Mixed Finite Elements for Geometrically Exact Beams using Discontinuous Rotations and Discrete Curvature
Pith reviewed 2026-05-20 23:51 UTC · model grok-4.3
The pith
A mixed finite-element formulation for geometrically exact beams introduces the moment vector to enable element-local discontinuous rotations.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
By treating the moment vector as an additional independent field, the mixed formulation allows an element-local, discontinuous approximation of rotations. The discrete curvature concept then provides a mathematically consistent treatment of these rotation discontinuities. For linear constitutive laws the mixed form follows from a Legendre transform of the curvature-related strain energy. Objectivity is retained at the discrete level through interpolation of relative rotations via a multiplicative split of the rotation field in a total Lagrangian setting, and path-independence follows directly from that setting.
What carries the argument
Mixed formulation obtained via Legendre transform of the curvature strain energy, paired with discrete curvature to accommodate rotation discontinuities.
If this is right
- Optimal convergence rates hold irrespective of beam slenderness.
- The lowest-order element requires no rotation interpolation and uses only element-constant rotations.
- Path-independence is preserved by the total Lagrangian setting.
- Accuracy remains high across different orders of approximation.
Where Pith is reading between the lines
- The same mixed structure could be adapted to nonlinear constitutive laws by replacing the Legendre transform with a suitable dual potential.
- Similar discontinuous-rotation ideas may simplify discretizations for shells or rods with more complex cross-sections.
- Reduced interpolation cost could improve performance in large-scale simulations of flexible multibody systems.
Load-bearing premise
The mixed form is derived under the assumption of linear constitutive laws via the Legendre transform, while objectivity is maintained by the multiplicative split of relative rotations in the total Lagrangian setting.
What would settle it
A large-rotation cantilever benchmark in which the lowest-order element fails to exhibit optimal convergence or produces path-dependent results would disprove the central claims.
read the original abstract
We propose a novel mixed finite-element formulation for geometrically exact (Simo--Reissner) beams that introduces the moment vector as additional independent field. The specific mixed form allows for an element-local, discontinuous approximation of rotations, which is key to a simple and efficient discretization framework. The concept of discrete curvature provides a mathematically consistent treatment of rotation discontinuities. For linear constitutive laws, the mixed form is derived via a Legendre transform of the curvature-related strain energy. Objectivity is retained at the discrete level by interpolating relative rotations through a multiplicative split of the rotation field; path-independence is inherent to the total Lagrangian setting and verified numerically. Several benchmarks demonstrate optimal rates of convergence and accuracy, irrespective of the beam's slenderness and order of approximation. Notably, the lowest-order element entirely avoids rotation interpolation by employing element-constant rotations only.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a novel mixed finite-element formulation for geometrically exact Simo-Reissner beams that introduces the moment vector as an additional independent field. This mixed form enables an element-local, discontinuous approximation of rotations via the concept of discrete curvature. For linear constitutive laws the formulation is obtained through a Legendre transform of the curvature-related strain energy; objectivity is preserved by a multiplicative split that interpolates relative rotations in a total-Lagrangian setting. Path-independence is verified numerically. Several benchmarks are presented that demonstrate optimal convergence rates and accuracy independent of beam slenderness and polynomial order, including a lowest-order element that employs only element-constant rotations and thereby avoids rotation interpolation altogether.
Significance. If the central claims hold, the work supplies a technically consistent and computationally attractive route to discontinuous rotation fields in geometrically exact beam elements. The element-local treatment and the lowest-order constant-rotation case are particularly attractive for large-scale or contact problems where rotation continuity is undesirable. The explicit numerical confirmation of path-independence and the reported optimal rates across slenderness regimes constitute concrete strengths that would be of immediate interest to the structural-mechanics and finite-element communities.
minor comments (3)
- [§2.2] §2.2: the definition of the discrete curvature operator should be accompanied by a short remark on its consistency with the continuous curvature measure when the rotation field is continuous across elements.
- [Table 1, Figure 4] Table 1 and Figure 4: the convergence plots would be clearer if the error norms were normalized by the exact solution values and if the slenderness ratios used in each series were stated explicitly in the caption.
- [§4.3] §4.3: the statement that the lowest-order element 'entirely avoids rotation interpolation' would benefit from a one-sentence reminder of how the constant rotation per element is updated multiplicatively at the quadrature points.
