Experimental and DEM investigation of geogrid–soil interaction under pullout loads

2016 ◽  
Vol 44 (3) ◽  
pp. 230-246 ◽  
Author(s):  
Zhijie Wang ◽  
Felix Jacobs ◽  
Martin Ziegler
Keyword(s):  
Pullout Loads

scholarly journals Novel Biodegradable Composite of Calcium Phosphate Cement and the Collagen I Mimetic P-15 for Pedicle Screw Augmentation in Osteoporotic Bone

Biomedicines ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1392
Author(s):  
Harald Krenzlin ◽  
Andrea Foelger ◽  
Volker Mailänder ◽  
Christopher Blase ◽  
Marc Brockmann ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Pedicle Screw ◽  
Calcium Phosphate Cement ◽  
Pedicle Screws ◽  
Osteoblastic Differentiation ◽  
Collagen I ◽  
Osteoporotic Bone ◽  
Mineral Density ◽  
Screw Augmentation ◽  
Pullout Loads

Osteoporotic vertebral fractures often necessitate fusion surgery, with high rates of implant failure. We present a novel bioactive composite of calcium phosphate cement (CPC) and the collagen I mimetic P-15 for pedicle screw augmentation in osteoporotic bone. Methods involved expression analysis of osteogenesis-related genes during osteoblastic differentiation by RT-PCR and immunostaining of osteopontin and Ca2+ deposits. Untreated and decalcified sheep vertebrae were utilized for linear pullout testing of pedicle screws. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DEXA). Expression of ALPI II (p < 0.0001), osteopontin (p < 0.0001), RUNX2 (p < 0.0001), and osteocalcin (p < 0.0001) was upregulated after co-culture of MSC with CPC-P-15. BMD was decreased by 28.75% ± 2.6%. Pullout loads in untreated vertebrae were 1405 ± 6 N (p < 0.001) without augmentation, 2010 ± 168 N (p < 0.0001) after augmentation with CPC-P-15, and 2112 ± 98 N (p < 0.0001) with PMMA. In decalcified vertebrae, pullout loads were 828 ± 66 N (p < 0.0001) without augmentation, 1324 ± 712 N (p = 0.04) with PMMA, and 1252 ± 131 N (p < 0.0078) with CPC-P-15. CPC-P-15 induces osteoblastic differentiation of human MES and improves pullout resistance of pedicle screws in osteoporotic and non-osteoporotic bone.

Strength Retention of a New Microbial Cellulose Scaffold and Existing Collagen-Based Scaffolds After In Vivo Implantation in a Rabbit Model

2009 ◽  
Author(s):  
Michael I. Dishowitz ◽  
Miltiadis H. Zgonis ◽  
Jeremy J. Harris ◽  
Constance Ace ◽  
Louis J. Soslowsky
Keyword(s):  
Mechanical Behavior ◽  
Healing Process ◽  
Rabbit Model ◽  
In Vivo Model ◽  
Microbial Cellulose ◽  
Poor Outcomes ◽  
Over Time ◽  
Pullout Loads

Rotator cuff tendon tears often require large tensions for repair [1] and these tensions are associated with poor outcomes including rerupture [2]. To address this, repairs are often augmented with collagen-based scaffolds. Microbial cellulose, produced by A. xylinum as a laminar non-woven matrix, is another candidate for repair augmentation [3]. An ideal augmentation scaffold would shield the repair site from damaging loads as they change throughout the healing process. Although the initial mechanical properties of clinically used scaffolds have been well characterized [4–6], their mechanical behavior following implantation is not known. As a result, the role of these scaffolds throughout the healing process remains unknown. Therefore, the objective of this study is to characterize the mechanical behavior of existing collagen-based scaffolds and a new, microbial cellulose scaffold over time using an in vivo model. We hypothesize that: 1) collagen-based scaffolds will show decreased stiffness (1a) and suture pullout loads (1b) over time when compared to initial values while the microbial cellulose scaffold will not; and 2) the collagen-based scaffolds will have decreased stiffness (2a) and suture pullout loads (2b) when compared to the new, microbial cellulose scaffold at all timepoints.

scholarly journals Properties of Sleeve Joints Made from Reduced Bamboo

2020 ◽  
Vol 10 (17) ◽  
pp. 5985
Author(s):  
Yiren Wang ◽  
Salim Hiziroglu
Keyword(s):  
Cross Sections ◽  
Failure Modes ◽  
Longitudinal Shear ◽  
Strength Properties ◽  
Phyllostachys Pubescens ◽  
Bamboo Species ◽  
Grass Family ◽  
Steel Sleeve ◽  
Effective Use ◽  
Pullout Loads

Bamboo is a fast-growing species in the grass family, with excellent tensile and compressive strength characteristics, in the plant kingdom. The tapered hollow thin-walled cylindrical configuration of the bamboo species, namely, Gui bamboo (Phyllostachys makinoi Hayata) and Moso bamboo (Phyllostachys pubescens) culm, adversely influences its longitudinal shear and transversal tensile strength properties for effective use in engineered joints. The objective of this study is to use the thermo–hydro–mechanical (THM) process to reduce the irregular shape of bamboo ends without damaging the culms. Samples from the two abovementioned bamboo species were used for the experiments. Pullout loads and failure modes of the sleeve bamboo joints assembled by gluing were also evaluated. Eighty-nine out of 96 tested bamboo culms were successfully reduced by the THM treatment to uniform circular cross-sections under the maximum reduction ratio of 0.15. Sleeved-joint samples made from Gui bamboo with wood fittings had the highest pullout loads and strength values. Based on the findings in this work, it appears that THM-treated reduced bamboo ends, being a sustainable resource, could have the potential to be manufactured as steel-sleeve joints to be used for different engineering applications.

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