Numerical Modelling Strategy Research Articles

Thin silicon sensors for extreme fluences: A doping compensation strategy

The CompleX project aims at extending the operation range of silicon detectors as 4D trackers up to 5 × 1017 neqcm−2. The project envisions achieving this unprecedented radiation tolerance through a novel comprehension of radiation damage saturation, and an innovative design for the Low-Gain Avalanche Diodes (LGADs) gain layer with compensated implants. This innovative LGAD design, featuring a co-implantation of acceptor and donor dopants, represents a paradigm shift in radiation-resistant sensor technology. It potentially enables compensated LGADs to maintain functionality at fluences exceeding 1017 neqcm−2, significantly extending the operational lifetime of conventional LGAD sensors under extreme fluence conditions. This advantage is further enhanced by the inherent radiation tolerance of thin substrates. This work presents simulations and measurements from the first compensated LGAD production (late 2022, FBK foundry) before and after neutrons irradiation. Numerical modeling strategies using state-of-the-art Technology-CAD tools quantify the reduction in acceptor removal rate due to carbon co-implantation and investigate the behavior of donor removal under irradiation. This comprehensive approach paves the way for the development of highly efficient tracking detectors for future collider experiments.

Eksperimentalno istraživanje konstrukcijskog reprofiliranja sljubnica cementno polimernim mortom i polipropilenskim trakama u ziđu

Unreinforced masonry structures are prevalent in urban areas. Many of these structures are vulnerable to earthquakes, which are the primary causes of damage and failure. Therefore, conducting comprehensive studies to assess the structural capacity of these buildings is crucial for understanding their behaviour and vulnerability and for proposing effective strengthening measures. This integrated experimental and numerical study explored the effectiveness of joint repointing as a viable method for strengthening masonry structures. A review of recent research on various joint repointing techniques and materials is presented in the first part of this paper. The experimental investigations of unreinforced and strengthened masonry panels, utilising cement-polymer mortar and polypropylene strips in bed joints subjected to compressive and diagonal compressive strengths, are detailed. The experimental results demonstrate that structural joint repointing significantly improves the strength and has a minor effect on the ductility of the masonry, particularly when the original mortar has low-strength properties, as expected in existing buildings. The obtained results enable the calibration of nonlinear numerical models and modelling strategies used to study the elements in a more extensive manner, allowing for parametric studies and the application of the findings to existing buildings.

Numerical modelling strategy and load resisting mechanism of palace-type traditional wooden frame

This paper is aimed at proposing the numerical modeling strategy of the palace-style traditional wooden frame in Chinese Song dynasty and revealing its load resisting mechanism. Firstly, the restoring moments of the column foot (CF) and column head (CH) of free-standing column are formulated, the proposed model of the frame with CF and CH is validated by the corresponding solid element models. Then, the mechanical behavior of the dowel at the CH is formulated based its deformation characteristics, and the proposed model of the frame with CF, CH and dowel is also validated by its solid element model. Finally, the effectiveness of the proposed model of the whole frame with CF, CH, dowel and dovetail mortise-tenon (DMT) joint is confirmed by the corresponding experimental and solid element models. The results show that difference of mechanical performance of the CF with compressive deformation parallel-to-grain and CH with compressive deformation perpendicular-to-grain is minor, the bending behavior of the dowel in the frame without lower beam has been changed into the shearing behavior of the dowel in the frame with lower beam. The rotational behaviors of the DMT at the two ends of the beam are different when the frame is lateral deformed, and the proportion of the lateral resistance provided by the column and DMT is more and less than 60 % and 30 %. And the upper beam of the wooden frame significantly increases its lateral resistance.

