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A solvent cast 3D printing (SC-3DP) technique was explored comprehensively to fabricate bioresorbable polymer matrix composite stent in the present study. The developed methodology was assessed by printing the customized shape stent on the rotating mandrel. The polymeric composite was developed by blending bioresorbable carbonyl iron powder (CIP) and polycaprolactone (PCL). The process parameter’s effect on percentage shrinkage in strut width and strut thickness, radial compression load and flexibility of stents was evaluated. Response surface methodology (RSM) was used for designing the experiments utilizing the process parameters like material compositions, printing speed and layer thickness. Analysis of variance was used to find out the significant parameters. The regression analysis was performed to obtain statistical equations with significant terms. It was noted that the reinforcement of CIP improved the fluidity of the material for better deposition as compared to pure PCL. The printing speed and layer thickness were observed to have a significant effect on the process. The significant interaction between layer thickness and printing speed parameters was also observed for shrinkage in width and thickness, compression and flexibility properties. Moreover, multi-objective optimization was performed using a genetic algorithm technique to minimize the percentage shrinkage of strut width and thickness, and load for bending to evaluate flexibility and maximize radial compression load. The method opens a unique way to fabricate patient-specific bioresorbable composite stents with customized properties.

In this paper, joint precast piles with a cross-section of 400 × 400 mm and a pin-joined connection were considered, and their interaction with the soil of Western Kazakhstan has been analyzed. The following methods were used: assessment of the bearing capacity using the static compression load test (SCLT by ASTM) method, interpretation of the field test data, and the dynamic loading test (DLT) method for driving precast concrete joint piles, including Pile Driving Analyzer (PDA by ASTM) and Control and Provisioning of Wireless Access Points (CAPWAP) methods. According to the results, the composite piles tested by the PDA (by ASTM) method differ by 15 percent compared to the static load method, while the difference between the dynamic DLT (by ASTM) method and the static load (by ASTM) method was only 7 percent. So, according to the results, the alternative dynamic method DLT (by ASTM) is very effective and more accurate compared to other existing methods.

Background Context: This study’s purpose was to evaluate the biomechanical performance of plate–nail and dual-plate fixation for the treatment of AO/OTA 41-C2 tibial plateau fractures. Methods: Twenty synthetic tibias were selected and randomly divided into a plate–nail group (n = 10) and a dual-plate group (n = 10). After the artificial tibias were osteotomized to simulate AO/OTA 41-C2 tibial plateau fractures in both groups, the plate–nail and the dual-plate methods, respectively, were used for fixation, and then axial compression loading, three-point bending, torsion, and axial failure tests were carried out. The data of each group were recorded and statistically analyzed. Results: In the axial compression test, the average stiffness of the plate–nail group was higher than that of the dual-plate group (p < 0.05). The displacement generated in the plate–nail group was significantly smaller than that in the dual-plate group (p < 0.05). In the resisting varus test, the stress of the plate–nail group was significantly higher than that of the dual-plate group (p < 0.05). In the resisting valgus test, the stress of the plate–nail group was slightly higher than that of the dual-plate group, but the difference was not statistically significant (p > 0.05). In the static torsion test, the load applied to the plate–nail group was smaller than that of the dual-plate group when rotated to 5° (p < 0.05). In the axial compression failure test, the average ultimate load of the plate–nail group was significantly higher than that of the dual-plate group (p < 0.05). Conclusion: The treatment of AO/OTA 41-C2 tibial plateau fractures with plate–nail fixation is superior to that with dual-plate fixation in resisting axial stress and preventing tibial varus deformity, while dual-plate fixation has better resisting torsional ability.

A thin-walled steel cylindrical shell is a common engineering structure that has an efficient load-carrying capacity. This structure is more easily subjected to partial axial compression loads in application, and buckling is the main failure mode. However, there are few available design methods for partial axially compressed steel cylindrical shells. Motivated by this, a design method called the localized perturbation load approach (LPLA) is proposed in this paper. The finite element framework for the application of LPLA is established. The location and number of perturbation loads are determined by considering the imperfection sensitivity and the buckling failure mode of partial axial compressed cylinders. A series of buckling experiments are carried out to validate the LPLA method. In addition, the reliability of LPLA for the design of cylindrical shells with different imperfection locations and dimensions is also verified. The results show that LPLA can give conservative and reliable lower-bound buckling loads. Therefore, LPLA can be used as a design method for thin-walled steel cylindrical shell structures under partial axial compression in actual engineering.

This study presents a comprehensive investigation of the in-plane response of unreinforced masonry shear walls with regular openings, under the action of monotonic lateral displacement. Walls are considered with several pre-compression loads as well as different window and door openings configurations. To this end, a group of masonry shear walls built with clay bricks and hydraulic lime-sand mortar was selected featuring regular opening layouts. The micro-modeling approach was utilized by considering complex constitutive laws for materials' nonlinear behavior for capturing damages in elements. Results from the nonlinear analysis of the walls were obtained, including the lateral load capacity of shear walls at different performance points, their lateral displacement, stiffness, ductility capacity, normalized absorbed energy, and the overstrength, force reduction, and response modification factors. Moreover, a full discussion is presented regarding the estimating equations from the ASCE 41–17 code on the maximum shear capacity of the walls including their accuracy to predict the shear capacity of URM walls with openings. It is observed that opening reduces the shear strength of the unreinforced masonry shear wall between 5 and 60% as well as a reduction of 10–85% in its effective stiffness, depending on the intensity of the pre-compression load. Moreover, the code’s estimation equations for shear strength of unreinforced masonry shear walls lead to an underestimation. For walls with two or more openings of window or door, the average strength from the upper and lower bound of the code-based strength seems appropriate, considering an intense pre-compression load on the wall.

