Fixed But Support

For releasing moments at supports, you do NOT need to define KMX, KMY or KMZ. To do that you simply need to check the appropriate boxes on the left under the Release. For example to define a pinned support but which is restrained from rotation about the global vertical axis (Y), you need check the boxes for MX and MZ.

You only need to specify KMX, KMY or KMZ when you want to define rotational springs. The unit is in kN-m/deg because the value you are expected to provide here is the value of moment ( in kN-m units ) that would cause a one degree rotation at the support.

Hi Sye, 

What I need is to reduce the amount of fixity in the fixed support in order to activate the extension of the beam and the back support. 

In case it was totally fixed , the back side of the beam will almost have a utilization factor of 0.00015 , when I added KMX= 300 kn.m-deg it gave a utilization factor of 0.3 .

So my aim is to allow to transfer moment to the back support. is the addition of spring release appropriate ?

attached latest model. 

One more thing, for the bracings I added a partial release of moments = 99% due to the warnings I received when marking complete release. 

Is the procedure followed correct . 

Thanks 

5661.Cantilever 2019 - Copy.std

If you have an idea of the rotational stiffness offered by the support you may use KMX. If you are using a trial value then you may as well consider using a PINNED support at these locations. Defining partial release is not a problem provided the connections at the end can take up any resulting moments that may be generated. I did not see any warnings without the releases when I run the file in the latest STAAD.Pro CE (22.01.00.39).

You may want to add the LOAD LIST 4 TO 11 command before the design to ensure that design is carried out for the load combinations only. A modified file is attached for your reference 5661.Cantilever 2019 - Copy_rev.std 

5661.Cantilever 2019 - Copy_reviyad.std

I meant when I release the moments and Fy on the bracings i get the following warnings 

attached file and warnings screen shot

Moreover, 

I need to keep the supports as fixed , due to the excessive deflection in the cantilever im trying to minimize  . The change from fixed with a trial KMX value to a pinned support resulted in an additional deflection in the last portion of the cantilever of about 3-5 mm . 

Moreover, 

I need to keep the supports as fixed , due to the excessive deflection in the cantilever im trying to minimize  . The change from fixed with a trial KMX value to a pinned support resulted in an additional deflection in the last portion of the cantilever of about 3-5 mm . 

3 - 5 mm deflection does not seem high unless the structure is really sensitive to deflection. Anyway you may use KMX but ensure that what you are using is realistic.  

the structure is sensitive indeed , where can i get more info about kmx and rotational stiffness to ensure my numbers are reasonable ?

This is an engineer's call. If you are unsure talk to other engineers involved in the project.