@article{Staat2021,
  author    = {Staat, Manfred},
  title     = {An extension strain type Mohr-Coulomb criterion},
  series = {Rock mechanics and rock engineering},
  volume    = {54},
  journal   = {Rock mechanics and rock engineering},
  number    = {12},
  publisher = {Springer Nature},
  address   = {Cham},
  issn      = {1434-453X},
  doi       = {10.1007/s00603-021-02608-7},
  pages     = {6207 -- 6233},
  year      = {2021},
  abstract  = {Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr-Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.},
  language  = {en}
}
@article{HacklBuessKammerlohretal.2021,
  author    = {Hackl, Michael and Buess, Eduard and Kammerlohr, Sandra and Nacov, Julia and Staat, Manfred and Leschinger, Tim and M{\"u}ller, Lars P. and Wegmann, Kilian},
  title     = {A "comma sign"-directed subscapularis repair in anterosuperior rotator cuff tears yields biomechanical advantages in a cadaveric model},
  series = {The american journal of sports medicine},
  volume    = {49},
  journal   = {The american journal of sports medicine},
  number    = {12},
  publisher = {Sage},
  address   = {London},
  issn      = {1552-3365},
  doi       = {10.1177/03635465211031506},
  pages     = {3212 -- 3217},
  year      = {2021},
  abstract  = {Background: Additional stabilization of the "comma sign" in anterosuperior rotator cuff repair has been proposed to provide biomechanical benefits regarding stability of the repair. Purpose: This in vitro investigation aimed to investigate the influence of a comma sign-directed reconstruction technique for anterosuperior rotator cuff tears on the primary stability of the subscapularis tendon repair. Study Design: Controlled laboratory study. Methods: A total of 18 fresh-frozen cadaveric shoulders were used in this study. Anterosuperior rotator cuff tears (complete full-thickness tear of the supraspinatus and subscapularis tendons) were created, and supraspinatus repair was performed with a standard suture bridge technique. The subscapularis was repaired with either a (1) single-row or (2) comma sign technique. A high-resolution 3D camera system was used to analyze 3-mm and 5-mm gap formation at the subscapularis tendon-bone interface upon incremental cyclic loading. Moreover, the ultimate failure load of the repair was recorded. A Mann-Whitney test was used to assess significant differences between the 2 groups. Results: The comma sign repair withstood significantly more loading cycles than the single-row repair until 3-mm and 5-mm gap formation occurred (P≤ .047). The ultimate failure load did not reveal any significant differences when the 2 techniques were compared (P = .596). Conclusion: The results of this study show that additional stabilization of the comma sign enhanced the primary stability of subscapularis tendon repair in anterosuperior rotator cuff tears. Although this stabilization did not seem to influence the ultimate failure load, it effectively decreased the micromotion at the tendon-bone interface during cyclic loading. Clinical Relevance: The proposed technique for stabilization of the comma sign has shown superior biomechanical properties in comparison with a single-row repair and might thus improve tendon healing. Further clinical research will be necessary to determine its influence on the functional outcome.},
  language  = {en}
}
@article{HacklNacovKammerlohretal.2021,
  author    = {Hackl, Michael and Nacov, Julia and Kammerlohr, Sandra and Staat, Manfred and Buess, Eduard and Leschinger, Tim and M{\"u}ller, Lars P. and Wegmann, Kilian},
  title     = {Intratendinous Strain Variations of the Supraspinatus Tendon Depending on Repair Technique: A Biomechanical Analysis Regarding the Cause of Medial Cuff Failure},
  series = {The American Journal of Sports Medicine},
  volume    = {49},
  journal   = {The American Journal of Sports Medicine},
  number    = {7},
  publisher = {Sage},
  address   = {London},
  issn      = {1552-3365},
  doi       = {10.1177/03635465211006138},
  pages     = {1847 -- 1853},
  year      = {2021},
  language  = {en}
}
@article{TranStaat2021,
  author    = {Tran, Ngoc Trinh and Staat, Manfred},
  title     = {Direct plastic structural design under random strength and random load by chance constrained programming},
  series = {European Journal of Mechanics - A/Solids},
  volume    = {85},
  journal   = {European Journal of Mechanics - A/Solids},
  number    = {Article 104106},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0997-7538},
  doi       = {10.1016/j.euromechsol.2020.104106},
  year      = {2021},
  language  = {en}
}