Vibration Response Analysis of a Main Landing Gear System for High In-Flight Dynamic Loadings

The prediction of aircraft vibrations is necessary for identifying possible design optimization points of each on-board system. In this context, the authors investigated the dynamic response of a Main Landing Gear (MLG) conceived for a fast helicopter when exposed to flight vibrations arisen from the engine propellers. The research activity falls within the Racer program of Clean Sky 2 framework, which aims to develop a novel high-speed rotorcraft. Relying on Airbus Helicopters operative requirements, this paper deals with the numerical procedure description of the MLG dynamic response assessment (resonance frequencies, accelerations amplitude, generalized masses) with respect to the expected in-flight vibrations levels. In particular, an equivalent combined load (sine and random spectrum) based on the normal modes and the corresponding modal mass distribution is employed for investigating the relevant effects on structural endurance. The central themes focus on the possible numerical modelling strategies and vibration loads analysis, which led safely to the qualification. This method could allow for performing sensitivity dynamic analyses in case of further design stiffness or weight changes.

Numerical Investigation of an Experimental Setup for Thermoplastic Fuselage Panel Testing in Combined Loading

The main purpose of this study comprises the design and the development of a novel experimental configuration for carrying out tests on a full-scale stiffened panel manufactured of fiber-reinforced thermoplastic material. Two different test-bench design concepts were evaluated through a numerical modeling strategy, which will be validated at the next stage using a targeted series of mechanical tests. A baseline experimental setup was developed after a number of candidate configurations were numerically investigated. The supporting elements along with the load introduction systems were defined in such a way as to represent the stiffness of a fuselage barrel section and its representative loading scenarios. The test rig and the investigated thermoplastic panel were numerically simulated to acquire valuable data pertaining to deformations and stresses when subjected to different loading combinations. Two distinct load cases were numerically examined: the first case was the in-plane compression of the thermoplastic panel, while the second case consisted of an internally applied pressure load introduced via an inflatable airbag, installed under the panel. Both loading scenarios were recreated inside the numerical virtual environment in order to examine two distinct stiffening configurations as well as to determine the maximum/limit loads to be used in the planned future experimental campaign. It was concluded that the designed test rig could successfully be used for the structural evaluation of fuselage panels under representative loading conditions.

Friction Saturated Limit Cycle Oscillations—Test Rig Design and Validation of Numerical Prediction Methods

Abstract In this paper, an experimental test rig for friction saturated limit cycle oscillations is proposed to provide a validation basis for corresponding numerical methods. Having in mind the application of turbine blades, an instrumented beam-like structure equipped with an adjustable velocity feedback loop and dry frictional contacts is designed and investigated. After dimensioning the test rig by means of a simplified one-dimensional beam model and time domain simulations, the specific requirements of limit cycle oscillations for the design of the frictional contact, the velocity feedback loop and the excitation system are discussed and possible solutions are presented. Also appropriate measuring principles and evaluation techniques are assessed. After commissioning of the test rig, the influence of the negative damping and the normal contact force on the limit cycle oscillations is measured and the practical stability is investigated. The test rig shows linear dynamics for sticking contact and highly repeatable limit cycles. The measured results are discussed regarding the consistency with theory and compared to the predictions of a three dimensional reduced order model solved in frequency domain by the harmonic balance solver OrAgL. It is demonstrated that the numerical modeling strategy is able to accurately reproduce the measured limit cycle oscillations, which stabilized for different contact normal forces and self-excitation levels.

Assessing shoreface sediment transport at Costinha beach, Aveiro, Portuguese Northwest coast

Coastal zones are dynamic environments where sediment transport significantly influences erosion, deposition, and ecosystem stability. Accurate modelling of the complex interactions between hydrodynamics, sediment transport, and morphological changes in high-energy shoreface areas is crucial for sustainable coastal management. This study aims to assess sediment dynamics and understand the dominant physical drivers of sediment transport in the shoreface by coupling high-resolution numerical modelling with a shoreface sand tracer experiment. Results from the field experiment showed high diffusion and a net onshore and downdrift movement of the tracer in agreement with the observed hydrodynamic data. The numerical modelling strategy, validated with in situ hydrodynamic data and tracer results, demonstrated good performance and highlighted the dominant modes of shoreface sediment transport. While during low energetic wave conditions, the dominant transport mechanism involves the slow-rate bed load sediment movement toward the shore, under moderate energetic wave conditions, longshore wave-induced suspended transport becomes the prevailing mode of transport. The study provides valuable insights to increase the understanding of sediment transport in the shoreface and highlights the importance of coupling numerical modelling with sediment tracer experiments.

