Test for Influence of Socket Connection Structure on Dynamic Response of Prefabricated Pier under Vehicle Collision

Yan Han,Zhihao Liu,Longlong Wang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.3

In order to obtain the difference of anti-collision performance between the socket assembled bridge pier and integral bridge pier, this research conducted the model test of the bridge piers subjected to vehicle impact. The influence of the socket connection form and structure parameters such as embedment depth, interface roughness, and reserved hole opening size on the response of bridge piers to vehicle collision was analyzed by comparing them with those of the cast-in-place bridge pier. Results show that vehicle speed and socket depth are important factors affecting the dynamic response of socket bridge piers to vehicle crash. The maximum impact force on a bridge pier is obviously affected by the embedment depth of the pier column, but no clear change rule exists between them. The opening size of the reserved cavity affects the impact force slightly when the vehicle speed is low, but gradually increases with the increase in vehicle speed. The damage degree of the bridge pier gradually decreases with the increase in the embedment depth of the pier column and increases with the increase in vehicle speed. The acceleration of the bridge pier tends to increase with the vehicle speed, but no clear law of change with the socket depth exists. The maximum strain of the steel bar at the root of the socket pier is greater than that of the impact position, and the maximum strain distribution of the steel bars of the pier column with the socket embedment depth greater than or equal to 1.0 times diameter of the column is similar to that of the cast-in-place one. The maximum strain of steel bars of the both are at the root of the pier column. The study results provide a data reference for further studying the actual vehicle bumping on socket bridge pier and prefabricated bridge anti-collision design.

Study of central buckle effects on flutter of long-span suspension bridges

Yan Han,Kai Li,C.S. Cai 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.5

To investigate the effects of central buckles on the dynamic behavior and flutter stability of long-span suspension bridges, four different connection options between the main cable and the girder near the mid-span position of the Aizhai Bridge were studied. Based on the flutter derivatives obtained from wind tunnel tests, formulations of self-excited forces in the time domain were obtained using a nonlinear least square fitting method and a time-domain flutter analysis was realized. Subsequently, the influences of the central buckles on the critical flutter velocity, flutter frequency, and three-dimensional flutter states of the bridge were investigated. The results show that the central buckles can significantly increase the frequency of the longitudinal floating mode of the bridge and have greater influence on the frequencies of the asymmetric lateral bending mode and asymmetric torsion mode than on that of the symmetric ones. As such, the central buckles have small impact on the critical flutter velocity due to that the flutter mode of the Aizhai Bridge was essentially the symmetric torsion mode coupled with the symmetric vertical mode. However, the central buckles have certain impact on the flutter mode and the three-dimensional flutter states of the bridge. In addition, it is found that the phenomenon of complex beat vibrations (called intermittent flutter phenomenon) appeared in the flutter state of the bridge when the structural damping is 0 or very low.

Flutter stability of a long-span suspension bridge during erection

Yan Han,Shuqian Liu,C.S. Cai,Chunguang Li 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.1

The flutter stability of long-span suspension bridges during erection can be more problematic and more susceptible to be influenced by many factors than in the final state. As described in this paper, numerical flutter stability analyses were performed for the construction process of Zhongdu Bridge over Yangtze River using the commercial FE package ANSYS. The effect of the initial wind attack angle, the sequence of deck erection, the stiffness reduction of stiffening girders, the structural damping, and the cross cables are discussed in detail. It was found that the non-symmetrical sequence of deck erection was confirmed to be aerodynamically favourable for the deck erection of long-span suspension bridges and the best erection sequence should be investigated in the design phase. While the initial wind attack angle of -3o is advantageous for the aerodynamic stability, +3o is disadvantageous compared with the initial wind attack angle of 0o during the deck erection. The stiffness reduction of the stiffening girders has a slight effect on the flutter wind speed of the suspension bridge during erection, but structural damping has a great impact on it, especially for the early erection stages.

Experimental and numerical studies of aerodynamic forces on vehicles and bridges

Yan Han,C.S. Cai,Jiexuan Hu,Zhengqing Chen,Chunguang Li 한국풍공학회 2013 한국풍공학회지 Vol.17 No.2

An accurate identification of the aerodynamic characteristics of vehicles and the bridge is the premise for the coupled vibration analysis of a wind-vehicle-bridge system. At present, the interaction of aerodynamic forces between the road vehicles and bridge is ignored in most previous studies. In the present study, an experimental setup was developed to measure the aerodynamic characteristics of vehicles and the bridge for different cases in a wind tunnel considering the aerodynamic interference. The influence of the wind turbulence, the wind speed, the vehicle interference, and the vehicle position on the aerodynamic coefficients of vehicles, and the influence of vehicles on the static coefficients of the bridge were investigated, based on the experimental results. The variations in the aerodynamic characteristics of vehicles and the bridge were studied and the measured results were validated according to the results of surface pressure measurements on the vehicle and the bridge. The measured results were further validated by comparing the measured results with values derived numerically. The measured results showed that the wind turbulence, the vehicle interference, and the vehicle position significantly affected the aerodynamic coefficients of vehicles. However, the influence of the wind speed on the aerodynamic coefficients of the studied vehicle is small. The static coefficients of the bridge were also significantly influenced by the presence of vehicles.

