Transformed Sections and Cracked Moment of Inertia
Ғылым және технология
Once a reinforced concrete beam is cracked, the section reduces dramatically from the gross moment of inertia to the cracked moment of inertia. This cracked section is active from the cracking moment up until the yielding moment, when the steel yields. Computing the cracked moment of inertia is important for finding deflections of concrete beams under service loads.
Chapters:
0:00 Introduction
1:02 Cracked MoI
5:12 Example
Пікірлер: 3
Thank you very much sir, this is a great work. Thanks alot
Sir, please let me know the derivation how it becomes nAs and significance of modular ratio n....
@StructuresProfH
Жыл бұрын
Reinforced concrete is a composite of concrete and steel. When we examine the stiffness of the section, for example when computing deflections, we are generally interested in the elastic modulus E multiplied by the moment of inertia I. However, we have two material with different modulus: steel Es and concrete Ec… so what do we use? To get around this, I can convert (or transform) my steel into an equivalent area of concrete. Steel has a higher modulus than concrete, and we represent this with the ratio n = Es/Ec. The transformed area nAs is the steel area converted into a larger area of concrete such that the total stiffness is unchanged. Using this transformed area, I can treat my section as though it’s 100% concrete, meaning I can now find a moment of inertia I with modulus Ec using traditional, single-material beam bending theory.