Existing stair seating seimic gap - Technical Issues

RE: Existing stair seating seimic gap

Khaled Eid — Tue, 26 Mar 2024 00:43:38 +0000

Thank you Nick for your response and clarification

RE: Existing stair seating seimic gap

Nic Brooke — Thu, 21 Mar 2024 23:27:27 +0000

Hi Khaled - thanks for the clarification. The SESOC website clearly identifies that versions 9 and 10 of the Interim Guidance are superceded, as shown at SESOC Interim Design Guidance Design of Conventional Structural Systems – SESOC.

The older versions are left online as a resource for situations where people are trying to understand design decisions made for older structures.

RE: Existing stair seating seimic gap

Khaled Eid — Thu, 21 Mar 2024 21:14:40 +0000

It was from Version No. 9 – 26 March 2013, which I downloaded from the SESOC website.

There is nothing to indicate it has been updated, but it appears to be a draft. I checked the revised copy, which is the SESOC guideline 0.9 from September 2019, and it shows 1.5/Sp but is marked with a strikethrough. saying **content below now superseded by Verification Methods**

~~SESOC Design panel joints to accommodate 1.5/Sp times the ULS~~
~~Recommendation: displacements.~~
It worth mentioning that MBIE Practice Advisory 13: Egress stairs – provides the 2 * ULS drift

Clearances and seatings for stairs should be capable of sustaining at least twice the Ultimate Limit State (ULS) inter-storey displacements (drift) as calculated in accordance with NZS 1170.5.

It is mainly to design a steel ledge support in an existing building

RE: Existing stair seating seimic gap

Nic Brooke — Thu, 21 Mar 2024 02:33:05 +0000

Assuming you are referring to the SESOC Interim Design Guidance - which version are you using? I don't think the current version contradicts C10, or NZS 1170.5A1 which is the basis for C10.

That aside - it should be noted that the SESOC Interim Design Guidance is intended for design, not assessment. While some parts of the guidance may be relevant to assessment, many parts would be overly conservative for assessment purposes.

Existing stair seating seimic gap

Khaled Eid — Wed, 20 Mar 2024 23:11:47 +0000

There is a conflict between the ESOC guide, it is recommended to design sliding joints for 1.5 times the ULS displacements. However, in the C10 guideline, the assessment is based on deformation uses 2/𝑆p?

In both cases, the assessment of the seismic gap will come up with a high value that for a draft of 1.5% will require say 45mm*1.5 which is 70mm gap would not that seem practically too large?