Calculation of Vehicle Impact Force on Socket Prefabricated Bridge Piers

Yan Han,Zhiming Huang,Zhaoxiang Li 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.10

The design and evaluation of bridge structural integrity following a collision accident heavily depend on the impact force of the vehicle colliding with the bridge piers. Socket prefabricated piers are commonly used in bridge engineering; however, limited research has been conducted on their impact force. To address this issue, this study employs finite element (FE) simulation to investigate the dynamic force and equivalent static force (ESF) of a vehicle colliding with socket prefabricated bridge columns. The study explores various parameters such as socket connection structural parameters, vehicle condition parameters, and pier parameters. Furthermore, the study evaluates four approaches, including the global average approach, local average approach, peak of the 25 ms moving average approach, and simplified pulse approach, to investigate the ESF. Results show that the impact force of the vehicle is significantly influenced by vehicle factors. Additionally, the socket depth of the pier has a great impact on heavy vehicle impacts. A suitable approach for calculating the ESF of a vehicle impacting socket prefabricated bridge piers was identified, and a corresponding calculation formula was developed. The formula is a function of the vehicle’s mass and velocity and the pier column socket depth, eliminating the need for cumbersome FE analyses.

The Protective Role of TLR3 and TLR9 Ligands in Human Pharyngeal Epithelial Cells Infected with Influenza A Virus

Yan Han,Ming-yu Xu,Nan Sun,Dan-hong Liu,Zhi-jian Bo 대한약리학회 2014 The Korean Journal of Physiology & Pharmacology Vol.18 No.3

In this study we aim to extensively investigate the anti-influenza virus immune responses in humanpharyngeal epithelial cell line (Hep-2) and evaluate the protective role of Toll-like receptor (TLR)ligands in seasonal influenza A H1N1 (sH1N1) infections in vitro. We first investigated the expressionof the TLRs and cytokines genes in resting and sH1N1 infected Hep-2 cells. Clear expressions of TLR3,TLR9, interleukin (IL)-6, tumour necrosis factor (TNF)-α and interferon (IFN)-β were detected inresting Hep-2 cells. After sH1N1 infection, a ten-fold of TLR3 and TLR9 were elicited. Concomitantwith the TLRs activation, transcriptional expression of IL-6, TNF-α and IFN-β were significantlyinduced in sH1N1-infected cells. Pre-treatment of cells with poly I:C (an analog of viral double-strandedRNA) and CpG-ODN (a CpG-motif containing oligodeoxydinucleotide) resulted in a strong reductionof viral and cytokines mRNA expression. The results presented indicated the innate immune responseactivation in Hep-2 cells and affirm the antiviral role of Poly I:C and CpG-ODN in the protectionagainst seasonal influenza A viruses.

The influence of vehicles on the flutter stability of a long-span suspension bridge

Yan Han,Shuqian Liu,C.S. Cai,Jianren Zhang,Suren Chen,Xuhui He 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.2

The presence of traffic on a slender long-span bridge deck will modify the cross-section profileof the bridge, which may influence the flutter derivatives and in turn, the critical flutter wind velocity of thebridge. Studies on the influence of vehicles on the flutter derivatives and the critical flutter wind velocity ofbridges are rather rare as compared to the investigations on the coupled buffeting vibration of thewind-vehicle-bridge system. A typical streamlined cross-section for long-span bridges is adopted for bothexperimental and analytical studies. The scaled bridge section model with vehicle models distributed on thebridge deck considering different traffic flow scenarios has been tested in the wind tunnel. The flutterderivatives of the modified bridge cross section have been identified using forced vibration method and theresults suggest that the influence of vehicles on the flutter derivatives of the typical streamlined cross-sectioncannot be ignored. Based on the identified flutter derivatives, the influence of vehicles on the flutter stabilityof the bridge is investigated. The results show that the effect of vehicles on the flutter wind velocity isobvious.

