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What are the basic rules for building design in structural engineering? Minimum standards in building design?
Basic rules in building design is important aspect for structural engineering, without knowing the minimum stands and basic concepts it is impossible to make the building structures. The structural components mainly related to the beams, plinth beams, columns, slab and foundation, if we design these components of the building properly then the rest of the structure will be stable.
In this article I will explain you what are the basic rules and minimum standards considered in building design. The standards are classified in to following categories.
- Basic rules for beam and plinth beam design.
- Basic rules in column design.
- Basic rules in slab design.
- Basic rules in foundation design.
Basic rules for beam and plinth beam design
Beams are the horizontal members in building they are mainly used to transfer the loading condition to the columns and foundation design. Depending upon the design of the building basic rules classified in to following 5 types.
Basic rules for minimum dimensions of beam
As per the standards the minimum dimensions for beam or plinth beam is 9”X9” or 230mmX230mm, this is applicable only if the building structure is comes under ground floor building. If the number of floors increases from ground to 2floors or 3 floors etc. we need to increase the dimensions of beam section.
Minimum area of tensile reinforcement
As per the design considerations the minimum area tensile reinforcement in beam or plinth beam is shown in the below expression.
As =(0.85bd)/σy
Where As is the tensile reinforcement
b= width of the beam
d=depth of the beam
σy=yield strength of steel
Basic rule in maximum tensile reinforcement
The maximum tensile reinforcement is also important rule we need to consider while designing the beam section. The maximum reinforcement values are depends upon the width and depth of the beam cross section.
In the beam designing the maximum tensile reinforcement as per the standards should not exceed 0.04bD. Where b=width of beam and D= depth of the beam.
Side reinforcement in building design
In the beams design basically top and bottom reinforcements is important to resists the total load which comes to the beam cross section. The side reinforcement in the beam section is provided if the depth of the beam exceeds the 750mm depth.
Minimum cover and number of bars in beam design
As per the code provisions the minimum cover of the section is taken as 10% of the higher dimensions of the beam or column. For example let us assume beam is having 350mmX450mm dimensions, here in this example the higher dimensions are 450mm, the 10% of 450mm is 45mm, so the cover should be provided as 450mm. The minimum cover for the 230mmX230mm beams provide as 20 to 25mm.
At least we will use 4 numbers of reinforced bars in beam section as per the code provisions.
Basic rules for column design
Columns are the vertical members used to resist the total loading of the building structure. The following are the basic 6 points considered in column design as per the standards.
Basic rules of minimum dimensions of column
For the column section also the minimum dimensions is considered as 9”X9” or 230mmX230mm, if the building is comes under ground floor , as per the code provisions this 9”X9” dimensions is sufficient for one and half storey.
Minimum diameter of bars and minimum grade of the concrete
12mm diameter of the bar is used as the minimum in building design as per the standards and do not used 10mm or 8mm diameter bars in column design. And the grade of the concrete is considered as M20 with mix proportion of 1:1.5:3.
Concrete cover in column
As i explained in beam rules above the column cover is also considered as 10% of higher dimensions of column in building design. The minimum of 25-50mm concrete cover is used in column design as per the standards. Use top and bottom reinforcement values should be same throughout the building section.
Shape of the column in building design
The shape of the column section is also effects the design considerations. Try to use square columns only in building design why because if we use rectangular or polygon or circular column sections the loading distribution values changes.
Number of Bars and Spacing of lateral ties
At lest we use minimum of 4 bars with 12mm diameter in ground floor building design. The spacing of the lateral ties should be used 100-200mm in the column design.
Center to center distance between the columns
The center to center distribution between the column section is mainly depends upon the loading condition on the structure, if the loading effect is less we need to provide minimum distance and if the loading condition is high we have to increase the column center to center distance. As per the standards in building design minimum center to center distance is taken as 3m and the maximum center to center distance between the column sections is taken as 5m.
Basic rules for slab design
Slab is the flat member used to transfer the loading condition live load to the beams and column section. The following are the basic rules we need to consider before designing the reinforcement values of the slab.
Basic rule in effective span
The effective span is considered mainly in simply supported slab or cantilever slab design sections. For the SSB it is the sum of the minimum clear span plus effective depth and for the cantilever slab it is the sum of the length up to the face of supports plus ½ of effective depth.
Limiting stiffness
Limiting stiffness is also an important aspect in slab design. It is having different values for cantilever slab, simply sported and continuous slab section. For the S cantilever slab it is considered as 7, for simply supported slab it is considered as 20 and for the continuous slab it is 26.
Minimum reinforcement and maximum diameter of the bars
As per the IS 456-2000 code the minimum reinforcement in slab section should not exceeds 0.5% and the maximum diameter of reinforcement bars not greater than 1/8th of slab thickness.
Spacing of the main reinforcement in building design
The spacing of the main reinforcement bars are taken is taken as the highest value of two factors one is 3tiems of effective depth and second one is 300mm whichever is less.
Distribution reinforcement and concrete cover of slab
The distribution reinforcement is not less than 0.15% as per IS 456-2000 code and the minimum concrete cover for slab is used as 20mm.
Basic rules in foundation design
Foundation is the concrete structure which exists below the ground level. The loading distribution will takes place through the column section. The following are the basic rules to be considered before designing the foundation in building.
Dimensions of foundation basic rules
A minimum of 1mX1mX1m pit dimension is considered for the foundation under the basic building design considerations. The depth, width, length of foundation increases if we increase the number of floors in building.
Minimum concrete block and foundation thickness
The concrete block is taken as minimum of 50mm for the basic buildings as per the IS code provisions and the foundation thickness is minimum is considered as 400mm dimensions.
Minimum diameter of reinforced bars and grade of the concrete
For the foundation design the 8mm or 10mm diameter bars are considered for basic buildings the diameter of the bars are increases depending upon the various factors like loading condition, number of floors and center to center distance between the columns etc.
For the foundation we need to use minimum of M20 grade concrete, below the M20 grade concrete is not acceptable in basic building designs. Also for the PCC minimum of M10 grade is considered.
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Basic Rules in beam design
Basic rules in column design
Basic Rules in Slab design
Basic Rules in foundation design
Conclusions of basic rules for building design in structural design
Well now the above explained concepts are related to the basic rules in building design as per standards. These are mainly basic rules in beam design, basic rules in column design, basic rules in slab design and basic rules in foundation design.
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