Evaluation of equivalent friction damping ratios at bearings of welded large-scale domes subjected to earthquakes

Huidong Zhang,Xinqun Zhu,Yuan-feng Wang,Shu Yao 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.4

The major sources of damping in steel structures are within the joints and the structural material. For welded large-scale single-layer lattice domes subjected to earthquake ground motions, the stick-slip phenomenon at the bearings is an important source of the energy dissipation. However, it has not been extensively investigated. In this study, the equivalent friction damping ratio (EFDR) at the bearings of a welded large-scale single-layer lattice dome subjected to earthquake ground motions is quantified using an approximate method based on the energy balance concept. The complex friction behavior and energy dissipation between contact surfaces are investigated by employing an equivalent modeling method. The proposed method uses the stick-slip-hook components with a pair of circular isotropic friction surfaces having a variable friction coefficient to model the energy loss at the bearings, and the effect of the normal force on the friction force is also considered. The results show that the EFDR is amplitude-dependent and is related to the intensity of the ground motions; it exhibits complex characteristics that cannot be described by the conventional models for damping ratios. A parametric analysis is performed to investigate in detail the effects of important factors on the EFDR. Finally, the friction damping mechanism at bearings is discussed. This study enables researchers and engineers to have a better understanding of the essential characteristics of friction damping under earthquake ground motions.

A numerical investigation of seismic performance of large span single-layer latticed domes with semi-rigid joints

Huidong Zhang,Qinghua Han 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.1

It is still inadequate for investigating the highly nonlinear and complex mechanical behaviors of single-layer latticed domes by only performing a force-based demand-capacity analysis. The energy-based balance method has been largely accepted for assessing the seismic performance of a structure in recent years. The various factors, such as span-to-rise ratio, joint rigidity and damping model, have a remarkable effect on the load-carrying capacity of a single-layer latticed dome. Therefore, it is necessary to determine the maximum load-carrying capacity of a dome under extreme loading conditions. In this paper, a mechanical model for members of the semi-rigidly jointed single-layer latticed domes, which combines fiber section model with semi-rigid connections, is proposed. The static load-carrying capacity and seismic performance on the single-layer latticed domes are evaluated by means of the mechanical model. In these analyses, different geometric parameters, joint rigidities and roof loads are discussed. The buckling behaviors of members and damage distribution of the structure are presented in detail. The sensitivity of dynamic demand parameters of the structures subjected to strong earthquakes to the damping is analyzed. The results are helpful to have a better understanding of the seismic performance of the single-layer latticed domes.

A numerical investigation of seismic performance of large span single-layer latticed domes with semi-rigid joints

Zhang, Huidong,Han, Qinghua Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.1

It is still inadequate for investigating the highly nonlinear and complex mechanical behaviors of single-layer latticed domes by only performing a force-based demand-capacity analysis. The energy-based balance method has been largely accepted for assessing the seismic performance of a structure in recent years. The various factors, such as span-to-rise ratio, joint rigidity and damping model, have a remarkable effect on the load-carrying capacity of a single-layer latticed dome. Therefore, it is necessary to determine the maximum load-carrying capacity of a dome under extreme loading conditions. In this paper, a mechanical model for members of the semi-rigidly jointed single-layer latticed domes, which combines fiber section model with semi-rigid connections, is proposed. The static load-carrying capacity and seismic performance on the single-layer latticed domes are evaluated by means of the mechanical model. In these analyses, different geometric parameters, joint rigidities and roof loads are discussed. The buckling behaviors of members and damage distribution of the structure are presented in detail. The sensitivity of dynamic demand parameters of the structures subjected to strong earthquakes to the damping is analyzed. The results are helpful to have a better understanding of the seismic performance of the single-layer latticed domes.

Effects of viscous damping models on a single-layer latticed dome during earthquakes

Huidong Zhang,Jinpeng Wang,Xiaoshuai Zhang,Guoping Liu 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.4

Rayleigh damping model is recommended in the recently developed Performance-Based Earthquake Engineering (PBEE) methodology, but this methodology does not provide sufficient information due to the complexity of the damping mechanism. Furthermore, each Rayleigh-type damping model may have its individual limitations. In this study, Rayleigh-type damping models that are used widely in engineering practice are discussed. The seismic performance of a large-span single-layer latticed dome subjected to earthquake ground motions is investigated using different Rayleigh damping models. Herein a simulation technique is developed considering low cycle fatigue (LCF) in steel material. In the simulation technique, Ramberg-Osgood steel material model with the low cycle fatigue effect is used to simulate the non-uniformly distributed material damping and low cycle fatigue damage in the structure. Subsequently, the damping forces of the structure generated by different damping models are compared and discussed; the effects of the damping ratio and roof load on the damping forces are evaluated. Finally, the low cycle fatigue damage values in sections of members are given using these damping models. Through a comparative analysis, an appropriate Rayleigh-type damping model used for a large span single-layer latticed dome subjected to earthquake ground motions is determined in terms of the existing damping models.

