Seismic vibration control for bridges with high-piers in Sichuan-Tibet Railway

Chen, Zhaowei,Han, Zhaoling,Fang, Hui,Wei, Kai Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.6

Aiming at widely used high-pier bridges in Sichuan-Tibet Railway, this paper presents an investigation to design and evaluate the seismic vibration reduction effects of several measures, including viscous damper (VD), friction pendulum bearing (FPB), and tuned mass damper (TMD). Primarily, according to the detailed introduction of the concerned bridge structure, dynamic models of high-pier bridges with different seismic vibration reduction (SVR) measures are established. Further, the designs for these SVR measures are performed, and the optimal parameters of these measures are investigated. On this basis, the vibration reduction effects of these measures are analyzed and assessed subject to actual earthquake excitations in Wenchuan Earthquake (M=8.0), and the most appropriate SVR measure for high-pier bridges in Sichuan-Tibet Railway is determined at the end of the work. Results show that the height of pier does not obviously affect the performances of the concerned SVR measures. Comprehensively considering the vibration absorption performance, installation and maintenance of all the employed measures in this paper, TMD is the best one to absorb vibrations induced by earthquakes.

Seismic vibration control for bridges with high-piers in Sichuan-Tibet Railway

Zhaowei Chen,Zhaoling Han,Hui Fang,Kai Wei 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.6

Aiming at widely used high-pier bridges in Sichuan-Tibet Railway, this paper presents an investigation to design and evaluate the seismic vibration reduction effects of several measures, including viscous damper (VD), friction pendulum bearing (FPB), and tuned mass damper (TMD). Primarily, according to the detailed introduction of the concerned bridge structure, dynamic models of high-pier bridges with different seismic vibration reduction (SVR) measures are established. Further, the designs for these SVR measures are performed, and the optimal parameters of these measures are investigated. On this basis, the vibration reduction effects of these measures are analyzed and assessed subject to actual earthquake excitations in Wenchuan Earthquake (M=8.0), and the most appropriate SVR measure for high-pier bridges in Sichuan-Tibet Railway is determined at the end of the work. Results show that the height of pier does not obviously affect the performances of the concerned SVR measures. Comprehensively considering the vibration absorption performance, installation and maintenance of all the employed measures in this paper, TMD is the best one to absorb vibrations induced by earthquakes.

Basement Design for Vibration Reduction of High-Rise Buildings under Metro Operation

Zhaowei Chen,Song Peng,Defeng Zeng,Qinglie He,Jing Tang,Mengqi Zhang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.4

Vibration induced by metro operation on the underground line is transmitted to the buildings above the line, which adversely affects on the normal life and work of human in the building. To study this problem, based on the plate-shell vibration theory, a plate-column-plate coupled model is constructed to analyze the influence of plate thickness, plate elastic modulus and column arrangement on the vibration in mechanism firstly. Relying on a practical engineering problem, two models are established, namely a train-track coupled dynamic model and a monolithic track bed-tunnel-soil-building model, loading fastener force from the train-track coupled dynamic model on the monolithic track bed, vibration propagates to high-rise building through soil-building coupling. Field test is conducted to verify the reliability of the numerical model. On the basis, the vibration law of building under different basement floor thicknesses, basement floor material and arrangement of non-permanent columns are studied. Results show that changing the basement design parameters has different effects. The Z vibration level of building floor decreases with the increase of basement floor thickness. Basement floor thickness increases by 0.02 m, the Z vibration level of the floor decreased by 1.4 – 2.2 dB at most. The decrease of elastic modulus leads to a slight decrease of the Z vibration level of building, the change is less than 1 dB. Without changing the arrangement of basement load-bearing columns, reducing non-permanent structural columns significantly reduces the Z vibration level, with attenuation of up to 5.1 dB.

Experimental study on fatigue behavior of innovative hollow composite bridge slabs

Yang Chen,Zhaowei Jiang,Qing Xu,Chong Ren 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.6

In order to study the fatigue performance of the flat steel plate-lightweight aggregate concrete hollow composite bridge slab subjected to fatigue load, both static test on two specimens and fatigue test on six specimens were conducted. The effects of the arrangement of the steel pipes, the amplitude of the fatigue load and the upper limit as well as lower limit of fatigue load on failure performance were investigated. Besides, for specimens in fatigue test, strains of the concrete, residual deflection, bending stiffness, residual bearing capacity and dynamic response were analyzed. Test results showed that the specimens failed in the fracture of the bottom flat steel plate regardless of the arrangement of the steel pipes. Moreover, the fatigue loading cycles of composite slab were mainly controlled by the amplitude of the fatigue load, but the influences of upper limit and lower limit of fatigue load on fatigue life was slight. The fatigue life of the composite bridge slabs can be determined by the fatigue strength of bottom flat steel plate, which can be calculated by the method of allowable stress amplitude in steel structure design code.