The purpose of the present study was to evaluate the mechanical resistance of elastodontic devices (ED): their maximum compression loads and plastic deformation under loading (percentage). An Instron universal machine (Model 3365, Instron, Industrial Product Group, Grove City, PA, USA) was employed with a 100 N load cell and with Bluehill software for loading analyses. Each device was submitted to a five-cycles test. The following ED were evaluated: A.M.C.O.P. (Micerium, Genova, Italy) in red color, in orange color, and in blue color; HealthyStart (Ortho-Tain, Winnetka, IL, USA), and T4K™ phase 1 (Myofunctional Research Co., Helensvale, Australia). During the five-cycles test, the Ortho-Tain device delivered the greatest compression load (7.56 N), with the lowest percentage of deformation (0.95%). For all devices, a slight plastic deformation of the material was registered, ranging from 0.95% to 1.75%. For the T4K device it was not possible to complete the five-cycles test. For all the analyzed ED, a slight plastic deformation under loading was registered, that in all cases can be considered clinically acceptable. Further studies are needed to test the appliances after clinical usage.

Foam concrete has recently become a key construction material in terms of meeting the special needs of modern engineering applications such as thermal insulation, absorption of static and dynamic loads. In this study, the effect of polypropylene fiber content and various uni- and tri-axial compression loads on the toughness response of polypropylene fiber-reinforced foam concrete was investigated. Up to a certain strain level (0.1 mm/mm), the ultimate compression stress of specimens under uni- and tri-axial loading increased from about 1 MPa to 16 MPa with the increased target densities of foam concrete. There was a strain-hardening capability of low-density foam concrete while the specimens failed by strain-softening in the high-density series. The optimum fiber amounts were found to be 3.9%, 4.6%, and 6.4% for low, medium, and high target densities of foam concrete, respectively. At low-density series, the bubbles were observed to be relatively bigger and mostly merged with each other. A reduction in foam content (vice versa, increasing target density of mixture) and the presence of fiber resulted in smaller pore size and a more homogenous distribution of them in the matrix. In conclusion, the desired pore structure and efficient bridging of fibers in the matrix allowed the production of favorable foam concrete with higher toughness.

Thin-walled galvanized helical corrugated steel tubes (HCSTs) filled with concrete are promising composite members, consisting of concrete, an anti-corrosion shell, and a multifunctional exterior corrugated steel tube. To investigate the synergistic working mechanism of concrete-filled HCSTs (CFHCSTs), six specimens were designed for axial compression tests, with the inner diameter of the column and the volumetric steel ratios of the longitudinal reinforcement as the variation parameters. The results show that HCSTs can better confine the concrete core and increase its strength. The failure mode of HCSTs is significantly influenced by the column’s diameter, and those with a smaller diameter are prone to slide failure and lock seam tearing. The strains and stresses on HCSTs are discussed in detail to elucidate the confinement effect. This paper proposes a suitable design method to predict the ultimate axial compression load capacity of CFHCST columns based on early studies on steel tube-confined concrete.

In recent years, the researches on concrete-filled steel tubular (CFST) intersecting nodes mainly focused on the plane intersecting nodes, while that on space intersecting nodes with off-plane angles was relatively less. In this study, the nonlinear analyses of CFST space intersecting node models established in ABAQUS were performed under the monotonic axial compression and reciprocal axial tension-compression loads, respectively. The stress distributions of steel tubes and core concrete were analyzed, and the hysteresis characteristics and stiffness degradation of the node were studied. The in-plane angle, off-plane angle, out-of-plane constraint effect, steel tube diameter-to-thickness ratio, and core concrete strength were used as control parameters to analyze their effects on the mechanical behavior of the nodes. The results show that the bearing capacity of the nodes meets the design requirements, the hysteresis loop is full, the initial stiffness is large and the stiffness degrades slowly. The off-plane angle, out-of-plane constraint effect, steel tube diameter-thickness ratio and core concrete strength have significant effects on the bearing capacity and lateral stiffness of the nodes. In order to reduce the adverse effect of out-of-plane displacement, the space intersecting nodes in practical engineering can use reinforced floor beams or prestressd cables to impose out-of-plane constraint, and the recommended value of out-of-plane constraint effect is 10–30 kN/mm.

The diffusion of Sulfate ions in concrete is a complex process and affects the performance of concrete. Experiments on the time-dependent distribution of sulfate ions in concrete under the coupling of pressure load, dry-wet circulation, and sulfate attack, and the diffusion coefficient of sulfate ions with various parameters was tested. The applicability of the cellular automata (CA) theory to simulate the diffusion of sulfate ions was discussed. In this paper, a multiparameter cellular automata (MPCA) model was developed to simulate the impacts of load, immersion ways, and sulfate solution concentration for the diffusion of sulfate ions in concrete. The MPCA model was compared with experimental data, considering compressive stress, sulfate solution concentration, and other parameters. The numerical simulations verify the calculation results based on the MPCA model are in good agreement with the test data. Finally, the applicability of the established MPCA model was also discussed.