About column engineering knowledge

Column  basics  types failure patterns and condition and design

Column definition

Column  is a long cylindrical member subjected to axial comparison column carries self weight and load coming on it generally load transfer through its longitudinal direction column is categorized based on its height these are 

Types of column 

• Short column 
• Long column

                                Short   column

If the length of column is 15 times the least dimension of its cross section then Kollam will be short column slenderness ratio of short column is up to 80. Slenderness ratio is the ratio between effective length of column and radius of gyration 

                          Long column

If cross sectional geometry of column is other than simple shape like circle square rectangle etc then radius of gyration is required for the calculation of ultimate load that column can carry minimum value of radius of gyration is adopted during the design of column for getting minimum value as minimum value of moment of inertia in the formula radius of grayson is directly proportional to the moment of inertia

Radius of gyration is the minimum reduced from the centroid of column cross section it is denoted by  'K' or 'R' it is measured in millimetre centimetre inches ect.

Radius of gyration formula

                i

K =   -----  

            A        

Mathematically reduce of gyration can be represented as  

Where

K= radius of gyration

I= moment of inertia

A= cross sectional area

Note: during the design of column minimum value of radius of grayson is adopted for that always take least  value of moment of inertia in formula

 failure patterns   

Column  loading patterns 

There are two types of column loading patterns patterns depend on the location where lord is acting these are

• Axially loaded column
• Eccentric loaded column

         Axially loaded column 

Axially loaded columns are the one where load at 8 the centroid of column cross-section these is also known as concentric loaded column resistance of Excel loaded column is more against buckling then eccentric loaded column as shown in figure below

Eccentric loaded column 

If load at away from centroid of column cross section then such column is now as eccentric loaded column resistance of ecentric loaded column against buckling is very less than conventionally  loaded Kolam if both type of loaded column have some cross section and material then axially loaded column will be considered as stronger

Buckling load

Buckling load is the minimum load which produce buckling in a column

Crushing load   

Crushing load is the minimum load which crash the column material value of buckling load will be similar than crossing load on the same column during the design of column neither crossing road no buckling is not considered but little laser value of lord is considered which is coming on column that value of lord is known as safe load structures remain safe under safe load

Factor of safety

Factor of safety is the ratio between crushing buckling load and safe load generally factor of safety value range between 2 and 5   for  structures 


Column and condition

How much load a colon can be here also depend on column and conditions Kolam with a fixed and condition at both and will be stronger than the second column of same size length and material but having both and free ability to carry load will be different for both columns

 effective length of a column is calculated after now in the column end  conditions effective length change with the change in column end conditions following are the column end  conditions 

• Both ends hinged
• Both ends fixed
• One end fixed and other hinged
• One end fixed and other end free

Both and hinged 

This is the standard column end condition effective length in this condition is equal to the length of column effective length of other end condition can be found with reference to this condition in this condition both and of column are either pinned pivoted or rounded as shown in figure below

        L

I= -----

       2        

Where 

I = EQUiualent length 

L= actual Length 

One end fixed and other hinged

In this condition one end of a column is stronger while the other end is very weak equivalent length for this end  is as flowing
         L
I= -------
      ÷2       

One end fixed other hinged


One end fixed and other free 

This and condition Makes column  to bear the smallest load than all other and condition column in such condition is very weak equivalent length for one and fixed and other free is as following 

I= 2L 

Column design formulas


There are two formulas used for the design of column these are

1. Euler's formula
2. Rankin's formula