1,721,000 research outputs found
A new modular structural system for tall buildings based on tetrahedral configuration
Full text linkInspired by the high mechanical performance of diagrid structures, the minimization of material consumption on braced tubes and the expressive potency of tensegrity modular structures, this work proposes an innovative three-dimensional system for tall buildings. A new modular structural system generated from the assembly of tetrahedral units is investigated. The paper integrates insights on the architectural implications and mechanical performance of the reticular system arranged in repetitive triangular-based modules. The impact of different geometric configurations of the structural members on the economic design is also discussed and recommendations for the optimal topology are made. Guidelines for the design and analytical formula for accessing preliminary member sizes are proposed on the basis of stiffness requirements
Evaluation of optimal lateral resisting systems for tall buildings subject to horizontal loads
Full text linkThe tendency of modern designs towards optimal structures often leads to the lightest and best performing choice among a large set of design alternatives. In a similar scenario, the introduction of automated tools to further guide designers in achieving efficient solutions has been a recurrent topic for mechanical and structural engineers, over the past decades. Nowadays, topology optimization is considered a powerful preliminary design tool to determine the optimal material distribution in a design domain, i.e. the most effective configuration that satisfies a given set of prescribed constraints while reducing the consumption of structural material. Among different applications in the field of Civil Engineering, this work focuses on the definition of optimal layouts of lateral resisting systems for multi-storey steel building frameworks subject to lateral loads using topology optimization techniques. The objective of the research is to illustrate the benefits deriving from the introduction of automated routines within the preliminary design stage and establish reliable guidelines for performing accurate and objective optimization procedures. Since the optimal material distribution follows the load flow within the structure, optimal topologies are especially sensitive to the alteration of support and loading conditions: different loading scenarios naturally lead to distinct optimal layouts. In order to avoid the loss of objectivity and preserve the optimality of the results, the effects that preliminary modelling and loading assumptions produce on final layouts are investigated. Numerical applications to high-rise building models are presented and discussed
Energy-Based Topology Optimization Under Stochastic Seismic Ground Motion: Preliminary Framework
No full textThe growing availability of suitable computational resources to support the design of complex and large buildings makes the topology optimization more and more attractive to achieve high structural performances while reducing the use of building materials and thus cutting the total costs. In case of buildings under dynamic loads, displacement- and acceleration-based criteria are most commonly employed in topology optimization for preventing damage in structural components and protecting high-frequency sensitive non-structural components, respectively. The present work introduces the energy-based topology optimization of large structures as a more effective design approach to mitigate damage due to earthquake. The inherent randomness of the seismic excitation is taken into account by means of the random vibration theory, in such a way to avoid the direct integration of the motion equations for a large number of records. Topology optimization is performed via Solid Isotropic Material with Penalization (SIMP) method and resorting to an analytical evaluation of the gradient. A stationary-type stochastic seismic ground motion is considered in the preliminary framework presented in this study, whereas the final case study here discussed is concerned the search of the optimal layout for a lateral resisting system in a multi-story building subjected to earthquake
Near-fault earthquakes with pulse-like horizontal and vertical seismic ground motion components: Analysis and effects on elastomeric bearings
No full textNear-fault earthquakes have been largely studied in the last years by paying special attention to the occurrence of a pulse-like horizontal seismic ground motion, and to the related effects on structural systems. Conversely, less attention has been paid on the vertical component of the ground motion in such seismic events. Within this framework, the present study is meant at investigating a fairly overlooked special case, that is the occurrence of near-fault earthquakes exhibiting a pulse-like seismic ground motion along the horizontal direction and the vertical one. Specifically, the variational mode decomposition technique is employed to prepare and characterize two subsets of near-fault earthquake records that consist of fault-normal and vertical seismic ground motion components. One subset collects earthquake records with pulse-like waveform in both velocity components, whereas a pulse-like waveform in the fault-normal velocity component only takes place in the earthquake records of the second subset. If both fault-normal and vertical components embed a dominant pulse-like waveform, then it is found that the ratio of the corresponding pulse periods well correlates with the pulse period along the fault-normal direction, while it is uncorrelated with respect to the pulse period along the vertical direction. Next, it is investigated the displacement demand of high-damping rubber bearings for base-isolated buildings under earthquake records characterized by a horizontal impulsive ground motion together with either a pulse-like or a nonpulse-like vertical shaking, provided that the pulse period in the horizontal direction is similar and the peak ground accelerations are individually the same after scaling. Final results shows that the maximum displacement of elastomeric bearings subjected to a pulse-like horizontal ground motion is moderately amplified, on average, when the vertical excitation is also pulse-like
EPATITI B E C: MA I PAZIENTI CONOSCONO I RISCHI?
No full textGli infermieri hanno una funzione primaria nell’educazione sanitaria dei pazienti affetti da epatiti emotrasmesse, fondamentali risultano gli interventi di educazione sanitaria finalizzati a migliorare il grado di conoscenze, sia riguardo alle modalità di diffusione sia riguardo le misure profilattiche efficaci a ridurre l’incidenza di tali patologie. Un’indagine conoscitiva, condotta da infermieri italiani presso un ospedale in Spagna, ha permesso di definire, su un campione di 50 pazienti, il grado di conoscenze che i pazienti affetti da epatite B o C hanno, riguardo alle modalità di trasmissione dei virus stessi. I risultati hanno sostanzialmente evidenziato un discreto livello globale di conoscenze riguardo le modalità di trasmissione degli agenti patogeni oggetto di discussione
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
Optimal lateral resisting systems for high-rise buildings under seismic excitations
Full text linkIt is generally presumed that the design of tall buildings is mainly dictated by wind loads rather than seismic actions because of the high flexibility and, therefore, long natural periods. However, slender buildings exhibit a complex dynamic behavior, and the involvement of higher modes can result in higher flexural and shear demands than expected. Overlooking the importance of strength, stiffness, and stability requirements in seismic design of tall buildings can thus leads to excessive damage, large residual deformations, and even failure. In this regard, since pure rigid frames alone are not sufficient to withstand lateral loads, as those due to earthquakes, bracing systems are often introduced to stiffen the steel frameworks of tall buildings. The design of lateral bracing systems, in turn, calls for the selection of a suitable pattern for the diagonals arrangement, which is commonly performed through trial-and-error procedures that can require many iteration cycles. It is too evident that this approach does not neither ensure the convergence towards a design solution able to fulfill all requirements, nor the achievement of an optimal solution that minimizes the consumption of structural material and thus the total construction costs. In this context, topology optimization might represent an effective tool for improving the design of tall buildings under earthquake. Therefore, a topology optimization methodology is here presented to support the selection of the most effective design solution for the lateral bracing systems of tall buildings, in such a way to meet minimum weight requirement while ensuring the highest structural performance. Specifically, a density-based approach is adopted to establish an optimization design procedure able to generate optimal lateral-resisting systems for tall buildings subjected to earthquakes. The optimum design is formulated in terms of minimum compliance, also to facilitate the comparison of the material distribution results with those already available in the literature. Numerical results presented in this work are concerned with two-dimensional case studies, which are envisioned as part of realistic tall buildings
- …
