@article{BhattaraiStaat2018,
  author    = {Bhattarai, Aroj and Staat, Manfred},
  title     = {Modelling of Soft Connective Tissues to Investigate Female Pelvic Floor Dysfunctions},
  series = {Computational and Mathematical Methods in Medicine},
  volume    = {2018},
  journal   = {Computational and Mathematical Methods in Medicine},
  number    = {Article ID 9518076},
  publisher = {Hindawi},
  address   = {New York, NY},
  issn      = {1748-6718},
  doi       = {10.1155/2018/9518076},
  pages     = {1 -- 16},
  year      = {2018},
  abstract  = {After menopause, decreased levels of estrogen and progesterone remodel the collagen of the soft tissues thereby reducing their stiffness. Stress urinary incontinence is associated with involuntary urine leakage due to pathological movement of the pelvic organs resulting from lax suspension system, fasciae, and ligaments. This study compares the changes in the orientation and position of the female pelvic organs due to weakened fasciae, ligaments, and their combined laxity. A mixture theory weighted by respective volume fraction of elastin-collagen fibre compound (5\%), adipose tissue (85\%), and smooth muscle (5\%) is adopted to characterize the mechanical behaviour of the fascia. The load carrying response (other than the functional response to the pelvic organs) of each fascia component, pelvic organs, muscles, and ligaments are assumed to be isotropic, hyperelastic, and incompressible. Finite element simulations are conducted during Valsalva manoeuvre with weakened tissues modelled by reduced tissue stiffness. A significant dislocation of the urethrovesical junction is observed due to weakness of the fascia (13.89 mm) compared to the ligaments (5.47 mm). The dynamics of the pelvic floor observed in this study during Valsalva manoeuvre is associated with urethral-bladder hypermobility, greater levator plate angulation, and positive Q-tip test which are observed in incontinent females.},
  language  = {en}
}
@article{ColomboDriraFrotscheretal.2022,
  author    = {Colombo, Daniele and Drira, Slah and Frotscher, Ralf and Staat, Manfred},
  title     = {An element-based formulation for ES-FEM and FS-FEM models for implementation in standard solid mechanics finite element codes for 2D and 3D static analysis},
  series = {International Journal for Numerical Methods in Engineering},
  volume    = {124},
  journal   = {International Journal for Numerical Methods in Engineering},
  number    = {2},
  publisher = {Wiley},
  address   = {Chichester},
  issn      = {1097-0207},
  doi       = {10.1002/nme.7126},
  pages     = {402 -- 433},
  year      = {2022},
  abstract  = {Edge-based and face-based smoothed finite element methods (ES-FEM and FS-FEM, respectively) are modified versions of the finite element method allowing to achieve more accurate results and to reduce sensitivity to mesh distortion, at least for linear elements. These properties make the two methods very attractive. However, their implementation in a standard finite element code is nontrivial because it requires heavy and extensive modifications to the code architecture. In this article, we present an element-based formulation of ES-FEM and FS-FEM methods allowing to implement the two methods in a standard finite element code with no modifications to its architecture. Moreover, the element-based formulation permits to easily manage any type of element, especially in 3D models where, to the best of the authors' knowledge, only tetrahedral elements are used in FS-FEM applications found in the literature. Shape functions for non-simplex 3D elements are proposed in order to apply FS-FEM to any standard finite element.},
  language  = {en}
}
@inproceedings{StaatTranPham2008,
  author    = {Staat, Manfred and Tran, Thanh Ngoc and Pham, Phu Tinh},
  title     = {Limit and shakedown reliability analysis by nonlinear programming},
  year      = {2008},
  abstract  = {7th International Conference on Reliability of Materials and Structures (RELMAS 2008). June 17 - 20, 2008 ; Saint Petersburg, Russia. pp 354-358. Reprint with corrections in red Introduction Analysis of advanced structures working under extreme heavy loading such as nuclear power plants and piping system should take into account the randomness of loading, geometrical and material parameters. The existing reliability are restricted mostly to the elastic working regime, e.g. allowable local stresses. Development of the limit and shakedown reliability-based analysis and design methods, exploiting potential of the shakedown working regime, is highly needed. In this paper the application of a new algorithm of probabilistic limit and shakedown analysis for shell structures is presented, in which the loading and strength of the material as well as the thickness of the shell are considered as random variables. The reliability analysis problems may be efficiently solved by using a system combining the available FE codes, a deterministic limit and shakedown analysis, and the First and Second Order Reliability Methods (FORM/SORM). Non-linear sensitivity analyses are obtained directly from the solution of the deterministic problem without extra computational costs.},
