. For tall buildings, towers, tunnels, roads, marine structures, bridges and even space stations, structural designers are called upon to provide their expertise to ensure the stability of the structures.
