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2019 Journal article Open Access OPEN

Automatic design of cable-tensioned glass shells
Laccone F., Malomo L., Froli M., Cignoni P., Pietroni N.
We propose an optimization algorithm for the design of post-tensioned architectural shell structures, composed of triangular glass panels, in which glass has a load-bearing function. Due to its brittle nature, glass can fail when it is subject to tensile forces. Hence, we enrich the structure with a cable net, which is specifically designed to post-tension the shell, relieving the underlying glass structure from tension. We automatically derive an optimized cable layout, together with the appropriate pre-load of each cable. The method is driven by a physically based static analysis of the shell subject to its service load. We assess our approach by applying non-linear finite element analysis to several real-scale application scenarios. Such a method of cable tensioning produces glass shells that are optimized from the material usage viewpoint since they exploit the high compression strength of glass. As a result, they are lightweight and robust. Both aesthetic and static qualities are improved with respect to grid shell competitors.Source: Computer graphics forum (Online) 39 (2019): 260–273. doi:10.1111/cgf.13801
DOI: 10.1111/cgf.13801

See at: ISTI Repository Open Access | Computer Graphics Forum Restricted | Computer Graphics Forum Restricted | Computer Graphics Forum Restricted | Computer Graphics Forum Restricted | onlinelibrary.wiley.com Restricted | Computer Graphics Forum Restricted | Computer Graphics Forum Restricted | CNR ExploRA Restricted


2019 Journal article Open Access OPEN

Dynamics of a new seismic isolation device based on tribological smooth rocking (TROCKSISD)
Froli M., Giresini L., Laccone F.
A novel isolation device is introduced to seismically protect slender structures or historic assets within the philosophy of Damage Avoidance Design (DAD). This device is conceived to allow smooth, controlled and damped rocking thanks to spherical contact surfaces, elastic springs which ensure re-centering, frictional layers and viscous elastic dampers able to dissipate energy during motion. The conceptual framework of the device is analyzed, and corresponding equations of motions obtained for the equivalent two degrees-of-freedom system. The proposed Performance Based Approach allows identifying geometric and mechanical features of the system. Extensive dynamic analyses with spectra-compatible ground motions are performed and the primary contribution of friction, developed by the relative slip of the two spherical surfaces, is discussed. Finally, the dynamic response under selected earthquakes is evaluated by comparing the isolated and the corresponding not isolated response, to highlight the beneficial effects produced by the proposed isolation technique.Source: Engineering structures 193 (2019): 154–169. doi:10.1016/j.engstruct.2019.05.014
DOI: 10.1016/j.engstruct.2019.05.014

See at: ISTI Repository Open Access | Engineering Structures Restricted | Engineering Structures Restricted | Engineering Structures Restricted | CNR ExploRA Restricted | Engineering Structures Restricted


2019 Conference article Open Access OPEN

Concept and cable-tensioning optimization of post-tensioned shells made of structural glass
Laccone F., Malomo L., Froli M., Cignoni P., Pietroni N.
Shells made of structural glass are charming objects from both the aesthetics and the engineering point of view. However, they pose two signicant challenges: the rst one is to assure adequate safety and redundancy concerning possible global collapse; the second one is to guarantee the economy for replacing collapsed components. To address both requirements, this research explores a novel concept where triangular panels of structural glass are both post-tensioned and reinforced to create 3D free-form systems. Hence, the ligree steel truss, made of edges reinforcements, is sized in performance-based perspective to bear at least the weight of all panels in the occurrence of simultaneous cracks (worst-case scenario). The panels are post-tensioned using a set of edge-aligned cables that add benecial compressive stress on the surface. The cable placement and pre-loads are optimized to minimize the tensile stress acting on the shell and match the manufacturing constraints. These shells optimize material usage by providing not only a transparent and fascinating building separation but also load-bearing capabilities. Visual and structural lightness are improved to grid shell competitors.Source: FORM and FORCE, IASS Symposium 2019 60th Anniversary Symposium of the International Association for Shell and Spatial Structures Structural Membranes 2019 9th International Conference on Textile Composites and Inflatable Structures, pp. 2133–2140, Barcelona, 7-10/10/2019

