Vertical response spectra 5

[RK Sriwastav]

How important is the vertical response spectra in the design of structures? What are the various international provisions for vertical spectra? How can we obtain vertical spectra from horizontal spectra?

Can Anybody suggest me latest papers on this?

Thank you.

Ravi K

 

[KevinNZ]

The New Zealand code (NZS 1170.5) recently increased the vertical actions after looking what happened in the Christchurch quake.

http://www.nzsee.org.nz/db/2013/Poster_2.pdf

 

[AWDMIKE]

There are provisions for establishing a vertical elastic response spectrum in EN 1998-1.

Also I know that the Mexican code (MDOC-CFE) has similar provisions. If I recall the two are not identical. When I was working on a project that used the MDOC-CFE I recall finding several references to a New Zealand code (as mentioned above).

I'll attach one paper I can share. I'm sure I can't share EN 1998-1 and I'm unsure about the MDOC CFE (for which I think 2008 was the most recent version).

 

[JasonMcKee71]

some codes recommend to take the vertical spectrum equal to the horizontal one, reduced by 30% and consider a behaviour factor not greater than 1.5.

Jason McKee
proud R&D Manager of
Cross Section Analysis & Design
Software for the structural design of cross sections
Moment Curvature Analysis
Interaction Diagrams
Reinforcement Design etc.

 

[wannabeSE]

In the USA with ASCE 7, there are vertical seismic forces, but I don't know if they can be called a "response spectra" because they don't vary by building period. The vertical acceleration is 20% of the short period design acceleration, S[sub]DS[/sub]. The S[sub]DS[/sub] varies by location and soil conditions. But the building response doesn't change it.


The verical forces are in the sesimic load combinations and scale the dead load. For LRFD combinations it is (1.2 + 0.2S[sub]DS[/sub][sub][/sub])D . . . and (0.9 - 0.2 S[sub]DS[/sub])D . . .

 

[RK Sriwastav]

@JasonMcKee7,

Can you tell me which codes talks about behaviour factor less then 1.5 for vertical spectra ?

Ravi K

 

[JasonMcKee71]

Eurocode EN1998

Jason McKee
proud R&D Manager of
Cross Section Analysis & Design
Software for the structural design of cross sections
Moment Curvature Analysis
Interaction Diagrams
Reinforcement Design etc.

 

[KevinNZ]

NZS 1170.5 vertical spectra does vary with soil type and structure period.

 

[RK Sriwastav]

Thank KevinNZ for this essential post.

Ravi K

 

[wannabeSE]

I just noticed that ASCE 7-16 has provisions for a vertical response spectrum. (Just paging through looking for something else. I haven't worked on anything with the new code). It appears to be optional and is the same as FEMA P-1050 Chapter 23A with background in the commentary.

https://www.fema.gov/media-library/assets/documents/107646

I have never paid attention to a buildings vertical period except to note that is very small. Has anyone seen any method to calculate a buildings approximate vertical period.