LS-DYNA Masonry Wall Model Deformed Shape
Seyhan Okuyan
l...@schwer.net
It is difficult to say that the only suspect problem in your model is the material model.
A non-softening, in uniaxial compression, concrete model you can try is MAT085 *MAT_WINFRITH_CONCRETE
Have you tried just elastic material so see if your tiebreak model works to fail your contacts?
--len
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James Kennedy
Dear Seyhan,
A note previously shared by Len Schwer:
Any of the LS-DYNA concrete models can be used to model both masonry blocks and mortar.
Assuming you do not have much material characterization data, I suggest trying one, or better more than one,
of the “simple input” concrete model: MAT016, MAT072R3, MAT084, MAT159, MAT272 and MAT273.
These models only require the unconfined compressive strength of the material. –len
Schwer, L.E., "Simple Input Concrete Constitutive Models: An Illustration of Brick Walls & Concrete
Cylinder Perforation", 10th International LS-DYNA Users Conference, Dearborn, Michigan, June, 2008.
http://www.dynalook.com/international-conf-2008/PenetrationBlast-4.pdf/
This introductory document described the basic plasticity model, the strain rate formulations and
tensile cracking options for the *MAT_084 model, another of the so called LS-DYNA ‘simple input’
concrete models:
Schwer, L.E., "The Winfrith Concrete Model: Beauty or Beast? - Insights into the Winfrith Concrete
Model", 8th European LS-DYNA Users Conference, Strasbourg, France, May, 2011.
http://www.dynamore.de/de/download/papers/konferenz11/papers/session12-paper2.pdf
The dynamic analysis code LS-DYNA provides a variety of constitutive models for concrete. The first
problem is how to select a proper constitutive model besides the related parameters. The theoretical back-
grounds of five simple input concrete models, namely, *MAT_016 (Pseudo Tensor), *MAT_072R3 (K&C),
*MAT_084 (Winfrith), *MAT_159 (CSCM) and *MAT_272 (RHT), were reviewed. The basic performances
of the five models in capturing the key concrete behaviors, such as axial tension and compression, triaxial
isotropic tension and compression, and triaxial shear, were examined through single element simulation:
Xiong, Y.-B., "Applicability Analysis of Simple Input Concrete Models in LS-DYNA", Acto Armamentarii,
Vol. 34, pp. 351-357. January, 2013.
The National Science Foundation (NSF) funded a study by the University of Missouri Kansas City
(UMKC) to perform a batch of blast resistance tests on reinforced concrete slabs (PI: Ganesh Thiagarajan).
Based on these results, a Blast Blind Simulation Contest was sponsored in collaboration with American
Concrete Institute (ACI) and UMKC School of Computing and Engineering. The goal of the contest was to
predict, using simulation methods, the response of reinforced concrete slabs subjected to blast loads.
*MAT_016, *MAT_072R3, *MAT_085, *MAT_159, *MAT_272, and *MAT_273 were the LS-DYNA
concrete material laws employed by the author in his investigation (other organizations participated in this
contest):
Schwer, L., "Blind Blast Simulation - Simple Input Concrete Modeling", 13th German LS-DYNA Forum,
Bamberg, Germany, October, 2014.
Numerous roadside safety systems are configured with reinforced concrete materials, such as bridge railings,
median barriers, and roadside parapets. The analysis and design of these structures may involve impact
simulation with finite element software, like LS-DYNA, which includes multiple concrete material models.
This Phase I study investigated the viability and performance of existing concrete material models to
simulate unreinforced components subjected to common loading conditions, such as compression, tension,
shear, and bending. For this study, five material models were evaluated – CSCM (*MAT_159), K&C
(*MAT_072R3), RHT (*MAT_272), Winfrith (*MAT_084), and CDPM (*MAT_273):
Winkelbauer, B.J., "Phase I Evaluation of Selected Concrete Material in LS-DYNA", Master’s Thesis,,
Department of Civil Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, December, 2015.
https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1087&context=civilengdiss
Winkelbauer, B.J., Faller, R.K., Bielenberg, R.W., Rosenbaugh, S.K., Reid, J.D., and Schmidt, J.D.,
"Phase I Evaluation of Selected Concrete Material in LS-DYNA", MwRSF Research Report No.
TRP-03-330-15, Midwest Roadside Safety Facility, University of Nebraska-Lincoln, Lincoln, Nebraska,
April, 2016.
http://nlcs1.nlc.state.ne.us/epubs/R6000/B016.0330-2016.pdf
Sincerely,
James M. Kennedy
KBS2 Inc.
September 28, 2023
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James Kennedy
A note shared by Bogdan Sakic,
have also been modelling masonry in LS DYNA for the last few years, so maybe I can give you some tips. As previously mentioned, all the above mentioned concrete material models can be used to represent masonry. It also depends which masonry you are modelling (clay, AAC etc), as orthotropy can have significant or less significant influence. My experience is that if you are modelling AAC bricks, you can use mat 96, as it represents a brittle material model, in which failure in tension is triggered once the 1 principal stress exceeds the tensile strength of the material. Comparison of the experimental and numerical results in my previous work led me to the fact that mainly AAC brick failure can be represented by such a material model and that the decoupled failure surfaces are most appropriate for AAC bricks. If you are modelling clay bricks and lack data, and orthotropy isn't such a big factor, I would recommend the usage of mat 72r3. In both cases, I was speaking about explicit analysis.
If orthotropy is a factor, my personal experience for the masonry is to use an implicit dynamics module and mat 273 (concrete damage plasticity) for the bricks. When using so, you can also model the holes in the bricks and implicit dynamics are in my personal experience, significantly faster then explicit analysis.
Furthermore, think about using contact( one/two way surface to surface contact) in order to model mortar, instead modelling solid elements. Also, define the appropriate penalty factor for the compression in such a contact. My experience is that contact modelling of mortar elements provides faster and more accurate results than small solid elements which should represent mortar. Moreover, if you are modelling mortar using solid elements, you should think about it that mortar tensile strength and mortar bond tensile/shear strength are not the same thing. It depends how important the cracks or stresses in the mortar are, for your investigation.
If you have any more questions, I will gladly help.
.
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