558 research outputs found
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Shear performance of replaced bolt shear connectors in prefabricated composite beams
No full textBolt shear connectors have the advantage of efficient installation and demolition when used in prefabricated composite beams. When bolt shear connectors are damaged in the service period and replaced by new ones, the shear performance of replaced bolts is to be affected by the existing structural damage. This paper investigates the shear performance of eleven re-assembled push-out specimens of bolt connectors. The experimental results show that the replaced bolts possess a similar shear resistance to the bolts in the original tests. In contrast, the relative slips at the interfaces between the steel beams and the prefabricated concrete (PC) slabs show a bigger scattering. A calculation method of shear resistance for the replaced bolts considering the influence of the existing damage was proposed based on the experiments, and comparisons show that the calculation values agree well with the experimental results.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite Structure
Rationale for simplifying the strength formulae for the design of multi-row bolted connections failing in net tension
No full textHart-Smith [1] developed a set of closed form strength formulae for a semi-empirical approach to determine the net tension strength of multi-row bolted connections with composite materials. Mottram [2] showed that, for a pultruded fibre reinforced polymer material, the approach to be reliable (and conservative) for the configuration comprising two rows with a single bolt per row. This led to the formulae being developed into clauses in an American pre-standard for Load and Resistance Factor Design (LRFD) of Pultruded Fiber-Reinforced Polymer (FRP) Structures [3]. Because the expressions in the Hart-Smith formulae are not simple, the message coming from the practitioners, on the ASCE/SEI Fiber Composites And Polymers Standards committee (FCAPS) tasked with developing the pre-standard [3] into a standard, is that they would not use them when designing bolted connections. Taking stock of the specified geometries, bolt details and design parameters permitted by the pre-standard [3] the author conducted an analytical
parametric study using the Hart-Smith formulae with the aim of establishing simplified forms that could be routinely used in the design office. Presented in this paper is the provenance to this code-specific work when the connection has more than a single row of bolts. A presentation is given to what has been lost, in terms of calculated net tension strength, by providing the
simplified strength formula in the mandatory part to the standard. To enable the designer to be able to take full advantage of the Hart-Smith design approach [1, 2], the ‘complicated’ formulae and their accompanying mandatory-style text are to be found in an appendix with the standard’s commentary [3]
Shearing Stress Model of Damage Bolt in Tunnel
No full textWhen bolt is damaged, character of stress is different from character of shear stress integrated bolt. Firstly, Based on the displacement formula of the tunnel surrounding rock，the shear stress and axial force calculation formula of integrated bolt are educed. Subsequence, based on the BOUSSINESG formula of displacement, models on fully grouted bolt shear stress and axial force of uniform rock are educed under pullout load. Consequently, the author deduces shear stress model of bolt damage (completely void of bolt and grouting), combining modes on shear stress and axial force of integrated bolt and shear stress model of bolt under pullout load..</jats:p
Finite element model study of the effect of corner rounding on detectability of corner cracks using bolt hole eddy current
No full textRecent work has shown that the detectability of corner cracks in bolt-holes is compromised when rounding of corners arises, as might occur during bolt-hole removal. Probability of Detection (POD) studies normally require a large number of samples of both fatigue cracks and electric discharge machined notches. In the particular instance of rounding of bolt-hole corners, the generation of such a large set of samples representing the full spectrum of potential rounding would be prohibitive. In this paper, the application of Finite Element Method (FEM) modeling is used to supplement the study of detection of cracks forming at the rounded corners of bolt-holes. FEM models show that rounding of the corner of the bolt-hole reduces the size of the response to a corner crack to a greater extent than can be accounted for by loss of crack area. This reduced sensitivity can be ascribed to a lower concentration of eddy currents at the rounded corner surface and greater lift-off of pick-up coils relative to that of a straight-edge corner. A rounding with a radius of 0.4 mm (.016 inch) showed a 20% reduction in the strength of the crack signal. Assuming linearity of the crack signal with crack size, this would suggest an increase in the minimum detectable size by 25%. Modeling results are consistent with measurements performed on cracks grown on bolt-hole samples extracted from service.</p
Thermal failure in a clamping bolt of a shunt reactor
