1,721,159 research outputs found
TOSCA: a Tool for Optimisation in Structural and Civil engineering Analyses
Full text linkMany structural engineering problems, e.g. parameter identification, optimal design and topology optimisation, involve the use of optimisation algorithms. Genetic algorithms (GA), in particular, have proved to be an effective framework for black-box problems and general enough to be applied to the most disparate problems of engineering practice. In this paper, the code TOSCA, which employs genetic algorithms in the search for the optimum, is described. It has been developed by the authors with the aim of providing a flexible tool for the solution of several optimisation problems arising in structural engineering. The interface has been developed to couple the programme to general solvers using text input/output files and in particular widely used finite element codes. The problem of GA parameter tuning is systematically dealt with by proposing some guidelines based on the role and behaviour of each operator. Two numerical applications are proposed to show how to assess the results and modify GA parameters accordingly, and to demonstrate the flexibility of the integrated approach proposed on a realistic case of seismic retrofitting optimal design
An experimental, numerical and analytical study of hybrid RC-encased steel joist beams subjected to shear
No full textThe use of Reinforced Concrete encased Steel Joist (RC-SJ) beams, consisting of a steel joist partially or totally embedded in the concrete, represents in some cases an effective alternative to more traditional structural systems. While a lot of effort has been devoted to understanding flexural behaviour of such structures, up to now shear strength is an open issue.
In this work, an experimental and numerical study on shear response of RC-SJ beams based on a preliminary test campaign is presented. Nine specimens were tested until collapse, which occurred due to shear failure. Numerical models obtained through the use of ABAQUS code were created, and different steel–concrete interfaces were used for the bottom steel plate.
Based on the main outcomes of the experimental and numerical study, a novel analytical model is presented, and it allows for the estimation of shear strength in such structural elements. Application of the model to the beams tested shows a good agreement with real collapse values when a minimum bond between base and concrete is provided. A parametric study has been carried out, and it has allowed for the analytical model to be validated
Elastoplastic dissipative devices for the mitigation of blast resisting cable-supported glazing façades
No full textThe paper investigates the dynamic behavior of a structural cable-supported glass–steel façade subjected
to high-level air blast loads. In order to describe accurately the dynamic response of the examined façade,
both a sophisticated FE-model and a geometrically simplified but equivalently accurate lumped-mass FEmodel
are presented. These models, appropriately calibrated to dynamic experimental and numerical
results on previous efforts, were used to highlight the criticalities of the façade (dynamic tensile stresses,
deflections and velocities of pretensioned cables and laminated glass panels). Since axial forces in cables
abruptly increase when explosion occurs, specific dissipative devices applied at the top or at the bottom
of the pretensioned cables are proposed to improve the global response of the glass–steel curtain wall
under the impact of a high-level blast loading, and their structural benefits are investigated. For the studied
cases, opportunely calibrated elastoplastic devices allow reducing the axial forces in cables and cutting
down lightly the maximum tensile stresses in glass panes. At last, by means of an energy-based
approach, a series of design rules are developed to estimate realistically the response of the cable-supported
façade and to define the optimal mechanical parameters for the proposed dissipative mechanism
Buckling analysis of simply supported flat glass panels subjected to in-plane uniaxial compressive and edgewise shear loads
No full textGlass panels are widely used in modern architectures in the form of stiffeners and load-carrying elements. The frequent use of structural glass and the lack of standardized rules for designers gradually increased the interesting of scientists and researchers in the analysis of structural behaviors associated to various combinations of boundary and loading conditions. Buckling failure certainly represents one of the most crucial condition of collapse. In the paper, particular attention is dedicated to the buckling response of simply supported glass panels subjected to combined in-plane compressive and shearing forces. Based on large series of numerical incremental simulations, the effects of loading ratios, imperfection shapes, slenderness ratios and glass types on their buckling response are investigated. At last, based on analytical interaction formulations of literature, a normalized domain is proposed for their stability check
Exploratory Finite-Element investigation and assessment of standardized design buckling criteria for two-side linear adhesively supported glass panels under in-plane shear loads
No full textIn this paper, the buckling response of glass panels linearly supported along the top and bottom edges, under the action of in-plane shear loads, is investigated by means of analytical and Finite-Element (FE) methods.