Driving safety analysis of various types of vehicles on long-span bridges in crosswinds considering aerodynamic interference

Yan Han,Jingwen Huang,C.S. Cai,Suren Chen,Xuhui He 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.4

Strong winds threaten the safety of vehicles on long-span bridges considerably, which could force traffic authorities to reduce speed limits or even close these bridges to traffic. In order to maintain the safe and economic operation of a bridge, a reasonable evaluation of the driving safety on that bridge is needed. This paper aims at carrying outdriving safety analyses for three types of vehicles on a long-span bridge in crosswinds by considering the aerodynamic interference between the bridge and the vehicles based on the wind-vehicle-bridge coupling vibration analysis. Firstly, CFD numerical simulations along with previously obtained wind tunnel testing results were used to determine the aerodynamic force coefficients of the three types of vehicles on the bridge. Secondly, the dynamic responses of the bridge and the vehicles under crosswinds were simulated, and based on those, the driving safety analyses for the three types of vehicles on the bridge were carried out for both cases considering and not considering the aerodynamic interference between the vehicles and the bridge. Finally, the effect of the aerodynamic interference on the safety of the vehicles was investigated. The results show that the aerodynamic interference between the bridge and the vehicles not only affects the accident critical wind speed but also the accident type for all three types of vehicles. Such effects are also different for each of the three types of vehicles being studied.

Enhanced Mechanical Properties and Thermal Conductivity for GNPs/Al2024 Composites with In Situ SiC Nanorods

Lili Chen,Yushi Qi,Yanhan Fei,Zhiming Du 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10

In order to significantly enhance the performance of graphene in metal matrix composites, in situ SiC nanorods were successfullyfabricated to enhance graphene nanoplatelets (GNPs)-reinforced Al2024 composite, which was prepared by powdersemi-solid processing and friction stir processing. The SiC–GNPs dispersed in the Al matrix uniformly, SiC nanorodswere randomly grown on GNPs sheets in any direction, bridging GNPs as well as GNPs and the Al matrix. Meanwhile, theinterfacial bonding was effective. The hybrid reinforcement of SiC and GNPs endowed composites with superior mechanicalproperties and thermal conductivity. The in situ SiC nanorods transfer phonons and reduce phonon scattering effect inthe through-plane direction of GNPs, which conducive to heat transmission. The composite exhibits improved mechanicalproperties, maximum tensile strength and hardness of 589 MPa and 193 HV are obtained, with 1.0 wt% GNPs addition,respectively. The thermal conductivity of composite increases with the content of SiC–GNPs. When the content of SiC–GNPsreaches 1.5 wt%, the composite has significantly enhanced thermal conductivity (224 W m−1 K−1), which is 115% timeshigher than that of Al2024. Moreover, the effects of SiC–GNPs on the properties were discussed.

Identification of genomic-wide genetic links between cutaneous melanoma and obesity-related physical traits via cFDR

Lin Shen,Shen Runnan,Huang Jingqian,Liu Yanhan,Li Hongpeng,Xu Qingfang 한국유전학회 2023 Genes & Genomics Vol.45 No.12

Background Both epidemiological and clinical studies have suggested the comorbidity between cutaneous melanoma (CM) and obesity-related physical traits. However, it remains unclear about their shared genetic architecture. Objective To determine the shared genetic architecture between CM and obesity-related physical traits through conditional false discovery rate (cFDR) analysis. Method Quantile–quantile plots were firstly built to assess the pleiotropic enrichment of shared single nucleotide polymorphisms between CM and each trait. Then, cFDR and conjunctional cFDR (ccFDR) were used to identify the shared risk loci between CM and each trait. Moreover, the functional evaluation of shared risk genes was carried out through analyses of expression quantitative trait loci (eQTL), Kyoto Encyclopedia of Genes and Genomes and gene ontology, respectively. Finally, single-cell sequence analysis was performed to locate the expression of eQTL-mapped genes in tissues. Results Successive pleiotropic enrichment was found between CM and 5 obesity-related traits or height. 24 shared risk loci were identified between CM and 13 traits except appendicular lean mass using ccFDR analysis, with 17 novel and 4 validated loci. The functions of ccFDR-identified and eQTL-mapped genes were revealed to be mainly involved in cellular senescence, proliferation, meiotic nuclear division, cell cycle, and the metabolism of lipid, cholesterol and glucose. Single-cell sequence analysis showed that keratinocytes contribute to the occurrence and aggressiveness of CM through secreting paracrine cytokines. Conclusion Our findings demonstrate the significant genetic correlation between CM and obesity-related physical traits, which may provide a novel genetical basis for the pathogenesis and treatment of CM.