No full textThis article presents the detection and analysis of a thermal failure produced in a core clamping bolt of a 5 MVAr gapped three-phase shunt reactor. Gases were detected in this shunt reactor during its operation at a substation in Mexico. Using dissolved gas analysis (DGA) and Duval’s triangle method, temperatures up to 700°C were estimated in the shunt reactor. Overheating evidence was detected in one of the core clamping bolts during an internal inspection of the shunt reactor. The author and the reactor manufacturer believe that the insulation of the clamping bolt was damaged by the loosening of the bolts produced by the vibration of the shunt reactor in conjunction with a possible low torque applied to the bolts. A short circuit between the bolt and the clamping frame was produced, generating the circulation of eddy currents in the bolt producing high temperatures and gasifying the insulating oil in the shunt reactor. Three-dimensional (3-D) finite element (FE) simulations were performed to verify the cause of the overheating issue in the clamping bolt of the shunt reactor, simulating the short circuit between the clamping bolt and the core frame. From the simulation results, the author determined that a short circuit between the bolt and the core frame generated the gases and the high temperatures in the shunt reactor. Finally, the manufacturer of the shunt reactor decided to reinforce the insulation of the clamping bolts using fiberglass to avoid future possible short circuit failures
Thermal failure in a clamping bolt of a shunt reactor
No full textThis article presents the detection and analysis of a thermal failure produced in a core clamping bolt of a 5 MVAr gapped three-phase shunt reactor. Gases were detected in this shunt reactor during its operation at a substation in Mexico. Using dissolved gas analysis (DGA) and Duval’s triangle method, temperatures up to 700°C were estimated in the shunt reactor. Overheating evidence was detected in one of the core clamping bolts during an internal inspection of the shunt reactor. The author and the reactor manufacturer believe that the insulation of the clamping bolt was damaged by the loosening of the bolts produced by the vibration of the shunt reactor in conjunction with a possible low torque applied to the bolts. A short circuit between the bolt and the clamping frame was produced, generating the circulation of eddy currents in the bolt producing high temperatures and gasifying the insulating oil in the shunt reactor. Three-dimensional (3-D) finite element (FE) simulations were performed to verify the cause of the overheating issue in the clamping bolt of the shunt reactor, simulating the short circuit between the clamping bolt and the core frame. From the simulation results, the author determined that a short circuit between the bolt and the core frame generated the gases and the high temperatures in the shunt reactor. Finally, the manufacturer of the shunt reactor decided to reinforce the insulation of the clamping bolts using fiberglass to avoid future possible short circuit failures
Monitoring bolt tightness of rail joints using axle box acceleration measurements
No full textRail joints are a weak component in railway tracks because of the large impact and wheel-rail contact forces. Every train passage contributes to the deterioration of rail joints, causing visible (e.g. battered rails) and invisible (e.g. loose bolts) damages. The invisible damage cannot be detected by the commonly performed visual inspection, which is labor intensive, unreliable, intrusive and unsafe. In this paper, a vehicle-borne monitoring system is used to automatically detect and assess the tightness condition of bolts at rail joints. The monitoring method is developed based on field Axle Box Acceleration (ABA) measurements using different bolt tightness conditions. The suitability of the method is assessed by bolt tightness prediction and verification of a set of rail joints in the tram network of Sheffield, United Kingdom. The results show that ABA system can be employed to monitor bolt tightness conditions at rail joints.With this information better planning for selective preventive maintenance actions can be taken over rail joints
On advanced numerical techniques for the modeling of bolt reinforced rock mass
No full textRock bolting plays an important role in different geo-engineering applications and its numerical modelling is crucial for the analysis and design of rock structures. Continuum modelling simulation of bolt-reinforced rock masses requires specific techniques to properly model the reinforcement system and its interaction with the rock mass, which often exhibits a nonlinear softening/brittle response. In this context, strain localization might occur, which, in turn, may affect numerical convergence and the quality of results. This paper presents some advanced numerical techniques implemented in PLAXIS to overcome the abovementioned challenges. Firstly, a regularization technique is implemented for an extended version of the Hoek-Brown failure criterion with strain softening. Secondly, the formulation of the structural bolt element interacting with the rock mass is developed. Finally, the robustness and accuracy of these techniques are discussed via a numerical example of a typical underground mining excavation problem.Geo-engineerin
EXPERIMENTAL STUDY ON SHAPED & INITIAL STIFFNESS OF HALF-MOON-SHAPED-BOLT.
No full textapplication/pdfThe author present the shear joint using half-moon-shaped-bolt. The half-moon-shaped-bolts always penetrate the connected steel plate so as to _ll up a hole. The bolt resists a sharing force as the bearing bolt. Moreover, the present shear joint maintains constant sti_ness during a large number of pulsating cyclic loadings.
An experimental study was carried out to clarify the sti_ness of the bolted joint. The slip of the half-moon-shaped bearing bolt occurred in the case of all parameter. The sti_ness of the half-moon-shaped-bolts was depended on half-moon-shaped bearing bolt cutting slope, set up angle.departmental bulletin pape
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