After perfoming analysis in Staad pro C.E, we are designing beams in RCDC,after importing the analysis file in RCDC the software will decide which beams will be secondary and which beams will be primary beams.
Before designing is it necessary to adjust the supporting conditions in continum and respecify the secondary and primary beams or the one assigned by the software itself will give the correct design?
The fixity condition of the secondary beams are to be considered in the STAAD.Pro CE modelling itself. You need to use appropriate release condition in the STAAD.Pro CE model. RCDC will read proper analysis result from STAAD.Pro CE.
Which release specification is used to specify that? may you help me with that procedure
In RCC secondary beams moments are released at the location where it is connected with primary beams.
Which moments are released?My and Mz or Mx and My?
What about if i have two secondary beams meeting at a point?
HiRCDC is a design software. it reads the geometry and design forces from analysis file. it doesn't change the forces fetched from the analysis.
RCDC has capability to identify the beam type as Primary, secondary. The primary beam are identified if the beam is resting at columns at bond ends. for secondary, beam should be supported at-least on one end of column or both end supported in beams.The Primary beams are considered for ductile design if user has selected as ductile design. Secondary beams are not considered as ductile as it doesn't contribute in lateral frame design.When any beam is identified as Secondary based in geometry, moments are kept same as available from analysis. Please note that the reinforcement in beams are provided based on available bending moments from analysis. if user has released Mz in analysis to treat as secondary beam, RCDC will only provide nominal reinforcement as per code requirements. if user doesn't want to release Mz in analysis for that secondary beam, its a user decision. RCDC will provide the reinforcement which is available from analysis at that end. Also, user can change the beam type in RCDC. But please note that changing the type of beam in RCDC doesn't change the forces available from analysis. example : if one beam is identified as Primary based on geometry and user wants it to be designed as secondary , then it will be design for available forces at ends and mid zone. As user has selected that as a secondary beams, ductile design and detailing clauses from design code will not be applicable to that beam
Answer Verified By: Abhijeet Gundaye
One more question,if i dont release moments in secondary beams,what will be the effect in primary and secondary beams,will they be overdesigned or underdesigned?
Higenerally, if you don't release the secondary beams and slab is not modelled at floor level, the primary beam which is supporting beam experienced torsion.if there is a slab at floor level which is acting as a diaphragm , then generally it resist primary beam to twist. In this case if slab exists at floor level but not modelled, user can release the end of secondary beams to design as simply supported as there is a lateral support to primary beam which resist it to twist.designing beam for torsion will give more reinforcement as per code requirements. it varies as per code.finally, it is a engineers choice to release of not-release the top moment of secondary beams based on his judgement and project requirements.
Ok and for the case where two beams cross each other and they are both not supported on column,how does RCDC consider that?
for cross beams, It will identified one of the beam as primary beam. Generally the beam having more depth is identified as primary and other beams as secondary.user can change the primary beam to secondary beam if required using Beam continuum tool.