Vibration reduction of cable-stayed bridge model retrofitted with SMA restrainers

Shape Memory Alloys (SMAs) are more and more frequently used in civil structures subjected to extreme dynamic loadings. Due to their unique properties, the SMAs are used for seismic retrofit of bridges, tall buildings and masts. The paper presents selected results of numerical calculations of a cable-stayed steel bridge model retrofitted with SMA restrainers. The original set of constitutive relationships describing pseudoelastic properties of SMA was used for this purpose. The formulation of SMA model is based on analysis of a special rheological scheme representing its constitutive properties. The SMA model was implemented within FEM software Abaqus using an user defined subroutine. It was proved that the application of SMA restrainers can reduce significantly vibrations and internal forces caused by seismic excitations

Predicting Performance of Aluminum - Glass Composite Facade Systems Based on Mechanical Properties of the Connection

In this paper, an extensive Finite-Element (FE) numerical study is carried out on a glass framing with point mechanical connectors. The models have been calibrated based on literature studies and field research. The simulations have been performed in order to assess the mechanical behavior of the examined glass-aluminum panels. In frame-support glass structures, such as curtain walls, where glass plates are mounted onto a metal framework, the composite behavior between glass and the supporting aluminum elements is usually a problem. It has been showed that an application of elastomer gaskets decreases the stress concentration at the interface between aluminum and glass while does not significantly change the working scheme of the profile. Based on the proposed models, the failure mechanism for wider set of geometrical configurations can be analyzed

Dual Geometry Schemes in Tetrel Bonds: Complexes between TF4(T = Si, Ge, Sn) and Pyridine Derivatives

When an N-base approaches the tetrel atom of TF4(T = Si, Ge, Sn) the latter moleculedeforms from a tetrahedral structure in the monomer to a trigonal bipyramid. The base can situateitself at either an axial or equatorial position, leading to two different equilibrium geometries.The interaction energies are considerably larger for the equatorial structures, up around 50 kcal/mol,which also have a shorter R(T··N) separation. On the other hand, the energy needed to deform thetetrahedral monomer into the equatorial structure is much higher than the equivalent deformationenergy in the axial dimer. When these two opposite trends are combined, it is the axial geometrywhich is somewhat more stable than the equatorial, yielding binding energies in the 8–34 kcal/molrange. There is a clear trend of increasing interaction energy as the tetrel atom grows larger: Si \u3c G

Theoretical Studies of IR and NMR Spectral Changes Induced by Sigma-Hole Hydrogen, Halogen, Chalcogen, Pnicogen, and Tetrel Bonds in a Model Protein Environment

Various types of σ-hole bond complexes were formed with FX, HFY, H2FZ, and H3FT (X = Cl, Br, I; Y = S, Se, Te; Z = P, As, Sb; T = Si, Ge, Sn) as Lewis acid. In order to examine their interactions with a protein, N-methylacetamide (NMA), a model of the peptide linkage was used as the base. These noncovalent bonds were compared by computational means with H-bonds formed by NMA with XH molecules (X = F, Cl, Br, I). In all cases, the A–F bond, which lies opposite the base and is responsible for the σ-hole on the A atom (A refers to the bridging atom), elongates and its stretching frequency undergoes a shift to the red with a band intensification, much as what occurs for the X–H bond in a H-bond (HB). Unlike the NMR shielding decrease seen in the bridging proton of a H-bond, the shielding of the bridging A atom is increased. The spectroscopic changes within NMA are similar for H-bonds and the other noncovalent bonds. The C=O bond of the amide is lengthened and its stretching frequency red-shifted and intensified. The amide II band shifts to higher frequency and undergoes a small band weakening. The NMR shielding of the O atom directly involved in the bond rises, whereas the C and N atoms both undergo a shielding decrease. The frequency shifts of the amide I and II bands of the base as well as the shielding changes of the three pertinent NMA atoms correlate well with the strength of the noncovalent bond

On the Ability of Pnicogen Atoms to Engage in Both σ and π-hole Complexes. Heterodimers of ZF\u3csub\u3e2\u3c/sub\u3eC\u3csub\u3e6\u3c/sub\u3eH\u3csub\u3e5\u3c/sub\u3e (Z = P, As, Sb, Bi) and NH\u3csub\u3e3\u3c/sub\u3e

