1,720,984 research outputs found
Lateral-torsional buckling of compressed and highly variable cross section beams
No full textIn the critical state of a beam under central compression
a flexural-torsional equilibrium shape becomes
possible in addition to the fundamental straight equilibrium
shape and the Euler bending. Particularly, torsional
configuration takes place in all cases where the line of
shear centres does not correspond with the line of centres
of mass. This condition is obtained here about a z-axis
highly variable section beam; with the assumptions that
shear centres are aligned and line of centres is bound to
not deform.
For the purpose, let us evaluate an open thin wall C-cross
section with flanges width and web height linearly variables
along z-axis in order to have shear centres axis approximately
aligned with gravity centres axis.
Thus, differential equations that govern the problem are
obtained.
Because of the section variability, the numerical integration
of differential equations that gives the true critical
load is complex and lengthy. For this reason, it is given
an energetic formulation of the problem by the theorem of
minimum total potential energy (Ritz-Rayleigh method).
It is expected an experimental validation that proposes the
model studied
The extensible Kapitza pendulum: some considerations on a classic stability problem
No full textSome plain considerations are provided on the influence of axial deformation on the stability of the upper equilibrium position of the Kapitza pendulum with respect to the linearisation or non-linearisation of the associated Lagrange’s equations. Following a very uncomplicated approach and fully accounting for the non-linearity of the problem, it is shown that in the case of the extensible Kapitza pendulum the dynamical behaviour of the system cannot be always correctly captured by a simple linearisation about the upper equilibrium point and a phenomenon related to the degree of approximation can take place for this dynamic system that replicates what happens in the case of the stability of equilibrium of simple axially extensible systems. Also, it is remarked that the introduction of axial deformation may play the same role as the addition of damping
Effective stiffness properties of multi-layered pentamode lattices in the stretching-dominated regime
No full textWe study the mechanics of pentamode metamaterials consisting of multi-layered pentamode lattices alternated with rigid plates. The examined systems respond in the stretching-dominated regime induced by the presence of perfectly hinged connections between the rods and the stiffening plates. We anakyze the variation of the effective stiffness properties of the examined systems with the lattice constant, the solid volume fraction, the cross-section area of the rods, and the number of layers
On the solitary wave dynamics of tensegrity lattices with stiffening response: A numerical study
No full textWe present some peculiar results about the solitary-wave dynamics of novel tensegrity-based metamaterials. It has been previously shown that one-dimensional chains of triangular tensegrity prisms with stiffening behavior support the propagation of compressive solitary waves. We show that such result can be generalized to two-dimensional and three-dimensional modular tensegrity lattices composed of polygonal and polyhedral units. Differently from the one-dimensional case, the stiffening response of these lattices originates at the interface between adjacent units, not from the unit themselves. We present numerical results on the response to impulsive loads of slender assemblies composed by square units in two-dimensions, and cubic units in three-dimensions. We observed compact compressive waves forming at impact locations, together with localized thermalization effects. Such compact waves propagate with nearly constant speed and energy, while maintaining their shape, and emerge from collision with other compact waves almost unaltered, losing a small fraction of their energy. These results suggest the investigation of the dynamics of regular and quasi-regular tessellations formed by other types of polygonal and polyhedral units
Dynamic testing and structural identification of innovative network structures
No full textThe experimental modal analysis is a kind of test in which input forces and structural responses are known. It is important to note that the dynamic behavior is a kind of "fingerprint", it depends only by intrinsic characteristics (mass, stiffness, damping, boundaries, degree of freedom, etc.) and not by the applied loads. Therefore, the structural response still remains unchanged in absence of modification (structural damage, etc⋯), otherwise a variation of frequencies and vibration modes occurs. The Experimental Modal Analysis of civil structures implies the use computer models, designed to predict the response of a structures and also to simulate the effects of eventual modifications in their structural parameters (stiffness, damping, degree of freedom, etc.). The FE updating techniques are available to correct the FE models, based on dynamic response records of the real structures. These updating processes usually consist of four phases: preliminary FE modeling, experimental modal identification, manual sensitivity analysis and updating the FE model. The present paper presents the dynamic identification of an innovative manufacturing and assembling building technology system allowing fast times to build up. The building has been subjected to an experimental investigation and to an accurate FE modelling. The experimental investigation has been carried out using a vibrodyne. The comparison between the experimental evidences with the results of FE models allowed us the dynamic identification of the structure. The dynamic structural identification is a non-destructive technique, so that it can be applied to existing and even historical buildings (for checking the health) to new structures, and to innovative structures (where there is not well defined design criteria)
SETTLEMENT-INDUCED DAMAGE ASSESSMENT IN UNILATERAL MASONRY-LIKE STRUCTURES: A PIECEWISE RIGID DISPLACEMENT APPROACH
No full textExploring the stainless-steel beam-to-column connections response: A hybrid explainable machine learning framework for characterization
No full textStainless-steel provides substantial advantages for structural uses, though its upfront cost is notably high. Consequently, it’s vital to establish safe and economically viable design practices that enhance material utilization. Such development relies on a thorough understanding of the mechanical properties of structural components, particularly connections. This research advances the field by investigating the behavior of stainless-steel connections through the use of a four-parameter fitting technique and explainable artificial intelligence methods. Training was conducted on eight different machine learning algorithms, namely, Decision Tree, Random Forest, K-nearest neighbors, Gradient Boosting, Extreme Gradient Boosting, Light Gradient Boosting, Adaptive Boosting, and Categorical Boosting. SHapley Additive Explanations was applied to interpret model predictions, highlighting features like spacing between bolts in tension and end-plate height as highly impactful on the initial rotational stiffness and plastic moment resistance. Results showed that Extreme Gradient Boosting achieved a coefficient of determination score of 0.99 for initial stiffness and plastic moment resistance, while Gradient Boosting model had similar performance with maximum moment resistance and ultimate rotation. A user-friendly graphical user interface (GUI) was also developed, allowing engineers to input parameters and get rapid moment–rotation predictions. This framework offers a data-driven, interpretable alternative to conventional methods, supporting future design recommendations for stainless-steel beam-to-column connections
A simple procedure for the non-linear optimization of cable tension for suspended bridges
No full textLong-span suspended bridges rely upon networks of tensed cables that carry the weight of the deck. The networks of cables are generally connected to a number of vertical towers (pylons) that transfer the forces to the foundations as in the case of cable-stayed bridge. Their structural behaviour is highly influenced by the pretension forces on account of the redundancy of the structure. Several methods have been proposed for determining pretension the forces in the cables, such as Load-Balance Method, Iterative Unit Load Method, Force Equilibrium Method, Zero Displacement Method. The present study aims to investigate the influence of geometrical nonlinearities on the optimization of the design. To this end, the Force Equilibrium Method is here extended and compared to the use of a Finite Element commercial package, since this is the standard method in everyday engineering practice. The comparison between the Force Equilibrium Method and FEM results shows that the first method, in spite of its simplicity, is able to provide a reasonable and reliable alternative to the more complex non-linear FE approaches
Effective stiffness properties of multi-layered pentamode lattices in the stretching-dominated regime
No full text- …
