Issue with Steel Beam to Column Offsets

[ByrnePM]

I have a one story steel frame braced structure

I am applying offsets to the simply supported beams that are connected to the flanges of the supporting columns so I can achieve the moment on the column from the eccentric connection 

I am applying the offsets to the ends of the beams using relative shortening 

Having done this for all simply supported beams I then check the exact deflection for the bars and thisis where the problem starts

I get a huge lateral deflection at one end of the structure 

I have deleted all of the offsets adjacent to this end of the structure and then tried applying the offsets one by one to the beams and running the analysis and checking the exact deflection each time

By doing this I have managed to single out one beam that seems to trigger the huge lateral deflections but I cannot figure out why 

I have checked releases at this beam location and everything seems fine

Has anyone any ideas?

I have attached an image of the location of this offending beam before i have applied the offset

[ByrnePM]

Investigating further I think that the issue lies with the fact that the other end of this offecnding beam is a beam to beam connection ?

This is leading to large lateral displacements in the direction of the beam 

[Rafacascudo]

Can you send the model?

[ByrnePM]

Hi Rafacascudo ,

I have attached a link to model below

http://we.tl/gKWuGdctQ7

Thanks

[napooil]

I try to change support to fix.

[ByrnePM]

Napooil,

Thanks, this could be a solution yes, however I am more interseted into why this strange lateral deflection occurs when the foundations are moddelled as pinned (as they will be built).

I dont see any reason as to why the pinned foundations allow this large deflection to occur as a result of the offsets

[Rafacascudo]

If you delete the all the bar offsets you will get similar nodal displacements or even higher !!

I don´t think this is caused by the offsets.

You don´t have enough bracings on the Y  and X directions .

I added some intermediary bracings( same sections as the already existent)

For load case 4 the difference is huge . from 24010 mm to 1000mm

[ByrnePM]

You're exactly correct ....what has happened is that I have imported this model from fastrak designer where the floor beams were designed as composite.

However, Ive deleted the the composite slabs before exporting to ROBOT to perform the 3D building design 

This means I have no horizontal floor bracing (slab or in-plane steel bracing) to transfer the lateral loads to my vertical braced bays 

I am going to introduce a slab to the floor plate to act as a diaphragm and transfer lateral loading to the vertical bays

This should hopefully get rid of the large deflections and the offset issues 

Thanks

[Max-88]

The structure does not have enough restraints and behaves like a mechanism.

I have isolated a frame on X direction and it looks like all connections are pinned which means it is an unstable structure.

If you delete all releases the structure is fine.