Research on the Law of Stress Development Along Backfi lling Process Between Crest and Valley of Buried Corrugated Steel Pipe Culverts

Baodong Liu,Haibo Sun,Weibo Xu,Yafei Shi,Beichen Zhang,Mengmeng Yao 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.1

Although buried corrugated steel pipe culverts have been studied intensively in the past decades, the stress development law between crest and valley during backfi lling process is still not analyzed suffi ciently, which is an important technical diffi culty for the construction of this kind of structures. In this paper, a three-dimensional fi nite element model (FEM) is developed to simulate the behavior of buried pipes during construction and the stress development law within a wavelength (curvature of corrugated pipe) ranging at the crown and the spring-line inside the pipe is proposed. Based on the measured stress data of a porous continuous corrugated steel plate pipe-arch culvert, the proposed three-dimensional FEM and stress development law are verifi ed. The results show that the stress variations in a wavelength range of corrugated steel plate are trigonometric curves. With the increase of the backfi lling height, the ratio of the stress at the crest or valley, to that of the spring-line is reduced, while the axial force is increased. The absolute value of the bending moment decays and the pipe culvert tends to be ring compression as the backfi lling height increased. The study verifi es the "ring compression theory" and the necessity of the minimum burial depth in design. Meanwhile, some design and construction guidelines which is necessary for the structure safety during backfi lling process are provided for buried corrugated steel pipe culverts.

Experimental Study on Flexural Behavior of Strengthened Corrugated Steel Plate

Baodong Liu,Fang Li,Haibo Sun,Zhihong Wang 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.1

Experimental study was conducted to verify the fl exural strength of corrugated steel plate (CSP) for various types of reinforcement which include without stiff ening ribs, with diff erent thicknesses of additional steel ribs, and with steel ribs fi lled with concrete. The test results showed that the fl exural strength of the strengthening structure of the additional steel plate using the same CSP as the main steel plate was more than 2 times that of the single CSP, and fl exural strength of the concrete-fi lled corrugated plates showed at least 3.3 times higher fl exural strength compared to the strength of single CSP. According to the force performance of the CSP strengthening structures, the nominal bearing capacity calculation formula was proposed. Specimens showed higher fl exural strength than the nominal fl exural capacity, indicating that the proposed formula of nominal fl exural strength can eff ectively evaluate the strength of strengthening structures. A fi nite element model was established in ABAQUS software to verify the feasibility of nonlinear fi nite element method analysis on CSP strengthening structures and the parameter analysis was carried out. The simulation results showed that the reinforcement ratio had a great infl uence on the bearing capacity of the strengthening structure, and the bolt spacing was second. the compressive strength of concrete was not a signifi cant improvement eff ect of the bearing capacity of concrete-encased corrugated stiff ener structure, and the strength of concrete can be negligible. The optimization suggestions were proposed for the strengthening structure concerning other factors such as bolt spacing and strengthening ratio.

Experimental Study of Rubber-Concrete-Filled CST Composite Column Under Axial Compression

Baodong Liu,Linlin Zhang,Mingyang Feng,Haibo Sun,Yankai Chai 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.1

Rubber concrete has been proposed to address the environmental challenges caused by waste tires and the shortage of natural aggregates worldwide; however, its strength and elastic modulus reduction hinder its wide application in structure members. This study proposes filling corrugated steel tubes with rubber concrete (RuCFCST) and using the non-uniform confinement provided by corrugated steel tubes (CSTs) to compensate for the loss in strength and elastic modulus of rubber concrete. We conducted monotonic axial compression tests on 12 tubular specimens to evaluate the effects of the steel tube type, loading mode, diameter-to-thickness ratio, and rubber concrete strength on the axial shortening behavior and strength. The test results confirmed the effectiveness of CST confinement in strengthening the axial behavior of rubber concrete and CST had a higher confinement efficiency than plain straight steel tubes. The strength and ductility indices of the specimens increased by 10% and 30%, respectively; however, the strength of the concrete core decreased by 38.4% owing to the incorporation of rubber particles. These results suggest that such columns can be used in infrastructure, such as in seismic bridge piers, mine roadway supports, and underground structural columns, where load-bearing capacity and ductility are required. The current specifications lack consistency in predicting the axial strength of RuCFCST columns and the results of our proposed modified formulas were in good agreement with the experimental data, and the formulas predicted the axial strength of piers well.

Experimental Study of the Mechanical Performance of Corrugated Steel Plate-Concrete Composite Structures

Baodong Liu,Zhenan Zhang,Minqiang Zhang,Xiaoxi Wang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3

This paper presents a comparative study on the composite structure of Corrugated Steel Plate (CSP) with normal and rubberized concrete. One CSP-normal-concrete plate and two CSP arch structures composited with diff erent concretes are established. A theoretical section-property deduction is derived, which demonstrated that the fl exural rigidity of such composite structure increased notably. Static and dynamic mechanical experiments are also conducted. Experimental results agree with expectations, and the measured results on plate structures verifi ed the eff ectiveness of the analytical and numerical solutions. Comparing the defl ection of two composite arches shows that the rubberized concrete composite arch has smaller fl exural and compressive stiff nesses, resulting in larger defl ection. The rubberized concrete composite arch has higher steel stress, lower concrete stress and better energy-dissipating capacity compared with the normal concrete composite arch. Therefore, the CSP-rubberized concrete composite structure is more suitable for anti-shock and earthquake-resistant structures.