Bed joint reinforcement of shear walls using threaded titanium rods

Shear walls in historic constructions often require retrofit. The lateral load capacity is frequently insufficient to withstand seismic actions. Threaded titanium rods embedded in mortar bed joints have emerged as a viable solution to reinforce brickwork shear walls. The use of a high tensile strength and ductile material (titanium alloys), with a high degree of reversibility of the retrofit intervention, is promising as it represents a new opportunity in masonry conservation. Aiming at studying the effectiveness of the titanium rod repair, this research had a twofold goal: 1. laboratory tests were performed to investigate the structural response of reinforced walls at macro-scale level; 2. a numerical modelling strategy was implemented to fill the knowledge gap regarding the material properties of brickwork masonry (English and Flemish bond). Quasi-static cycling loading tests performed on full scale (1200x1200 mm, two wythes thickness) specimens demonstrated how bed joint reinforcement using threaded titanium rods produced a significant increase in the lateral load and deformation capacities. To provide an effective tool for predicting all material parameters, as input data, and for designing the proposed strengthening system, a step-by-step procedure - based on the use of digital image processing (DIP) techniques, homogenization theories and micro-modelling strategies - was therefore proposed.

Numerical modeling strategies and parametric analyses of platform-type and balloon-type cross-laminated timber (CLT) shear walls under lateral loads

Despite great contributions having been made on the topic of numerical modeling methods for cross-laminated timber (CLT) shear walls under lateral loads, it is still challenging to simulate the nonlinear wall behavior with both computational efficiency and modeling accuracy. In this paper, a series of novel modeling strategies are developed, aiming to provide a potential solution to this challenge. The modeling strategies involve the revised version of a uniaxial hysteretic model for dowel-type timber joints, physical and phenomenological modeling methods for typical CLT connections (i.e., hold-down and angle bracket connections), and a fiber-section-based modeling method for CLT shear walls. The modeling strategies were validated by existing experimental data, and the modeling results showed that the proposed fiber-section-based model is capable of simulating the lateral performance of both platform-type and balloon-type CLT shear walls with sufficient accuracy while maintaining desirable computational efficiency. The fiber-section-based model was then used to conduct parametric studies, investigating the influence of construction methods, wall aspect ratios, connection stiffness, and vertical load magnitudes on the lateral performance of CLT shear walls. The studies showed that the initial stiffness and ductility ratio of balloon-type CLT shear walls were 39.1–47.1% and 13.7–19.4% larger than the platform-type ones, while the ultimate capacity was less affected by construction methods. Slenderer CLT shear walls had lower ultimate capacities and initial stiffnesses, as well as smaller ductility ratios. Stiffer hold-down connections contributed to larger initial stiffness but resulted in the CLT shear wall failing in a less ductile manner. The vertical load had positive impacts on the ultimate capacity, initial stiffness, and ductility ratio of CLT shear walls, although the effect on the ultimate capacity was quite limited.

A modeling strategy for the flexural performance prediction of UHPC beams accounting for variability of properties

The Reinforcing Ratio (RR) is a major factor governing the ductility of UHPC beams. Previous works have demonstrated that beams with low RR (less than2.0 %) exhibit a sudden drop in load after the peak. The first part of the present paper reports the results of an experimental program comparing the responses of beams made with conventional concrete and UHPC for two different RR (0.44 % and 1.78 %). The results confirm that UHPC increases the load-carrying capacity by up to 135 %, allowing for multiple cracking with finer cracks. Using the post-peak drift method, it is shown that the ductility of the UHPC beams with RR = 1.78 % was about 2.6 times greater than that for RR = 0.44 %. In the second part of the work, a numerical finite element modeling strategy accounting for the inhomogeneous fiber distribution is developed and validated against the experiments. It is shown that the homogenous models cannot simulate the crack localization associated with weak regions in UHPC and, therefore, overpredict member ductility. Finally, the numerical model is used to design optimized UHPC beams with the same strength as the tested reinforced concrete beams. It is shown that half of the cross-section width is necessary, resulting in greater RR values that ultimately increase the ductility by 275 % and 167 %, respectively, for beams reinforced with RR = 0.44 % and 1.78 %.

