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1

Bearing capacity and seismic performance of Y-shaped reinforced concrete bridge piers in a freeze-thaw environment

Li Yanfeng, Li Jialong, Guo Tianyu, Zhao Tongfeng, Bao Longsheng, Sun Xinglong

Archives of Civil Engineering

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2023

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Vol. 69, nr 1

367--384

EN

A quantitative study is performed to determine the performance degradation of Y-shaped reinforced concrete bridge piers owing to long-term freeze-thaw damage. The piers are discretized into spatial solid elements using the ANSYS Workbench finite element analysis software, and a spatial model is established. The analysis addresses the mechanical performance of the piers under monotonic loading, and their seismic performance under low-cycle repeated loading. The influence of the number of freeze-thaw cycles, axial compression ratio, and loading direction on the pier bearing capacity index and seismic performance index is investigated. The results show that freeze-thaw damage has an adverse effect on the ultimate bearing capacity and seismic performance of Y-shaped bridge piers in the transverse and longitudinal directions. The pier peak load and displacement ductility coefficient decrease with increasing number of freeze-thaw cycles. The axial compression ratio is an important factor that affects the pier ultimate bearing capacity and seismic performance. Upon increasing the axial compression ratio, the pier peak load increases and the displacement ductility coefficient decreases, the effects of which are more significant in the longitudinal direction.

2

Recovery of Fe and V via selective reduction–magnetic separation of vanadium-titanium magnetite concentrate

Liu Liwei, Li Guofeng, Zhao Libing, Li Jinpeng, Li Yanfeng

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 1

50--62

EN

With the aim of separating Fe and V, a vanadium-titanium magnetite concentrate was selectively reduced, followed by magnetic separation. The processes accompanying reduction of the vanadium-titanium magnetite concentrate were investigated using thermodynamic simulation, experiments, scanning electron microscopy, and electron probe microanalysis. Appropriate reduction conditions and controlling the amount of CaCO3 promoted the reduction of Fe-containing minerals to metallic Fe. V was released from magnetite, ilmenite, and titanomagnetite, and was inhibited to reduce to metallic V, leading to V enrichment in the non-magnetic products in the form of oxides. Moreover, the Fe particles wrapped the slag phase when the amount of CaCO3 exceeded 8%, which is unfavourable for the magnetic separation of Fe and V. Magnetic products with an Fe content of 87.19%, Fe recovery of 82.62%, V content of 0.09% and non-magnetic products with a V content of 1.00% and a V recovery of 85.49% were obtained when the vanadium-titanium magnetite concentrate was reduced for 100 min at 1623 K with a C/O molar ratio of 2.5 and 8% CaCO3, followed by separating at a magnetic field strength of 85 mT.

3

Study on sling replacement of concrete-filled steel tube arch bridge

Zhang Kexin, Qi Tianyu, Xue Xingwei, Li Yanfeng, Zhu Zhimin

Archives of Civil Engineering

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2021

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Vol. 67, nr 2

597--610

EN

Concrete-filled steel tube arch bridge is filled with concrete inside the steel tube. The radial constraint of the steel tube limits the expansion of the compression concrete, which makes the concrete in the three-way compression state, thus significantly improving the compressive strength of the concrete. At the same time, it can simplify the construction process and shorten the construction period. Since the rapid development of concrete-filled steel tubular tied arch bridge in the 1990s, a large number of such Bridges have suffered from the defects of steel concrete, loose tie rod, and hanger rod rust, etc. Therefore, the reinforcement technology for various diseases has been studied, among which the reinforcement technology for hanger rod replacement is the most complicated and more difficult. As more and more bridges of this type enter the period of reinforcement, it is more and more urgent to study the reinforcement technology of suspenders. Taking a bridge that has been in service for 23 years as an example, this paper discusses the construction method and construction monitoring of replacing the suspender, so as to guide the construction monitoring of the bridge. Finally, the construction monitoring results of the bridge are given, which can provide reference for the replacement of the suspender of this type of bridge.

