7/23/2019 Steel Design Notes

http://slidepdf.com/reader/full/steel-design-notes 1/3

Steel design Notes

Circular columns are recommended in the areas of heavy wind; because the wind

forces on such columns are minimized irrespective of the direction of wind.

Maximum permissible radius for the circular column is 65 x thickness of the

section wall; to account for the imperfections in the manufacture.

l/r; where l = distance between the connections, r = radius of gyration; chec l/r

from sp! "old handboo# then $nd its allowable %fe&; multiply it with C'(, which

should be greater than the load coming.

( box section is immune from torsional bucling.

)igher l/r ratio leads to the more stress bearing capacity of the steel column and

hence minimizes the steel re*uirement.

 +he designer should select largest possible radius of gyration, without increasing

the area of section and the largest radius of gyration is obtained when more

material is farthest from the centroid.

 +he lacing and battens of column are not load carrying members and they are

 ust meant to hold the load carrying members in position.

 +he gusset plate is used to connect the truss members due to insu-cient space

available for welding members at a common position. +he thicness of the

gusset plate used should be 01mm in roof truss and goes around 11mm incase of bridge truss. ! mm thicness can be used in case the span of

7/23/2019 Steel Design Notes

http://slidepdf.com/reader/full/steel-design-notes 2/3

truss is 01 m i.e. small span means small load coming on the gusset plate.

 +russ members have good inplane sti2ness but very less out of plane sti2ness

and hence bracing in done out of plane.

 +russes3 members which are normally under tension may experience reversal of

stress from tension to compression due to wind or earth*uae forces lie in

bridges"due to vehicle load# and roof truss "due to dead and live load

combinations#which should be considered in the design.

7/23/2019 Steel Design Notes

http://slidepdf.com/reader/full/steel-design-notes 3/3

Note: It should be ensured that the compression members do not sag

1/1th of their length!

4t is a common practice to specify minimum angle size to 56 7 56 7 ! mm in case

of roof truss.

 "oncrete notes:

( short column when subected to axial force of su-cient magnitude then it may

fail by bulging out or shear if the material is brittle. 4n case of the long column

the failure will occur at lower loads compared to the short column for same

dimensions and strength.

8n increasing the load, when 9uler load is reached, the :ending sti2ness"94 or

lexural rigidity# becomes zero, but that does mean theoretically that on

increasing the load in$nitesimally, the column will de<ect inde$nitely although

within a speci$ed range by 9uler. :ut practically, de<ections become acontinuous process of loads although bucling remains discontinuous still.

Short column compresses until it fails b# crushing and long column

buckles b# showing de$ection! %nd this is the main di&erence between

the two!