Hi,
How can I use SeismoStruct to carry out a moment-curvature analysis?
I have tried using a simple cantilever model subjected to a tip transverse load, but obtained inconsistent moment-curvature results. Am I doing something wrong?
Many thanks.
Moment-curvature analysis
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seismosoft
- Posts: 1316
- Joined: 06 Jul 2007, 04:55
Re: Moment-curvature analysis
Hi,
As described in the Help System ('Material Inelasticity' section) if one uses elements with 2-3 integration points, then the end integration sections will not coincide with the extremities of the element, and hence one will obtain curvature values that are not in correspondence with the moments (computed at the element extremities) - interpolation/extrapolation will be needed.
A good way in which to obtain moment-curvature relationships through analysis of fibre elements is perhaps to run a 'pushover analysis' on a two-elements beam restrained using a pin at the first end and a pin-on-a-roller at the other end, subjected to incremental end rotations. This will allow to read both moment and curvature values without a need to interpolate/extrapolate results since the moment is constant along the beam (unlike when a transverse load is imposed on a cantilever).
One may read the curvature values at one of the integration sections close to mid-span and the moment values at the central node - this is important, since at mid-span the tangent to the deformed shape is horizontal, hence parallel to the direction of the external force used to represent the axial load, thus reducing the effects of axial load-moment interaction present in large displacement analysis.
Seismosoft Support
As described in the Help System ('Material Inelasticity' section) if one uses elements with 2-3 integration points, then the end integration sections will not coincide with the extremities of the element, and hence one will obtain curvature values that are not in correspondence with the moments (computed at the element extremities) - interpolation/extrapolation will be needed.
A good way in which to obtain moment-curvature relationships through analysis of fibre elements is perhaps to run a 'pushover analysis' on a two-elements beam restrained using a pin at the first end and a pin-on-a-roller at the other end, subjected to incremental end rotations. This will allow to read both moment and curvature values without a need to interpolate/extrapolate results since the moment is constant along the beam (unlike when a transverse load is imposed on a cantilever).
One may read the curvature values at one of the integration sections close to mid-span and the moment values at the central node - this is important, since at mid-span the tangent to the deformed shape is horizontal, hence parallel to the direction of the external force used to represent the axial load, thus reducing the effects of axial load-moment interaction present in large displacement analysis.
Seismosoft Support
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civil_neri
- Posts: 3
- Joined: 01 Mar 2013, 11:50
Re: Moment-curvature analysis
good morning
I need to evaluate the moment-curvature diagram in some columns in a non regular building subject to an earthquake with a specific time history, and not for a push-over analysis. how can i do?
Can you suggest me some paper about this topic?
Best regards
Giammarco Neri.
I need to evaluate the moment-curvature diagram in some columns in a non regular building subject to an earthquake with a specific time history, and not for a push-over analysis. how can i do?
Can you suggest me some paper about this topic?
Best regards
Giammarco Neri.
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seismosoft
- Posts: 1316
- Joined: 06 Jul 2007, 04:55
Re: Moment-curvature analysis
Why don't you simply output and read the columns' strain-stress values at each time-step of your dynamic analysis?
Seismosoft Support
Seismosoft Support
Re: Moment-curvature analysis
quote:Originally posted by seismosoft
Hi,
As described in the Help System ('Material Inelasticity' section) if one uses elements with 2-3 integration points, then the end integration sections will not coincide with the extremities of the element, and hence one will obtain curvature values that are not in correspondence with the moments (computed at the element extremities) - interpolation/extrapolation will be needed.
A good way in which to obtain moment-curvature relationships through analysis of fibre elements is perhaps to run a 'pushover analysis' on a two-elements beam restrained using a pin at the first end and a pin-on-a-roller at the other end, subjected to incremental end rotations. This will allow to read both moment and curvature values without a need to interpolate/extrapolate results since the moment is constant along the beam (unlike when a transverse load is imposed on a cantilever).
One may read the curvature values at one of the integration sections close to mid-span and the moment values at the central node - this is important, since at mid-span the tangent to the deformed shape is horizontal, hence parallel to the direction of the external force used to represent the axial load, thus reducing the effects of axial load-moment interaction present in large displacement analysis.
Seismosoft Support
If element is modeled using five integration sections, then the end integration sections have coordinates -L/2, L/2. In 'Element action effects'' module, moments at sections A, B are provided. Section A (B) coincides with integration section 1 (5), isn't it? Same thing with 3 integration sections (-L/2, 0, L/2)...
Hi,
As described in the Help System ('Material Inelasticity' section) if one uses elements with 2-3 integration points, then the end integration sections will not coincide with the extremities of the element, and hence one will obtain curvature values that are not in correspondence with the moments (computed at the element extremities) - interpolation/extrapolation will be needed.
A good way in which to obtain moment-curvature relationships through analysis of fibre elements is perhaps to run a 'pushover analysis' on a two-elements beam restrained using a pin at the first end and a pin-on-a-roller at the other end, subjected to incremental end rotations. This will allow to read both moment and curvature values without a need to interpolate/extrapolate results since the moment is constant along the beam (unlike when a transverse load is imposed on a cantilever).
One may read the curvature values at one of the integration sections close to mid-span and the moment values at the central node - this is important, since at mid-span the tangent to the deformed shape is horizontal, hence parallel to the direction of the external force used to represent the axial load, thus reducing the effects of axial load-moment interaction present in large displacement analysis.
Seismosoft Support
If element is modeled using five integration sections, then the end integration sections have coordinates -L/2, L/2. In 'Element action effects'' module, moments at sections A, B are provided. Section A (B) coincides with integration section 1 (5), isn't it? Same thing with 3 integration sections (-L/2, 0, L/2)...
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seismosoft
- Posts: 1316
- Joined: 06 Jul 2007, 04:55
Re: Moment-curvature analysis
Correct, from v6 onwards, infrm elements with 3 integration sections feature integration sections at their end points (as was happening already when more than 3 integrations sections were employed).
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Seismosoft Support