GBT Displacement parameters

Distortional Mechanics

Distortion of Beam
Distortional Mechanics is a research topic associated with the distortional behaviour of thin-walled beams, which are so thin-walled that they cannot be assumed to maintain their cross sectional shape during axial or transverse loading. An important aspect is how to join distorting beam elements at joints.

Simple Spring Models, Generalized Beam Theories (GBT), Finite Strip Methods (FSM), Recursive Finite Elements Method (RecFEM) or conventional Finite Element Methods (FEM) are the main methods of distortional mechanics analysis.

Distortional modes of open cross section
The distortional behaviour of thin-walled beams with transverse loads involves distortional deformation, which may be described by linear elastic distortional theories. For pure axial loading there is no (first order) distortion of the cross section, however the thin-walled cross sections are prone to local and distortional buckling, which often decreases the global buckling capacity. Furthermore local and distortional buckling will also decrease the capacity for transverse loading. Both local and distortional deformation as well as buckling may often be observed during loading of the thin-walled members and due to the stable post-buckling behaviour the loading may increase until local plastic mechanisms or excess deformations occur.

PhD Dissertations

  1. Andreassen, Michael Joachim Distortional Mechanics of Thin-Walled Structural Elements Kgs. Lyngby: Technical University of Denmark. 2012. PhD thesis (BYG Rapport).

Journal Papers

  1. Andreassen, Michael Joachim and Jeppe Jönsson. "A distortional semi-discretized thin-walled beam element". Thin-Walled Structures. 2013, 62. 142-157. Available: 10.1016/j.tws.2012.07.011 
  2. Andreassen, Michael Joachim and Jeppe Jönsson. "Distortional buckling modes of semi-discretized thin-walled columns". Thin-Walled Structures. 2012, 51. 53-63. Available: 10.1016/j.tws.2011.11.002
  3. Andreassen, Michael Joachim and Jeppe Jönsson. "Distortional solutions for loaded semi-discretized thin-walled beams". Thin-Walled Structures. 2012, 50(1). 116-127. Available: 10.1016/j.tws.2011.08.013
  4. Jönsson, Jeppe and Michael Joachim Andreassen. "Distortional eigenmodes and homogeneous solutions for semi-discretized thin-walled beams". Thin-Walled Structures. 2011, 49(6). 691-707. Available: 10.1016/j.tws.2010.12.009
  5. Jönsson, Jeppe. "Distortional warping functions and shear distributions in thin-walled beams". Thin-Walled Structures. 1999, 33(4). 245-268. Available: doi:10.1016/S0263-8231(98)00048-2
  6. Jönsson, Jeppe. "Distortional theory of thin-walled beams". Thin-Walled Structures, 1999, 33(4). 269-303. Available: doi:10.1016/S0263-8231(98)00050-0
  7. Jönsson, Jeppe. "Determination of shear stresses, warping functions and section properties of thin-walled beams using finite elements". Computers & Structures, 1998, 68(4). 393-410. Available: doi:10.1016/S0045-7949(98)00070-4

Conference Papers

  1. Hansen, Aners Bau and Jeppe Jönsson "A GBT‐framework towards modal modelling of steel structures". Eurosteel 2017 Proceedings in ce/papers Volume 1, Issue 2-3, 1822–1830, 2017. Available: doi: 10.1002/cepa.226
  2. Andreassen, Michael Joachim and Jeppe Jönsson "A semi-discretization approach to buckling behavior of thin-walled members". Proceedings of the 7th European conference on steel and composite structures (EUROSTEEL 2014). University of Naples Federico II. 2014.
  3. Andreassen, Michael Joachim and Jeppe Jönsson "A semi-discretized thin-walled beam element including distortion". Research and Applications in Structural Engineering, Mechanics and Computation. C R C Press LLC. 2013. 1003–1008. Available: 10.1201/b15963-184
  4. Jönsson, Jeppe and Michael Joachim Andreassen "A Semi-Discretization Approach to Generalized Beam Theory and Analytical Solutions of the Generalized Column Equations". and Holzapfel, Gerhard A. Ogden, Ray W. (ed.). Proceedings of the 8th European Solid Mechanics Conference. 2012.
  5. Andreassen, Michael Joachim and Jeppe Jönsson "Distortional eigenmodes and solutions for thin-walled beams". and Dubina, Dan Ungureanu, Viorel (ed.). Thin-Walled Structures: Recent Research Advancences and Trends. ECCS - European Convention for Constructional Steelwork. 2011.
  6. Jönsson, Jeppe and Michael Joachim Andreassen "Distortional Modes of Thin-Walled Beams". and Ambrósio, Jorge Silva, Miguel T. (ed.). Proceedings of the 7th EUROMECH Solid Mechanics Conference - Mini-Symposia. 1. udg., Portugal: APMTAC - Portugese Association for Theoretical, Applied and Computational Mechanics, Laboratorio Nacional de Egenharia Civil, Av. do Brasil, 101, 1700-066 Lisboa. 2009. 0680.

Student Projects

  1. Ali Mansour Hariri, Generalized Beam Theory - Distortional mechanics of thin walled structures using an energy and equilibrium approach, BSc Project, DTU Civil Engineering, July 2014.
  2. Yutong Zhu, DTU-TD - A User Interface for Thin-walled Distortion, MSc Project, DTU Civil Engineering, August 2013.
  3. Lotte Brad Sander, Beam Theory and Modelling of Distortion, MSc Project, DTU Civil Engineering, March 2013.
  4. Martin Mygin,  Advanced Beam Elemnts with Distorting Cross Sections, MSc Project, DTU Civil Engineering, February 2013.
  5. Ali Kazim Jawad Thari, Bjælkemekanik med tværsnitsdeformation, BSc Project, DTU Civil Engineering, Spring 2013.
  6. Michael Teilmann Nielsen, Avancerede bjælkeelementer med tværsnitsdeformation, MSc Project, DTU Civil Engineering,Spring 2012.
  7. Robert Cybulski, Statics and stability for thin-walled shear beam with cross-section distortion, MSc Project, DTU Civil Engineering, July 2010.


Jeppe Jönsson
DTU Civil Engineering
+45 45 25 17 07


Michael Joachim Andreassen
Associate Professor
DTU Civil Engineering
+45 45 25 18 14


Anders Bau Hansen
Industrial PhD
DTU Civil Engineering
21 FEBRUARY 2018