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Sulla generazione della forma di gusci in c.a. di superficie minima mediante un algoritmo euristico
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A method of shaping R/C shells with heuristic algorithms and with reference to Musmeci’s work
No full textBy designing R/C shells we can easily have membrane forces in almost the entire structure except
in some regions, for instance close to the constraints. Therefore, having assigned the loads and
their position as well as the constraints, there are a great number of membrane shapes that can
solve the design problem, both with normal internal forces only in compression, and in
compression and tension. On the other hand, given loads and constraints, by using suitable
algorithms and/or physical models, tension structures may be designed in order to find their shape
with membrane tensile forces and minimal area. By taking into account tension structures
properties as well as those of natural membranes, and after in-depth and pioneering studies in
optimum design, Sergio Musmeci - a well known designer of bridges and concrete shell roofs of
the second half of the past century - studied how to design R/C shells with minimal area. By using
physical models, he shaped some of his shell constructions as a tension structure with the same
loads and constraints, as well as the same normal internal forces but with the opposite sign. His
design tools were empirical analysis, physical models, and mathematical analysis, which he used
with a bright structural intuition. Nowadays these methods can be supported by modern heuristic
and evolutionary algorithms. In this paper we analyse the “shaping” as well as the “form finding”
of R/C shells by following Musmeci’s design method coupled with an heuristic algorithm, the
“simulated annealing”. With progressive iterations, we search for stiffer shells with minimal area
and only membrane compressive forces. The algorithm simulates the progressive elimination of
defects on a crystal structure, that is obtained by reheating before cooling at a lower rate, namely
through the annealing process. A number of applications are proposed; firstly we test the
algorithm to find the shape of the shell of the famous Musmeci’s bridge on the Basento river in
Potenza, and successively, by using the same design method, we shape a R/C pedestrian crossing
of a deep canyon in an urban context
On the conceptual design of R/C footbridges with the deck supported by shells of minimal surface
No full textDesigning footbridges (pedestrian bridges) with the deck supported by R/C shells is an interesting approach, that is illustrated in this paper. The advantage of this structural solution is that R/C shells can be shaped in accordance with the “minimal surface” criterion. In so doing, the shells are mainly subjected to biaxial compression with membrane stresses.
The shape of the minimal surface shells is first studied by suitably choosing the position of the boundary restraints and of the applied forces. Then, through a form-finding process containing an
optimisation algorithm, different R/C footbridges with architecturally-valuable shapes are worked out. It is also shown how Maillart’s bridges can be re-shaped in order to avoid the well known undesired bending effects, even though some tensile stresses may occur.
In the case of footbridges having a straight deck, it is shown how: (a) the choice of the position of the deck supports, (b) the shape of the shell close to the abutments, (c) the arrangement of the
shell edges along the abutments, and (d) the stiffening beams (if any) along the free edges can
minimize the bending effects and improve the behaviour of this type of structures
The design of RC bridges with shell of minimal area made of fibre reinforced concrete: an application to a pedestrian bridge
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Conceptual approach to the design of glass objects from a structural point of view
No full textThe study of the behaviour of brittle materials has allowed an increasing structural use of glass in buildings. The development of knowledge of fracture mechanics allows us to better control fracture danger. Within a whole structural use, glass can be considered a new material, and in the last years some designers have proposed small constructions whose resistance is wholly due to glass; for instance, some small pedestrian crossings between two close buildings
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
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