Fire Performance of Continuous Steel-Concrete Composite Bridge Girders

Gang Zhang,Chaojie Song,Xuyang Li,Shuanhai He,Qiao Huang 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.3

This paper presents a detailed investigation in to fire resistance along with failure mode in continuous steel-concrete composite twin I-shaped bridge girders under different localized fire through considering fire severity and fire exposure positions namely; mid-span zone in one of the two span, hogging moment zone and side-support zone. A 3-D finite element (FE) model, built utilizing the computer program ANSYS, is used to track structural fire performance in a typical two span of continuous composite twin I-shaped bridge girders (fabricated with twin I-shaped plates supporting a concrete slab) dependent on thermo-mechanical coupled analysis. The model validation is undertook through comparison of temperature and deflection response attained from a scaled composite single I-shaped girder tested exposed to ISO834 fire. The numerical analysis results show that the developed model can be favorably used to analyze the behavior and failure mode of continuous steel-concrete composite twin I-shaped bridge girders during entire range of fire exposure. Fire severity and fire exposure positions present critical influence in to the fire resistance of continuous composite bridge girders. Fire exposure prevention on hogging moment zone can significantly extend failure time of continuous girders, and further hold back progressive structural collapse. Web buckling based failure criterion can be applicable to calculate fire resistance of realistic continuous girders under simultaneous structural loading together with localized fire. Continuous composite bridge girders subjected to localized fire present highly significant local deformation response in the fire exposed bridge girder span.

An Intrusion Prevention Technology Based on Dynamic Random Password Authentication in Wireless Sensor Networks

Gang He,Yanna Zhu,Guisheng Zhang,Guotong Qiao 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.12

Security is an important problem in wireless sensor networks. Intrusion detection system is one of the most common methods of network security, for which more and more people have shown solicitude. In this paper, a dynamic random password authentication (DRPA) method is proposed for the identity authentication of communication nodes, which can detect and prevent malicious behavior at each stage of the network operation. This paper introduces the method of automatic generation of random passwords. When a user wants to communicate, the password will be verified to confirm whether it is a normal user or a malicious user. The password’s generation and verification process is very suitable for wireless sensor networks. By using NS2, the simulation experiments are carried out and the results show that this method is superior to the other methods.

Determination and Application of Optimum Abrasive Mass Flow Rate of Abrasive Waterjet

Gang Wang,Shifan Qiao,Guang Wang,Qingzhao Jiang,Jenisha Singh 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.12

Abrasive waterjet can be effectively used in cutting reinforced concrete (RC) piles. The cutting performance increases with abrasive mass flow rate, but as the abrasive mass flow rate increases, damage of abrasive particles also increases. Using optimum abrasive mass flow rate in cutting RC piles, which is determined by considering damage of abrasive particles, can improve cutting performance. In this paper, quantification of effect of abrasive waterjet parameters on cutting performance is simplified by using maximum kinetic energy as medium to relate abrasive waterjet parameters to cutting depth. The damage of abrasive particles during acceleration is related to mixing tube diameter, abrasive material properties and gradation, and is independent of pump pressure, water mass flow rate, transverse speed, standoff distance (SOD), jet impingement angle, and number of cuts. It is found that damage of abrasive particles leads to a reduction of effective kinetic energy used in cutting RC structures. The model for prediction of optimum abrasive mass flow rate is proposed by introducing coefficient of momentum transfer, which considers loss of kinetic energy during acceleration. The optimum abrasive mass flow rate calculated based on proposed model is then used in field test, which shows obvious improvement of cutting performance.

Behavior of composite box bridge girders under localized fire exposure conditions

Gang Zhang,Venkatesh Kodur,Weifa Yao,Qiao Huang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.2

