On the mechanism of vertical stabilizer plates for improving aerodynamic stability of bridges

Airong Chen,Zhiyong Zhou,Haifan Xiang 한국풍공학회 2006 Wind and Structures, An International Journal (WAS Vol.9 No.1

On the mechanism of vertical stabilizer plates for improving aerodynamic stability of bridges

Chen, Airong,Zhou, Zhiyong,Xiang, Haifan Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.1

Vertical stabilizer plates have been found to be an effective aerodynamic measure to improve the aerodynamic stability of bridges either with an open cross section or with a streamlined box cross section in wind tunnel testings and have been adopted in some long span bridges. By taking an open deck II-shaped section and a closed box section as examples, the mechanism of vertical stabilizer plates for improving aerodynamic stability are investigated by using numerical simulation based on Random Vortex Method. It is found that vertical stabilizer plates can increase the amplitude of the heaving motion, and decrease that of the rotational motion of the bridge decks.

Effect of high-strength concrete on shear behavior of dry joints in precast concrete segmental bridges

Airong Liu,Haibo Jiang,Ying Chen,Tianlong Wang,Zhuangcheng Fang 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.5

The use of high-strength concrete (HSC) in precast concrete segmental bridges (PCSBs) can minimize the superstructure geometry and reduce beam weight, which can accelerate the construction speed. Dry joints between the segments in PCSBs introduce discontinuity and require special attention in design and construction. Cracks in dry joints initiate more easily than those in epoxy joints in construction period or in service. Due to the higher rupture strength of HSC, the higher cracking resistance can be achieved. In this study, shear behavior of dry joints in PCSBs was investigated by experiments, especially focusing on cracking resistance and shear strength of HSC dry joints. It can be concluded that the use of HSC can improve the cracking resistance, shear strength, and ductility of monolithic, single-keyed and three-keyed specimens. The experimental results obtained from tests were compared with the AASHTO 2003 design provisions. The AASHTO 2003 provision underestimates the shear capacity of single-keyed dry joint C50 and C70 HSC specimens, underestimates the shear strength of three-keyed dry joint C70 HSC specimens, and overestimates the shear capacity of three-keyed dry joint C50 HSC specimens.

Coupled buffeting response analysis of long-span bridges by the CQC approach

Ding, Quanshun,Chen, Airong,Xiang, Haifan Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.5

Based on the modal coordinates of the structure, a finite-element and CQC (complete quadratic combination) method for analyzing the coupled buffeting response of long-span bridges is presented. The formulation of nodal equivalent aerodynamic buffeting forces is derived based on a reasonable assumption. The power spectral density and variance of nodal displacements and elemental internal forces of the bridge structure are computed using the finite-element method and the random vibration theory. The method presented is very efficient and can consider the arbitrary spectrum and spatial coherence of natural winds and the multimode and intermode effects on the buffeting responses of bridge structures. A coupled buffeting analysis of the Jiangyin Yangtse River Suspension Bridge with 1385 in main span is performed as an example. The results analyzed show that the multimode and intermode effects on the buffeting response of the bridge deck are quite remarkable.

A state space method for coupled flutter analysis of long-span bridges

Ding, Quanshun,Chen, Airong,Xiang, Haifan Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.4

A state-space method is proposed to analyze the aerodynamically coupled flutter problems of long-span bridges based on the modal coordinates of structure. The theory about complex modes is applied in this paper. The general governing equation of the system is converted into a complex standard characteristic equation in a state space format, which contains only two variables. The proposed method is a single-parameter searching method about reduced velocity, and it need not choose the participating modes beforehand and has no requirement for the form of structure damping matrix. The information about variations of system characteristics with reduced velocity and wind velocity can be provided. The method is able to find automatically the lowest critical flutter velocity and give relative amplitudes, phases and energy ratios of the participating modes in the flutter motion. Moreover, the flutter analysis of Jiangyin Yangtse suspension bridge with 1385 m main span is performed. The proposed method has proved reliable in its methodology and efficient in its use.

Vehicle-induced aerodynamic loads on highway sound barriers part 2: numerical and theoretical investigation

Dalei Wang,Airong Chen,Benjin Wang 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.17 No.5

The vehicle-induced aerodynamic loads bring vibrations to some of the highway sound barriers, for they are designed in consideration of natural wind loads only. As references to the previous field experiment, the vehicle-induced aerodynamic loads is investigated by numerical and theoretical methodologies. The numerical results are compared to the experimental one and proved to be available. By analyzing the flow field achieved in the numerical simulation, the potential flow is proved to be the main source of both head and wake impact, so the theoretical model is also validated. The results from the two methodologies show that the shorter vehicle length would produce larger negative pressure peak as the head impact and wake impact overlapping with each other, and together with the fast speed, it would lead to a wake without vortex shedding, which makes the potential hypothesis more accurate. It also proves the expectation in vehicle-induced aerodynamic loads on Highway Sound Barriers Part1: Field Experiment, that max/min pressure is proportional to the square of vehicle speed and inverse square of separation distance.

