1,721,086 research outputs found
Going 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
Shear yielding strength of gusset plates in lap splice joints
No full textFillet welded Lap Splice Joints are commonly used to connect tension members to a gusset plate. In most cases, the shear yielding strength, or Base Metal Shear Yielding (BMSY) strength, of the gusset plates controls the capacity of the connection. The stress from tension members is transferred to the gusset plate through fillet welds, causing the yielding of the gusset plate. In current engineering practice, designers use the “Shear of Elements in Shear” equation from the AISC-10 to estimate the BMSY strength of gusset plates. The gross area subjected to shear is assumed to be the product of weld length and thickness of the gusset plate. However, the approach does not account for the material adjacent to the weld. Shear stress can travel away from the welds, increasing the gross area and total BMSY strength of the gusset plate. Six lap welded specimens were tested in this research to serve two purposes. One specimen was used to study the stress profiles on the gusset plate and tension members. The remaining specimens were tested to determine the actual shear yielding strength of the gusset plates. A new analytical mode was created from test results to predict shear yielding strength more accurately. In addition, fifteen finite element models were analyzed to study the effects of the geometric parameter such as weld length, edge distance, and weld separation. The results of the research provide designers flexibility to increase the BMSY strength of the gusset plate, thus possibly increasing the capacity of the connection
Design Approach for RC Panels (Shells) in Industrial Facilities Based on ACI Codes
No full textCurrently, the design of Reinforced Concrete (RC) walled type structures such as RC containments in nuclear power plants (NPPs), offshore oil platforms, and other industrial facilities are designed following the Element-by-Element Level (ELD) technique. In this technique, the walls are not considered as single isolated units, and different portions (or sections) of the walls, which will be referred in this document as RC panels, need to be designed. As commonly accepted, the design demands of RC panels are a combination of in-plane and out-of-plane forces/moments, which interact simultaneously. The ACI 349 and the ACI 318.2-19, do not provide a clear design guideline for the design of RC panels, and for this reason, a new design approach based on the design concepts and formulations of these ACI codes will be proposed and developed in this thesis. The results of this ACI-Panel-Based-Design-Approach (PACI) will be verified by using experimental data of twenty-one RC panels subjected to different combinations of in-plane and out-of-plane forces. The results from the PACI approach –represented in the suggested reinforcement areas, and in the estimated nominal capacities of the panels resulting after introducing those suggested reinforcement areas into calibrated numerical models developed in Abaqus and/or Shell 2000– will be compared against the experimental results. These results will also be compared against the results of the more sophisticated “sandwich” model approach applicable for RC shells (or panels) proposed by the Eurocode. Finally, after designing a critical panel of a typical Steel Composite (SC) RP-1000 power plant, the applicability of the PACI design approach will be verified for use in industrial applications
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
Numerical Investigations of the In-Plane Behavior of Reinforced-Concrete (RC) Walls: Cyclic and Accident Thermal Loadings
No full textThis study aims at the development, and experimental validation of 3D finite element models to investigate the seismic response of reinforced concrete (RC) squat shear walls subjected to postulated high energy thermal accident. Behavior is simulated using commercially available robust finite element modeling software LS-DYNA, employing explicit time stepping algorithm for calculating nodal forces and displacements. The basic performance of four constituent material models in capturing the seismic response is examined via material and component level simulations. Comparisons between the theoretical knowledge and analytical results presented herein will help in making the users cognizant of the inherent strengths and limitations associated with these material models. Performance validation of the nonlinear analysis is carried out with the help of experimental program executed in the BOWEN laboratory at PURDUE university. Tests are conducted on four specimens, under force and displacement controlled loading conditions, each having an aspect ratio of 0.6. Design parameters include reinforcement ratio, concrete and steel material strength, duration, and the maximum amplitude of thermal loading obtained from initial findings of the project. Two heating protocols: continuous and cyclic are used to depict accident thermal loads at 300F and 450F. The results include global force-displacement and thermal responses as well as damage progression during explicitly accounted material and geometric nonlinearities. Predicted responses are in a reasonable agreement with measured values. Based on the numerical and experimental studies, walls are found out to be flexural shear and shear critical. Numerical simulations also confirm the measured response that accident thermal loads during the first 15 to 30 minutes cause a reduction of around 10 to 35% in the overall secant stiffness depending upon the pre-heated cracking, and as the non-linear temperature gradient reduces with the passage of time, the subsequent reduction in stiffness is mainly due to mechanical damage. Additionally, the studies reveal no significant impact of the duration and exposure to abnormal loading conditions on the peak shear strength of the walls
Behavior of Planar Concrete-Filled Composite Plate Shear Walls for High-Rise Buildings
Get PDFConcrete-Filled Composite Plate Shear Walls (CF-CPSW) consist of pre-fabricated steel modules filled with plain concrete. During construction, the empty steel modules are designed to support multiple floors of the steel framing before the concrete is infilled, and they act as permanent formwork. CF-CPSW systems can lead to improved constructability and reduced construction schedules. In coupled CF-CPSW lateral force resisting systems, the coupled walls resist global over turning moment through an axial force couple and individual wall flexural resistance. Therefore, in order to design the coupled CF-CPSW system, the wall’s flexural behavior under axial load must be evaluated. This study reports the results of an experimental investigation of the contributions of axial loading, tie reinforcement ratio, and plate slenderness ratio on the cyclic flexural behavior of planar rectangular CF-CPSWs with flange plate boundary elements under compressive axial load. The lateral force-displacement behavior, plastic rotation capacity, and moment-curvature response of three wall specimens were experimentally evaluated in this thesis. A fiber analysis model for calculating the section moment-curvature behavior of the planar walls was developed and validated using the experimental results. An increase in axial load level resulted in an increase in flexural capacity of the wall. All three wall specimens showed high ductility in their experimental moment-curvature responses and a minimum plastic rotation capacity of 0.0141 radians. The peak point of the fiber analysis moment-curvature curve occurs after the compression strain in the steel exceeds 2εy
