jaabell

Nicolás Galano defends his MS Thesis

Wed, 09 Sep 2020 by jaabell / GroupNews

Congratulations Nico!

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Paper04 - Modelling the cyclic ratcheting of sands through memory-enhanced bounding surface plasticity.

Paper04 - Modelling the cyclic ratcheting of sands through memory-enhanced bounding surface plasticity.

Tue, 30 Jun 2020 by jaabell / Publications

This is the first paper fruit of the on-going collaboration with Federico Pisanò at TU Delft. Here we tackle the problem of formulating a constitutive model, derived from the SAniSand framework by Yannis Dafalias, which can replicate the ratcheting phenomenon on sands.

What is ratcheting?

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Large earthquake in Mexico triggers tsunami warnings

Tue, 23 Jun 2020 by jaabell / Earthquakes

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#EngineeringWizardry | 00 | new series

Fri, 12 Jun 2020 by jaabell / EngineeringWizardry

Stuck teaching during COVID-19 lockdowns in Chile has reminded me one crucial thing about statics (the class I'm teaching this first semester in the southern hemisphere): it can be very frustrating for students. This frustriation comes from unmet expectations. They're just finishing their early maths and physics formation (Calculus, Linear Algebra, Differential Equations, physics etc. ), an ideal world where problems have nice answers such as \(\sqrt{2} \pi\) or no answer at all. Then, along comes statics, and the world seems upside down.

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Using my gmshtranslator python tool to interface gmsh with opensees.

Using my gmshtranslator python tool to interface gmsh with opensees.

Mon, 26 Feb 2018 by jaabell / Tutorials

I wrote the gmshtranslator tool a while back during my …

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Paper03 - Earthquake Soil Structure Interaction of Nuclear Power Plants, differences in response to 3-D, 3 × 1-D, and 1-D excitations

Paper03 - Earthquake Soil Structure Interaction of Nuclear Power Plants, differences in response to 3-D, 3 × 1-D, and 1-D excitations

Tue, 20 Feb 2018 by jaabell / Publications

Summary: Finally! First paper since PhD was accepted for publication …

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Video of 2-D SSI model of an RC Shear Wall Building

Thu, 09 Nov 2017 by jaabell / ResearchHighlight

The RC shear-wall building is modeled in OpenSees using non-linear fiber based beam column elements. Soil is modeled as a continuum using quad elements and linear stress-strain relationship. Soil shear wave-speed is varied in depth such as to obtain a \(V_{s30}\) consistent with a class B site according to chilean seismic code. Lysmer-Kulhemeyer dashpots are used along the soil boundary to model seismic radiation and earthquake wave-field input.

The performance of the building will be assessed for varying site fundamental periods. This is an aspect of SSI that is not covered by the chilean seismic code, and has been shown to be a problem in past earthquakes.

This is part of an on-going study with Prof. Carolina Magna from Adolfo Ibañez Unversity and her MS student Miguel Ángel Rodriguez from UDP.

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New cable element in OpenSees

Thu, 07 Sep 2017 by jaabell / ResearchHighlight

With my student, Pablo Ibañez, we implemented a new catenary cable element in OpenSees. This element is based on the work by Salehi et al[1].

The stiffness of this element is obtained using a flexibility formulation. Basically the shape of the cable is determined by the integral:

$$ \newcommand{\pare}[1]{\left( #1 \right)} \newcommand{\brak}[1]{\left[ #1 \right]} \newcommand{\brac}[1]{\left\lbrace #1 \right\rbrace} \newcommand{\vect}[1]{\boldsymbol{#1}} \newcommand{\uv}[1]{\hat{\boldsymbol{#1}}} \newcommand{\ud}{\,\mathrm{d}} \begin{align*} \vect{x}(s) = \vect{x}_1 - \int_0^s \dfrac{\vect{w}s + \vect{f}}{\Vert \vect{w}s + \vect{f} \Vert^2}\pare{\dfrac{\Vert \vect{w}s + \vect{f} \Vert}{EA} + \pare{1 + \alpha \Delta T}} \ud s \\ \vect{w} = \brak{w_1,\, w_2,\, w_3}^T \qquad \vect{f} = \brak{f_1,\, f_2,\, f_3}^T \end{align*} $$

Where \(\vect{x_1}\) is the position of the first node of the cable, \(\vect{w}\) is the weight vector in each direction, \(EA\) is the stiffness, \(\alpha \Delta T\) is the change in strain due to temperature and \(\vect{f}\) is the force vector at the start node. This equation is iterated (with the forces as variable) upon until the the shape of the cable matches the nodal postiions imposed by the finite element program (trial displacements). Then it is used to derive a stiffness matrix.

The element, as is, passes all our static verification tests. With the additional assumption of a lumped-mass matrix, we're currently working on a dynamic verification suite as well as some validation experiments.

The animation above was created using OpenSees to simulate the cable and Blender to render it.

Reference

[1] Salehi Ahmad Abad, M., Shooshtari, A., Esmaeili, V., & Naghavi Riabi, A. (2013). Nonlinear analysis of cable structures under general loadings. Finite Elements in Analysis and Design, 73, 11–19. https://doi.org/10.1016/j.finel.2013.05.002

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OpenSees coming to python!

Sat, 14 Jan 2017 by jaabell / Blog

One of the gripes a lot of people have with …

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Finite Elements for Shallow Water Equations

Tue, 22 Nov 2016 by jaabell / Teaching

$$ \newcommand{\pare}[1]{\left( #1 \right)} \newcommand{\brak}[1]{\left …

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Talk Given at IngeoKring 2016 - Physics-Based Earthquake-Soil-Structure Interaction for Near-Field Induced Seismicity

Fri, 18 Nov 2016 by jaabell / ResearchHighlight

This is a talk given at the IngeoKring 2016 Autumn …

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NTS-02. On Rayleigh damping coefficients for FE analysis

Tue, 30 Sep 2014 by jaabell / ipython_notebooks

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Testing IPython Notebook integration into Pelican

Tue, 24 Jun 2014 by jaabell / ipython_notebooks

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SNE # 01. Example of ESSI simulation and visualization with visitESSI

Fri, 16 May 2014 by jaabell / Small Numerical Experiments

These are the results of a simple elastic-domain simulation. Mesh …

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NTS (Note-To-Self): Creating dynamically linked libraries

Mon, 28 Oct 2013 by jaabell / NTS

A nice extensive tutorial can be found here.

In a …

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SNE # 0. Stochastic inverse pendulum

Wed, 09 Oct 2013 by jaabell / Small Numerical Experiments

This is the first installment of "Small Numerical Experiments" (SNE …

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