Simulated Author's Rebuttal
We thank the referee for the positive assessment of our work and the recommendation for minor revision. The report correctly identifies the key contributions of the mixed formulation, including the use of an independent moment field to enable element-local discontinuous rotations via discrete curvature, the preservation of objectivity through the multiplicative split, and the numerical verification of path-independence together with optimal convergence rates across slenderness regimes.
Circularity Check
Derivation self-contained; no load-bearing reductions to inputs or self-citations
full rationale
The paper derives the mixed formulation explicitly via Legendre transform of the curvature strain energy (restricted to linear laws) and retains objectivity through a multiplicative split of relative rotations in a total Lagrangian frame. These steps are standard, explicitly scoped, and do not reduce the final discrete curvature or element-local rotation approximation to a fitted parameter or prior self-referential result. Path-independence is verified numerically rather than assumed by construction. No self-citation is invoked as a uniqueness theorem or to smuggle an ansatz; the lowest-order element-constant rotation case follows directly from the independent moment field and discrete curvature definition. The central claims therefore remain independent of the paper's own inputs.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Linear constitutive laws relating curvature to moment for the Legendre transform step.
- standard math Standard finite-element approximation theory and total Lagrangian kinematics for beams.
Reference graph
Works this paper leans on
-
[1]
Marc-Michel Bousquet et Soc., Lausanne (1744)
Euler, L.: Methodus Inveniendi Lineas Curvas Maximi Minimive Proprietate Gaudentes, Sive Solutio Problematis Isoperimetrici Lattissimo Sensu Accepti. Marc-Michel Bousquet et Soc., Lausanne (1744)
-
[2]
Kirchhoff, G.: Ueber das Gleichgewicht und die Bewegung eines unendlich dünnen elastischen Stabes. Journal für die reine und angewandte Mathematik 1859(56), 285–313 (1859) https: //doi.org/10.1515/crll.1859.56.285
-
[3]
On the correction for shear of the differential equation for transverse vibrations of prismatic bars
Timoshenko, S.P.: LXVI. On the correction for shear of the differential equation for transverse vibrations of prismatic bars. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 41(245), 744–746 (1921) https://doi.org/10.1080/14786442108636264
-
[4]
Zeitschrift für angewandte Mathematik und Physik (ZAMP) (1972) https://doi.org/10.1007/BF01602645
Reissner, E.: On one-dimensional finite-strain beam theory: The plane problem. Zeitschrift für angewandte Mathematik und Physik (ZAMP) (1972) https://doi.org/10.1007/BF01602645
-
[5]
Studies in Applied Mathematics 52(2), 87–95 (1973) https://doi.org/10.1002/sapm197352287
Reissner, E.: On One-Dimensional Large-Displacement Finite-Strain Beam Theory. Studies in Applied Mathematics 52(2), 87–95 (1973) https://doi.org/10.1002/sapm197352287
-
[6]
Reissner, E.: On finite deformations of space-curved beams. ZAMP Zeitschrift für angewandte Mathematik und Physik 32(6), 734–744 (1981) https://doi.org/10.1007/BF00946983
-
[7]
Antman, S.S.: The Theory of Rods. In: Truesdell, C. (ed.) Linear Theories of Elasticity and Thermoelasticity vol. VIa/2, pp. 641–703. Springer, Berlin Heidelberg (1973). https: 25 //doi.org/10.1007/978-3-662-39776-3_6
-
[8]
The three-dimensional dynamic problem
Simo, J.C.: A finite strain beam formulation. The three-dimensional dynamic problem. Part I. Computer Methods in Applied Mechanics and Engineering 49(1), 55–70 (1985) https: //doi.org/10.1016/0045-7825(85)90050-7
-
[9]
part II: Computational aspects
