1,094 research outputs found
On the equilibrium problem and infinitesimal mechanisms of class theta tensegrity systems
No full textThis work presents a study on the equilibrium problem and the infinitesimal mechanisms of class θ= 1 tensegrity prisms. Local solutions of the self-equilibrium problem are numerically obtained through Newton-Raphson iterations. The presented results suggest that the analyzed structures can be usefully employed as building blocks of novel tensegrity metamaterials, due to their rich kinematic response and the considerably large number of infinitesimal mechanisms. © 2019 Author(s)
Symplecticity properties of Euler-Maclaurin methods
No full textIn this note we consider the use of Euler-Maclaurin methods for the solution of canonical Hamiltonian problems. As a subclass of multi-derivative Runge-Kutta methods, these integrators cannot be symplectic, however they turn out to be conjugate symplectic. The numerical solutions provided by a conjugate symplectic integrator essentially share the same qualitative long time behavior as those yielded by a symplectic integrator. This aspect, along with an efficient evaluation of the derivatives, suggests that Euler-Maclaurin methods could play an interesting role in the context of geometric integration
Design of steel moment resisting frames for real scale pseudodynamic tests
No full textThis paper shows the design procedure of a Real Scale two stories steel Moment Resisting Frame (MRF) with different beam-to-column connections for Pseudo-dynamic tests. The main results of the preliminary analysis are presente
Large scale seismic vulnerability and risk evaluation of a masonry churches sample in the historical centre of Naples
No full textThis paper investigates about the seismic vulnerability and risk of fifteen masonry churches located in the historical centre of Naples. The used analysis method is derived from a procedure already implemented by the University of Basilicata on the churches of Matera. In order to evaluate for the study area the seismic vulnerability and hazard indexes of selected churches, the use of appropriate technical survey forms is done. Data obtained from applying the employed procedure allow for both plotting of vulnerability maps and providing seismic risk indicators of all churches. The comparison among the indexes achieved allows for the evaluation of the health state of inspected churches so to program a priority scale in performing future retrofitting interventions
Full 3D CAD procedure for the speedy evaluation of the seismic vulnerability of masonry towers
No full textA very straightforward 3D CAD approach for the speedy evaluation of the seismic vulnerability of existing masonry towers is presented. The procedure requires only the detailed 3D geometric model of the structure and automatically calculates the collapse acceleration on a user defined failure mechanism. In this paper, few pre-assigned mechanisms are tested, as for instance vertical splitting, simple overturning at the base, rocking with inclined yield lines and combined rocking and vertical splitting. The restriction of the possible tower failure within such a few mechanisms grounds on previous numerical research in the field and post-earthquake surveys experience. In any case, any user can define his own mechanisms according to the specificity of the case-study under consideration, directly shaping distinct volumes inside the CAD software. The procedure is automatized and the direct application of the principle of virtual works-assuming that masonry behaves as a no-tension material-allows the immediate evaluation of the horizontal acceleration at collapse. The mechanism associated to the minimum acceleration, in agreement with the kinematic theorem of limit analysis, is that most probably would occur in reality during a seismic event. The approach allows a straightforward evaluation of the seismic vulnerability of a tower and can be used even by practitioners not familiar with advanced FE computations and limit analysis concepts, so adapting well to the heterogeneous community involved in cultural heritage preservation. The automatized procedure is applied in this paper to a historical tower located in central Italy, to show the capabilities of the approach. © 2019 Author(s)
Mechanical-physical experimental tests on lime mortars and bricks reinforced with hemp
No full textHemp is an agricultural product used for various applications. In the Civil Engineering field, only a limited use of this natural material, called the “green pig” since exploitation of all its constituent parts is allowed, has been done. For this reason, in the paper an experimental activity on lime mortars and bricks reinforced with hemp components has been performed. Compression and bending tests have been carried out on specimens manufactured with hemp shives and fibres, respectively. The achieved results have shown that hemp products change the failure modes from brittle to ductile, leaving basically unaltered the strength capacity of reinforced specimens with respect to unreinforced ones
Using stochastic activity networks to study the energy feasibility of automatic weather stations
No full textAutomatic Weather Stations (AWSs) are systems equipped with a number of environmental sensors and communication interfaces used to monitor harsh environments, such as glaciers and deserts. Designing such systems is challenging, since designers have to maximize the amount of sampled and transmitted data while considering the energy needs of the system that, in most cases, is powered by rechargeable batteries and exploits energy harvesting, e.g., solar cells and wind turbines. To support designers of AWSs in the definition of the software tasks and of the hardware configuration of the AWS we designed and implemented an energy-aware simulator of such systems. The simulator relies on the Stochastic Activity Networks (SANs) formalism and has been developed using the Mobius tool. In this paper we first show how we used the SAN formalism to model the various components of an AWS, we then report results from an experiment carried out to validate the simulator against a real-world AWS and we finally show some examples of usage of the proposed simulator
Principles of Stochastic Geometric Numerical Integrations: Dissipative Problems and Stochastic Oscillators
No full textSafety assessment of historical masonry churches based on pre-assigned kinematic limit analysis, FE limit and pushover analyses
No full textThis study presents some results of a comprehensive numerical analysis on three masonry churches damaged by the recent Emilia-Romagna (Italy) seismic events occurred in May 2012. The numerical study comprises: (a) pushover analyses conducted with a commercial code, standard nonlinear material models and two different horizontal load distributions; (b) FE kinematic limit analyses performed using a non-commercial software based on a preliminary homogenization of the masonry materials and a subsequent limit analysis with triangular elements and interfaces; (c) kinematic limit analyses conducted in agreement with the Italian code and based on the a-priori assumption of preassigned failure mechanisms, where the masonry material is considered unable to withstand tensile stresses. All models are capable of giving information on the active failure mechanism and the base shear at failure, which, if properly made non-dimensional with the weight of the structure, gives also an indication of the horizontal peak ground acceleration causing the collapse of the church. The results obtained from all three models indicate that the collapse is usually due to the activation of partial mechanisms (apse, facade, lateral walls, etc.). Moreover the horizontal peak ground acceleration associated to the collapse is largely lower than that required in that seismic zone by the Italian code for ordinary buildings. These outcomes highlight that structural upgrading interventions would be extremely beneficial for the considerable reduction of the seismic vulnerability of such kind of historical structures
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