Design of a tensegrity servo-actuated structure for civil applications

The use of glass elements in civil engineering is spreading in the last years beyond merely aesthetic functions for their ease of installation and production. Nonetheless, the structural performance of such materials in any condition of use is object of investigation. In this scenario, the paper analyses the performance of an innovative concept of tensegrity floor (Patent no 0001426973) characterized by a particular steel-glass adhesive junction that permits a profitable structural cooperation between such basically different materials. As known, at the base of the effectiveness of tensegrity structures lies the correct tensioning of metal strands which are devoted at keeping the rigid elements compressed. The tensioning level is then responsible of the actual deformation of the structure, which is of course of uttermost importance while speaking of civil applications. To address this issue with the adequate level of confidence required by construction practice, a mechatronic servo-system is proposed, aimed at maintaining, and modifying when needed, the stress state of the metal cables to adjust the deformation of the upper plane in response to varying loads. Three different actuation schemes, with different levels of realization complexity, are analysed and compared in simulated environment by means of a hybrid multibody-finite elements model.

Parametric Shape and Manufacturing Optimization of Customized Kitesurf Hydrofoils

To minimize the costs of the current manufacturing of kitesurf hydrofoil wings, a workflow using a finite elements model was developed. By coupling a computational fluid dynamic (CFD) analysis with a structural finite element analysis (FEA), an optimization based on a genetic algorithm is implemented. The design space of the optimization is defined by the manufacturing processes. This enables the algorithm to find wing shapes which are not only suitable for the rider’s weight and preferred take-off speed but can also be produced directly on a universal mold surface. To reduce the amount of cut-off material and sustain the mechanical stresses, the output of the optimization contains the required number and orientation of all fiber layers within the reinforcement structure. This research shows that a single mold can produce different wing shapes to satisfy the needs of a wide range of customers.

THE INFLUENCE OF PLASTIC STRAINS ON THE DEPTH OF OPEN RESIDUAL CRACKS IN COMPRESSED ZONE PF CONCRETE

A significant part of the territory of Russian Federation refers to seismically dangerous areas. In the current code in design of reinforced concrete buildings for seismic loads the development of plastic strains is supposed. They are taken into account while determining loads by introduction of reducing factor K1, but their influence on the strength of elements is neglected. Plastic strains of reinforcement lead to appearance of residual cracks in compressed zone of concrete and due to this the reduction of bearing capacity of bending elements takes place on following loading cycles. The approximate method of determination of the depth of open cracks and of the residual height of sections when changing the sign of internal forces after reaching the maximum deflection has been proposed. The depth of residual crack is determined from the condition of equilibrium of longitudinal forces with regard to stress-strain state of a section at three stages of loading: at a moment of achievement of maximum plastic strains, at the unloading stage and at a moment of the beginning of crack formation after changing the sign of internal forces. The comparison of results obtained by the approximate method and results of calculation of finite elements model of a beam has been carried out.

A Novel Gap Element for the Coupling of Incompatible Interface in Component Mode Synthesis Method

The component mode synthesis (CMS) methods are often utilized for modal analysis to investigate the vibration characteristics of the complex structures which are commonly divided into several substructures. However, non-matching finite element meshes may occur at the interfaces between components and virtual gaps are easily produced along the curved interfaces, which limit the application of CMS and lead to larger numerical errors for vibration analysis. To overcome the problem, a novel gap element method (GEM) is employed into a free-interface CMS method in this paper, where both displacements and forces of the nodes on the incompatible interfaces are introduced by two independent Lagrange multipliers to enforce the compatibility conditions. Two-dimensional numerical examples are given to validate the effectiveness of the proposed method. The results of natural frequencies and modal shapes obtained using the proposed method agree very well with the ones obtained using full finite elements model, no matter the gaps along the interface exist or not. The influence of the number of nodes on the non-matching interfaces on the accuracy of frequencies is also discussed.

Investigation of Mechanical Behaviour of the Bone Cement (PMMA) under Combined Shear and Compression Loading

Generally, implants fixations in orthopedic surgery are insured by bone cement; which is generated mainly from polymer polymethylmethacrylate (PMMA). Since, the cement is identified as the weakest part among bone-cement-prosthesis assembly. Hence, the characterization of mechanical behaviour is of a crucial requirement for orthopaedic surgeon’s success. In this study, we investigates the failure behaviour of bone cement, under combined shear and compression loading, for the aim to determine the strengths of bone cement for different mode loading conditions. Therefore, experimental cylindrical specimens has been tested to assess different shear-compression stresses. Based on the mechanical tests, a finite elements model of cylindrical specimens was developed to evaluate stresses distribution in the bone cement under compression, shear and combined shear-compression loading. Results show that, the load which leading to the failure of the cement decreased with increasing of the specimen angle inclination with respect of loading direction.

Effect of Tension on Collapse Performance of Flexible Pipes

This paper investigates the effect of tension on collapse performance of flexible pipes. In the design of flexible pipelines for offshore field developments, one of the failure modes being associated with external pressure and bending loadings is the hydrostatic collapse. In accordance with standards, TechnipFMC methodology for flexible pipe collapse resistance determination ensures a robust design. The model has an analytical basis, leading to a fast and straightforward use. It has been validated with more than 200 tests performed on all possible pipe constructions on straight and curved configurations. TechnipFMC and IFP Energies nouvelles have also developed and improved over the past few years a Finite Elements Model dedicated to flexible riser studies. It takes full advantage of the structure periodicities such that a whole riser can be studied with a short length and low CPU cost model associated to specific periodicity conditions. The model is able to represent bent risers in various configurations (bending cycles, internal and external pressure, axial tension, torsion) and has been used for collapse prediction of flexible risers under tension. Additionally, a specific test protocol has been developed to be able to carry out a collapse test associated to tension. The purpose of this paper is to present the collapse test result, the specific development of the model for collapse and tension and the corresponding calculations performed with the Finite Elements Model on several structures, demonstrating that there is no negative influence of tension on collapse mode. It also gives a better understanding on the interaction between tension in the armor layers and collapse phenomenon.