Multi-Hazard Resilience of Steel MFR Buildings
No full textMulti-hazard analyses can be used to create more sustainable and resilient structural designs by considering cascading hazards and the overall system performance of structures exposed to multiple hazard types. This dissertation develops a methodology to assess building resilience for seismic, wind, fire, and post-earthquake fire scenarios. Special emphasis is placed on understanding the interdependencies and relationships between earthquake and fire damage in the assessment of structures for post-earthquake fire. The proposed methodology includes designing a building structure according to the latest building codes, developing a three-dimensional (3D) finite element method (FEM) computer model to represent building behavior, and conducting incremental dynamic and incremental fire analyses as a means to assess building performance to multiple cascading hazards. The approach is articulated by analyzing two 10-story steel structures. These structures were designed for hazard levels in Chicago, IL and Los Angeles, CA. The buildings have the same geometry and gravity framing, but vary in the design of the perimeter moment resisting frames (MRFs). Detailed 3D FEM building models were developed in ABAQUS in order to more adequately simulate real-building behavior. The framing members are modeled using beam elements and the composite floor slabs are modeled as shell elements. This model provides building level response to earthquakes, wind, fires, and fires following earthquakes. It permits redistribution of loading through catenary action during column failure in a fire event and can simulate connection and member failures. In order to simulate seismic hazards, nonlinear time history ground displacement records were applied to the base of the building and Rayleigh damping was implemented. Because ABAQUS is not traditionally used to simulate seismic building behavior, the seismic response was validated using another computer program. Fire loads were modeled using parametric time-temperature curves from Eurocode to simulate compartment fires at the first, fifth and ninth stories of the buildings. Damage from the seismic structural model was imported into the fire structural model in order to capture post-earthquake fire behavior. The level of modeling within each model varied as necessary in order to adequately capture building behavior for each hazard, while maintaining computational efficiency. The findings of this study show that post-earthquake fire resilience for structures in high and low seismic areas are the same regardless of seismic damage, as long as moment frame connections have not fractured. For compartment fires where there is no seismic damage (no plastic hinging or fracture of members), the system responds the same as a fire-only scenario. Gravity columns are the most vulnerable components because of their high utilization ratio. Buckling of gravity columns can cause column, bay or system failures in the corner, edge and interior compartments, respectively. The perimeter moment frame system can help to prevent system collapse due to gravity column failure, but it cannot prevent the gravity column failure from occurring. In some cases, moment frame connection fractures may result in additional, subsequent failure modes (such as system collapse) that occur after gravity column failure initiates. Pilot studies show that increasing gravity column sizes or its fireproofing can increase the multi-hazard resilience of the system. These modifications can prevent gravity column failure from occurring and, in turn, any subsequent failures that may occur in response. In addition, implementing a rebar mat within the composite slab can help to redistribute loads and prevent progressive collapse in interior compartments. Studies were also performed to examine the effect of fireproofing damage on the fire resilience of the structure
Post-Fire Assessment of Concrete in Bridge Decks
No full textIn recent years, there have been a number of truck fires involving bridges with concrete components. If the fire burns for a significant period of time, the structural integrity of concrete components could be damaged due to fire. Research-based guidance for evaluating the level of fire damage is currently unavailable and would be beneficial for post-fire bridge inspectors.This research project focused on evaluating the effects of fire induced damage on concrete bridge deck elements. In order to achieve this goal, a series of controlled heating experiments and material analysis were conducted. Two concrete bridge deck specimens from the I-469 bridge over Feighner Road were heated for different time durations (40 - 80 min.) following the ISO-834 temperature-time curve. The deck specimens were cooled naturally after the specific heating durations. The temperature profiles through the depth of deck specimens were measured during heating and cooling. After testing, concrete samples were taken from the deck specimens for material analysis. Different types of material tests were conducted on samples taken from the undamaged and damaged deck specimens. The material test results were used to evaluate the effects of fire induced damage on the concrete microstructure, and to correlate the microstructure degradation with the through-depth temperature profiles of deck specimens.From the experimental results, several critical parameters that can affected by fire temperature and duration were discussed: (i) through-depth temperature profiles of deck specimens, (ii) cracks on the exposed surface of deck specimens, (iii) color changes of deck specimens, (iv) microstructure of heated concrete samples, (v) content of calcium hydroxide in fire damaged concrete samples at various depths. Based on the results from heating experiments and observations from material analysis, recommendations and guidance for evaluating concrete decks subjected to realistic fire scenarios are provided to assist bridge inspectors
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