Application of galactinol to tomato enhances tolerance to cold and heat stresses

Liu Yudong,Zhang Li,Ma Jian,Meng Sida,Pang Chunpeng,Zhao Xiaomeng,Zhang Huidong,Wang Shou,Xu Tao,He Yi,Liu Yufeng,Qi Mingfang 한국원예학회 2022 Horticulture, Environment, and Biotechnology Vol.63 No.3

Galactinol, a galactosyl donor, is the key substrate in raffinose family oligosaccharide (RFO) biosynthesis pathways. Many studies proved that galactinol also regulates some defense-related genes to be transcribed as a sugar signal under biotic and abiotic stresses. There are four galactinol synthase (SlGolS) genes in tomato. In this study, SlGolS1, SlGolS2, and SlGolS4 responded to cold stress, especially SlGolS1 stems treated for 12 h and SlGolS4 stems treated for 24 h. Under heat stress, the expression levels of SlGolS1, SlGolS2, and SlGolS3, especially SlGolS1 and SlGolS2, increased in leaves, roots, and stems. When expressed in E. coli cells, SlGolS2 and SlGolS4 enhanced cold tolerance, whereas SlGolS1 and SlGolS3 improved heat tolerance. These results suggested that SlGolS family members played different roles in tolerance to cold and heat stresses. In addition, the application of galactinol or galactinol + α-galactosidase inhibitor (DGJ) improved the cold and heat tolerances of tomato plants, whereas the single application of DGJ had no effect. Interestingly, the applications of DGJ, galactinol, and galactinol + DGJ also affected the expression levels of SlRS, SlSTS, and SlAGAL under cold and heat stresses. These findings indicated that galactinol was involved in the biosynthesis pathways of RFOs as a galactosyl donor and regulated the expression levels of RFO biosynthesis and breakdown-related genes as a sugar signal under cold and heat stresses.

Study on the Application of Canola Oil and Cottonseed Oil in SolutionPolymerized Styrene-butadiene Rubber

Yuan Jing,Chunwei Zhang,Su Zhang,Guangyi Lin,Huidong Cao,Jiahui Wen,Zonglong Wang,Yuanyuan Niu,Zetao Lin 한국고분자학회 2023 폴리머 Vol.47 No.6

The application of vegetable oil-based softeners canola oil and cottonseed oil in Solution polymerized styrene-butadiene rubber (SSBR) system composites was investigated. The results showed that when the aromatic oil was replaced by 5 parts of vegetable oil-based softeners in equal amounts in the base formulation of SSBR system, the work-ing performance of the rubber was better, the tear strength and elongation at break were improved and the tensile strength was reduced; the vulcanization time of the rubber prepared with vegetable oil-based softeners was significantly reduced compared with that of aromatic oil; the glass transition temperature of the rubber was significantly reduced and the cold resistance and snow performance of the rubber were improved.

A New Practical System for Evaluating the Pharmacological Properties of Uricase as a Potential Drug for Hyperuricemia

Juan Feng,Xiang Li,Xiaolan Yang,Chun Zhang,Yonghua Yuan,Jun Pu,Yunsheng Zhao,Yanling Xie,Huidong Yuan,Youquan Bu,Fei Liao 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.11

The use of uricase-deficient mammals to screen formulations of engineered uricases as potential drugs for hyperuricemia involves heavy costs and presents a technical bottleneck. Herein, a new practical system was investigated to evaluate the pharmacological significance of a bacterial uricase based on its ability to eliminate uric acid in plasma in vitro, its pharmacokinetics in vivo in healthy rats, and the modeled pharmacodynamics in vivo. This uricase, before and after modification with the monomethyl ether of poly(ethylene glycol)-5000, effectively eliminated uric acid in vitro in rabbit plasma, but its action was susceptible to xanthine inhibition. After intravenous injection of the modified uricase without purification, a bi-exponential model fit well to uricase activities in vivo in the plasma of healthy rats; the half-life of the modified uricase was estimated without interference from the unmodified uricase leftover in the sample and was nearly 100-fold longer than that of the unmodified uricase. Using a model of the elimination of uric acid in vivo taking into account of uricase pharmacokinetics and xanthine inhibition, modeled pharmacodynamics supported that the half-life of uricase and its susceptibility to xanthine are crucial for the pharmacological significance of uricase. Hence,this practical system is desirable for doing preliminary screening of formulations of engineered uricases as potential drugs for hyperuricemia.

Carbon Paper-Supported NiCo/C–N Catalysts Synthesized by Directly Pyrolyzing NiCo-Doped Polyaniline for Oxygen Reduction Reaction

Zhongliang Deng,Qingfeng Yi,Yuanyuan Zhang,Huidong Nie,Guang Li,Liang Yu,Xiulin Zhou 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.1

In this study, we report the findings that the C–N composites containing Ni and Co (Ni1Co1/C–N, Ni3Co1/C–N, Ni6Co1/C–N, Ni9Co1/C–N, Ni10Co0/C–N and Ni0Co10/C–N) can be produced by direct pyrolysis of the NiCo-doped polyaniline (PANI) precursors in N2 atmosphere at 800 ℃ and show efficient electroactivity for oxygen reduction reaction (ORR) in alkaline media. Distribution and compositions of the catalysts were characterized by SEM, TEM, EDS and XRD techniques. The catalysts were loaded on carbon paper to prepare gas diffusion electrodes, in which electrocatalytic activity for ORR in alkaline media was investigated by voltammetric techniques. The ORR current density on these carbon paper-supported NiCo/C–N catalysts exhibits a linear increase with the negative shift of ORR potential. The ORR onset potential is around 0.2 V (versus Ag/AgCl) in alkaline media. Among the prepared catalysts, the catalyst Ni6Co1/C–N presents the largest ORR current density, which is 68.5 mA cm -2@-0.8 V (versus Ag/AgCl) in alkaline media. Moreover, Ni6Co1/C–N catalyst also presents good electrocatalytic activity stability for ORR.