Basic Interview questions- Civil structural design

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Basic Interview questions for Civil Design Engineer

01. What is the Minimum reinforcement percentage for a column? 
Answer: The minimum reinforcement percentage is 0.8% of the cross-sectional area of a column or Ast= 0.85db / fy.
02. What is the Maximum reinforcement percentage for a column? 
Answer: The minimum reinforcement percentage is 6.0% of the cross-sectional area of a column or 0.04 bD.

03. How do we determine the effective length of a column?
Answer: The effective length of a column is expressed as Leff = k x L
                Where k stands for effective length ratio.
                            L stands for unsupported length or clear height of the column.

 04. What is the Effective length ratio of a column?
Answer: The effective length ratio is basically a constant depending upon the degree of rotational & translational restraints at the ends of the column.

05. Define Slenderness Limits of a column?
Answer: The Slenderness Limits of a column ensures that failure shall only occur due to material failure and not because of buckling. Therefore, the column is checked for slenderness limit, which shall never exceed 60 times the least lateral dimension of the column. 

 06. How to classify short columns & long or slender columns?
Answer: When the slenderness ratio's Lex/D & Ley/b are less than 12, the column is termed as a short column, whereas if the value is greater than or equal to 12 then it is termed as a slender or long column.
                Where Lex stands for effective length in respect of the major axis.
                            D stands for depth in respect of the major axis.
                            Ley stands for effective length in respect of the minor axis.
                            b stands for the width of the column.

 07. What is the minimum eccentricity of the column that needs to be taken into consideration during designing?
Answer: The minimum eccentricity of the column that needs to be taken into consideration during designing is emin  = L/500 + D/30, but not less than 20 mm.
                Where L stands for unsupported length or clear height of the column.
                            D stands for the lateral dimension in the plane of bending.

 08. What is the maximum moment that occurs in a column & where does it occur?
Answer: The maximum moment that occurs in a column is expressed as Mmax = P (e + Δmax)
                Where P stands for the load on the column.
                            Î”max stands for the lateral deflection of the longitudinal axis.

 09. What are the non-dimensional parameters used for designing a column with uniaxial eccentric loading?
Answer: The non-dimensional parameters used for designing a column with uniaxial eccentric loading are Pu/b.d.fck & Mu/b.d2fck  .   

 10. What is the codal method (IS Code) for designing a compression member subjected to biaxial bending?
Answer: The codal methods suggests the use of Bresler's empirical formula which is expressed as follows - (Mux / Mux1)αn + (Muy / Muy1)αn ≤ 1.0.
                Where Mux stands for the moment about X-axis due to design loads on the column.
                            Muy stands for the moment about Y-axis due to design loads on the column.
                            Mux1 stands for the maximum uniaxial moment capacity with as axial load Pu  & bending about X-axis.    
                            Muy1 stands for the maximum uniaxial moment capacity with as axial load Pu  & bending about Y-axis.
                               Î±n is an exponent whose value depends upon the ratio (Pu/Puz) 

11. What shall be the overall depth to width ratio of a beam?
Answer: The overall depth to width ratio of a beam shall lie between 1.5 to 2. However, there are other types of beams such as hidden/concealed beams that don't follow this criterion.

12. What are the hidden/concealed beams?
Answer: The hidden/concealed beams are those beam whose depth equals the depth of the slab.  When there is a restriction in providing a beam in between slabs due to architectural features, a hidden/concealed beam is used.

13. What is the minimum & maximum number of bars to be used as tension reinforcement in a beam?
Answer: The minimum number of bars to be used as tension reinforcement in a beam is 2 & a maximum of 6 numbers of bars can be placed in a single layer.

14. What is the minimum percentage of tension reinforcement to be provided in a beam?
Answer: The minimum percentage of tension reinforcement to be provided in a beam shall be 0.3% of the crossectional area of the beam.

15. What is the effective width of a flanged beam?
Answer: The effective width of a flanged beam shall not be greater than the breadth of the web of the beam plus half the sum of the clear distances to the adjacent beams on either side. It is computed by the following equations-  
  1. For T-beam: bf = [ (Lo/6) + bw + 6 Df ]
  2. For L-beam: bf = [ (Lo/12) + bw + 3 Df ]
Where bf stands for effective width of the flange
            Lo stands for the distance between points of zero moments
            bw stands for the breadth of the web           
            Df stands for the thickness of the flange

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