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- 저자 : Yongchao Liang (검색결과 5 건)
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Liang Cao,Yongchao Tan,Jiang Li 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.5
In this study, the vibration serviceability of a composite steel-bar truss slab with steel girder system considering the human-structure interaction was investigated systematically through the on-site testing. Impulse excitations (heel-drop and jumping) and steady-state motions (walking and running) were performed to capture the primary vibration parameters (natural frequency, model shape, and damping ratio) and the distribution of peak accelerations. The composite floor possesses a low frequency of approximately 7.90 Hz and the damping ratio of ≈ 2.10%. The walking and running excitations by one person (single excitations) were considered to evaluate the vibration serviceability of the composite floor. The measured accelerations show a satisfactory vibration perceptibility. For design convenience and safety, a crest factor βrp (the ratio of peak acceleration to root-mean-square acceleration induced from an excitation) is proposed. Comparisons of the modal parameters determined from the tests (walking, running, heel-drop, and jumping) reveal there is an interaction exists between the human excitation and the composite floor. This interaction effect reduces the damping ratio of the composite floor.
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Theoretical formulation for vehicle-bridge interaction analysis based on perturbation method
Yongchao Tan,Liang Cao,Jiang Li 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.2
A three-mass vehicle model including one rigid mass and two unsprung masses is adopted to predict the vehicle-bridge interaction (VBI) and to establish the nonlinear coupled governing equations. To overcome the numerical instability and large computation problems concerning the vehicle-bridge system, the perturbation method is used to convert the nonlinear coupled governing equations into a set of linear uncoupled equations. Formulas for bridge’s natural frequencies considering both the VBI and the dynamic responses of bridge and vehicle are proposed. Compared with the numerical results obtained by the Newmark-β method, the theoretical solutions for natural frequencies and dynamic responses are validated. The effects of the important factors of unsprung mass, vehicle damping, surface irregularity on the natural frequencies and dynamic responses of bridge and vehicle are discussed, based on the theoretical solutions.
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Changhu Liang,Yongchao Lu,Bin Zhao,Yinglin Du,Cuiyan Wang,Wanli Jiang 대한영상의학회 2014 Korean Journal of Radiology Vol.15 No.6
The primary importance of magnetic resonance (MR) imaging in evaluating anal fistulas lies in its ability to demonstrate hidden areas of sepsis and secondary extensions in patients with fistula in ano. MR imaging is relatively expensive, so there are many healthcare systems worldwide where access to MR imaging remains restricted. Until recently, computed tomography (CT) has played a limited role in imaging fistula in ano, largely owing to its poor resolution of soft tissue. In this article, the different imaging features of the CT and MRI are compared to demonstrate the relative accuracy of CT fistulography for the preoperative assessment of fistula in ano. CT fistulography and MR imaging have their own advantages for preoperative evaluation of perianal fistula, and can be applied to complement one another when necessary.
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Huizhi Guo,Huasheng Huang,Yang Shao,Qiuli Qin,De Liang,Shuncong Zhang,Yongchao Tang 대한척추신경외과학회 2021 Neurospine Vol.18 No.4
Objective: Pulmonary cement embolism (PCE) is an underestimated but potentially fatal complication after cement augmentation. Although the treatment and follow-up of PCE have been reported in the literature, the risk factors for PCE are so far less investigated. This study aims to identify the preoperative and intraoperative risk factors for the development of PCE. Methods: A total of 1,373 patients treated with the polymethylmethacrylate (PMMA) augmentation technique were retrospectively included. Patients with PCE were divided into vertebral augmentation group and screw augmentation group. Possible risk factors were collected as follows: age, sex, bone mineral density, body mass index, diagnosis, comorbidity, surgical procedure, type of screw, augmented level, number of augmented vertebrae, fracture severity, presence of intravertebral cleft, cement volume, marked leakage in the paravertebral venous plexus, and periods of surgery. Binary logistic regression analyses were used to analyze independent risk factors for PCE. Results: PCE was identified in 32 patients, with an incidence rate of 2.33% (32 of 1,373). For patients who had undergone vertebral augmentation, marked leakage in the paravertebral venous plexus (odds ratio [OR], 1.2; 95% confidence interval [CI], 0.1–10.3; p=0.000) and previous surgery (OR, 16.1; 95% CI, 4.2–61.0; p=0.007) were independent risk factors for PCE. Regarding patients who had undergone screw augmentation, the marked leakage in the paravertebral venous plexus (OR, 4.2; 95% CI, 0.5–37.3; p=0.004) was the main risk factor. Conclusion: Marked leakage in the paravertebral venous plexus and previous surgery were significant risk factors related to PCE. Paravertebral leakage and operator experience should be concerned when performing PMMA augmentation.
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