  subject      = {Finite-Elemente-Methode},
  language  = {en}
}
@inproceedings{DuongJungFrotscheretal.2016,
  author    = {Duong, Minh Tuan and Jung, Alexander and Frotscher, Ralf and Staat, Manfred},
  title     = {A 3D electromechanical FEM-based model for cardiac tissue},
  series = {ECCOMAS Congress 2016, VII European Congress on Computational Methods in Applied Sciences and Engineering. Crete Island, Greece, 5-10 June 2016},
  booktitle = {ECCOMAS Congress 2016, VII European Congress on Computational Methods in Applied Sciences and Engineering. Crete Island, Greece, 5-10 June 2016},
  editor    = {Papadrakakis, M.},
  pages     = {13 S.},
  year      = {2016},
  language  = {en}
}
@article{NguyenDuongTranetal.2012,
  author    = {Nguyen, Nhu Huynh and Duong, Minh Tuan and Tran, Thanh Ngoc and Pham, Phu Tinh and Grottke, O. and Tolba, R. and Staat, Manfred},
  title     = {Influence of a freeze-thaw cycle on the stress-stretch curves of tissues of porcine abdominal organs},
  series = {Journal of Biomechanics},
  volume    = {45},
  journal   = {Journal of Biomechanics},
  number    = {14},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1873-2380},
  doi       = {10.1016/j.jbiomech.2012.07.008},
  pages     = {2382 -- 2386},
  year      = {2012},
  abstract  = {The paper investigates both fresh porcine spleen and liver and the possible decomposition of these organs under a freeze-thaw cycle. The effect of tissue preservation condition is an important factor which should be taken into account for protracted biomechanical tests. In this work, tension tests were conducted for a large number of tissue specimens from twenty pigs divided into two groups of 10. Concretely, the first group was tested in fresh state; the other one was tested after a freeze-thaw cycle which simulates the conservation conditions before biomechanical experiments. A modified Fung model for isotropic behavior was adopted for the curve fitting of each kind of tissues. Experimental results show strong effects of the realistic freeze-thaw cycle on the capsule of elastin-rich spleen but negligible effects on the liver which virtually contains no elastin. This different behavior could be explained by the autolysis of elastin by elastolytic enzymes during the warmer period after thawing. Realistic biomechanical properties of elastin-rich organs can only be expected if really fresh tissue is tested. The observations are supported by tests of intestines.},
  language  = {en}
}
@article{StaatTrenzLohmannetal.2012,
  author    = {Staat, Manfred and Trenz, Eva and Lohmann, Philipp and Frotscher, Ralf and Klinge, Uwe and Tabaza, Ruth and Kirschner-Hermanns, Ruth},
  title     = {New measurements to compare soft tissue anchoring systems in pelvic floor surgery},
  series = {Journal of Biomedical Materials Research Part B: Applied Biomaterials},
  volume    = {100B},
  journal   = {Journal of Biomedical Materials Research Part B: Applied Biomaterials},
  number    = {4},
  publisher = {Wiley},
  address   = {Hoboken, NJ},
  issn      = {1552-4981},
  doi       = {10.1002/jbm.b.32654},
  pages     = {924 -- 933},
  year      = {2012},
  abstract  = {Suburethral slings as well as different meshes are widely used treating stress urinary incontinence and prolaps in women. With the development of MiniSlings and special meshes using less alloplastic material anchorage systems become more important to keep devices in place and to put some tension especially on the MiniSlings. To date, there are many different systems of MiniSlings of different companies on the market which differ in the structure of the used meshes and anchors. A new objective measurement method to compare different properties of MiniSling systems (mesh and anchor) is presented in this article. Ballistic gelatine acts as soft tissue surrogate. Significant differences in parameters like pull-out strength of anchors or shrinkage of meshes under loading conditions have been determined. The form and size of the anchors as well as the structural stability of the meshes are decisive for a proper integration. The tested anchorings sytems showed markedly different mechanical function at their respective load bearing capacity. As the stable fixation of the device in tissue is a prerequisite for a permanet reinforcement, the proposed test system permits further optimisation of anchor and mesh devices to improve the success of the surgical treatment},
