Mesoscale finite element modelling of failure behaviour of steel-bar reinforced UHPFRC beams with randomly distributed fibres

This study develops a nonlinear finite element model for simulation of complicated failure behaviour of ultra high performance fibre reinforced concrete (UHPFRC) beams reinforced with steel bars and stirrups. In this model, the continuum damage plasticity model is used as the constitutive law for the UHPC matrix, and cohesive elements are used to simulate the softening bond-slip behaviour of the steel fibres/bars-UHPC matrix interfaces. Both the steel fibres and bars are modelled by elastic-plastic beam elements. As such, all the potential failure modes, including the matrix cracking and crushing, yielding and breakage of steel bars and fibres, and debonding of interfaces, can be simulated. A beam under four-point loading with various shear span versus beam depth ratios was simulated to validate the model. The results were compared well with experiments in terms of load-deflection curves and failure behaviour

Bond Dissociation Energies and Equilibrium Structures of Cu⁺(MeOH)<i>_x</i>, <i>x</i> = 1−6, in the Gas Phase: Competition between Solvation of the Metal Ion and Hydrogen-Bonding Interactions

The solvation of Cu+ by methanol (MeOH) was studied via examination of the kinetic energy dependence of the collision-induced dissociation of Cu+(MeOH)x complexes, where x = 1−6, with Xe in a guided ion beam tandem mass spectrometer. In all cases, the primary and lowest-energy dissociation channel observed is the endothermic loss of a single MeOH molecule. The primary cross section thresholds are interpreted to yield 0 and 298 K bond dissociation energies (BDEs) after accounting for the effects of multiple ion−neutral collisions, kinetic and internal energy distributions of the reactants, and lifetimes for dissociation. Density functional theory calculations at the B3LYP/6-31G* level are performed to obtain model structures, vibrational frequencies, and rotational constants for the Cu+(MeOH)x complexes and their dissociation products. The relative stabilities of various conformations and theoretical BDEs are determined from single-point energy calculations at the B3LYP/6-311+G(2d,2p) level of theory using B3LYP/6-31G*-optimized geometries. The relative stabilities of the various conformations of the Cu+(MeOH)x complexes and the trends in the sequential BDEs are explained in terms of stabilization gained from sd hybridization, hydrogen-bonding interactions, electron donor−acceptor natural bond orbital stabilizing interactions, and destabilization arising from ligand−ligand repulsion

Perfect Absorption Metasurfaces with Multiple Meta-Resonances

We show that the hybrid resonances of a DMR backed by a cavity are meta-resonances, in that they can be made as perfect as possible by fine tuning the structural parameters but without the requirements of extreme materials properties, such as zero dissipation. Instead, dissipation in the DMR is essential for the realization of perfect meta-resonances. We experimentally demonstrate such perfection by tuning the structure of a HMR till its reflection is as low as 0.426 % . Besides the primary meta-resonances that are originated from the strong resonances of the DMR, weak hitchhiker resonances can also produce meta-resonances as perfect as the primary ones. The depth of the reflection dips is insensitive to the strength of the resonances involved, but critically depends on the degree of impedance match to air brought mostly by fine tuning the structure parameters, such as the cavity volume, the mass of the platelet, or the pre-tension in the membrane. Using the eccentricity of the platelet position in the DMR, a number of resonances and anti-resonances are generated, resulting in up to five meta-resonances within the range of 200 Hz to 1000 Hz, with the highest reflection being 7 % and the lowest being 1.2 % . Other means of introducing hitchhiker meta-resonances are also reported

ℏ_<i>θ</i>-curve.

<p>ℏ_<i>θ</i>-curve.</p

Convergence of the derived solutions.

<p>Convergence of the derived solutions.</p

Influence of thermophoresis and Brownian motion on Nusselt number.

<p>Influence of thermophoresis and Brownian motion on Nusselt number.</p

Streamlines for Newtonian model.

<p>Streamlines for Newtonian model.</p

Influence of convection parameter on concentration.

<p>Influence of convection parameter on concentration.</p

ℏ_<i>f</i>-curve.

ℏf-curve.</p

Influence of convection on velocity.

Influence of convection on velocity.</p