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Output-only modal parameter identification of civil engineering structures
Wei-Xin Ren,Zhou-Hong Zong 국제구조공학회 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3-4
The ambient vibration measurement is a kind of output data-only dynamic testing where the traffics and winds are used as agents responsible for natural or environmental excitation. Therefore an experimental modal analysis procedure for ambient vibration testing will need to base itself on output-only data. The modal analysis involving output-only measurements presents a challenge that requires the use of special modal identification technique, which can deal with very small magnitude of ambient vibration contaminated by noise. Two complementary modal analysis methods are implemented. They are rather simple peak picking (PP) method in frequency domain and more advanced stochastic subspace identification (SSI) method in time domain. This paper presents the application of ambient vibration testing and experimental modal analysis on large civil engineering structures. A 15 storey reinforced concrete shear core building and a concrete filled steel tubular arch bridge have been chosen as two case studies. The results have shown that both techniques can identify the frequencies effectively. The stochastic subspace identification technique can detect frequencies that may possibly be missed by the peak picking method and gives a more reasonable mode shapes in most cases.
Output-only modal parameter identification of civil engineering structures
Ren, Wei-Xin,Zong, Zhou-Hong Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3
The ambient vibration measurement is a kind of output data-only dynamic testing where the traffics and winds are used as agents responsible for natural or environmental excitation. Therefore an experimental modal analysis procedure for ambient vibration testing will need to base itself on output-only data. The modal analysis involving output-only measurements presents a challenge that requires the use of special modal identification technique, which can deal with very small magnitude of ambient vibration contaminated by noise. Two complementary modal analysis methods are implemented. They are rather simple peak picking (PP) method in frequency domain and more advanced stochastic subspace identification (SSI) method in time domain. This paper presents the application of ambient vibration testing and experimental modal analysis on large civil engineering structures. A 15 storey reinforced concrete shear core building and a concrete filled steel tubular arch bridge have been chosen as two case studies. The results have shown that both techniques can identify the frequencies effectively. The stochastic subspace identification technique can detect frequencies that may possibly be missed by the peak picking method and gives a more reasonable mode shapes in most cases.
Empirical formulas to estimate cable tension by cable fundamental frequency
Ren, Wei-Xin,Chen, Gang,Hu, Wei-Hua Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.3
The cable tension plays an important role in the construction, assessment and long-term health monitoring of cable structures. The cable vibration equation is nonlinear if cable sag and bending stiffness are included. The engineering implementation of a vibration-based cable tension evaluation is mostly carried out by the simple taut string theory. However, the simple theory may cause unacceptable errors in many applications since the cable sag and bending stiffness are ignored. From the practical point of view, it is necessary to have empirical formulas if they are simple and yet accurate. Based on the solutions by means of energy method and fitting the exact solutions of cable vibration equations where the cable sag and bending stiffness are respectively taken into account, the empirical formulas are proposed in the paper to estimate cable tension based on the cable fundamental frequency only. The applicability of the proposed formulas is verified by comparing the results with those reported in the literatures and with the experimental results carried out on the stay cables in the laboratory. The proposed formulas are straightforward and they are convenient for practical engineers to fast estimate the cable tension by the cable fundamental frequency.
Ren Xin,Dengshan Bi,Wei Huang 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.4
Aiming to examine different failure patterns in multistory URM walls, two 1/3 scaled three-story and three-bay URM models were designed for the quasi-static loading tests to contrastively investigate the failure processes and characteristics of the multistory URM walls. Two different failure responses were observed with special attention paid to the behavior of spandrelfailure mode. By evaluating the seismic performance and deformation behavior of two test walls, it is demonstrated that spandrels, that haven’t been properly designed in some codes, are of great significance in the failure of entire URM walls. Additionally, compared with pier-failure mode, spandrel-failure for multistory URM building is more reasonable and advisable as its effectively participation in energy dissipation and its efficiently improvement on seismic capacity and deformation in the overall structure. Furthermore, the experimental results are beneficial to improve seismic design and optimize reinforcement method of URM buildings.
