Bending moment using clear span
Hi @Anonymous
what the Rc code has to do with this issue ?
When you use the RC Beam module as stand alone rather than import a beam from a model for selected codes (e.g. BAEL) there is a functionality that allows you to calculate bending in the way you described in your original post
For ACI and wide support you may decide on applying loads in a different way
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Artur Kosakowski
Hi @Anonymous
Before proposing a solution I'd like to understand what you actually are dealing with. What I mean is how you manage to 'connect' a beam to a wide support in such way that there is no negative bending at the support? Do you assume that it the actual point of rotations at the edge of the support and the part of the beam being beyond this rotation point and over the support is uplifted due to the load applied to its span? The additional question is what is this support (column/wall) and if a column - do you need to design reinforcement for it as well?
Artur Kosakowski
Indeed what I proposed doesn't 'reduce' the span however within the option you have got in the RC Beam module stand alone this is the only way of reducing the value of the bending in the mid-span I can think of.
On the other hand I'm not quite sure if I fully understand the situation you have in mind (see my post above). If I remember correctly some codes for simply supported beams actually suggest using 1.05L rather than 1.0L (L being the distance between theoretical axes of supports) and the approach we are discussing IMHO is more for a beam defined between two shear walls being in the same plane as the beam itself when you have bending moment transfer among all 3 of them. I'd be grateful for some education in this area 
Artur Kosakowski
I am not talking about a specific case, I'm talking in general as we know when computing the bending moment in any case using ACI code we use the clear span length and not the middle to middle length. Even in a full model why robot will calculate the moment using the middle to middle length if we dnt change it or assign rigid links ?? Robot is taking directly middle to middle span, so every time I want a correct design I should create a model with rigid links to get exact values as in the picture
Accepted solution
Hi @Anonymous
I don't think you are right and what is more this seems to entirely different issue than calculating moments as if the spans were shorter for simply supported beam (ql^2/8). Actually for concrete type supports the values for design of RC Beam reinforcement are taken from the faces of the supports so there is no need for using rigid links.
See the slide from the 4th RSA webinar
You can also see that on the bending moment diagram
Looking at your screen capture assumption is that you applied load to the beam elements for both model so the upper one has got 'more' of them. If you 'reduce' the load for the upper frame in the way I suggested in my previous post you should have also smaller value in the mid-span. Please mind that bar elements are dimensionless (sections are just the attributes). If you want to consider their sizes (exactly as they are) in the analysis you should model wide supports as walls (panels) or use offsets in the way shown below instead.
I hope this helps.
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Artur Kosakowski
Hi @Anonymous
Assuming that the supports are indeed wide I'd say that you may try to replace a multi span beam with number of single span ones with ('narrow') fixed supports.
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Artur Kosakowski
HI @Anonymous
One more 'workaround' for you 
If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.
Artur Kosakowski