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RISS 인기검색어
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- 저자 : Zhiwu Yu (검색결과 5 건)
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Zhiwu Yu,Xiaoyong Lv,Yujie Yu,Faxing Ding,Xiaodan Peng 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.7
This paper proposes a new kind of U-type reinforcement ferrule (URF) connection for the assembly of precast concrete (PC) components, which has a good fault-tolerance ability and low cost of construction with a simple postgrouting process. The modified connection features welded U ferrules, which can increase the bonding mechanism and internal stress transmission in the spliced region. A series of quasi-static cyclic tests were performed on URF-connected PC columns with different welding patterns. Comprehensive comparisons were performed on the load-bearing capacity, the plastic energy dissipation ability, the internal force transmission, the column ductility and the stiffness. The results indicated that PC columns with welded URF connections can ensure better lateral resistance than the cast-in-place concrete column. The weld type and length influence the connection performance, and the 15d-welded and full-length welded URF connections presented better connection performance and were suggested for the assembly of PC columns. Then, finite element analyses were performed to further reveal the working and failure mechanisms and the affecting mechanism of some working parameters. Parametric simulations indicated that the increase in the axial load ratio and the concrete strength in the postcast region had a slight but limited effect on improving the lateral resistance of the column connection.
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A model for investigating vehicle-bridge interaction under high moving speed
Hanyun Liu,Zhiwu Yu,Wei Guo,Yan Han 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.5
The speed of rail vehicles become higher and higher over two decades, and China has unveiled a prototype highspeed train in October 2020 that has been able to reach 400 km/h. At such high speeds, wheel-rail force items that had previously been ignored in common computational model should be reevaluated and reconsidered. Aiming at this problem, a new model for investigating the vehicle-bridge interaction at high moving speed is proposed. Comparing with the common model, the new model was more accurate and applicable, because it additionally considers the second-order pseudo-inertia forces effect and its modeling equilibrium position was based on the initial deformed curve of bridge, which could include the influences of temperature, pre-camber, shrinkage and creep deformation, and pier uneven settlement, etc. Taking 5 km/h as the speed interval, the dynamic responses of the classical vehicle-bridge system in the speed range of 5 km/h to 400 km/h are studied. The results show that ignoring the second-order pseudo-inertia force will underestimate the dynamic response of vehicle-bridge system and make the high-speed railway bridge structure design unsafe.
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Facility Performance Indexes and Rapid Test Feasibility Evaluation Method of Shaking Tables
Wei Guo,Zhipeng Zhai,Zhiwu Yu,Yan Long 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.7
Shaking table test is widely used as the main experimental approach to evaluate seismic performance of structures, and it usually consumes huge funds and labors. To ensure success of the tests, it is essential to evaluate the feasibility and accuracy before the test is conducted. However, research on test feasibility has rarely been reported. In recent years, complexity of shaking table tests has increased significantly due to the increasing demand of testing facility performance. Hence, feasibility evaluation becomes more and more important. In this paper, main performance indexes of the shaking table facility are expounded. According to the performance indexes of actuator parameters, a rapid feasibility evaluation method is then proposed based on the equilibrium between the facility capacity and the table output demand. Subsequently, applicability of the evaluation method is validated by evaluating the practical tests. The results show that the maximum acceleration targets in horizontal and vertical direction are mutually restrained under threedimensional excitations. For the feasibility evaluation of large-scale model tests, the eccentric and overturning moment of specimen are the main performance control indexes due to their adverse influences on the facility. And the overturn-resistance of shaking table will be enhanced significantly by vertical actuators during the absence of vertical excitations. In the shaking table array test, millimeter-scale relative displacement between tables may lead to accidental damage of the test specimen or not working of the facility when the reinforced concrete foundation crosses the shaking tables. Therefore, attentions should be paid to the design of the test scheme.
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Cooperative Work of CRTS II Slab Ballastless Track-32m Simply Supported Girder under Pier Settlement
Zhihui Zheng,Peng Liu,Lei Liu,Zhiwu Yu,Wei Zhu,Sasa He 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.2
Compared with the previous model, a simplified mapping model of CRTS II slab ballastless track between pier settlement and the vertical deformation of rail was proposed based on Timoshenko’s beam theory. A cooperative finite element analysis model was established for verification purpose and the analysis of interlaminar stress. The results showed that the emergence of pier settlement causes the appearance of the void of the sliding layer between the base plate and the box girder above the piers, and the shear cogging reduces the void length to a certain extent. It was also observed that the rail is deformed cambered at the side pier (the pier with no settlement on both sides of the middle pier) and downwards at the middle pier (the pier with settlement). Moreover, the comparison between the theoretical value of the rail deformation and the finite element result demonstrated that the proposed mapping model can precisely characterize the relevant relationship. A conclusion also can be drawn that the pier settlement is attributed to the additional stress on the interface between the track slab and cement and asphalt mortar (CA mortar), and the interfacial stress is increased due to the effect of shear cogging.
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Shear strength evaluation of RC solid piers of high-speed railway bridges in China
Wei Guo,Chao Fan,Yao Cui,Chen Zeng,Lizhong Jiang,Zhiwu Yu 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.4
Piers are the main lateral force-resisting members of high-speed railway (HSR) bridges used in China and are characterized by low axial load ratios, low longitudinal reinforcement ratios, low stirrup ratios, and high shear span ratios. It is well known that flexural, flexural-shear, and shear failures of piers may occur during an earthquake. In this study, a new shear strength model was developed to simulate the seismic failure of HSR solid piers accurately. First, low cyclic-loading test data of solid piers obtained in recent years were collected to set up a database for model verification. Second, based on the test database, the applicability of existing shear strength models was evaluated. Finally, a new shear strength model for HSR solid piers with round-ended cross-sections was derived based on the truss model and ultimate equilibrium theory. In comparison with existing models, it was demonstrated that the proposed model could be used to predict the shear strength of HSR piers more accurately.
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