Research on the Approximate Calculation Method of the Fundamental Frequency and Its Characteristics on a Tensioned String Bridge

As a new type of composite bridge, the dynamic structural characteristics of a tensioned string bridge need to be deeply studied. In this paper, based on the structural characteristics of a tensioned string bridge, the Rayleigh method is used to derive formulas for calculating the frequencies of vertical, antisymmetric and lateral bending vibrations. The characteristics of the vertical and lateral bending vibration frequencies are summarized. The fundamental frequencies of the antisymmetric vertical bending and lateral bending of the tensioned string bridge are the same as that of the single-span beam under the corresponding constraint conditions. The shape and physical characteristics of the main cable have no effect on the frequency. The vertical bending symmetrical vibration frequency of the tensioned string bridge is greater than the corresponding symmetrical vibration frequency of the simply supported beam. The shape and physical characteristics of the main cable have a greater impact on the vertical bending symmetrical vibration frequency than the lateral bending frequency, and the vertical bending symmetrical vibration frequency increases with an increasing rise-to-span ratio. The tension force of the main cable has no influence on the frequency of tensioned string bridges. The first-order frequency of the tensioned string bridge is generally the vertical bending symmetrical vibration frequency. By adopting a tensioned string bridge structure, the fundamental frequency of a structure can be greatly increased, thereby increasing the overall rigidity of the structure. Finally, an engineering example is applied with the finite element parameter analysis method to study the vibration frequency characteristics of the tensioned string bridge, which verifies the correctness of the formula derived in this paper. The finite element analysis results show that the errors between the derived formula in this paper and the finite element calculation results are less than 2%, indicating that the formula derived in this paper has high calculation accuracy and can meet the calculation accuracy requirements of engineering applications.

Conductivity Studies on K-Carrageenan-Methyl Cellulose Blend as Bio-Polymer Electrolyte

Solid polymer-based electrolyte materials are a great interest due to their many interesting characteristics such as flexibility and it is easily prepared into films with a large surface area. Two sets of k-carrageenan-methyl cellulose samples were prepared using the solution casting method. Set 1, the wt% of k-Carrageenan was fixed at 0.1 wt%, while methyl cellulose and NH4I was varied. Set 2, the wt% of methyl-cellulose was fixed to 0.1 wt% and the carrageenan and NH4I was varied. The functional group of samples were studied using FTIR spectroscopy and the ionic conductivity were studied using impedance spectroscopy, EIS at room temperature. FTIR spectra from set 1 show a small hump at between the 1500 cm-1 to 1000 cm-1 spectra’s which O=S=O symmetrical vibration from methyl cellulose component. This hump was shifted to higher wavenumber due to the increasing of NH4I wt% in the samples. The second region of set 2’s spectra shows the wavenumber between of 2000 cm-1 to 1500 cm-1 is the deformation of H-O-H band interactions and its wavenumber decreasing as the addition of salts increasing. The third region of spectra between 1500 cm-1 to 1000 cm-1 represents the band of O=S=O symmetrical vibration. This bands shifted to the lower wavenumber due to addition of salts and it became less intense towards salt addition. On the other hand, the best conductivity is 6.00 x 10-8 S cm-1 which belongs to B2 of set 2 with a composition of 0.3 wt% k-carrageenan with 0.1 wt% methylcellulose and 0.6 wt% NH4I salt and the lowest conductivity is 3.19 x 10-9 S cm-1 which its composition is 0.1 wt% k-carrageenan with 0.4 wt% methylcellulose and 0.5 wt% NH4I salt in sample D1 of set 1. As a conclusion, the optimum component by weight percentage of k-carrageenan: methyl cellulose: NH4I is 0.3:0.1:0.6.

Sulfonated (1→6)-β-d-Glucan (Lasiodiplodan)

Sulfonated derivatives of lasiodiplodan (LAS-S) with different degrees of substitution (1.61, 1.42, 1.02 and 0.15) were obtained and characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal and solubility analyses. Antimicrobial, antioxidant and cytotoxic potential were also assessed. The sulfonation was confirmed by FTIR analysis with specific bands at 1250 cm–1 (S=O, strong asymmetrical stretching vibration) and at 810 cm–1 (C-O-S, symmetrical vibration associated with the C-O-SO3 group) in the sulfonated samples. SEM demonstrated that sulfonation promoted morphological changes on the surface of the biopolymer with heterogeneous fibrillary structures appearing along the surface following chemical modification. LAS-S showed high thermal stability, with mass loss due to oxidation at temperatures close to 460 °C. Sulfonation increased the solubility of LAS, and in addition, increased the antimicrobial activity, especially against Candida albicans (fungicidal) and Salmonella enterica Typhimurium (bacteriostatic). Native lasiodiplodan (LAS-N) showed higher OH˙ removal capacity, while LAS-S had higher ferric ion reducing antioxidant power (FRAP) potential. LAS-N and LAS-S did not demonstrate lethal cytotoxicity against wild and mutant strains of Saccharomyces cerevisiae. Samples with higher degree of substitution (1.42 and 1.61) showed lower potential to induce oxidative stress.