Moment Diagrams 6

[DaveAtkins]

One thing that irritates me a little about RISA-3D is that it draws the moment diagram upside down -- at least based on my educational background. For example, I was taught that for a simple span beam with uniform load, the parabolic moment diagram is drawn ABOVE the horizontal line. However, I do know that some schools teach this differently. I'm wondering -- do most of you draw moment diagrams as I do? If so, I may call RISA to ask them to change their graphics.

DaveAtkins

 

[nrguades]

lippie.

What command in staad that will allow you to change the bending moment on the tension side (as positive) or compression side (as positive)? Havent seen it...

 

[lippie]

nrguades

In SAP, I dont know - I have just heard. We use STAAD 2003 and the option is inside the INI file. They don't expose it through the graphical side because according to their people at the REI Conference, "Tech Support would be confused if they were looking at bending moment diagrams, not knowing the setting chosen by the user". So you have to open their staadpro20030.ini file in notepad and change the [MOMENT DIRECTION] = 1. I am not sure what thye have done in their new 2004.

 

[J1D]

DaveAtkins,

I used Risa-3D for quite a while, but not realized it cannot convert bending moment diagram, maybe because that's way I've got used to, and seems better as mentioned by Yalpol.

It is indeed very irritating when one got used to one way of looking but encountered a upside down picture. The converting capacity should be standard.

 

[paullaup]

I always draw the moment diagram on the tension side so I can instantly identify the tension side, and see which way the members will bend toward. It’s really helpful for identifying the deflected shape.

I feel this method intuitively goes hand-in-hand with concrete design, where you don’t want to make silly mistakes because you mixed up "positive" and "negative" moment.

I never think of bending moment as positive or negative, because it doesn’t serve any good purpose. I do, however, reference the moment to the side of the member it's on. Top moment, bottom moment. Top moment=top steel. Bottom moment=bottom steel.