Numerical Modelling of Traditional Timber Columns Resting on Stone Bases

ABSTRACT Columns in traditional timber structures are commonly seen resting on stone bases and are very important in resisting lateral loads. This paper numerically modeled the lateral resistance of the columns combined with experimental investigation. Different numerical models were developed, based on which sensitivity analyses were performed. A practical numerical modelling strategy was further proposed and verified. The analysis results indicated that instead of material properties and contact area, the columns’ lateral performance was much more sensitive to the variation of surface curvature at bottom surface. Without consideration of the surface curvature, the modeling error in the initial stiffness and peak load of a column was more than 607% and 8%, respectively. By best matching the load–displacement curves of tested column specimens, the optimal surface curvature was identified as 1/20306.5 mm−1. Then, a practical finite numerical model, characterized by the optimal curvature at the bottom surface, was proposed. This modelling method was validated by use of existing test results of traditional timber columns with different diameters and vertical compression loads. The modelling load–displacement curves agreed well with experimental curves both in terms of the initial lateral stiffness and peak load. Detailed simulation results based on the practical modelling strategy were presented and discussed.

Numerical Modeling of Early-age Effects on the Mechanical Behavior of Concrete Gravity Dams

The control of thermal cracks induced by the effect of early age are the main concerns in concrete dam during the construction stage. Despite its importance, detailed thermal analysis of concrete gravity dams during the construction period is relatively rarely in the literature, eventually because prediction the behavior of concrete gravity dam on early stage requires taking into account the several phenomena and interaction, demands a considerable computational effort. To overcome this drawback, the present paper proposes a numerical modeling strategy to predict the thermo-mechanical behavior of concrete gravity dams during construction periods considering the effect of early age and the construction schedule. The proposed strategy is also used to study the effect of pre-cooling methods on the thermal-mechanical fields on concrete gravity dam during construction process. For this purpose, a Chemo-Thermo-Mechanical model is developed for predicting the behavior of a gravity dam at early stages. Firstly, temperature field model was established and verified with the results reported in the literature. Furthermore, the thermo-mechanical behavior of a concrete gravity dam is performed for two configurations: Early age state with pre-cooling and early age without pre-cooling. Thermal stress analysis was also conducted and results showed that the greatest tensile stresses after construction are developed at the heel of dams and resumption of concreting interface due to the internal restraint imposed by the concrete. The numerical results showed that the pre-cooling methods is an effective way to reduce both the hydration temperature and tensile stress induced by the effect of early age.

Analysis of numerical modeling strategies to improve the accuracy of polymer injection molding simulations

Analysis of numerical modeling strategies to improve the accuracy of polymer injection molding simulations

Seismic performance of buildings with novel self‐centering base isolation system for earthquake resilience

AbstractThis study presents a novel self‐centering (SC) base isolation system enabled by traditional lead rubber bearing (LRB) incorporating superelastic shape memory alloy (SMA) U‐shaped dampers (hereinafter referred to as SMA‐LRB). This system is particularly suitable for some important structures (e.g., hospital buildings) that require high seismic performance and rapid recovery of normal serviceability after a severe earthquake. The working mechanism of the SMA‐LRBs is first illustrated, followed by a comparative experimental study on the traditional LRB and the emerging SMA‐LRB. Test results confirm the satisfactory flag‐shaped hysteresis loops of SMA‐LRB associated with significantly reduced residual deformation under cyclic loading. Subsequently, a refined numerical modeling strategy for these bearings is developed. The seismic performances of the SMA‐LRBs are examined systematically through two comparative reinforced concrete (RC) frame buildings, namely, the traditionally isolated and the SC isolated cases under far‐ and near‐field earthquakes. Seismic fragility analyses are further carried out through incremental dynamic analysis (IDA). The seismic responses demonstrate that the SC isolated building can match or improve the behavior of the traditional isolated buildings. Compared with the considerable residual deformation of the traditional isolated system under some earthquake events, the SC isolated system exhibits negligible residual deformation that can significantly avoid normal serviceability disruption while achieving the high‐performance objectives. The SC base isolation system can provide a promising type of advanced seismic protection device for earthquake resilient design.

