Round Bar Tension Resistance: Critical Area
When a round bar is subjected to tension, especially if it is threaded, the point where the cross-sectional area is smallest determines its ultimate tensile strength. This minimum area is referred to as the net area.
Identifying the Critical Section
Consider a threaded round bar under tension:
- The main body of the bar has a larger solid cross-sectional area.
- The process of creating threads removes material, forming grooves.
- The root of the thread is the deepest part of these grooves, where the bar's diameter is smallest.
- This reduction in diameter at the root of the thread results in a smaller cross-sectional area compared to the unthreaded portion (mid-section).
Therefore, the stress concentration is highest at the root of the thread, making this the critical section that limits the bar's tension resistance. The net area is the cross-sectional area calculated at this specific point.
Conclusion
The net area of round bars to resist tension is determined by the cross-section at the root of the thread, as this is where the material is most reduced and thus weakest under tensile load.
Important Questions from Tension Member
The following are the statements about lug angle used to connect heavily loaded tension member to gusset plates.
(i) The length of end connection is reduced
(ii) By using lug angles there will be saving in the gusset plate
(iii) Cost of connection increases due to additional fasteners and angle required.
A structural member subjected to tensile force in a direction parallel to its longitudinal axis is generally known as
When the length of a tension member is too long:
The allowable stress in axial tension is generally kept less if the thickness of the member is more than
A single angle in tension is connected by one leg only. If the areas of connecting and outstanding legs are respectively a and b, then what is the net effective area of the angle?
A) \(a-\frac{b}{1+0.35\times\frac{b}{a}}\)
B) \(a+\frac{b}{1+0.35\times\frac{b}{a}}\)
C) \(a-\frac{b}{1+0.20\times\frac{b}{a}}\)
D) \(a+\frac{b}{1+0.20\times\frac{b}{a}}\)