Simo, J.C., Vu-Quoc, L.: A three-dimensional finite-strain rod model. part II: Computational aspects. Computer Methods in Applied Mechanics and Engineering 58(1), 79–116 (1986) https://doi.org/10.1016/0045-7825(86)90079-4
-
[10]
Journal of Applied Mechanics 53(4), 849–854 (1986) https://doi
Simo, J.C., Vu-Quoc, L.: On the Dynamics of Flexible Beams Under Large Overall Motions— The Plane Case: Part I. Journal of Applied Mechanics 53(4), 849–854 (1986) https://doi. org/10.1115/1.3171870
-
[11]
Journal of Applied Mechanics 53(4), 855 (1986) https://doi.org/ 10.1115/1.3171871
Simo, J.C., Vu-Quoc, L.: On the Dynamics of Flexible Beams Under Large Overall Motions— The Plane Case: Part II. Journal of Applied Mechanics 53(4), 855 (1986) https://doi.org/ 10.1115/1.3171871
-
[12]
Acta Mechanica 206(1-2), 1–21 (2009) https://doi.org/10.1007/ s00707-008-0085-8
Irschik, H., Gerstmayr, J.: A continuum mechanics based derivation of Reissner’s large- displacement finite-strain beam theory: the case of plane deformations of originally straight Bernoulli–Euler beams. Acta Mechanica 206(1-2), 1–21 (2009) https://doi.org/10.1007/ s00707-008-0085-8
work page 2009
-
[13]
Irschik, H., Gerstmayr, J.: A continuum-mechanics interpretation of Reissner’s non-linear shear-deformable beam theory. Mathematical and Computer Modelling of Dynamical Systems 17(1), 19–29 (2011) https://doi.org/10.1080/13873954.2010.537512
-
[14]
Humer, A., Irschik, H.: The Lu-Pister Multiplicative Decomposition Applied to Thermoelastic Geometrically-Exact Rods. Computer Modeling in Engineering & Sciences 129(3), 1395–1417 (2021) https://doi.org/10.32604/cmes.2021.017944
-
[15]
Acta Mechanica 224(7), 1493–1525 (2013) https://doi.org/10.1007/s00707-013-0818-1
Humer, A.: Exact solutions for the buckling and postbuckling of shear-deformable beams. Acta Mechanica 224(7), 1493–1525 (2013) https://doi.org/10.1007/s00707-013-0818-1
-
[16]
Acta Mechanica (2019) https://doi.org/ 10.1007/s00707-019-02472-1
Humer, A., Pechstein, A.S.: Exact solutions for the buckling and postbuckling of a shear- deformable cantilever subjected to a follower force. Acta Mechanica (2019) https://doi.org/ 10.1007/s00707-019-02472-1
-
[17]
Bathe, K.-J., Bolourchi, S.: Large displacement analysis of three‐dimensional beam structures. International Journal for Numerical Methods in Engineering 14(7), 961–986 (1979) https: //doi.org/10.1002/nme.1620140703
-
[18]
Cardona, A., Geradin, M.: A beam finite element non‐linear theory with finite rotations. International Journal for Numerical Methods in Engineering 26(11), 2403–2438 (1988) https: //doi.org/10.1002/nme.1620261105
-
[19]
Ibrahimbegović, A., Frey, F., Kožar, I.: Computational aspects of vector‐like parametriza- tion of three‐dimensional finite rotations. International Journal for Numerical Methods in Engineering 38(21), 3653–3673 (1995) https://doi.org/10.1002/nme.1620382107
-
[20]
Ibrahimbegovic, A.: On the choice of finite rotation parameters. Computer Methods in Applied Mechanics and Engineering 149(1-4), 49–71 (1997) https://doi.org/10.1016/ S0045-7825(97)00059-5
work page 1997
-
[21]
Meier, C., Popp, A., Wall, W.A.: Geometrically Exact Finite Element Formulations for Slen- der Beams: Kirchhoff–Love Theory Versus Simo–Reissner Theory. Archives of Computational 26 Methods in Engineering 26(1), 163–243 (2019) https://doi.org/10.1007/s11831-017-9232-5
-
[22]
Proceedings of the Royal Society of London
Crisfield, M.A., Jelenić, G.: Objectivity of strain measures in the geometrically exact three- dimensional beam theory and its finite-element implementation. Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 455(1983), 1125–1147 (1999) https://doi.org/10.1098/rspa.1999.0352
-
[23]
Jelenić, G., Crisfield, M.A.: Geometrically exact 3D beam theory: implementation of a strain- invariant finite element for statics and dynamics. Computer Methods in Applied Mechanics and Engineering 171(1-2), 141–171 (1999) https://doi.org/10.1016/S0045-7825(98)00249-7
