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Excellent answer by @Badar (BAZ) like always. I will add to the last item posted that you can do quick plate analysis and get max moments. If you choose to proceed this way, after get your analysis results, please add you Mx and Mxy together and design the slab for this total moment. Thanks.

My name is Badar. You are addressing me with the wrong name. It seems that you are not able to realize that the eccentric nature of connection between cast-in-place beam and pre-cast hollow core slab will transfer torsion in addition to the UDL in the beam. It is better, in this case, to design the beam for the torsion due to eccentric transfer to shear between slab-beam interface. Do not use 0.35 modifier for torsional constant. The practice of using a modifier <1 for torsional constant is for monolithic construction involving combability torsion, which is due to the transfer of negative moment from slab end to the supporting beam (you do not have these moments because of your connection detail).

This approach will give you the same behavior as membrane. I am not sure about your intent. The UDL is not the only effect of connection that you intend to use. Let me explain it this way: The beams supporting the ends of one-way ribs of hollow-core floor system will need to be loaded with the line load and torsion. See the attachment.

Manual calculations can be done by using one of the various moment coefficients methods, which are based on elastic thin plate theory. You can consult following references which gives moment coefficients for various end conditions of plate: 1) Moments and reactions for rectangular plates-Engineering Monograph 27. Here is the link: https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/EM/EM27.pdf 2) Rectangular concrete tanks, 5th Edition by Javed Munshi 3) Reinforced Concrete Designers Handbook_11th Edition by Reynolds & Steedman Needless to say that you can also use software.

Assalam O Alykum Small question The hollow core slabs are defined as a membrane or shell element ( In the direction of hollow core panels) As a hollow core slabs are rests by bearing on the beams with grout and screed on the top with no composite action between beams and hollow core slab. Thank you

How to design this type of flat slab? It does not fulfil the DDM criteria. First image is UGWT top slab and second one is OHWT top slab

I do not have enough information about your framing to comment on that. Generally speaking, this assignment, in most cases, has a limited effect on elements of Vertical Lateral load resisting system. When Structural Engineers intend to check forces in chord members of diaphragm, for the purpose of estimating its suitability to transfer lateral forces to vertical elements, they use this semi-rigid option. The rigid-option does not let you check these diaphragm forces. The assignment also depends on your structural system. CSi has a simple video on it. You cannot assign membrane behavior to column. You can assign membrane behavior to shear walls. It is reasonable simplification for a majority of design scenarios.

Thank you Badar for your continuous support. You are right I am unable to realize How much will be the torsional constant shall I consider design the beams. apologies if you advice about the below as well Diaphragm I applied as a semi rigid. Building components such as columns , shear walls will be designed based on the membrane as well or can say shell with stiffness modifier 0.01? shall I say like that

Yes, membrane assignment will do the job assuming that you are only concerned abut estimation of demands on the frame elements and not the hollow-core slab itself. With your shear connection detail between beam and slab in the form of rebar-dowels, it would be wrong to model the slab with flexural stiffness (shell) , as it would lead to an underestimation of flexural demands on beams.

This structural element has shear, flexural and axial stiffness. It is not a membrane. Having said that, you can model it as membrane; You need to decide about the modelling approach based on your design assumptions for supporting members and structural system as whole.

Assalamo alaikum! Good quality seismic hazard maps of BCP-2021 and Tabulated values of Short-period Spectral Acceleration Ss & Long-period Spectral Acceleration S1 etc. for major cities of Pakistan, are available at this Link. Regards.

Salam, You can make an envelope for load combinations, and check the forces corresponding to the enveloped combination. in this way you will be able to check against the governing load combination. hope it helps!

You can use default design combinations in ETABS, but make sure you design preferences are accurate before using default design combos. For Loads on structures kindly watch this: https://www.linkedin.com/posts/mqasimnawaz_structural-concrete-design-activity-6905953661353357312-8R9q

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