See at: ISTI Repository Open Access | CNR ExploRA Open Access


2019 Conference article Open Access OPEN

A new seismic isolation device based on tribological smooth rocking (TROCKSISD)
Froli M., Giresini L., Laccone F.
In the field of seismic risk mitigation of art objects, an innovative isolation device is here il-lustrated. The device, called TROCKSISD (Tribological ROCKing Seismic ISolation Device), couples multiple components to dissipate energy and control smooth rocking: spherical con-tact surfaces with frictional layers, elastic springs ensuring re-centering and viscous elastic dampers. The conceptual idea is described and the equations of motions of the two degrees of freedom system presented, discussing the performance-based structural behaviour and the mechanical/geometric parameters involved. Moreover, dynamic analyses are performed to understand the role of the frictional layers with respect to the peripheral dampers in the miti-gation of motion under spectrum compatible seismic records. The results in terms of rocking spectra are presented and comparisons with the equivalent single degree of freedom system without the isolation device are made.Source: COMPDYN 2019 - 7th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, pp. 750–760, Crete, Greece, 24-26 June 2019
DOI: 10.7712/120119.6954.19893

See at: arpi.unipi.it Open Access | ISTI Repository Open Access | CNR ExploRA Open Access | www.eccomasproceedia.org Open Access | academic.microsoft.com Restricted


2019 Conference article Open Access OPEN

FlexMaps Pavilion: a twisted arc made of mesostructured flat flexible panels
Laccone F., Malomo L., Perez J., Pietroni N., Ponchio F., Bickel B., Cignoni P.
Bending-active structures are able to eciently produce complex curved shapes starting from flat panels. The desired deformation of the panels derives from the proper selection of their elastic properties. Optimized panels, called FlexMaps, are designed such that, once they are bent and assembled, the resulting static equilibrium conguration matches a desired input 3D shape. The FlexMaps elastic properties are controlled by locally varying spiraling geometric mesostructures, which are optimized in size and shape to match the global curvature (i.e., bending requests) of the target shape. The design pipeline starts from a quad mesh representing the input 3D shape, which denes the edge size and the total amount of spirals: every quad will embed one spiral. Then, an optimization algorithm tunes the geometry of the spirals by using a simplied pre-computed rod model. This rod model is derived from a non-linear regression algorithm which approximates the non-linear behavior of solid FEM spiral models subject to hundreds of load combinations. This innovative pipeline has been applied to the project of a lightweight plywood pavilion named FlexMaps Pavilion, which is a single-layer piecewise twisted arc that ts a bounding box of 3.90x3.96x3.25 meters.Source: FORM and FORCE, IASS Symposium 2019 60th Anniversary Symposium of the International Association for Shell and Spatial Structures Structural Membranes 2019 9th International Conference on Textile Composites and Inflatable Structures, pp. 498–504, Barcelona, 7-10/10/2019

See at: ISTI Repository Open Access | CNR ExploRA Open Access


2019 Doctoral thesis Open Access OPEN

Reinforced and post-tensioned structural glass shells: Concept, morphogenesis and analysis
Laccone F.
The relationship between architecture and structure is a key point in the conceptual phase of a building or one of its components. Glass structures can be considered optimal from the material usage viewpoint because they simultaneously offer transparency, an idea always pursued by architects, and good structural performances. Transparent and free-form glass shells are fascinating objects from both the aesthetic and structural engineering point of view, but are practically difficult to realize, apart from limited favourable cases, and have a low safety level. This work explores a new structural concept for triangulated glass shells, in which the glass panels are both reinforced and post-tensioned. Hence, the net formed by the reinforcements constitutes a redundancy barrier to avoid global collapse in case of glass cracking. In order to ensure an adequate safety level, glass should be prevented from carrying tensile stresses. To this aim, a novel algorithm is developed for the automatic design of the piecewise geometry of the shell and the derivation of the optimal cables distribution with respective preloads. Global nonlinear analyses have been performed to prove the feasibility of the concept and to highlight the advantages that these structures offer with respect to the grid shells competitors. At the local level, the main components of these systems are investigated: the node is tested experimentally and its behaviour is successively described numerically, and the triangular laminated panels are explored with parametric nonlinear models. The thesis is written as a monograph. Some papers prepared during the study are included as part of the work.

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