-
[24]
Wehage, R.A.: Quaternions and Euler Parameters — A Brief Exposition. In: Haug, E.J. (ed.) Computer Aided Analysis and Optimization of Mechanical System Dynamics, pp. 147–180. Springer, Berlin, Heidelberg (1984). https://doi.org/10.1007/978-3-642-52465-3_5
-
[25]
Nikravesh, P.E., Wehage, R.A., Kwon, O.K.: Euler Parameters in Computational Kinematics and Dynamics. Part 1. Journal of Mechanisms, Transmissions, and Automation in Design 107(3), 358–365 (1985) https://doi.org/10.1115/1.3260722
-
[26]
Zupan, E., Saje, M., Zupan, D.: The quaternion-based three-dimensional beam theory. Computer Methods in Applied Mechanics and Engineering 198(49-52), 3944–3956 (2009) https://doi.org/10.1016/j.cma.2009.09.002
-
[27]
Acta Mechanica 224(8), 1709–1729 (2013) https://doi.org/10.1007/s00707-013-0824-3
Zupan, E., Saje, M., Zupan, D.: On a virtual work consistent three-dimensional Reissner– Simo beam formulation using the quaternion algebra. Acta Mechanica 224(8), 1709–1729 (2013) https://doi.org/10.1007/s00707-013-0824-3
-
[28]
Wasmer, P., Betsch, P.: A projection‐based quaternion discretization of the geometrically exact beam model. International Journal for Numerical Methods in Engineering 125(20), 7538 (2024) https://doi.org/10.1002/nme.7538
-
[29]
Sonneville, V., Cardona, A., Brüls, O.: Geometrically exact beam finite element formulated on the special Euclidean group. Computer Methods in Applied Mechanics and Engineering 268, 451–474 (2014) https://doi.org/10.1016/j.cma.2013.10.008
-
[30]
Sonneville, V., Brüls, O., Bauchau, O.A.: Interpolation schemes for geometrically exact beams: A motion approach. International Journal for Numerical Methods in Engineering 112(9), 1129–1153 (2017) https://doi.org/10.1002/nme.5548
-
[31]
Harsch, J., Sailer, S., Eugster, S.R.: A total Lagrangian, objective and intrinsically locking- free Petrov–Galerkin SE (3) Cosserat rod finite element formulation. International Journal for Numerical Methods in Engineering 124(13), 2965–2994 (2023) https://doi.org/10.1002/ nme.7236
work page 2023
-
[32]
Noor, A.K., Peters, J.M.: Mixed models and reduced/selective integration displacement mod- els for nonlinear analysis of curved beams. International Journal for Numerical Methods in Engineering 17(4), 615–631 (1981) https://doi.org/10.1002/nme.1620170409
-
[33]
Nukala, P.K.V.V., White, D.W.: A mixed finite element for three-dimensional nonlinear anal- ysis of steel frames. Computer Methods in Applied Mechanics and Engineering 193(23-26), 2507–2545 (2004) https://doi.org/10.1016/j.cma.2004.01.029
-
[34]
Herrmann, M., Castello, D., Breuling, J., Garcia, I.C., Greco, L., Eugster, S.R.: A mixed Petrov-Galerkin Cosserat rod finite element formulation. arXiv. arXiv:2507.01552 [math] (2026). https://doi.org/10.48550/arXiv.2507.01552 27
-
[35]
International Journal of Solids and Structures 26(8), 887–900 (1990) https://doi.org/10
Saje, M.: A variational principle for finite planar deformation of straight slender elastic beams. International Journal of Solids and Structures 26(8), 887–900 (1990) https://doi.org/10. 1016/0020-7683(90)90075-7
work page 1990
-
[36]
Computers & Structures 39(3-4), 327–337 (1991) https://doi.org/10.1016/0045-7949(91) 90030-P
Saje, M.: Finite element formulation of finite planar deformation of curved elastic beams. Computers & Structures 39(3-4), 327–337 (1991) https://doi.org/10.1016/0045-7949(91) 90030-P
-
[37]
Computers & Structures 225, 106109 (2019) https://doi.org/10.1016/j.compstruc.2019
Neunteufel, M., Schöberl, J.: The Hellan–Herrmann–Johnson method for nonlinear shells. Computers & Structures 225, 106109 (2019) https://doi.org/10.1016/j.compstruc.2019. 106109
-
[38]
Neunteufel, M., Schöberl, J.: A voiding membrane locking with Regge interpolation. Computer Methods in Applied Mechanics and Engineering 373, 113524 (2021) https://doi.org/10.1016/ j.cma.2020.113524
