End Release in Secondary Beam | Release of Partial Fixity of Secondary Beam | End BM Release in SB
End release does not mean that the Bending moment that we are releasing will goo out of the structure, instead it will be redistributed from the End to the Center of the beam.
Lets take an example of Fixed End Beam and Simply Supported beam of length L with uniformly distributed load W over it. Both the beam will respond in different way but ultimately the load they carry is. WL.
In case of Fixed Support, BM at mid is WL2/24 and at the support it will be WL2/12 and in case of SSB, there will be no BM at support but at mid span it is WL2/8. From this we can clearly understand that if we release the rotation of the fixed support, the moment a the end will shift towards the center and it will behave like SSB. This simple concept of moment redistribution will be applicable in End release case.
When sufficient length is not available there for development length, it will not be able to quality as a fixed connection. In order to model the actual behavior, we should release the end moment.
BM from secondary beam could cause the torsion in main beam, to avoid this effect designer could intentionally release end moment even if there will be space for development length.
Sometimes the purpose is to avoid the congestion of reinforcement in the primary beam at the intersection of the secondary beam.
Ends are not restricted against rotation, moment will not be able to transfer towards the support. In order to idealize this effect on the beam, we need end release.