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[pvspk132]

This is regarding few clarifications and suggestions on code clarifications.

1. IS16700:2023 (Sep 2023 Issued) have relaxed to use time period as per mode shapes having max. Time period as per 6.3.4 for evaluating Seismic forces. Does this clause overrides/supercedes Fundamental time period calculation defined in IS 1893:2016???I am raising this query as during working, when we evaluated for a building of 60m we are obtaining 60-70% reduction from this new formulae.

2. IS 1893:2016 talks about Structural wall system where Frames are not participating or not fulfilling dual system requirements. For a case where we have Frame only in one direction and other direction only peripheral beam, making complete one-way slab system, We can use R=4 for ductile wall system ??  Or as there is no frame, we shall use Flat slab /Plate approach for one direction ???

3. height of building convention as per IS16700 shall be considered till last connected height. But this includes mumpty or Raised portion of 15-25% of plan area of building . I.e only 25% of plan area is being raised for 7-10m, Does this needs to be considered in evaluating height of building in evaluating timeperiods ???

Please guide me over the above understanding which will be very much helpful.

[alpa_sheth]

Hi,


1. Please refer to Clause 1.6 of IS 16700-2023 and Clause 6.3.4 first sentence. Together they will answer your query 1. I am assuming your structure is >50 m height else you cannot use the equations of 6.3.4


2. You are at liberty to use a different R in the two different orthogonal directions, based on your Lateral load resisting system  in each of the directions. I am sure you are aware that you cannot use a Flat slab/ flat plate as a Lateral Load resisting system. You may want to ensure that you have sufficient structural walls in both the directions as a building > 50 m height will not work without structural walls and just a perimeter frame or a moment frame alone in any direction may not work.  Do take a look at Table 1 of IS 16700-2023 and check for conformance


Best regards,


Alpa Sheth


1. IS16700:2023 (Sep 2023 Issued) have relaxed to use time period as per mode shapes having max. Time period as per 6.3.4 for evaluating Seismic forces. Does this clause overrides/supercedes Fundamental time period calculation defined in IS 1893:2016???I am raising this query as during working, when we evaluated for a building of 60m we are obtaining 60-70% reduction from this new formulae.

2. IS 1893:2016 talks about Structural wall system where Frames are not participating or not fulfilling dual system requirements. For a case where we have Frame only in one direction and other direction only peripheral beam, making complete one-way slab system, We can use R=4 for ductile wall system ??  Or as there is no frame, we shall use Flat slab /Plate approach for one direction ???

3. height of building convention as per IS16700 shall be considered till last connected height. But this includes mumpty or Raised portion of 15-25% of plan area of building . I.e only 25% of plan area is being raised for 7-10m, Does this needs to be considered in evaluating height of building in evaluating timeperiods ???

Please guide me over the above understanding which will be very much helpful.[/quote]