1,721,028 research outputs found
Multiscale topology optimization with embedded TPMS architected materials
No full textTopology optimization has emerged as a critical computational tool for designing lightweight, robust, resilient and efficient structures. Recent advances in additive manufacturing technologies enable the production of complex objects across multiple scales, fostering the development of novel architectures endowed with diverse topologies and material classes, tailored to specific performance requirements. In this work we explore the use of Triply Periodic Minimal Surface (TPMS) architected materials, which mimic natural and biological systems to achieve exceptional mechanical efficiency and scalability. To this aim, we present a multiscale, multi-material topology optimization framework that leverages a gradient-based scheme to minimize compliance under multiple volume constraints. TPMS microstructures are generated via the Fourier Series Function (FSF) method, seamlessly integrated into the optimization process through homogenization theory. The Solid Isotropic Material with Penalization (SIMP) model is coupled with Discrete Material Optimization (DMO) interpolation, introducing a continuation parameter that transitions smoothly from a convex problem to a non-convex problem. To handle volume constraints effectively, the ZPR-BFGS design variable update scheme is adapted to the continuum setting, allowing constraints to be updated independently, sequentially, or in parallel. This framework enables flexible volume constraints, which can govern either all or a subset of materials at both global and local scales. Additionally, we introduce a voxel-based post-processing strategy to ensure scalable designs, smooth material transitions, and tunable scale separation. Key insights are illustrated through meaningful numerical examples, demonstrating the effectiveness of the proposed framework. The methodology highlights the versatility of TPMS-based architectures in achieving optimal material distribution with arbitrary geometric complexity
Multi-scale topology optimization for innovative 3D-printed walls and shell structures
No full textTopology optimization is a computational design tool that allow to optimize specific properties in a design domain imposing a priori conditions. A common topology optimization formulation adopted for civil engineering problem is the minimization of compliance, which is equivalent to maximize the stiffness. In this work, we propose a homogenization-based multiscale approach with a compliance minimization formulation for large-scale 3D printing of innovative in-plane loaded walls and shells for building engineering. This approach entails a two-dimensional structural optimization scheme, that accounts for the presence of predefined microstructures and different material properties. Afterwards, the three-dimensional layout of the optimized structure is reconstructed at the micro-scale starting from the obtained optimal layout by means of a specifically tailored 2.5-D post-processing algorithm. The proposed multiscale topology optimization approach is demonstrated by several meaningful numerical examples
Special Issue on Natural Hazards Risk Assessment for Disaster Mitigation
No full textEditorial for the Special Issue on Natural Hazards Risk Assessment for Disaster Mitigatio
Analysis of Gothic Masonry Arches Through a Fully Three-Dimensional Kinematic Limit Analysis Approach
No full textA kinematic limit analysis approach for three-dimensional curved rigid blocks is presented. To maintain the exact geometry of curved structures in a three-dimensional context, NURBS solids are used. Under the hypotheses of rigid elements and frictional behavior at interfaces, a kinematic limit analysis problem is defined and solved through a linear programming formulation. The Gothic arches in the Carmo convent, Lisbon (Portugal), are studied to prove the efficiency of the method
Base isolation of heavy non-structural monolithic objects at the top of a masonry monumental construction
No full textThe present paper deals with the relevant topic of seismic protection of heavy non-structural monolithic objects, which are usually placed at the top of masonry monumental constructions for mainly decorative purposes, like pinnacles and heavy artwork. Even if, after seismic events, most of the losses are due to structural collapse of buildings and other structural systems, heavy non-structural objects of the kind considered in the present work represent a serious potential hazard for both human lives and cultural heritage. During earthquakes, such objects undergo large base accelerations, which may eventually cause their collapse by rocking and overturning. In the present contribution, the seismic protection of eleven ancient marble decorative pinnacles placed at the top of the three-arched masonry city gate in Ferrara (Italy) is illustrated as a case study. In particular, a method for assessing the safety level of these systems under the action of seismic excitations is outlined and base isolation is proposed as a very promising technique for the seismic retrofit of heavy non-structural monolithic objects. The dynamical response to seismic actions of the underlying masonry construction is assessed through time-history dynamic analyses and the amplification of the ground accelerations at the base of the pinnacles is evaluated. Furthermore, the pinnacles are modeled as rigid bodies and their rocking behavior under base excitations is discussed. Finally, the effectiveness of the proposed base isolation system is assessed through non-linear dynamic numerical simulations
Fragility functions for masonry infill walls with in-plane loading
No full textRecent seismic events have provided evidence that damage to masonry infills can lead not only to large economic losses but also to significant injuries and even fatalities. The estimation of damage of such elements and the corresponding consequences within the performance-based earthquake engineering framework requires the construction of reliable fragility functions. In this paper, drift-based fragility functions are developed for in-plane loaded masonry infills, derived from a comprehensive experimental data set gathered from current literature, comprising 152 masonry infills with different geometries and built with different types of masonry blocks, when tested under lateral cyclic loading. Three damage states associated with the structural performance and reparability of masonry infill walls are defined. The effect of mortar compression strength, masonry prism compression strength, and presence of openings is evaluated and incorporated for damage states where their influence is found to be statistically significant. Uncertainty due to specimen-to-specimen variability and sample size is quantified and included in the proposed fragility functions. It is concluded that prism strength and mortar strength are better indicators of the fragility of masonry infills than the type of bricks/blocks used, whose influence, in general, is not statistically significant for all damage states. Finally, the presence of openings is also shown to have statistically relevant impact on the level of interstory drift ratio triggering the lower damage states
