Search Results (6)

This research focuses on the design and performance of Steel Fiber-Reinforced High-Strength Concrete (SFRHSC) to identify the optimal fiber content. The critical challenges involve the fiber content optimization and the effect of fiber distribution on the SFRHSC’s mechanical properties. This study uses the fiber weight ratio as it is more precise for quantifying fiber content than the traditional volume one. The available data obtained from experimental investigations of fifteen cylindrical specimens with systematically varied fiber ratios ranging from 0 to 60 kg/m³ were used. Following the experimental data, a 30 kg/m³ fiber content optimizes the mechanical properties of concrete with a compressive strength of 85–90 MPa, showing a superior Poisson ratio, energy dissipation, and structural ductility. To further recognize and replicate these findings, the behavior of SFRHSC cylinders was simulated using the Lattice Discrete Particle Model (LDPM). In the first stage, the parameters were calibrated by curve-fitting the experimental results with simulations of cube specimens for a uniaxial compression test. Then, the model was validated by simulating a loading–unloading cycle to fit the results. Subsequently, the effect of cracking for each fiber content and verbal compressive strength on the energy dissipation was examined for different SFRHSC strength values. These findings provide valuable insights for developing and optimizing SFRHSC for advanced structural applications. Full article

The use of fibre-reinforced concrete (FRC) has been substantially increasing in the last few years, in different fields of the construction industry. Recently, many experiments have been performed to observe the short- and long-term mechanical behaviour of FRC, and several models have been formulated to capture its mechanical response. In this work, the mechanical behaviour is simulated through the Lattice Discrete Particle Model (LDPM) and its extension to fibre-reinforced cementitious composites (LDPM-F). This paper aims to provide insights into the calibration process and potential pitfalls in a case where only limited experimental data are available—in this case, unconfined uniaxial compression and three-point bending tests on different mixes of polypropylene and steel fibre-reinforced concretes. As a first step, a sensitivity analysis is performed to weight the effect of each governing mesoscale parameter on the simulated macroscale behaviour. Then, for each mix at issue, different sets of model parameters are identified as capable of accurately matching the experimental evidence. As a validation, each calibrated set is used to simulate energy absorption tests on round panels. The validation stage shows that one of the identified sets, for the FRC with polypropylene fibres, accurately matches the round panels’ response, while the others result in acceptable predictions. For the mix with steel fibres, instead, none of the sets captures the experimental results, likely due to the different post-cracking behaviour detected in fracture and energy absorption tests. Finally, a parametric study showcases how the LDPM-F might serve as tool to optimise the mix design without extensive experimental investigations. Full article

Many applications benefit from the prediction of 3D human motion based on past observations, e.g., human–computer interactions, autonomous driving. However, while existing methods based on encoding–decoding achieve good performance, prediction in the range of seconds still suffers from errors and motion switching scarcity. In this paper, we propose a Latent Diffusion and Physical Principles Model (LDPM) to achieve accurate human motion prediction. Our framework performs human motion prediction by learning information about the potential space, noise-generated motion, and combining physical control of body motion, where physics principles estimate the next frame through the Euler–Lagrange equation. The framework effectively accomplishes motion switching and reduces the error accumulated over time. The proposed architecture is evaluated on three challenging datasets: Human3.6M (Human 3D Motion Capture Dataset), HumanEva-I (Human Evaluation dataset I), and AMASS (Archive of Motion Capture as Surface Shapes). We experimentally demonstrate the significant superiority of the proposed framework in the prediction range of seconds. Full article

This paper deals with the blast-resistant performance of steel fiber-reinforced concrete (SFRC) and polyvinyl alcohol (PVA) fiber-reinforced concrete (PVA-FRC) panels with a contact detonation test both experimentally and numerically. With 2% fiber volumetric content, SFRC and PVA-FRC specimens were prepared and comparatively tested in comparison with plain concrete (PC). SFRC was found to exhibit better blast-resistant performance than PVA-FRC. The dynamic mechanical responses of FRC panels were numerically studied with Lattice Discrete Particle Model-Fiber (LDPM-F) which was recently developed to simulate the meso-structure of quasi-brittle materials. The effect of dispersed fibers was also introduced in this discrete model as a natural extension. Calibration of LDPM-F model parameters was achieved by fitting the compression and bending responses. A numerical model of FRC contact detonation was then validated against the blast test results in terms of damage modes and crater dimensions. Finally, FRC panels with different fiber volumetric fractions (e.g., 0.5%, 1.0% and 1.5%) under blast loadings were further investigated with the validated LDPM-F blast model. The numerical predictions shed some light on the fiber content effect on the FRC blast resistance performance. Full article

Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches. Full article

Modeling the complex behavior of concrete for a specific mixture is a challenging task, as it requires bridging the cement scale and the concrete scale. We describe a multiscale analysis procedure for the modeling of concrete structures, in which material properties at the macro scale are evaluated based on lower scales. Concrete may be viewed over a range of scale sizes, from the atomic scale (10⁻¹⁰ m), which is characterized by the behavior of crystalline particles of hydrated Portland cement, to the macroscopic scale (10 m). The proposed multiscale framework is based on several models, including chemical analysis at the cement paste scale, a mechanical lattice model at the cement and mortar scales, geometrical aggregate distribution models at the mortar scale, and the Lattice Discrete Particle Model (LDPM) at the concrete scale. The analysis procedure starts from a known chemical and mechanical set of parameters of the cement paste, which are then used to evaluate the mechanical properties of the LDPM concrete parameters for the fracture, shear, and elastic responses of the concrete. Although a macroscopic validation study of this procedure is presented, future research should include a comparison to additional experiments in each scale. Full article