-
[39]
Acta Mechanica (2025) https://doi.org/10.1007/s00707-025-04255-3
Platzer, S., Pechstein, A., Humer, A., Krommer, M.: Viscoelastic Kirchhoff–Love shells at finite strains: constitutive modeling and mixed low-regularity finite elements. Acta Mechanica (2025) https://doi.org/10.1007/s00707-025-04255-3
-
[40]
ISSS Journal of Micro and Smart Systems (2025) https://doi.org/10.1007/s41683-025-00138-w
Platzer, S., Pechstein, A., Humer, A., Krommer, M.: A low-regularity finite element approach for dielectric viscoelastic Kirchhoff–Love shells. ISSS Journal of Micro and Smart Systems (2025) https://doi.org/10.1007/s41683-025-00138-w
-
[41]
Computational Mechanics 66(6), 1377–1398 (2020) https://doi.org/10.1007/s00466-020-01907-0
Steinbrecher, I., Mayr, M., Grill, M.J., Kremheller, J., Meier, C., Popp, A.: A mortar-type finite element approach for embedding 1D beams into 3D solid volumes. Computational Mechanics 66(6), 1377–1398 (2020) https://doi.org/10.1007/s00466-020-01907-0
-
[42]
Cambridge university press, Cambridge, GB (1998)
Shabana, A.A.: Dynamics of Multibody Systems, 2nd ed edn. Cambridge university press, Cambridge, GB (1998)
work page 1998
-
[43]
Wiley, Chichester Weinheim (2001)
Géradin, M., Cardona, A.: Flexible Multibody Dynamics: a Finite Element Approach. Wiley, Chichester Weinheim (2001)
work page 2001
-
[44]
Crisfield, M.A.: Non-linear Finite Element Analysis of Solids and Structures. 2: Advanced Topics, Repr. with corr edn. Wiley, Chichester (2003). Num Pages: 494
work page 2003
-
[45]
Computational Mechanics 57(5), 817–841 (2016) https://doi.org/10
Sander, O., Neff, P., Bîrsan, M.: Numerical treatment of a geometrically nonlinear planar Cosserat shell model. Computational Mechanics 57(5), 817–841 (2016) https://doi.org/10. 1007/s00466-016-1263-5
work page 2016
-
[46]
Computer Graphics Forum 25(3), 547–556 (2006) https://doi.org/10.1111/ j.1467-8659.2006.00974.x
Grinspun, E., Gingold, Y., Reisman, J., Zorin, D.: Computing discrete shape operators on general meshes. Computer Graphics Forum 25(3), 547–556 (2006) https://doi.org/10.1111/ j.1467-8659.2006.00974.x
-
[47]
Koschnick, F., Bischoff, M., Camprubí, N., Bletzinger, K.-U.: The discrete strain gap method and membrane locking. Computer Methods in Applied Mechanics and Engineering 194(21- 24), 2444–2463 (2005) https://doi.org/10.1016/j.cma.2004.07.040
-
[48]
Journal of Structural Mechanics 11(2), 153–176 (1983) https://doi.org/ 10.1080/03601218308907439
Stolarski, H., Belytschko, T., Carpenter, N.: Bending and Shear Mode Decomposition in C ◦ Structural Elements. Journal of Structural Mechanics 11(2), 153–176 (1983) https://doi.org/ 10.1080/03601218308907439
-
[49]
Meier, C., Popp, A., Wall, W.A.: A locking-free finite element formulation and reduced mod- els for geometrically exact Kirchhoff rods. Computer Methods in Applied Mechanics and Engineering 290, 314–341 (2015) https://doi.org/10.1016/j.cma.2015.02.029 28
-
[50]
Harsch, J., Capobianco, G., Eugster, S.R.: Finite element formulations for constrained spatial nonlinear beam theories. Mathematics and Mechanics of Solids 26(12), 1838–1863 (2021) https://doi.org/10.1177/10812865211000790
-
[51]
Multibody System Dynamics 20(1), 51–68 (2008) https://doi.org/10.1007/s11044-008-9105-7
Romero, I.: A comparison of finite elements for nonlinear beams: The absolute nodal coordi- nate and geometrically exact formulations. Multibody System Dynamics 20(1), 51–68 (2008) https://doi.org/10.1007/s11044-008-9105-7
-
[52]
Eugster, S.R., Hesch, C., Betsch, P., Glocker, Ch.: Director-based beam finite elements relying on the geometrically exact beam theory formulated in skew coordinates. International Journal for Numerical Methods in Engineering 97(2), 111–129 (2014) https://doi.org/10.1002/nme. 4586 29
work page doi:10.1002/nme 2014
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.