4

Research on reinforcement technology of existing double-way curved arch bridge

Zhang Kexin, Qi Tianyu, Xue Xingwei, Li Yanfeng, Zhu Zhimin

Archives of Civil Engineering

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2021

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Vol. 67, nr 2

581--595

EN

Two-way curved arch bridges inherit the fine tradition of masonry structures, making full use of the advantages of prefabricated assembly, it adapts to the situation of no support construction and no large lifting machine and tools, and has the characteristics of convenient construction method and saving material consumption. In appearance, the two-way curved arch bridge has strong national cultural characteristics. The prefabricated components of the two-way curved arch bridge are fragmentary, complicated in bearing and poor in integrity. Most of the two-way curved arch bridges in service have been built for a long time and lack of maintenance and management. Increasing the cross-section reinforcement method is one of the two-way curved arch reinforcement methods. It has a significant effect, convenient construction, good rigidity and stability characteristics after the reinforcement. Through theoretical analysis, combined with a static load test results of the assessment of the bridge reinforcement effect. Through load test, it is found that the deflection of the arch rib after reinforcement is reduced by 9%~19% and the strain of the arch rib is reduced by 12%~22%. Through finite element calculation, the crack width of the reinforced arch rib decreases by 8.3%~14.2%. The results show that the stress and deflection are greatly improved by the method of increasing section.

5

Numerical and theoretical research on spatial shear lag effect of self-anchored suspension bridge steel box girder

Li Yanfeng, He Ying, Bao Longsheng, Sun Baoyun, Wang Qinghe

Archives of Civil Engineering

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2021

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Vol. 67, nr 2

631--651

EN

The shear lag effect of the steel box girder section in a self-anchored suspension bridge was investigated in this study. Finite element analysis software Midas Civil was used to discretize the girder under analysis into space plate elements and establish a plate element model. The law of shear lag in the longitudinal direction of the girder in the construction and completion stages was determined accordingly. The shear lag coefficient appears to change suddenly near the side support, middle support, side cable anchorage area, and near the bridge tower support of the steel box girder under the imposed load. The most severe shear lag effect is located near the side support and near the side cable anchorage area. Steel box girder sections are simulated before and after system conversion to analyze the shear lag coefficient in the bridge construction stage. The results show that the shear lag coefficient markedly differs before versus after system conversion due to the different stress mechanisms. The finite element analysis results were validated by comparison with the results of an analysis via analogous rod method.

6

Experimental and theoretical research on large-diameter rock-socketed pile embedded depth

Li Yanfeng, Zhao Jihe, Xiong Ying, Wang Qinghe

Archives of Civil Engineering

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2021

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Vol. 67, nr 2

537--550

EN

A theoretical formula for large-diameter rock-socket depth is developed to support pail embedding in a large bridge pile foundation project. There is a horizontal additional stress concentration at the place where the soil around the rock-socketed pile meets the soil layer under the horizontal load. When the rock-socketed tip stress and bending moment of the pile are relatively small, the pile shows favourable embedment effect and the pile foundation can be considered safe. The function curve of soil resistance around the pile under the action of horizontal force was obtained by finite element analysis. The force characteristics reveal the depth of the largediameter rock-socketed pile under the horizontal load. As the rock-socketed pile rotates under the action of horizontal force, the rock mass resistance around the pile changes according to the cosine. The distribution of pileside soil resistance is proportional to the displacement and distributed according to the sine. A comprehensive correction coefficient of pile shaft resistance β is introduced to deduce the theoretical formula of the depth hr of the large-diameter rock-socketed pile embedded in the bedrock. It is verified through both experiments and numerical analysis.

7

Determination of force in single cable plane prestressed concrete polygonal line tower cable-stayed bridge based on minimum bending energy

Li Yanfeng, Guo Tianyu, Bao Longsheng, Wang Fuchun

Archives of Civil Engineering

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2021

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Vol. 67, nr 3

565--579

EN

The cable force of a cable-stayed bridge plays a vital role in its internal force state. Different cable forces on both sides of the main tower make the force characteristics of the polygonal-line tower quite different from those of the straight-line tower. Therefore, the determination of the cable force of the polygonal-line tower cable-stayed bridge is a crucial aspect of any evaluation of its mechanical characteristics. A single-cable plane prestressed concrete broken-line tower cable-stayed bridge is taken as a case study to conduct a model test and theoretical cable force determination. The reasonable cable force of the bridge is determined by the minimum bending energy method combined with false load and internal force balance methods. analysis includes a comparison between cable force calculation results, model test results, and the design value of the actual bridge. The distribution law of the dead load cable force of the completed bridge is determined accordingly.