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Assalam o alaikum, i m confused whether collectors and chords are only required in Flat plates/slabs or also required in beam slabs? because in beam slab we are having beams at perimeter of every panel and they can act as chords and for diaphragm bending and as collectors at junction of slab to shear wall. Usually, in seismic zone 4, i dont design diaphragm exclusively. i just design it as simple slab and design my beams in SMRF or Dual Frame in etabs. Also i m confused in excerpt from a document stating The Special Seismic Load combination is also indirectly identified in Chapter 18, Section 1809, Foundation Construction – Seismic Zones 3 and 4. 1809.3 Superstructure-to-Foundation Connection. The connection of superstructure elements to the foundation shall be adequate to transmit to the foundation the forces for which the elements were required to be designed. For instance, since Section 2213.5 Column Requirements specifically identifies the Ω0 factor, Section 1809.3 requires the column-to-foundation connection to be designed for a load combination which includes the Ω0 factor. What does it mean? In seismic zone 3 or 4, we need to design foundations for special seismic combos ALWAYS or only if we r having discontinuous system? The full document is also attached. Thanks. OmegaFactorDiscussion.pdf

Assalam o alaikum.. My building is in zone 3 and it has a 2 inch expansion joint in it... So my building is divided into two blocks. Now I m worried when my structure will go under seismic excitation, Whether both blocks of structure will behave exactly same and will have same frequency of vibrations or will both of them can move towards each other causing collision.. Maximum story displacement for my structure is 0.81 inch. and I have assigned it value of R as 8.5. So maximum inelastic response displacement will be 0.7 x 8.5 x 0.81 = 4.82 inch. which is more than expansion joint. Both of blocks are NOT SYMMETRICAL. So both may not be having same stiffness.