This paper presents results from experimental and numerical studies on the response of steel-concrete composite box bridge girders under certain localized fire exposure conditions. Two composite box bridge girders, a simply supported girder and a continuous girder respectively, were tested under simultaneous loading and fire exposure. The simply supported girder was exposed to fire over 40% of its span length in the middle zone, and the two-span continuous girder was exposed to fire over 38% of its length of the first span and full length of the second span. A measurement method based on comparative rate of deflection was provided to predict the failure time in the hogging moment zone of continuous composite box bridge girders under certain localized fire exposure condition. Parameters including transverse and longitudinal stiffeners and fire scenarios were introduced to investigate fire resistance of the composite box bridge girders. Test results show that failure of the simply supported girder is governed by the deflection limit state, whereas failure of the continuous girder occurs through bending buckling of the web and bottom slab in the hogging moment zone. Deflection based criterion may not be reliable in evaluating failure of continuous composite box bridge girder under certain fire exposure condition. The fire resistance (failure time) of the continuous girder is higher than that of the simply supported girder. Data from fire tests is successfully utilized to validate a finite element based numerical model for further investigating the response of composite box bridge girders exposed to localized fire. Results from numerical analysis show that fire resistance of composite box bridge girders can be highly influenced by the spacing of longitudinal stiffeners and fire severity. The continuous composite box bridge girder with closer longitudinal stiffeners has better fire resistance than the simply composite box bridge girder. It is concluded that the fire resistance of continuous composite box bridge girders can be significantly enhanced by preventing the hogging moment zone from exposure to fire. Longitudinal stiffeners with closer spacing can enhance fire resistance of composite box bridge girders. The increase of transverse stiffeners has no significant effect on fire resistance of composite box bridge girders.

The expression of Rab5 and its effect on invasion, migration and exosome secretion in triple negative breast cancer

Lei Qiao,Chao Dong,Jiaojiao Zhang,Gang Sun 대한약리학회 2023 The Korean Journal of Physiology & Pharmacology Vol.27 No.2

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer and current therapeutic strategies are limited in their effectiveness. The expressions of Rab5 and the M2 tumor-associated macrophage marker CD163 in tissues were detected by Western blot. The migration and invasion of cells were determined using a Transwell assay. The expressions of the exosome markers were evaluated by Western blot. The polarization of human macrophages (THP-1) was determined by incubation of THP-1 cells with conditioned medium or exosomes collected from MDA-MB-231 cells with indicated transfections or by a coculture system of THP-1 and MDA-MB-231 cells. The M1 and M2 macrophage markers were evaluated by qRT-PCR. The expression of Rab5 in TNBC was significantly higher than that in normal breast tissue. Rab5 expressions in triple-negative and luminal A breast cancer were higher than those in other molecular subtypes. Higher CD163 expression was observed in triple-negative breast cancer and in triple-negative and luminal B subtypes. Rab5 knockdown suppressed but Rab5 overexpression promoted the migration and invasion capacity of MDA-MB-231 cells. The levels of CD63 and CD9 in the medium of Rab5 knockdown cells were lower than those in control cells, whereas higher levels of CD63 and CD9 were observed in Rab5 overexpression cells. Rab5 knockdown decreased the excretion but did not alter the diameter of the exosomes. Knockdown of Rab5 facilitated the anti-tumor polarization of macrophages, which was partially reversed by Rab5 overexpression. Therefore, Rab5 is expected to be a potential therapeutic target for triple-negative breast cancer.

Tensile-Mechanical Degradation-Properties and J-C Constitutive Model of Studs after Strong-Acid Corrosion

Wenjing Qiao,Hao Zhang,Gang Zhang,Fan Yang,Zhiguo Liu 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.9

This paper presents an investigation on strong-acid relations between corrosion rate and corrosion time in 30 studs, dipped into 36% industrial hydrochloric acid through 0.5 h, 1 h, 2 h, 4 h, 8 h, 12 h, 24 h, 48 h, and 72 h, respectively. These corroded studs are performed tensile tests to study failure mode and stress-strain curves in studs with different corrosion time. Thereafter, a 3-D finite element is established through computer program to validate test results, and then analyze mechanical properties along with failure mode of studs exposed to strong-acid corrosion. The analysis results show that the failure mode gradually changes from ductile-damage state to brittle-damage state. The corrosion rates present a non-linear elevation with an increase of strong-acid-corrosion time. The nominal yield strength, the nominal ultimate strength, and the elongation in the corroded studs exhibit a fast-downward trend when increasing corrosion time. However, the degradation of elastic modulus turn into a slow step and the yield strength ratio in studs tends to be steady. The J-C model (Johnson-Cook Constitutive) with updated coefficients can be applied to reflect the constitutive relations in studs after strong-acid corrosion under quasi-static tension conditions. Further, this model can simulate stress flows within studs after strong-acid corrosion. This research results can provide a guide for long-lifetime construction and safe maintenance in steel structural bridge.

