Shear capacity

03-Analytical/modelling capabilities
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andrea.turchi
Posts: 2
Joined: 29 Jul 2021, 16:12

Shear capacity

Post by andrea.turchi »

Dear Seismobuild team,
After having carried out a pushover analysis of a building, I am comparing the values obtained by the Seismobuild software of a beam, with the calculations done by hand. In particular, as regards the shear capacity, following the formula (A.12) EC8 – PART 3. I would like to ask you how Seismobuild calculates these two quantities (I searched the manual but it doesn't mention them):
x: the compression zone depth
dx: the depth of inclined strut

Thank you in advance,
Andrea
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z.gronti
Posts: 681
Joined: 16 Oct 2013, 08:14

Re: Shear capacity

Post by z.gronti »

Dear andrea.turchi,

SeismoBuild uses fiber-section model. Hence, through sectional analysis we are able to know which fibers are under tension or compression.

You may export these values for all the calculations by exporting the Annex (analytical calculations) in your Report. All the information needed for the hand calculations are available in this Annex.
Zoi Gronti
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andrea.turchi
Posts: 2
Joined: 29 Jul 2021, 16:12

Re: Shear capacity

Post by andrea.turchi »

Dear SeismoBuild team,

I would like to ask you about the axial force generated in Shear Capacity checks in the beams. In particular, a very high value comes out; I understood that this is a fictitious force that comes out of the interaction between beam and slab and what I wanted to know is if there is a way to decrease it to real values. If I consider N = 0 the shear capacity goes down considerably. Also, does this axial force only affect capacity or does it also affect demand?

Secondly, I wanted to ask about the Shear Capacity formula (A.12) EC8 – PART 3. SeismoBuild replaces the quantity (h-x)/(2Lv) with dx/L: what is the reason for this?

Thank you very much for your time,
Andrea
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seismosoft
Posts: 1007
Joined: 06 Jul 2007, 04:55

Re: Shear capacity

Post by seismosoft »

1) Shear Capacity checks in the beams¨This is a known problem of all fibre-based frame models. In SeismoBuild and SeismoStruct, you can calculate the shear capacity of the beams without considering the fictitious axial force by unchecking the corresponding checkbox in Advanced Settings>ELements in SeismoBuild or in Project Settings>Elements in SeismoStruct.
2) Shear Capacity formula (A.12) EC8 – PART 3: Regaridng the axial force term of the shear capacity, we replaced the (h-x)/(2Lv) term because its contribution becomes extremely unstable with very small or very large values of Lv, i.e. in members when either Q or M is close to zero in one of its edges (which is not rare at all). Note that the approach that we followed is whe accepted by the academic community (e.g. see Seismic shear strength of reinforced concrete columns. MJN Priestley, R Verma, Y Xiao - Journal of structural engineering, 1994) and that the two approaches are theoretically equivalent.
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