Stress-related energy dissipation and damping model of concrete considering moisture content

Liu, Baodong,Zhang, Pengyuan,Lyu, Wenjuan Techno-Press 2022 Advances in concrete construction Vol.13 No.6

Although the influence of moisture content on the mechanical properties of concrete has been studied for a long time, research related to its influence on the damping and energy dissipation property of concrete structure is still very limited. In this paper, the relationship between damping property and moisture content of concrete using cyclic uniaxial compression is firstly presented, and the mechanism of the influence of moisture content on concrete damping and energy dissipation capacity is analyzed. Based on the experimental research, moisture-related damping and energy dissipation model is proposed. Results show that the dissipated energy of concrete and loss factor increase as the moisture content increasing. The energy dissipation coefficient reflecting the influence of stress level of concrete under cyclic load, decreases first and then increases as the moisture content increasing. The mechanism of moisture-related energy dissipation behavior can be divided into the reactive force of water, the development of the internal micro cracks and the pore water pressure. Finally, the proposed moisture-related damping and energy dissipation model are verified.

Identification of the Jiles-Atherton Model Parameters Using Simulated Annealing Method

Bai, Baodong,Wang, Jiayin Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.2

This paper presents a method and the experimental measurement system for the determination of Jiles-Atherton model parameters of the 30ZH120 electrical steel sheet. The paper utilizes Epstein Square devices to proceed with the experiment and measurement on a group of hysteresis loops of some certain transformers which use the 30ZH120 electrical steel sheet under two different lap ways. The approach relies on the simulated annealing optimization method in order to minimize the error between the measured and modeled hysteresis curves and yield the best five Jiles-Atherton model parameters. A convenient program, based on the Simulink platform, that can identify the J-A model parameters automatically from the experimental saturated hysteresis loop which is used to model the nonlinear characteristics of the electrical steel sheet, is developed. Research shows that the simulated annealing optimization method gets satisfactory results.

Long-term development of compressive strength and elastic modulus of concrete

Shuzhen Yang,Baodong Liu,Mingzhe Yang,Yuzhong Li 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.2

Compressive strength and elastic modulus of concrete are constantly changing with age. In order to determine long-term development of compressive strength and elastic modulus of concrete, an investigation of C30 concrete cured in air conditions was carried out. Changes of compressive strength and elastic modulus up to 975 days were given. The results indicated that compressive strength and elastic modulus of concrete rapidly increased with age during the initial 150 days and then increased slowly. The gain in elastic modulus was slower than that of compressive strength. Then relationships of time-compressive strength, time-elastic modulus and compressive strength-elastic modulus were proposed by regression analysis and compared with other investigations. The trends of time-compressive strength and time-elastic modulus with age agreed best with ACI 209R-92. Finally, factors contributed to long-term development of compressive strength and elastic modulus of concrete were proposed and briefly analyzed.

Vector Control of Permanent Magnet Synchronous Motor by Using Single Current Sensor

Shixiao Li,Baodong Bai,Dezhi Chen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

In recent years, with the continuous updating of power electronic devices, mathematical signal processors and high-quality rare earth permanent magnet materials, permanent magnet AC servo systems have been widely used. And modern permanent magnet synchronous motors mostly use closed-loop vector control drive systems, which need to detect the rotor position and phase winding current value in real time. However, the excess number of sensors increases the cost of the drive system and is not conducive to improving the reliability of the system. In this paper, the improved current reconstruction technology and SMO-based position sensorless control technology are combined to realize the vector control of permanent magnet synchronous motor by using single current. Current reconstruction is achieved by measuring only the voltage source inverter DC link current.

Hopf bifurcation in numerical approximation of the sunflower equation

Chunrui Zhang,Baodong Zheng 한국전산응용수학회 2006 Journal of applied mathematics & informatics Vol.22 No.1-2

In this paper we consider the numerical solution of the sun- flower equation. We prove that if the sunflower equation has a Hopf bifurcation point at a = a0, then the numerical solution with the Euler-method of the equation has a Hopf bifurcation point at ah = a0 + O(h).

Effects of environmental temperature and age on the elastic modulus of concrete

Shuzhen Yang,Baodong Liu,Yuzhong Li,Minqiang Zhang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.6

Concrete mechanical properties change constantly with age, temperature, humidity and the other environmental factors. This research studies the effects of temperature and age on the development of concrete elastic modulus by a series of prism specimens. Elastic modulus test was conducted at various temperatures and ages in the laboratory to examine the effects of temperature and age on it. The experimental results reveal that the concrete elastic modulus decreases with the rise of temperature but increases with age. Then, a temperature coefficient K is proposed to describe the effects of temperature and validated by existing studies. Finally, on the basis of K, analytical models are proposed to determine the elastic modulus of concrete at a given temperature and age. The proposed models can offer designers an approach to obtain more accurate properties of concrete structures through the elastic modulus modification based on actual age and temperature, rather than using a value merely based on laboratory testing.