Transverse buckling analysis of spatial diamond-shaped pylon cable-stayed bridge based on energy approach

Xing Zheng,Qiao Huang,Qing-gang Zheng,Zhen Li 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.1

The stability of cable-stayed bridges is an important factor considered during design. In recent years, the novel spatial diamond-shaped bridge pylon has shown its advantages in various aspects, including the static response and the stability performance with the development of cable-stayed bridge towards long-span and heavy-load. Based on the energy approach, this paper presents a practical calculation method of the completed state stability of a cable-stayed bridge with two spatial diamond-shaped pylons. In the analysis, the possible transverse buckling of the girder, the top pylon column, and the mid pylon columns are considered simultaneously. The total potential energy of the spatial diamond-shaped pylon cable-stayed bridge is calculated. And based on the principle of stationary potential energy, the transverse buckling coefficients and corresponding buckling modes are obtained. Furthermore, an example is calculated using the design parameters of the Changtai Yangtze River Bridge, a 1176 m cable-stayed bridge under construction in China, to verify the effectiveness and accuracy of the proposed method in practical engineering. The critical loads and the buckling modes derived by the proposed method are in good agreement with the results of the finite element method. Finally, cable-stayed bridges varying pylon and girder stiffness ratios and pylon geometric dimensions are calculated to discuss the applicability and advantages of the proposed method. And a further discussion on the degrees of the polynomial functions when assuming buckling modes are presented.

Researth on Factors Affecting Employees' Security Behavior Based on Structural Equation Model

Yanna Zhu,Gang He,Xianfei Zhu,Guotong Qiao,Guisheng Zhang,Lianwei Heng 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.8

관광목적지로써 지각된 위험에 대한 방한 중국관광객의 인식차이에 관한 연구

교만 ( Man Qiao ),정강환 ( Gang Hoan Jeong ),김주호 ( Juho Kim ) (사)한국마이스관광학회(구 한국컨벤션학회) 2016 MICE관광연구 Vol.16 No.2

This study selected Chinese tourists in Korea as target population, and tested how risk factors influence outbound tourism destination, as well as how to improve the likelihood of revisit. The empirical analysis is summarized as below. Based on a cutoff value of an Eigen-value of 1.0 or above after Exploratory Factor Analysis, five risk factors were obtained. These factors were labelled as ``healthy risk``, ``safety risk``, ``economic risk``, ``political risk``, ``cultural shock risk``. There are significant differences between risk perceptions and social demographic characters, such as age, educational level, occupation, monthly income. The result of this study suggests as below: First of all, there must be some guarantee to make tourists feel safe. Secondly, at maximum reduce inconvenience and dissatisfaction of Chinese tourists in Korea, improve customer satisfaction and revisit level and build appropriate international marketing strategies. Thirdly, need to make particular tourism products according to Chinese market and satisfy Chinese individual tourists`` needs. Fourthly, shopping tourism is temporary. Korea tourism market needs to establish a long-term tourism marketing strategy with diversification of tourism products and projects

Designing method for fire safety of steel box bridge girders

Xuyang Li,Gang Zhang,Venkatesh Kodur,Shuanhai He,Qiao Huang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.6

This paper presents a designing method for enhancing fire resistance of steel box bridge girders (closed steel box bridge girder supporting a thin concrete slab) through taking into account such parameters namely; fire severity, type of longitudinal stiffeners (I, L, and T shaped), and number of longitudinal stiffeners. A validated 3-D finite element model, developed through the computer program ANSYS, is utilized to go over the fire response of a typical steel box bridge girder using the transient thermo-structural analysis method. Results from the numerical analysis show that fire severity and type of longitudinal stiffeners welded on bottom flange have significant influence on fire resistance of steel box bridge girders. T shaped longitudinal stiffeners applied on bottom flange can highly prevent collapse of steel box bridge girders towards the end of fire exposure. Increase of longitudinal stiffeners on bottom flange and web can slightly enhance fire resistance of steel box bridge girders. Rate of deflection-based criterion can be reliable to evaluate fire resistance of steel box bridge girders in most fire exposure cases. Thus, T shaped longitudinal stiffeners on bottom flange incorporated into bridge fire-resistance design can significantly enhance fire resistance of steel box bridge girders.