Influence of some key factors on material damping of steel beams

Wang, Yuanfeng,Pan, Yuhua,Wen, Jie,Su, Li,Mei, Shengqi Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.3

Material damping affects the dynamic behaviors of engineering structures considerably, but up to till now little research is maintained on influence factors of material damping. Based on the damping-stress function of steel, the material damping of steel beams is obtained by calculating the stress distribution of the beams with an analytical method. Some key influence factors of the material damping, such as boundary condition, amplitude and frequency of excitation, load position as well as the cross-sectional dimension of a steel beam are analyzed respectively. The calculated results show that even in elastic scope, material damping does not remain constant but varies with these influence factors. Although boundary condition affects material damping to some extent, such influence can be neglected when the maximum stress amplitude of the beam is less than the fatigue limit of steel. Exciting frequency, load position and cross-section dimension have great effects on the material damping of the beam which maintain the similar changing trend under different boundary conditions respectively.

Influence of some key factors on material damping of steel beams

Yuanfeng Wang,Yuhua Pan,Jie Wen,Li Su,Shengqi Mei 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.3

Material damping affects the dynamic behaviors of engineering structures considerably, but up to till now little research is maintained on influence factors of material damping. Based on the damping-stress function of steel, the material damping of steel beams is obtained by calculating the stress distribution of the beams with an analytical method. Some key influence factors of the material damping, such as boundary condition, amplitude and frequency of excitation, load position as well as the cross-sectional dimension of a steel beam are analyzed respectively. The calculated results show that even in elastic scope, material damping does not remain constant but varies with these influence factors. Although boundary condition affects material damping to some extent, such influence can be neglected when the maximum stress amplitude of the beam is less than the fatigue limit of steel. Exciting frequency, load position and cross-section dimension have great effects on the material damping of the beam which maintain the similar changing trend under different boundary conditions respectively.

Influence of creep on dynamic behavior of concrete filled steel tube arch bridges

Yuan-Feng Wang,Yi-Shuo Ma,Li Su,Shengqi Mei 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.1

Concrete creep, while significantly changing the static behaviors of concrete filled steel tube (CFST) structures, do alter the structures' dynamic behaviors as well, which is studied quite limitedly. The attempt to investigate the influence of concrete creep on the dynamic property and response of CFST arch bridges was made in this paper. The mechanism through which creep exerts its influence was analyzed first; then a predicative formula was proposed for the concrete elastic modulus after creep based on available test data; finally a numerical analysis for the effect of creep on the dynamic behaviors of a long-span half-through CFST arch bridge was conducted. It is demonstrated that the presence of concrete creep increases the elastic modulus of concrete, and further magnifies the seismic responses of the displacement and internal force in some sections of the bridge. This influence is related closely to the excitation and the structure, and should be analyzed case-by-case.

Seismic analysis of bridges based on stress-dependent damping

Li Su,Yuanfeng Wang,Pengfei Li,Shengqi Mei,Kun Guo 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.3

Damping value has considerable influence on the dynamic and seismic behaviors of bridges. However, currently the constant damping ratios that are prescribed by most bridge seismic design codes can’t truly represent the complicated damping character of actual structures. In this paper, a cyclic loading experiment was conducted to study the effect of stress amplitude on material damping of concrete to present an analyzing model of the material damping of concrete. Furthermore, based on the fundamental damping of structure measured under ambient vibration, combined with the presented stress-dependent material damping concrete, the seismic response of a bridge pier was calculated. Comparison between the calculated and experiment results verified the validity of the presented damping model. Finally, a modified design and analysis method for bridge was proposed based on stress-dependent damping theory, and a continuous rigid frame bridge was selected as the example to calculate the actual damping values and the dynamic response of the bridge under different earthquake intensities. The calculation results indicated that using the constant damping given by the Chinese seismic design code of bridges would overestimate the energy dissipation capacity of the bridge.

Amentoflavone protects the hematopoietic system of mice against γ‑irradiation

Xin-yan Qu,Qingjun Li,Xiao-juan Zhang,Zhaofen Wang,Shengqi Wang,Zhe Zhou 대한약학회 2019 Archives of Pharmacal Research Vol.42 No.11

Some flavonoids have been shown to exhibitgood antioxidant activity and protect mice from damageinduced by radiation. Amentoflavone (AMF), a biflavonoidderived from the traditional herb-Selaginella tamariscina,has been reported to have antioxidant properties. The protectiveeffects and mechanism of action of AMF against radiationinjury remain unknown. In this study, male C57BL/6mice were subjected to total-body 60Co γ-irradiation at 7.5or 3.0 Gy. The survival rate and mean survival time wereevaluated to determine the radioprotective effect of AMF. Number of peripheral blood cells, frequency of colony formingunit-granulocytes, monocytes and micronuclei weremeasured to assess the protective effects of AMF on thehematopoietic system. Levels of superoxide dismutase andglutathione, and pathological changes in the bone marrowwere determined. Additionally, next-generation sequencingtechnology was used to explore potential targets of AMF. Weobserved that AMF markedly extends average survival time,reduces injury to the hematopoietic system and promotes itsrecovery. Furthermore, treatment with AMF significantlyattenuated radiation-induced oxidative stress. In addition,AMF had a significant effect on gene tumor necrosis factor alpha-induced protein 2. Together, the results of this studysuggest that AMF is a potential protective agent againstradiation injury.

Radionuclide identification method for NaI low-count gamma-ray spectra using artificial neural network

Sheng Qi,Shanqiang Wang,Ye Chen,Kun Zhang,Xianyun Ai,Jinglun Li,Haijun Fan,Hui Zhao 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.1

An artificial neural network (ANN) that identifies radionuclides from low-count gamma spectra of a NaIscintillator is proposed. The ANN was trained and tested using simulated spectra. 14 target nuclides wereconsidered corresponding to the requisite radionuclide library of a radionuclide identification devicementioned in IEC 62327-2017. The network shows an average identification accuracy of 98.63% on thevalidation dataset, with the gross counts in each spectrum Nc ¼ 100~10000 and the signal to noise ratioSNR ¼ 0.05e1. Most of the false predictions come from nuclides with low branching ratio and/or similardecay energies. If the Nc>1000 and SNR>0.3, which is defined as the minimum identifiable condition, theaveraged identification accuracy is 99.87%. Even when the source and the detector are covered with leadbricks and the response function of the detector thus varies, the ANN which was trained using nonshieldingspectra still shows high accuracy as long as the minimum identifiable condition is satisfied. Among all the considered nuclides, only the identification accuracy of 235U is seriously affected by theshielding. Identification of other nuclides shows high accuracy even the shielding condition is changed,which indicates that the ANN has good generalization performance.