The typical buckling behaviour is first assessed in the hypothesis of fully neglecting the possible deformability contribution of adhesive linear supports, while successively the effects of linear, flexible sealant joints on the overall structural response of the same panels are also properly taken into account and highlighted. Based on extended parametric FE linear buckling and nonlinear incremental simulations, the influence of initial geometrical imperfections with various shapes and amplitudes, adhesive stiffnesses and glass types is investigated, both for monolithic and laminated glass panels. In the latter case, the accuracy of an equivalent thickness approach derived from early contributions is also demonstrated. Analytical approximating curves are proposed for the fitting of numerically derived buckling coefficients, so that they could represent a practical tool in the calculation of the expected Euler’s critical load. A normalized buckling curve for ideally simply supported glass panels under in-plane shear loads is finally recalled from past research projects and proposed as a rational design method for the examined loading and boundary condition
ADAS dampers for the hazard protection of multi-storey buildings with glazing envelopes: a feasibility study
No full textGlass façades are generally intended as static structural partitions in buildings, aimed to separate the occupants from the environment. In this regard, especially under the action of extreme design loads, they require specific design concepts voted to protect the building occupants. In this paper, following earlier research efforts, the potential of a design concept, involving the same façades to act as a distributed-Tuned Mass Damper (TMD) in multi-storey buildings, is assessed. Special mechanical connectors interposed at the interface between a given primary building and the glazing façadeare investigated via accurate finite element (FE) models, under the action seismic and explosive loads. Both the global and local effects and the possible benefits due to additional Vibration Control Systems (VCSs) are hence numerically explored, giving evidence of the activation - once properly designed - of the feasibility of the so achieved distributed-TMD concept. Taking advantage of earlier studies, where viscoelastic dampers have been investigated, careful consideration is especially paid for of elasto-plastic VCSs, giving evidence of their response for the same case study building under several hazards. Parametric FE results are hence preliminary discussed, to assess the feasibility of the distributed-TMD concept, as a function of VCSs input features, as well as compared to viscous dampers
Viscoelastic spider connectors for the mitigation of cable-supported façades subjected to air blast loading
No full textThe paper investigates the behavior of a cable-supported glazing façade subjected to high-level and medium-level air blast loads. To describe realistically the dynamic response of the studied system, nonlinear dynamic analyses were performed using a sophisticated FE-model (M01). This model, opportunely calibrated to dynamic experimental and numerical results on previous efforts, was used to highlight the criticalities of the façade with ‘‘rigid’’ spider connectors (RSCs). Since the glass panels and the cables are subjected to elevated tensile stresses when an explosion occurs, viscoelastic spider connectors (VESCs) are presented to improve the global response of the glass-steel curtain wall, and their structural benefits are investigated (M02 FE-model). As a result, maximum tensile stresses in glass panes and in pretensioned cables appear strongly reduced. At the same time, the proposed dissipative spiders do not trouble the esthetics of such transparent structural systems. At last, by means of an energy-based approach, design rules are proposed to estimate the response of the cable-supported façade subjected to dynamic loads of generic intensity and to calibrate the mechanical parameters characterizing the proposed VESC
Buckling of flat laminated glass panels under in-plane compression or shear
No full textBecause of evident aesthetic, lighting and architectural advantages, glass curtain walls are largely used to
clad modern buildings. Since these elements are considered to constitute purely architectural systems,
they are essentially designed to resist loads acting orthogonally to the plane of the façade (e.g. wind
loads). Contrarily, glass elements are frequently used as structural components able to sustain in-plane
loads (e.g. columns, stiffening fins, beam elements, stairs, etc.), thus to preserve their integrity a buckling
verification could assume great importance.
In order to overcome these problems, an analytical formulation is proposed for the estimation of the
buckling resistance of flat laminated glass panels under in-plane compression or shear. Two different
design approaches are taken into account and compared: the first one directly derives from the theory
of sandwich panels, whereas the second one is based on the approximate concept of equivalent thickness.
As discussed in the paper, this last approach constitutes a useful design expedient for the deformability
and resistance check of buckled laminated panels under in-plane compression or shear, in presence of
different boundary conditions. Since the resistance of such brittle elements directly depends on the level
of connection between the glass panes offered by the interlayer, the effects of possible temperature and
time-loading variations are highlighted. The obtained analytical results are in agreement with sophisticated
numerical simulations
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