IL-17A Secreted by Th17 Cells Is Essential for the Host against Streptococcus agalactiae Infections

( Jing Chen ),( Siyu Yang ),( Wanyu Li ),( Wei Yu ),( Zhaowei Fan ),( Mengyao Wang ),( Zhenyue Feng ),( Chunyu Tong ),( Baifen Song ),( Jinzhu Ma ),( Yudong Cui ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 Journal of microbiology and biotechnology Vol.31 No.5

Streptococcus agalactiae is an important bacterial pathogen and causative agent of diseases including neonatal sepsis and meningitis, as well as infections in healthy adults and pregnant women. Although antibiotic treatments effectively relieve symptoms, the emergence and transmission of multidrug-resistant strains indicate the need for an effective immunotherapy. Effector T helper (Th) 17 cells are a relatively newly discovered subpopulation of helper CD4⁺ T lymphocytes, and which, by expressing interleukin (IL)-17A, play crucial roles in host defenses against a variety of pathogens, including bacteria and viruses. However, whether S. agalactiae infection can induce the differentiation of CD4⁺ T cells into Th17 cells, and whether IL-17A can play an effective role against S. agalactiae infections, are still unclear. In this study, we analyzed the responses of CD4⁺ T cells and their defensive effects after S. agalactiae infection. The results showed that S. agalactiae infection induces not only the formation of Th1 cells expressing interferon (IFN)-γ, but also the differentiation of mouse splenic CD4⁺ T cells into Th17 cells, which highly express IL-17A. In addition, the bacterial load of S. agalactiae was significantly increased and decreased in organs as determined by antibody neutralization and IL-17A addition experiments, respectively. The results confirmed that IL-17A is required by the host to defend against S. agalactiae and that it plays an important role in effectively eliminating S. agalactiae. Our findings therefore prompt us to adopt effective methods to regulate the expression of IL-17A as a potent strategy for the prevention and treatment of S. agalactiae infection.

Assessment and Control of Metro-induced Vibration and Secondary Noise of TOD Buildings

Defeng Zeng,Zhaowei Chen,Qinglie He 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.2

Metro-induced vibration and structural secondary noise are becoming increasingly outstanding, which greatly restrict the further development of TOD (Transit-oriented development) project. To solve this problem, an evaluation methodology and dynamic model of vibration and secondary noise induced by metro train is developed firstly. Then the characteristic and distribution of vibration and secondary noise of the TOD subject to running train are studied. Finally, the control effect of steel-spring floating slab track (FST) on vibration and secondary noise of TOD project is evaluated. Results show that: when evaluating environmental problem caused by metro train, the standard of secondary noise is more strict than that of vibration. Main frequency of metro-induced vibration is concentrated in 40 − 63 Hz, and the second main frequency is concentrated in 6.3 − 16 Hz. The business building has the largest vibration due to its closest distance to the metro line. Secondary noises of most of the TOD buildings exceed the limit value, and the maximum exceeding value is 11.7 dB(A). FST is effective in controlling train-induced vibration and secondary noise of TOD buildings. FST cannot reduce vibrations in full frequency band, and vibration in some frequency bands are even amplified according to the stiffness of steel spring.

Constraints on sulfide saturation by crustal contamination in the Shitoukengde Cu-Ni deposit, East Kunlun orogenic belt, northern Qinghai-Tibet Plateau, China

Chiyuan Wang,Zhaowei Zhang,Chengjiang Zhang,Cuihua Chen,Yin Li,Bing Qian 한국지질과학협의회 2021 Geosciences Journal Vol.25 No.3

