In an under reinforced section, the depth of actual neutral axis is# in PSSSB Jr. Draftsman Official Paper Download PDF Attempt Online View all PSSSB Junior Draftsman Papers >
In an under reinforced section, the depth of actual neutral axis is# in PSSSB Jr. Draftsman Official Paper Download PDF Attempt Online View all PSSSB Junior Draftsman Papers > Correct Answer less that the maximum depth of neutral axis or X<sub>u</sub> < X<sub>umax</sub>
Concept:
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a) If the depth of actual neutral axis (n) is lesser than the depth of critical neutral axis (nc) then the section is called as under reinforced section and in this case the steel in the tensile zone attains its maximum stress earlier than the concrete in compressive zone.
b) If the depth of actual neutral axis (n) is greater than the depth of critical neutral axis (nc) then the section is called as over reinforced section and in this case the concrete in compressive zone attains its maximum stress earlier than the steel in the tensile zone.
c) If the depth of actual neutral axis (n) is equal to the depth of critical neutral axis (nc) then the section is called as balanced section and in this case the concrete in compressive zone and the steel in the tensile zone attains their maximum stress simultaneously.
Important Points:
This concept of under reinforced and over reinforced sections are independent of nature of beam means weather the beam is singly reinforced or doubly reinforced. So, this concept is true for singly reinforced beam also.
In fact, for doubly reinforced section first the steel in compressive zone converted into equivalent concrete section and then this concept is applied.