When bound to a pair of F atoms and a phenyl ring, a pyramidal pnicogen (Z) atom can form a pnicogen bond wherein an NH3 base lies opposite one F atom. In addition to this σ-hole complex, the ZF2C6H5 molecule can distort in such a way that the NH3 approaches on the opposite side to the lone pair on Z, where there is a so-called π-hole. The interaction energies of these π-hole dimers are roughly 30 kcal/mol, much larger than the equivalent quantities for the σ-hole complexes, which are only 4–13 kcal/mol. On the other hand, this large interaction energy is countered by the considerable deformation energy required for the Lewis acid to adopt the geometry necessary to form the π-hole complex. The overall energetics of the complexation reaction are thus more exothermic for the σ-hole dimers than for the π-hole dimers

Constitutive models of pavement asphaltic layers based on mixture compositions

 The design of flexible and semi-rigid pavements by applying mechanistic-empirical methods involves the determination of the stress and strain states in accordance with the assumptions of continuum mechanics. Advanced computational models should take into account the rheological properties of asphalt layers. Precise identification of visco-elastic parameters of asphalt aggregate mixtures requires a lot of expensive laboratory experiments. The objective of this paper is to propose a new method allowing the identification of visco-elastic constitutive parameters based only on the mixture composition. The effectiveness of the proposed approach is exemplified in the paper by numerical calcu­lations. Two linear rheological models were analyzed: the classical Burgers model and the Huet-Sayegh model described by fractional derivatives. Constitutive parameters of both models were obtained from the appropriate optimization algo­rithms and numerical techniques for determining inverse Laplace transforms. First published online: 13 Jun 201

The influence of patient-controlled epidural analgesia on labor progress and neonatal outcome

Abstract Aim: The aim of the study was to check the influence of patient control epidural analgesia on labor progress and neonatal outcome. Material and methods: 144 parturients were included into the clinical trial. In 73 cases patient control epidural analgesia was used and in 71 cases pethidine (meperidine) solution was given intravenously. Apgar score, umbilical artery pH, pain intensity, the time of the first, second and third stage of labor, the rate of episiotomy and uterine postpartum abrasions and the rate of caesarean sections and vaginal operative delivery were compared. Results: The time of the second stage of labor was significantly longer in the study group (40.99 vs 26.49min, p

Optimization and evaluation of structural and shielding concrete for IFMIF-DONES

The aim of this study was to optimize and evaluate structural and shielding concrete for the IFMIF-DONES building. An ordinary concrete of lime-dolomite aggregate from local sources has been chosen for structural concrete and magnetite aggregate was chosen for heavy-weight radiation shielding. The reference for concrete materials design was the one used in the ITER project. After investigations of raw materials, a group of pre- batches were prepared and technical properties – density of compressive strength, were measured. Finally, two compositions have been elaborated – one for structural concrete of density 2.5 g/cm$^3$ and the second for radi- ation shielding concrete of density 3.9 g/cm$^3$. Then a set of 50 × 50 × 5 cm$^3$ slabs were prepared and sent to the Nuclear Physics Institute of the CAS in the Czech Republic for shielding mock-up experiments. Also the other technical properties like E-modulus, bending strength etc. have been determined. Additionally, radiation shielding efficiency has been calculated based on atomic composition

Pregnancy, delivery and puerperium in a patient with lysinuric protein intolerance – a case report

The paper presents the course of pregnancy, delivery and early postpartum period in a 23-year-old woman with lysinuric protein intolerance (LPI). The pregnancy was uneventful and resulted in a caesarean birth to a healthy baby at 37 weeks gestation. Nevertheless, the course of pregnancy in women with LPI is associated with a significantly increased risk of serious complications, including acute hyperammonemia, preeclampsia and postpartum bleeding, as well as fetus intrauterine growth retardation. In many cases, intensive metabolic monitoring and a proper diet with protein limitation and appropriate amino acids supplementation may significantly reduce the risk for both the mother and the newborn