Post-tensioned rocking dissipative timber wall systems: Numerical prediction

Low-damage post-tensioned technologies were born with the aim to obtain structural solutions able to guarantee, in case of seismic events, not only the safeguarding of human life, but also the rapid re-use of the buildings without permanent damage. In this context, structural systems based on rocking dissipative timber walls have been introduced, in which rocking behavior is entrusted to post-tensioned bars, and the dissipative contribution is provided by steel dampers, easily replaceable after an intense seismic event. The paper presents a nonlinear numerical model to predict the response of different configurations of Post-Tensioned (PT)-timber wall systems, particularly useful to support the design phase. More in detail, the geometrical non-linearity due to the rocking behavior of the system and material non-linearities that characterize the dampers are taken explicitly into account. The proposed numerical modelling strategy has been validated on different experimental literature tests performed by non-linear static analyses on both single and double wall systems equipped with different damper configurations. The comparison between numerical and experimental results is performed to demonstrate the effectiveness of the proposed model in predicting the behavior of post-tensioned walls subjected to cyclic loads. Further, parametric analyses have been developed in order to investigate the effect of different parameters, such as wall dimensions, initial post-tensioned force in the bars, number of axial and shear dampers, on the global behaviour of post-tensioned timber systems.

Cyclic model of post-tensioned low damage timber walls with dissipative devices

Post-tensioned rocking dissipative timber wall systems born from the idea to obtain structural solutions able to guarantee, after a seismic event, a rapid re-use of the buildings without permanent damage, as well as to guarantee the safeguarding of human life. In this framework, the rocking of timber walls is entrusted to post-tensioned bars, placed in ad hoc cavities of the panel, while the dissipative contribution is provided by steel dampers, which are sacrificial elements subjected to damage easily replaceable after an intense seismic event. In this context, it can be helpful to have a numerical model in order to support the design phase; indeed, the paper presents a non-linear numerical model of post-tensioned rocking dissipative timber walls able to predict the response of this innovative system. In particular, geometrical and material non-linearities, due to the rocking behavior of the system and to the material that characterize the dampers, are taken explicitly into account. Further, the proposed numerical modelling strategy has been validated on literature experimental campaigns performed on both single and double wall systems, with different damper configurations. The comparison between experimental and numerical cyclic responses are shown in term of global results, i.e. force/displacement curves and post-tension variation of the bars. The comparison demonstrates the effectiveness of the proposed model in predicting the behavior of post-tensioned walls subjected to cyclic loads.

A new Distinct Element meso‐model for simulating the rocking‐dominated seismic response of RC columns

AbstractThe rocking‐dominated seismic response of reinforced concrete (RC) columns is a complex mechanism that entails P‐Δ effects, concrete crushing and spalling, rupture and dislocation of steel bars and stirrups, as well as combined localized failures causing splitting and shear‐flexure cracking. In this paper, we present a new meso‐scale numerical modeling strategy for the detailed simulation of the rocking response of slender RC columns under seismic actions. This work advances the current state‐of‐the‐art by exploring the unprecedented use of the Distinct Element Method (DEM), originally conceived for geotechnical studies and whose applicability in earthquake engineering has been primarily limited to the assessment of unreinforced masonry sub‐structures. To decrease analysis time and enable the use of DEM for RC problems, concrete is herein idealized as an assembly of solid macro‐block layers of size directly proportional to their distance from expected plastic hinges. These layers are connected by nonlinear interface springs to simulate tensile and shear cracking via a simplified Mohr‐Coulomb criterion. Crushing of concrete in deformable blocks is modeled using the Feenstra and De Borst strain‐softening linearized compression law, while confinement and combined failures are accounted for numerically through the explicit representation of longitudinal and transversal reinforcement bars, idealized as link elements. Previous experimental static and dynamic tests on full‐scale RC column specimens and results from fiber‐based Finite Element and sectional analysis models are used to evaluate DEM results and quantify the influence of key modeling parameters, including block number and deformability, as well as the amount of damping. The agreement between simulated failure modes and force and displacement capacities and their experimental counterparts demonstrate the applicability of the proposed approach, while demonstrating the pros and cons of simplified numerical methods.

