1,720,963 research outputs found
Friction connections with slotted holes for wind towers
No full textIn a constantly increasing and competitive market the efficiency of the whole wind power plant is an issue. The tubular steel towers supporting wind turbines account for about 15 to 20% of the total installation costs and their optimization may lead to substantial savings with regard to costs and use of material. One important aspect of the design is the connection between tower's sections. The currently used solution with bolted ring flanges is prone to low fatigue resistance which imposes limitations that can impair the overall efficiency. Improvement could be achieved by implementing friction connections. This idea is investigated and the principles of a new type of friction connection are presented. Long open slotted holes are used to facilitate assembly and the segments are clamped with Tension Control Bolts which can safely and easily be tightened from within the tower. In the first part, the behaviour of segment specimens is investigated experimentally by mean of static and long term tests as well as numerical analyses. Two types of surfaces are considered: ethyl silicate zinc rich paint and corroded weathering steel. The influence of hole's geometry as well as connection configuration are studied. Particular focus is given to the variations of bolt force and the slip resistance. In the second part, the resistance function of the tested connections is derived from statistical analysis according to Annex D of EN1990. The influence of environmental parameters and workmanship on the pretension achieved by TCBs is also investigated to provide recommendation on optimal handling and design pretension. Finally, a method is proposed to design friction connections for wind towers. It is compared to the design of current L flange connections. One example of a 80m-high tower is shown. It highlights the potential benefits of using friction connections as the design is made simpler and material costs savings of up to 80% could be achieved.Godkänd; 2008; 20081202 (ysko
Friction connections with slotted holes for wind towers [Elektronisk resurs]
No full textIn a constantly increasing and competitive market the efficiency of the whole wind power plant is an issue. The tubular steel towers supporting wind turbines account for about 15 to 20% of the total installation costs and their optimization may lead to substantial savings with regard to costs and use of material. One important aspect of the design is the connection between tower's sections. The currently used solution with bolted ring flanges is prone to low fatigue resistance which imposes limitations that can impair the overall efficiency. Improvement could be achieved by implementing friction connections. This idea is investigated and the principles of a new type of friction connection are presented. Long open slotted holes are used to facilitate assembly and the segments are clamped with Tension Control Bolts which can safely and easily be tightened from within the tower. In the first part, the behaviour of segment specimens is investigated experimentally by mean of static and long term tests as well as numerical analyses. Two types of surfaces are considered: ethyl silicate zinc rich paint and corroded weathering steel. The influence of hole's geometry as well as connection configuration are studied. Particular focus is given to the variations of bolt force and the slip resistance. In the second part, the resistance function of the tested connections is derived from statistical analysis according to Annex D of EN1990. The influence of environmental parameters and workmanship on the pretension achieved by TCBs is also investigated to provide recommendation on optimal handling and design pretension. Finally, a method is proposed to design friction connections for wind towers. It is compared to the design of current L flange connections. One example of a 80m-high tower is shown. It highlights the potential benefits of using friction connections as the design is made simpler and material costs savings of up to 80% could be achieved.</p
Behaviour of a friction connection using TCB in long slotted holes
No full textWith constantly increasing demand for renewable energies the cost optimization of steel towers supporting multi-mega-watt wind turbines becomes important. Luleå University of Technology currently coordinate European research project (RFCS), including partners from 5 countries, which aim is to ensure the high competitiveness of the next generation of steel towers produced in Europe. One innovation investigated within this project is the use of friction grip connection with long slotted holes to connect the steel tower sections. This paper presents a part of ongoing experimental program and result of three segment tests performed with weathering steel plates and M20 Tension Control Bolts. Experimental results are compared to the prediction according to European structural code EN 1993-1-8 Furthermore a three dimensional numerical model was used to describe behaviour of the connection with a long slotted hole together and a thick cover plate FE-analysis of the preliminary experiments was used to endorse conclusions from the experiments.Godkänd; 2007; 20071010 (ysko
Behaviour of a friction connection using TCB in long slotted holes [Elektronisk resurs]
No full textWith constantly increasing demand for renewable energies the cost optimization of steel towers supporting multi-mega-watt wind turbines becomes important. Luleå University of Technology currently coordinate European research project (RFCS), including partners from 5 countries, which aim is to ensure the high competitiveness of the next generation of steel towers produced in Europe. One innovation investigated within this project is the use of friction grip connection with long slotted holes to connect the steel tower sections. This paper presents a part of ongoing experimental program and result of three segment tests performed with weathering steel plates and M20 Tension Control Bolts. Experimental results are compared to the prediction according to European structural code EN 1993-1-8 Furthermore a three dimensional numerical model was used to describe behaviour of the connection with a long slotted hole together and a thick cover plate FE-analysis of the preliminary experiments was used to endorse conclusions from the experiments.</p
Innovative connections in tubular steel towers : experiments on segment specimens under static loading
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
