Anchorage Mechanisms Research Articles

Experimental Investigation on Anchorage Mechanisms of Self-Locked Anchor under Combined Tension and Shear

Self-locked anchor is a new type of underreamed anchor, and which is more and more frequently used in both new construction and structural retrofitting or strengthening projects. Nevertheless, current design codes do not contain suitable design recommendations for these anchors. This study investigates the anchorage mechanisms of self-locked anchor under combined tension and shear loadings. The experimental parameters mainly include anchor diameters (Φ16 and Φ20) and loading angles (0°, 30°, 45°, and 60°). The present results indicate the characters of axial and transverse deformations, the ultimate bearing capacity, the fracture pattern of anchor, and the breakout model of concrete.

Enthesitis: an autoinflammatory lesion linking nail and joint involvement in psoriatic disease

The traditional model for psoriasis and psoriatic arthritis (PsA) is that autoimmunity directed against a common skin and joint autoantigen leads to chronic autoreactive T cell driven inflammation. However, recent imaging, histological and genetic studies have challenged this view, especially with respect to joint and nail disease, and provide a broader insight into the pathogenesis of PsA and associated nail involvement. Clinically unrecognized enthesitis (inflammation at tendon and ligament attachments) is commonly seen in early PsA at all sites of the disease. Specifically, enthesitis is associated with adjacent osteitis or bone and synovial inflammation. Even in normal joints, normal insertions are associated with microdamage and inflammatory change, strongly suggesting that local tissue specific, or what has been described as autoinflammatory factors, may dictate disease expression. Distal interphalangeal (DIP) joint disease in PsA is associated with diffuse inflammation that envelops the nail root and adjacent bone. In fact, the nail is intimately linked to entheses, with the extension tendon of the DIP joint sending fibres from bone that envelop the nail root in an interdigitating fashion. Furthermore, the joint collateral ligament enthesis has fibres that merge with the lateral borders of the nail. Other anchorage mechanisms include fibres that directly tether the nail plate to the underlying periosteum, which itself is closely anchored to the extension tendon. The frequent microdamage and tissue repair at normal enthesis attachment sites in healthy joints has resulted in a proposed new model of PsA pathogenesis embracing the concept of autoinflammation, whereby tissue specific factors, including microtrauma, lead to regional innate immune activation and persistent inflammation, as an alternative to primary immunopathology driven by T and B cell abnormalities. Unlike the classical autoimmune diseases, which may attack a completely normal organ, autoimmunity in psoriatic disease is likely to involve tissues where there is intrinsic dysregulation of the target tissues. These tissue specific factors related to the enthesis appear to be key to the phenotypic expression of diseases hitherto regarded as autoimmune. The pathogenesis of PsA, nail disease and to a lesser extent psoriasis therefore appear to have an autoinflammatory (innate immune driven) rather than autoimmune basis. Taken together, these findings are important for better understanding PsA, nail disease and psoriasis, and for conceptualizing the immunopathogenic basis of these diseases and further exploring the role of enthesitis in their pathophysiology.

A generic 3D finite element model of tree anchorage integrating soil mechanics and real root system architecture

Understanding the mechanism of tree anchorage in a forest is a priority because of the increase in wind storms in recent years and their projected recurrence as a consequence of global warming. To characterize anchorage mechanisms during tree uprooting, we developed a generic finite element model where real three-dimensional (3D) root system architectures were represented in a 3D soil. The model was used to simulate tree overturning during wind loading, and results compared with real data from two poplar species (Populus trichocarpa and P. deltoides). These trees were winched sideways until failure, and uprooting force and root architecture measured. The uprooting force was higher for P. deltoides than P. trichocarpa, probably due to its higher root volume and thicker lateral roots. Results from the model showed that soil type influences failure modes. In frictional soils, e.g., sandy soils, plastic failure of the soil occurred mainly on the windward side of the tree. In cohesive soils, e.g., clay soils, a more symmetrical slip surface was formed. Root systems were more resistant to uprooting in cohesive soil than in frictional soil. Applications of this generic model include virtual uprooting experiments, where each component of anchorage can be tested individually.

Numerical study of mono-strand anchorage mechanism under service load

Anchorage devices play an important role in post-tensioned bridge structures since they must sustain heavy loads in order to permit the transfer of the prestressing force to the structure. In external prestressing, the situation is even more critical since the anchorage mechanisms, with the deviators, are the only links between the structure and the tendons throughout the service life of the structure. The behaviour of anchorage devise may be studied by using the finite element method. To do so, each component of the anchorage must be adequately represented in order to approximate the anchor mechanism as accurately as possible. In particular, the modelling of the jaw/tendon device may be carried out using the real geometry of these two components with an appropriate constitutive contact law or by replacing these components by a single equivalent. This paper presents the numerical study of a mono-strand anchorage device. The results of a comparison between two different representations of the jaw/tendon device, either as two distinct components or as a single equivalent, will be examined. In the double-component setup, the influence of the wedge configuration composing the jaw, and the influence of lubrication of the anchor, will be assessed.

Posttranslational modifications required for cell surface localization and function of the fungal adhesin Aga1p.

Adherence of fungal cells to host substrates and each other affects their access to nutrients, sexual conjugation, and survival in hosts. Adhesins are cell surface proteins that mediate these different cell adhesion interactions. In this study, we examine the in vivo functional requirements for specific posttranslational modifications to these proteins, including glycophosphatidylinositol (GPI) anchor addition and O-linked glycosylation. The processing of some fungal GPI anchors, creating links to cell wall beta-1,6 glucans, is postulated to facilitate postsecretory traffic of proteins to cell wall domains conducive to their functions. By studying the yeast sexual adhesin subunit Aga1p, we found that deletion of its signal sequence for GPI addition eliminated its activity, while deletions of different internal domains had various effects on function. Substitution of the Aga1p GPI signal domain with those of other GPI-anchored proteins, a single transmembrane domain, or a cysteine capable of forming a disulfide all produced functional adhesins. A portion of the cellular pool of Aga1p was determined to be cell wall resident. Aga1p and the alpha-agglutinin Agalpha1p were shown to be under glycosylated in cells lacking the protein mannosyltransferase genes PMT1 and PMT2, with phenotypes manifested only in MATalpha cells for single mutants but in both cell types when both genes are absent. We conclude that posttranslational modifications to Aga1p are necessary for its biogenesis and activity. Our studies also suggest that in addition to GPI-glucan linkages, other cell surface anchorage mechanisms, such as transmembrane domains or disulfides, may be employed by fungal species to localize adhesins.

Theoretical Versus Experimental Modeling of the Anchorage Capacity of Geotextiles in Trenches

The behavior of the anchorage of geotextile sheets at the top of a slope is a decisive factor when determining the dimensions of geosynthetic lining systems on slopes. In order to optimize the geometry of the structures in question (to reduce the area taken up by the anchorage at the top of the slope), anchorage solutions using trenches of varying forms are sometimes used. Calculating the required dimensions of this anchorage remains problematic. To improve knowledge of the behavior of anchor trenches, experimental studies and numerical studies were developed. Full-scale pullout tests were carried out on anchored geotextile sheets (run-out anchorage and anchor trenches). Two types of soil were studied: sand and sandy silt. The numerical modeling proposed was based on the Discrete Element Method (DEM). This method is particularly well suited to the problem being addressed, for it enables consideration of major movements and large-scale deformation of the soil (rotation, compression, and lifting) as well as large displacements between the geotextile and the soil. Comparisons between the experimental and numerical results provide practical conclusions concerning anchorage mechanisms.