An effective numerical modelling strategy for FRCM strengthened curved masonry structures

Fabric Reinforced Cementitious Matrix (FRCM) composites are currently considered a very effective solution for strengthening masonry constructions. However, the mechanical interactions governing the response and the strength of FRCM reinforced masonry structures are very complex, especially in the case of curved structures. Moreover, these interactions involve several interfaces between different materials. Thus, the development of accurate numerical models for curved FRCM reinforced masonry structures comes up against several difficulties, and models too complex for practical applications can be obtained. In addition, several mechanical parameters needed for the calculations are generally inaccessible by conventional experimental tests.Here, a suitable numerical modelling strategy for FRCM strengthened curved masonry structures is proposed to combine the accuracy in simulating the actual behaviour in terms of stiffness, strength and collapse mechanisms with a reasonable simplicity, making the proposed approach usable also by practitioners, by adopting commercial codes and at a moderate computational effort. The relatively small number of mechanical parameters characterizing the model can be determined by ordinary experimental tests on materials or by literature formulations.The proposed modelling strategy is validated with respect to experimental data found in literature concerning a FRCM reinforced masonry barrel vault, and then is employed for studying the seismic capacity of the vault through a pushover analysis. A broad sensitivity analysis sheds light on the effect of variations of the mechanical parameters on the predicted overall behaviour, showing the robustness of the results obtainable through the proposed approach concerning inaccuracies in the determination of the parameters often very difficult to determine by ordinary experimental tests on masonry structures.

Masonry Elements Strengthened with TRM: A Review of Experimental, Design and Numerical Methods

Textile-Reinforced Mortar (TRM) is a modern and compatible strengthening strategy for existing masonry, which consists in plastering the walls by means of mortar layers with embedded grids or textiles made of long fibers. TRM can be very useful for the reduction of the seismic vulnerability of masonry buildings, since the fiber-based reinforcement, carrying high tensile stresses, opposes the widening of cracks and provides “pseudo-ductility” to the masonry. The increasing number of available studies on the subject testifies to its relevance but also the lack of a standardized or well-establish approach to quantify the benefits of these systems on the performance of masonry. The present review is aimed at providing a broad overview of how the study of TRM-strengthened masonry elements has been addressed in the literature. In particular, the main features of the different experimental tests are compared, dealing with both in-plane and out-of-plane behavior. Moreover, the different design methods and numerical modeling strategies are presented and discussed.

Spatial variability and stochastic finite element model of unreinforced masonry veneer wall system under Out-of-plane loading

Inconsistency in the quality of workmanship, the weather during construction, and materials may result in the high unit-to-unit spatial variability of mechanical properties in the same masonry structure. This paper develops a numerical modelling strategy and focuses on the stochastic assessment of unreinforced masonry (URM) veneer walls with spatially variable wall constituent material properties subjected to out-of-plane loading. 3-D finite element modelling of experimentally tested veneer walls was conducted using a micro-modelling approach combined with the Monte Carlo Simulation technique. Spatial stochastic finite element analysis considered the spatial variability of the properties of the wall components (mortar flexural tensile strength) and compared them with non-spatial analysis. The non-spatial analysis overestimates the wall system failure compared to spatial analysis, and the spatial analysis is considered to more realistically represent the variabilities of the URM veneer wall system. Sensitivity analysis is conducted to check the sensitivity of the veneer system behaviour to variability in the various input parameters. The variability of experimental results obtained in a parallel study are quantified and compared with stochastic finite element analysis (SFEA) results. The SFEA model developed in this study can estimate the behaviour and system peak load reasonably and are considered to be from the similar population as test results. Model errors are also included to assess the efficiency of the SFEA model.