Research on the probability model of basic wind speed estimation in China

Cheng Xiang,Airong Chen,Qiheng Li,Rujin Ma 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.6

Wind speed is one of the most critical parameters in predicting structural performance under wind effects. In most of the current standards and codes, the design reference wind speed is usually determined by fitting a typical probability distribution model based on the historical wind speed data. However, a single distribution model is generally insufficient to reflect the regional differences in wind characteristics. Therefore, in this research, the optimal probability is selected to determine the extreme wind speed in different regions in China based on the fourth-order linear moment method (FLMM). Firstly, several probability models for estimating extreme wind speed distribution are introduced. Then, the optimal model, as well as the relative parameters, are determined by the linear moments (L-moments) method, and the one with the minimum value of the fourth-order linear moment between the probability model and the sample is taken as the optimal distribution. Finally, the extreme wind speed of each meteorological station is estimated according to the obtained optimal distribution, and the results are compared with the recorded extreme wind speed of typical metrological stations as well as that in the previous version of specification (JTG/T D60-01-2004). Compared with the traditional method that adopting a single distribution model-based wind speed estimation, the extreme wind speed obtained by the proposed method possessed higher accuracy.

Numerical simulation approach for structural capacity of corroded reinforced concrete bridge

Zhou, Xuhong,Tu, Xi,Chen, Airong,Wang, Yuqian Techno-Press 2019 Advances in concrete construction Vol.7 No.1

A comprehensive assessing approach for durability of reinforced concrete structures dealing with the corrosion process of rebar subjected to the attack of aggressive agent from environment was proposed in this paper. Corrosion of rebar was suggested in the form of combination of global corrosion and pitting. Firstly, for the purposed of considering the influence of rebar's radius, a type of Plane Corrosion Model (PCM) based on uniform corrosion of rebar was introduced. By means of FE simulation approach, global corrosion process of rebar regarding PCM and LCM (Linear Corrosion Model) was regressed and compared according to the data from Laboratoire $Mat{\acute{e}}riaux$ et $Durabilit{\acute{e}}$ des Constructions (LMDC). Secondly, pitting factor model of rebar in general descend law with corrosion degree was introduced in terms of existing experimental data. Finally, with the comprehensive numerical simulation, the durability of an existing arch bridge was studied in depth in deterministic way, including diffusion process and sectional strength of typical cross section of arch, crossbeam and deck slab. Evolution of structural capacity considering life-cycle rehabilitation strategy indicated the degradation law of durability of reinforced arch bridges.

Chloride diffusivity of concrete: probabilistic characteristics at meso-scale

Zichao Pan,Xin Ruan,Airong Chen 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.13 No.2

This paper mainly discusses the influence of the aggregate properties including grading, shape, content and distribution on the chloride diffusion coefficient, as well as the initiation time of steel corrosion from a probabilistic point of view. Towards this goal, a simulation method of random aggregate structure (RAS) based on elliptical particles and a procedure of finite element analysis (FEA) at meso-scale are firstly developed to perform the analysis. Next, the chloride diffusion coefficient ratio between concrete and cement paste ??app??cp is chosen as the index to represent the effect of aggregates on the chloride diffusion process. Identification of the random distribution of this index demonstrates that it can be viewed as actually having a normal distribution. After that, the effect of aggregates on ??app??cp is comprehensively studied, showing that the appropriate properties of aggregates should be decided by both of the average and the deviation of ??app??cp . Finally, a case study is conducted to demonstrate the application of this mesoscopic method in predicting the initiation time of steel corrosion in reinforced concrete (RC) structures. The mesoscopic probabilistic method developed in this paper can not only provide more reliable evidences on the proper grading and shape of aggregates, but also play an important role in the probability-based design method.

Mechanical Behavior and Analysis of Composite Bridges with Corrugated Steel Webs: State-of-the-Art

Jun He,Yuqing Liu,Airong Chen,Teruhiko Yoda 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.3

The composite bridges with corrugated steel webs have excellent properties, such as lightness of girders, efficiency of introducing prestress forces, short construction period, optimum force distribution, good seismic performance, and aesthetics appearance etc., which have greatly promoted the application of such bridges. The objective of this paper is to provide and summarize important references related to the analysis, design and construction of composite bridges with corrugated steel webs. Subjects discussed in this review include (1) structural configuration and application; (2) shear behavior; (3) bending behavior; (4) torsional behavior; (5) patch loading resistance; (6) dynamic behavior; (7) long-term behaviors including fatigue and creep; (8) component connections; (9) analysis method and theory; (10) new concept application. The literature survey presented herein mainly focuses on papers written in English, Japanese, German and Chinese in relation to composite bridges with corrugated steel webs.