  language  = {en}
}
@inproceedings{TranStaatStavroulakis2014,
  author    = {Tran, Ngoc Trinh and Staat, Manfred and Stavroulakis, G. E.},
  title     = {A multicriteria method for truss optimization},
  series = {11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20-25, 2014, Barcelona},
  booktitle = {11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20-25, 2014, Barcelona},
  editor    = {Onate, E.},
  organization    = {World Congress on Computational Mechanics <11, 2014, Barcelona>},
  pages     = {1 -- 12},
  year      = {2014},
  language  = {en}
}
@article{NovacekTranKlingeetal.2012,
  author    = {Novacek, V. and Tran, Thanh Ngoc and Klinge, U. and Tolba, R. H. and Staat, Manfred and Bronson, D. G. and Miesse, A. M. and Whiffen, J. and Turquier, F.},
  title     = {Finite element modelling of stapled colorectal end-to-end anastomosis : Advantages of variable height stapler design},
  series = {Journal of Biomechanics},
  volume    = {45},
  journal   = {Journal of Biomechanics},
  number    = {115},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1873-2380},
  doi       = {10.1016/j.jbiomech.2012.07.021},
  pages     = {2693 -- 2697},
  year      = {2012},
  abstract  = {The impact of surgical staplers on tissues has been studied mostly in an empirical manner. In this paper, finite element method was used to clarify the mechanics of tissue stapling and associated phenomena. Various stapling modalities and several designs of circular staplers were investigated to evaluate the impact of the device on tissues and mechanical performance of the end-to-end colorectal anastomosis. Numerical simulations demonstrated that a single row of staples is not adequate to resist leakage due to non-linear buckling and opening of the tissue layers between two adjacent staples. Compared to the single staple row configuration, significant increase in stress experienced by the tissue at the inner staple rows was observed in two and three rows designs. On the other hand, adding second and/or third staple row had no effect on strain in the tissue inside the staples. Variable height design with higher staples in outer rows significantly reduced the stresses and strains in outer rows when compared to the same configuration with flat cartridge.},
  language  = {en}
}
@article{Staat2005,
  author    = {Staat, Manfred},
  title     = {Direct finite element route for design-by-analysis of pressure components},
  year      = {2005},
  abstract  = {In the new European standard for unfired pressure vessels, EN 13445-3, there are two approaches for carrying out a Design-by-Analysis that cover both the stress categorization method (Annex C) and the direct route method (Annex B) for a check against global plastic deformation and against progressive plastic deformation. This paper presents the direct route in the language of limit and shakedown analysis. This approach leads to an optimization problem. Its solution with Finite Element Analysis is demonstrated for mechanical and thermal actions. One observation from the examples is that the so-called 3f (3Sm) criterion fails to be a reliable check against progressive plastic deformation. Precise conditions are given, which greatly restrict the applicability of the 3f criterion.},
  subject      = {Einspielen <Werkstoff>},
  language  = {en}
}
@article{HacklWegmannKahmannetal.2017,
  author    = {Hackl, Michael and Wegmann, Kilian and Kahmann, Stephanie Lucina and Heinze, Nicolai and Staat, Manfred and Neiss, Wolfram F. and Scaal, Martin and M{\"u}ller, Lars P.},
  title     = {Radial shortening osteotomy reduces radiocapitellar contact pressures while preserving valgus stability of the elbow},
  series = {Knee Surgery, Sports Traumatology, Arthroscopy},
  volume    = {25},
  journal   = {Knee Surgery, Sports Traumatology, Arthroscopy},
  number    = {7},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1433-7347},
  doi       = {10.1007/s00167-017-4468-z},
  pages     = {2280 -- 2288},
  year      = {2017},
  language  = {en}
}