The Shitoukengde Cu-Ni deposit is located in the eastern part of the East Kunlun Orogenic Belt (EKOB). The overall complex underwent emplacement into the surrounding rock, including the gneiss and marble. The ore-bodies exist in complex I, which is composed of peridotite, pyroxenite, and gabbro. The petrogeochemical characteristics of the rocks show that the m/f values range from 1.93 to 5.97, and the Fe3+/ΣFe ratios of the spinel are < 0.3, indicating that the Shitoukengde complexes have the potential to form a Cu-Ni ore deposit. Based on the evidence of marble and gneiss xenoliths, there are higher CaO and Al2O3 contents in the peridotite and pyroxene, there are Nb and Ta depletions, in the Shitoukengde; these results indicate that the ore-forming parental magma has been obviously contaminated by crustal material during the evolution process and that the materials responsible for the contamination mainly originated from the middle-upper crust. The mafic-ultramafic complex, which is closed to marble, has higher CaO and Al2O3 contents; higher (87Sr/86Sr)i values and lower Ni contents; thus, it is reasonable to infer that the Shitoukengde mafic-ultramafic rocks assimilated some marble, and the contamination of marble without sulfide suppresses the sulfide saturation. The pyroxenite with better mineralization is mainly orthopyroxene, and the increase in the sulfur isotope values in the pyroxenite and peridotite is accompanied by an increase in the Ni content; these results suggest that the SiO2 and S of biotite-plagioclase gneisses, especially the S addition, were important for the Shitoukengde intrusion to reach sulfide saturation. The whole-rock Ni content in the peridotite shows a positive relationship with the FeO content of spinel, indicating that the crystallization of spinel has little effect on sulfide saturation. The capable of crystallizing olivine with Fo content as high as 89.3 mol% and olivine Fo value exhibits a positive relationship with the olivine NiO content, indicating that olivine fractional crystallization did not play a significant role in sulfide saturation. The δ34SV-CDT value of the giant Xiarihamu deposit is much higher than that of Shitoukengde. The degree of crustal S contamination is probably responsible for the difference in the scale and ore grade of the Cu-Ni sulfide deposits in the East Kunlun area. The above indicators could guide the exploration and evaluation of similar deposits in the EKOB.

An intelligent recoil controller for riser system based on fuzzy control theory

Liu Xiuquan,Liu Zhaowei,Wang Xianglei,Qiu Na,Zhang Nan,Chang Yuanjiang,Chen Guoming 대한조선학회 2022 International Journal of Naval Architecture and Oc Vol.14 No.1

Riser recoil control is a complicated nonlinear control problem. An intelligent control methodology is proposed to control the complicated riser recoil response based on fuzzy control theory. A dynamic nonlinear model of drilling riser/tensioner coupling system is established for riser recoil analysis. The riser system is divided into several elements and the coupling effect between the riser and discharged mud is considered in the dynamic model. A fuzzy controller for the opening of the recoil control valve is designed for the riser recoil control. A comprehensive analysis method is proposed for riser recoil control simulation. Simulation results show that the designed fuzzy controller can effectively control the riser recoil response. The adaptability of the designed controller is also proved by the simulation results. The application of the designed controller can reduce the risk of accidents during riser recoil process.

Dynamic analysis of metro vehicle traveling on a high-pier viaduct under crosswind in Chongqing

Yunfei Zhang,Jun Li,Zhaowei Chen,Xiangyang Xu 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.5

Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train under crosswind. Compared with the conditions of no-wind, crosswind triggers severer vibration of the dynamic system; compared with the short-pier viaduct, the high-pier viaduct has worse stability under crosswind. For these reasons, the running safety of the metro vehicle traveling on a high-pier viaduct under crosswind is analyzed to ensure the safe operation in metro lines in mountain cities. In this paper, a dynamic model of the metro vehicle-track-bridge system under crosswind is established, in which crosswind loads model considering the condition of wind zone are built. After that, the evaluation indices and the calculation parameters have been selected, moreover, the basic characteristics of the dynamic system with high-pier under crosswind are analyzed. On this basis, the response varies with vehicle speed and wind speed are calculated, then the corresponding safety zone is determined. The results indicate that, crosswind triggers drastic vibration to the metro vehicle and high-pier viaduct, which in turn causes running instability of the vehicle. The corresponding safety zone for metro vehicle traveling on the high-pier is proposed, and the metro traffic on the high-pier bridge under crosswind should not exceed the corresponding limited vehicle speed to ensure the running safety.

Running safety of metro train over a high-pier bridge subjected to fluctuating crosswind in mountain city

Yunfei Zhang,Jun Li,Zhaowei Chen,Xiangyang Xu 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.2

Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train subjected to fluctuating crosswind. To ensure the safe operation in metro lines in mountain cities, running safety of the metro train over the high-pier bridge under crosswind is analyzed in this paper. Firstly, the dynamic model of the wind-train-bridge (WTB) system is built, in which the speed-up effect of crosswind is fully considered. On the basis of time domain analysis, the basic characteristics of the WTB system with high-pier are analyzed. Afterwards, the dynamic responses varies with train speed and wind speed are calculated, and the safety zone of metro train over a high-pier bridge subjected to fluctuating crosswind in mountain city is determined. The results indicate that, fluctuating crosswind triggers drastic vibration to the metro train and high-pier bridges, which in turn causes running instability of the train. For this reason, the corresponding safety zone for metro train running on the high-pier is proposed, and the metro traffic on the high-pier bridge should be closed as the mean wind speed of standard height reaches 9 m/s (15.6 m/s for the train).