Test Results and Nonlinear Analysis of RC T-beams Strengthened by Bonded Steel Plates
Wei Ren,Lesley H. Sneed,Yiting Gai,Xin Kang 한국콘크리트학회 2015 International Journal of Concrete Structures and M Vol.9 No.2
This paper describes the test results and nonlinear analysis of reinforced concrete T-beams strengthened by bonded steel plates under increasing static loading conditions. The first part of this paper discusses the flexural tests on five T-beams, including the test model design (based on similarity principles), test programs, and test procedure. The second part discusses the nonlinear numerical analysis of the strengthened beams, in which a concrete damage plasticity model and a cohesive behavior were adopted. The numerical analysis results are compared with experimental data and show good agreement. The area of bonded steel plate and the anchor bolt spacing were found to have an impact on the cracking load, yield load, and ultimate load. An increase in the area of steel plate and a reduction of the anchor spacing could significantly improve the cracking and ultimate loads and decrease the damage of the beam.
Anti-HIV-1 Activity of Lignans from the Fruits of Schisandra rubriflora
Wei-Lie Xiao,Rui-Rui Wang,Wei Zhao,Ren-Rong Tian,Shan-Zhai Shang,Liu-Meng Yang,Jian-Hong Yang,Jian-Xin Pu,Yong-Tang Zheng,Han-Dong Sun 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.5
This study investigated the 70% aqueous acetone extract of the fruits of Schisandra rubriflora which led to the isolation of eight lignans, including a new isolate, rubrisandrin C (1), and seven known lignans (2-8) . The structure of 1 was established by extensive 1D and 2D NMR spectroscopy and its absolute stereochemistry was determined by CD spectrum. Compounds 1-5 and 7-8 were evaluated for their anti-HIV-1 activity that showed inhibitory activity on HIV-1IIIB induced syncytium formation with EC50 values in the range of 2.26~20.4 μg/mL. Compounds 1 and 7 exerted their obvious protection of HIV-1IIIB inducted MT-4 host cells lytic effects with a selectivity index of 15.4 and 24.6, respectively.
Response of Esophagus to High and Low Temperatures in Patients With Achalasia
( Yutang Ren ),( Meiyun Ke ),( Xiucai Fang ),( Liming Zhu ),( Xiaohong Sun ),( Zhifeng Wang ),( Ruifeng Wang ),( Zhao Wei ),( Ping Wen ),( Haiwei Xin ),( Min Chang ) 대한소화기기능성질환·운동학회 2012 Journal of Neurogastroenterology and Motility (JNM Vol.18 No.4
Background/Aims Achalasia patients would feel exacerbated dysphagia, chest pain and regurgitation when they drink cold beverages or eat cold food. But these symptoms would relieve when they drink hot water. Reasons are unknown. Methods Twelve achalasia patients (mean age, 34 ± 10 years, F:M, 3:9) who never had any invasive therapies were chosen from Peking Union Medical College Hospital. They were asked to fill in the questionnaire on eating habits including food temperature and related symptoms and to receive high-resolution manometry examination. The exam was done in 2 separated days, at swallowing room temperature (25oC) then hot (50oC) water, and at room temperature (25oC) then cold (2oC) water, respectively. Parameters associated with esophageal motility were analyzed. Results Most patients (9/12) reported discomfort when they ate cold food. All patients reported no additional discomfort when they ate hot food. Drinking hot water was effective in 5/8 patients who ever tried to relieve chest pain attacks. On manometry, cold water increased lower esophageal sphincter (LES) resting pressure (P = 0.003), and prolonged the duration of esophageal body contraction (P = 0.002). Hot water decreased LES resting pressure and residue pressure during swallow (P = 0.008 and P = 0.002), increased LES relaxation rate (P = 0.029) and shortened the duration of esophageal body contraction (P = 0.003). Conclusions Cold water could increase LES resting pressure, prolong the contraction duration of esophageal body, and exacerbate achalasia symptoms. Hot water could reduce LES resting pressure, assist LES relaxation, shorten the contraction duration of esophageal body and relieve symptoms. Thus achalasia patients are recommended to eat hot and warm food and avoid cold food. (J Neurogastroenterol Motil 2012,18:391-398)
Wang Xin,Du Jun,Wei Zhengying,Zhang Shan,Zhao Guangxi,Ren Chuanqi,Bai Hao 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2
In order to achieve good interlayer metallurgical bonding in the metal fused-coating additive manufacturing, the finite element thermal analysis model was established and the influences of different heating temperatures of fused coating nozzle and substrate on the interlayer remelting was analyzed. The maximum remelting depth under different temperature conditions was obtained. The multi-layer forming experiments were performed under different temperature conditions, and the results showed that increasing the heating temperature of nozzle or substrate will effectively increase the remelting depth, that the surface forming quality is better when the remelting depth is in the range of 0.1~0.2 mm, and that the deviation between the remelting depth and the calculated value is less than 15 %. So, the model can predict the remelting depth of the intermetallic microstructure.