Collapse behavior of masonry domes under seismic loads: An adaptive NURBS kinematic limit analysis approach
No full textThe ultimate limit state behavior of masonry domes under axisymmetric gravity loads is nowadays well known and it has been proved how a generalization of the thrush line method used successfully for arches is quite effective also in this case. However, the behavior of a dome under horizontal loads, which is important in case of seismic action, becomes incredibly hard to tackle and still remains an open issue. The present paper aims at presenting a fast and reliable automatized kinematic limit analysis approach able to accurately predict the actual behavior of masonry domes subjected to horizontal static loads. The model uses a rough discretization of the dome obtained by means of few rigid-infinitely resistant NURBS generated elements, adapting step by step the initial mesh in order to progressively overlap the element edges (where all dissipation is lumped) with the hinges forming the failure mechanism. The adoption of a rough mesh makes the code extremely fast, much more competitive than a standard FE model, allowing at the same time to approximate the actual geometry and load distributions in an extremely accurate way. The utilization of geometries obtained with laser scanner acquisitions is straightforward and the presence of pre-existing cracks can be accounted for as well. Three complex case studies are analyzed in detail to benchmark the approach proposed, relying into existing domes belonging to the Italian cultural heritage. The first example has the geometrical parameters of a typical late Renaissance dome, the Cathedral of Montepulciano, the second is the dome of Anime Sante church (collapsed during the L'Aquila 2009 earthquake with a paradigmatic failure mechanism) and the last is the dome of Caracalla baths, whose causes of collapse remain still unknown. In all cases inspected, the approach proposed quickly provides collapse accelerations and active failure mechanisms at a fraction of the time needed by non-linear FE analyses, providing interesting hints into the actual behavior of such kind of structures under horizontal loads
Homogenization models for nonlinear and limit analysis of FRP-strengthened masonry
No full textThis chapter discusses two advanced numerical approaches for the analysis of fiber reinforced polymer (FRP)-reinforced masonries, namely a novel adaptive upper bound limit analysis (UBLA) and a nonlinear procedure with rigid elements based on sequential quadratic programming. Both are tools for an effective structural analysis of FRP-reinfoced masonry, requiring a preliminary homogenization of the masonry material at the mesoscale. When dealing with the UB limit analysis approach, a genetic algorithm (GA)-nonuniform rational b-spline (NURBS)-based general framework suitable for a mesh adaptation-applied to curved masonry structures is discussed. A given FRP-reinforced masonry vault can be geometrically represented by a NURBS parametric surface, and a NURBS mesh of the given surface can be generated. Each element of the mesh is a NURBS surface itself and can be idealized as a rigid body. An UBLA formulation, which takes into account the main characteristics of masonry material and FRP reinforcement, is deduced, with internal dissipation allowed exclusively along element interfaces. GA helps in progressively adjusting the shape of the NURBS elements to closely approximate the real failure mechanism activating. When dealing with the nonlinear approach, finite element discretization without mesh adaptation constituted by both rigid wedge elements (masonry) and rigid triangular elements (FRP) interconnected by nonlinear homogenized interfaces is discussed. The step-by-step nonlinear problem is solved as constrained minimization of the quadratic energy function. Both approaches are capable of well predicting the load-bearing capacity of any kind of FRP-reinforced masonry structure (in particular, vaults of arbitrary shape, which are the most complex), with the nonlinear model having the additional features of accurately predicting initial stiffness, postpeak behavior, and displacements at failure. Both approaches are benchmarked through a number of numerical simulations applied to FRP-reinforced masonry structures tested in experiments taken from the literature
On virtual element solutions of unilateral contact problems
No full textThis contribution investigates the capabilities of an arbitrary order virtual element approach to solve a special class of contact problems, i.e. the unilateral contact between a two-dimensional elastic body and a rigid frictionless foundation of arbitrary shape, which is known as the Signorini problem. In order to account for the presence of the rigid obstacle, the virtual element formulation has been coupled to a Projected Successive Over-Relaxation (PSOR) algorithm. Due to its unique features, the Virtual Element Method (VEM) proves to be very versatile when dealing with the need of inserting new nodes on the contact surface and when a higher order interpolation field along element edges is required. The salient features of the method have been illustrated through a simple but insightful numerical example
Advanced numerical strategies for seismic assessment of historical masonry aggregates
No full textRecent seismic events in Italy have emphasized the high vulnerability of masonry buildings in historical centers, which were generally erected in continuity to each other over time, resulting in aggregates of constructions. The study of the seismic behavior of masonry aggregates can turn into a very difficult task, usually because of the difficulties to achieve a complete knowledge of geometrical evolutions, state of the connections between structural units, and interventions carried out in the course of time. A wide number of local collapses has been observed after recent earthquakes in Italy, highlighting that collapse under horizontal loads may take place mainly through failure mechanisms of single portions of the aggregate. According to Italian Code, both global and local analyses can be adopted in the seismic assessment of single structural units. Therefore, the aim of this study is to investigate different approaches for the evaluation of the seismic vulnerability of historical masonry aggregates. A masonry aggregate located in the historical center of Arsita (Central Italy), which was hit by the 2009 L'Aquila earthquake, has been chosen as a representative case study and a wide set of local and global analyses has been carried out. Local analyses have been conducted through a new upper-bound limit analysis based on NURBS and mesh adaptation, and a kinematic limit analysis applied to the most common local mechanisms. Global analyses have been performed through pushover analyses using the Equivalent Frame Method, and pushover and nonlinear dynamic analyses on a detailed FE model with appropriate constitutive laws. Finally, a discussion about the effectiveness of the different analysis approaches is presented with reference to the results obtained in this study
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