Rigid diaphragm in the drawing of each floor
In CYPECAD, the requirements analysis is carried out via a spatial analysis in 3D, using matrix methods for stiffness, that forms all the elements defining the structure: columns, RC shear walls, walls, beams and floor slabs.
The compatibility of deformations in all the nodes is established, considering 6 degrees of freedom, and the hypothesis of non-deformability for the drawing of each floor is created in order to simulate the rigid behaviour of the floor slab, preventing relative displacements between nodes of the same rigid diaphragm. Therefore, each floor can only be rotated and displaced as a whole (3 degrees of freedom).
In CYPECAD versions prior to 2012.a, the rigid diaphragm consideration for each independent zone of a floor is maintained even if beams and walls, but not floor slabs, are introduced into the floor.
As of version 2012.a, CYPECAD allows beams that are not in contact with floor slabs to be disconnected from the rigid diaphragm, and automatically eliminates the assumption of rigid diaphragm at floor level in walls that are not in contact with any floor slab.
In any version of the program, when there are independent zones on the same floor, each of these shall be considered as a different part with respect to the non-deformability of that zone and shall not be taken into account as a whole. Therefore, the floors shall act as independent non-deformable planes. A non-connected column is considered as an independent zone.
Rigid diaphragm in unconnected beams
As of version 2012.a, it is now possible to eliminate the consideration of the rigid diaphragm in unconnected beams, i.e. beams that are introduced in the floor plan from the types in the Current beam dialogue box that are not touching any panel (except for the External fixity and Non-structural beam or limit beam types).
By default, all beams are considered to be “connected” to the rigid diaphragm and therefore have three degrees of freedom, and the rigid diaphragm hypothesis is maintained. For example, a continuous beam supported by several columns, even if it has no floor slab, will still retain the rigid diaphragm hypothesis.
As of version 2012.a, users can now disconnect the beams not connected to the rigid diaphragm by means of the Rigid diaphragm in unconnected beams (Beam definition tab > Beams/Walls menu). The beams that are disconnected using this option now have six degrees of freedom at each end with the corresponding forces: axial, moment in the vertical and transverse plane, vertical and transverse shear, and torsional moment; and, therefore, the reinforcement will be designed for all of them.
For the purpose of considering the buckling of horizontal, steel or concrete unconnected beams, the buckling length is considered to be the clear length of the beam in both the vertical and horizontal planes.
Rigid diaphragm in reinforced concrete walls, masonry walls and reinforced concrete block walls
In versions prior to 2012.a, any wall in contact with a floor slab, beam or another wall was considered to be a rigid diaphragm at floor level. As of version 2012.a, the consideration of rigid diaphragm at floor level is only maintained if the wall is in contact with a floor slab. Therefore, if the wall is unconnected at floor level or only comes into contact with unconnected beams or other walls, every node of the bar that is generated at the intersection of that floor, and the nodes in the triangular finite elements of the wall will have 6 degrees of freedom.
If the wall comes into contact with any panel along any part of its layout on a floor, the entire wall will be connected to the rigid diaphragm of that floor, even in the spans where there are no panels. However, users can partially eliminate the consideration of rigid diaphragm by means of the Divide beam option (Beam definition tab > Beams/ Walls menu), so that applying this division at the transition points between the part with rigid diaphragm and the unconnected part, will leave the latter free or unconnected with 6 degrees of freedom in those exempt sections.
If the option for reinforcing wall crown beams is activated (Project menu > General data > By position button for Steel in Bars > Beam options button > Beam reinforcement within walls and crown beams option), the top beams that are located on the wall sections without floor slabs (if the user has applied the Divide beam option to disconnect this span), or the top beams of the walls without floor slabs along their entire length, are designed for the six acting forces.
The design of the beams that coincide with the intermediate floors and crowning in masonry and precast concrete block walls is carried out in the same way if this option is activated for these typologies, although it is also carried out at the intermediate floor level.
