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RISS 인기검색어
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- 저자 : Weizhen Chen (검색결과 6 건)
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Improvement of Extrapolation of Traffic Load Effect on Highway Bridges Based on Rice’s Theory
Weizhen Chen,Cheng Ma,Zhenlin Xie,Bochong Yan,Jun Xu 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.3
It is a primary strategy in assessment, maintenance and rehabilitation of existing bridges in China to analyze structural safety using real traffic load data. For medium and large span bridges, the most common approach to extrapolate extreme load effect takes advantage of the Rice's theory. The method, however, has a problem of determining optimal starting effect interval for tail histogram curve fitting of crossing rate. At present, the problem is generally solved using the approach proposed by Cremona. But the approach is essentially subjective in computing procedure. This paper carries out the test and verification of Cremona’s approach, discovering remarkable discreteness of extrapolated extreme load effects, and in-depth study reveals further flaws-improper understanding of statistical concept, miscalculation of significance level, and deviation of extrapolation by linear fitting method. To solve these issues, this paper develops a new method of determining optimal starting interval for tail histogram fitting. Instead of direct application of the Kolmogorov theory to crossing rate histogram, the new method starts analysis with the sample empirical distribution of effect at arbitrary time in stochastic process. By characteristics analysis of Kolmogorov distribution variable, it figures out whether the stochastic process variable complies with the hypothesis of the Rice's theory or the fitting curve tails with its theoretical curve (identification of optimal starting interval). Through in-depth analysis and case study, it can be seen that the proposed method can best reduce subjectivity in analysis procedure and improve on the load effect extrapolation based on Rice’s theory.
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Yibo Yang,Baixi Chen,Weizhen Zeng,Yanjun Li,Qiaohui Chen,Wenying Guo,Hengchang Wang,Yingqin Chen 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.5
To reduce the cost of lightweight concrete (LWC) partition panels and to address recycling concrete waste, this work utilized completely recycled fine aggregate (CRFA) to replace the natural fine aggregate and ceramsite in the preparation of LWC and LWC partition panels. To this end, an autoclave-free curing process and an air-entraining agent were used to prepare the CRFA-LWC. The workability, compressive strength, drying shrinkage, and pore structure of the CRFA-LWC and the performance of the CRFA-LWC partition panels were then investigated. The results show that the optimal ratio of the CRFA to the cement is 2.2 for the lightweight concrete, and the optimal panel cross section is a rounded rectangular one. All the pores in the CRFA-LWC have a diameter of smaller than 0.17 mm, and the diameter of 89% of them is less than 0.05 mm. In order to satisfy the drying shrinkage requirements stipulated by Chinese code JC/T 169-2016, the CRFA-LWC should be cured for at least 10 days. The economic analysis concludes that the material cost of CRFA-LWC is 40% lower than that of the autoclaved ceramsite concrete. In addition, utilizing CRFA in lightweight concrete can ease the shortage of natural aggregate.
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Reinforcement Analysis of Rigid Hangers for Existing Old Arch Bridges: A Case Study of Ling Bridge
Shuai Yuan,Weizhen Chen,Fan Yang,Tiantao He,Guoxian Liu 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.6
Ling Bridge, built in 1936, is an old half-through riveted steel arch bridge with rigid hangers and a fl oating deck system. The eff ects of various factors, such as temperature, vehicle load, and crowd load, have caused large additional stresses on the rigid hangers. According to the inspection in 2011, the bridge was in a dangerous state. Therefore, improving the structural strength of the bridge and prolonging the service life for another 40 years while protecting the cultural relic were major problems. This study analyzes rigid hangers on the premise that the reinforcement schemes of other bridge components have been determined. First, the damage situation, material properties and mechanical behaviors of old hangers are evaluated. Second, an appropriate reinforcement method is proposed. Third, mechanical and fatigue analyses are conducted on the new structures to prove the rationality of the reinforcement method. For the undemolished old structures, a fracture assessment of existing damage is performed to obtain the evolution laws and ensure safety. Finite element calculations and fatigue fracture analyses show that the proposed reinforcement method for the hanger system can reduce all hangers’ stresses eff ectively to prolong service life and protect the cultural relic.
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Internal Mammary Sentinel Lymph Node Biopsy after Neoadjuvant Chemotherapy in Breast Cancer
Zhao Bi,Peng Chen,Jingjing Liu,Yanbing Liu,Pengfei Qiu,Qifeng Yang,Weizhen Zheng,Yongsheng Wang 한국유방암학회 2018 Journal of breast cancer Vol.21 No.4
Purpose: The definition of nodal pathologic complete response (pCR) after a neoadjuvant chemotherapy (NAC) just included the evaluation of axillary lymph node (ALN) without internal mammary lymph node. This study aimed to evaluate the feasibility of internal mammary-sentinel lymph node biopsy (IM-SLNB) in patients with breast cancer who underwent NAC. Methods: From November 2011 to 2017, 179 patients with primary breast cancer who underwent operation after NAC were included in this study. All patients received radiotracer injection with modified injection technology. IM-SLNB would be performed on patients with internal mammary sentinel lymph node (IMSLN) visualization. Results: Among the 158 patients with cN+ disease, the rate of nodal pCR was 36.1% (57/158). Among the 179 patients, the visualization rate of IMSLN was 31.8% (57/179) and was 12.3% (7/57) and 87.7% (50/57) among those with cN0 and cN+ disease, respectively. Furthermore, the detection rate of IMSLN was 31.3% (56/179). The success rate of IM-SLNB was 98.2% (56/57). The IMSLN metastasis rate was 7.1% (4/56), and all of them were accompanied by ALN metastasis. The number of positive ALNs in patients with IMSLN metastasis was 3, 6, 8, and 9. The pathology nodal stage had been changed from pN1/ pN2 to pN3b. The pathology stage had been changed from IIA/ IIIA to IIIC. Conclusion: Patients with visualization of IMSLN should perform IM-SLNB after NAC, especially for patients with cN+ disease, in order to complete lymph nodal staging. IM-SLNB could further improve the definition of nodal pCR and guide the internal mammary node irradiation.
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Isogeometric analysis of gradient-enhanced damaged plasticity model for concrete
Jun Xu,Shuai Yuan,Weizhen Chen 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.3
This study proposed a new and efficient 2D damage-plasticity model within the framework of Isogeometric analysis (IGA) for the geometrically nonlinear damage analysis of concrete. Since concrete exhibits complicated material properties, two internal variables are introduced to measure the hardening/softening behavior of concrete in tension and compression, and an implicit gradient-enhanced formulation is adopted to restore the well-posedness of the boundary value problem. The numerical results calculated by the model is compared with the experimental data of three benchmark problems of plain concrete (threepoint and four-point bending single-notched beams and four-point bending double-notched beam) to illustrate the geometrical flexibility, accuracy, and robustness of the proposed approach. In addition, the influence of the characteristic length on the numerical results of each problem is investigated.
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