what moment formula should I use ?

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Jovan Pacasum T...
Jovan Pacasum Tomawis's picture
what moment formula should I use ?

I'm working on a design analysis of a multistorey building(residential)
I'm totally new to this then I came across this when I started to design beams . . .
1)how do I know if 1 end is restrained or unrestrained ?
2)a and b conditions under negative moment seems the same, which am I supposed to use ? can someone cite an example as to when exactly this formulas are to be used because although it was explained there in text, I somewhat can't fully understand their conditions.

Jhun Vert
Jhun Vert's picture

Let me explain with the use of an example. Consider a concrete T-beam along the span A-B-C. This is similar to CE Board Exam Nov. 2012 problem.



At the supports, the moment is negative and at the midspans of AB and BC, the moment is positive.

The moment at support B is under this code description: Negative moment at exterior face of first interior supports for two spans, Mu = wu Ln2 / 9

For the positive moment at midspan, it is under this definition: End span, when discontinuous end integral w/ support, Mu = wu Ln2 / 14

I hope it helps.

Jovan Pacasum T...
Jovan Pacasum Tomawis's picture

Salamat po


Well explained by sir Romel. In addition to that, if you are designing an actual building, I will recommend using Three Moment Equation (examples with different situations are also presented in this site, appreciation goes to the author) for a more economical section and/or number of bars furnished. ACI moment is a fast way to solve the moments of a considered span or continuous which meets the code restrictions.

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