Why we use steel in column

 Why we use steel in column?

in this article we discuss why do we use Steel reinforcement bars in concrete or why we use Steel reinforcement bar in columns and beams

After reading this article you will be able to answer why do we use Steel reinforcement bars in in concrete beams and columns so 

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Columns are often subjected to differing types of loading thus they ought to resist these loads by different means. Firstly, allow us to start with colums subjected to axial compressive loading only; concrete alone could be sufficient in resisting this applied force,but why can we put steel?

Steel during this case is provided thanks to these reasons:

1)Steel compressive strength is false equal as its tensile one ( its obstacle is its lateral instability thanks to buckling which is why and for one reason stirrups are added).Thus, steel will help concrete in resisting compressive loads so now we will diminish the dimensions of concrete section.

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2)According to Euler critical buckling load columns(specially slender ones) must be designed to resist this lateral deformationm thanks to this axial load; and since concrete material is brittle in its behavoir; longitudinal steel(ductile and hard material) should be provided to stop a sudden total collapse or failure.(steel especially the low carbon content one can absorb and dissipate energy more effectively)

3)Cracks might occur in concrete thanks to rapid hydration development for instance or lack of curing, thus these cracks induce tension stresses that has got to be countered by tension resisting steel.

4)The bond between the column and beam must be provided using those steel bars

Columns also are often subjected to combined loading(axial + applied moment).This moment might be thanks to the frame action( fixed column-beam connection or partial fixed) or thanks to a primary order or second order eccentricity which induce tension part section within the column(re-distribution of stresses) leading to applied moment.

In this case the steel will act in tension or in compression depending the purpose of application of the load.

Furthermore, steel in columns is provided to relocate the position of plastic hinges during which the instant resisting of columns must be greater than 30% the instant resisting of beams which what we call “Strong Column - Weak Beam” hence, abstaining the plastic hinge to occur at the columns thus reducing the danger of incremental or progressive collapse.

Note: Frame action may be a seismic rigid solution for resisting lateral seismic forces