Design Guide 9 Calculations 2

[alex2000junio]

Hello guys,

I have some quick questions about the examples of Design Guide 9 that are not 100% clear to me.
- Why does V_u, in example 5.1, is divided by 2? Example 5.4 does not divide.
- In Example 5.1, both τ_bw and τ_bf uses Vu. Shouldn't it be V_y for the web one and "V_x divided by 2" for the flange one (divided because there are two flanges)? It makes sense to me since the shear applied in x is different from the one applied in y. Also, why does it uses I_x for both cases?
In my case, I have separate values for shear, I mean, I have V1, V2 and V3 (Vx, Vy and Vz). So, am I correct at the second sentence?

 

[BulbTheBuilder]

Why does V_u, in example 5.1, is divided by 2? Example 5.4 does not divide.

Pu is rather divided by 2 to determine the shear force of a simply supported beam. P/2=V.

In example 5.4, there are 2 point loads 310k and 420kips. V(max at right support) = [310(7.5)+420(25-7.5)]/25=387kips

You can refer to table 3-23 AISC for shear equations
Both examples uses shear

In Example 5.1, both τ_bw and τ_bf uses Vu

Shear flow, thus Vu. But the equation is for flexural shear stress for the flange and web. You can Google to read on that.

Also, why does it uses I_x for both cases?

Vu is along Y-axis hence the moment of inertia is that about the perpendicular axis for the flexural shear stress flow.

You have the shear in only one direction, along Y-axis (V2). The point load isn't inclined. You will then proceed to use the Vu(shear along Y to find your shear flow to determine the stress across your section; at the web or flange).

 

[alex2000junio]

Another very quick question:
Thanks a lottt Bulb the Builder! I really appreciate you help

 

[BulbTheBuilder]

Another very quick question:

I don't see any question.

Thanks a lottt Bulb the Builder! I really appreciate you help

You're welcome!