Static performance of a new GFRP–metal string truss bridge subjected to unsymmetrical loads

Dongdong Zhang,Jiaxin Yuan,Qilin Zhao,Feng Li,Yifeng Gao,Ruijie Zhu,Zhiqin Zhao 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.5

A unique lightweight string truss deployable bridge assembled by thin-walled fiber reinforced polymer (FRP) and metal profiles was designed for emergency applications. As a new structure, investigations into the static structural performance under the serviceability limit state are desired for examining the structural integrity of the developed bridge when subjected to unsymmetrical loadings characterized by combined torsion and bending. In this study, a full-scale experimental inspection was conducted on a fabricated bridge, and the combined flexural–torsional behavior was examined in terms of displacement and strains. The experimental structure showed favorable strength and rigidity performances to function as deployable bridge under unsymmetrical loading conditions and should be designed in accordance with the stiffness criterion, the same as that under symmetrical loads. In addition, a finite element model (FEM) with a simple modeling process, which considered the multi segments of the FRP members and realistic nodal stiffness of the complex unique hybrid nodal joints, was constructed and compared against experiments, demonstrating good agreement. A FEM-based numerical analysis was thereafter performed to explore the effect of the change in elastic modulus of different FRP elements on the static deformation of the bridge. The results confirmed that the change in elastic modulus of different types of FRP element members caused remarkable differences on the bending and torsional stiffness of the hybrid bridge. The global stiffness of such a unique bridge can be significantly enhanced by redesigning the critical lower string pull bars using designable FRP profiles with high elastic modulus.

Experimental and Theoretical Study of the Torsional Mechanism of a Hybrid FRP-aluminum Triangular Deck-truss Structure

Dongdong Zhang,Qilin Zhao,Fei Li,Feng Li 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.6

This paper investigates the torsional mechanism of a hybrid FRP-aluminum triangular deck-truss structure composed of modular structural units. A pure torsion test was conducted on a 6-m cantilever specimen to characterize the structural responses. Based on the experimental results and structural layout, a simplified analytical model is established to predict the torsional stiffness of the hybrid triangular deck-truss structure. The derivation procedures and formulae are experimentally calibrated, finding that the formulae can be conveniently used with satisfactory accuracy. It is ultimately confirmed that the torsional center of the entire triangular truss collocates with the center of the orthotropic deck. The external torsional moment is primarily resisted by the FRP lower chords and the aluminum longitudinal beams, particularly for the FRP lower chords which should be given a great consideration in the torsion design.

Finite Element Model Methodology for Asphalt-coated Anchor used in Underground Main Powerhouse Anchored-on-rock Crane Girder

Dongdong Li,Ming Xiao,Juntao Chen,Jian Zhao 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.6

Uncoated or grout-coated rock anchoring systems are used in underground engineering to increase the carrying capacity of surrounding rock. 3D modeling has been used to simulate grout-coated anchor characteristics, but for less common coatings, e.g., asphalt, existing Finite Element (FE) models contain too many nodes and elements to be computationally efficient. Using AutoCAD and OpenGL visual FE modeling, a methodology is proposed for asphalt element generation in FE models; FORTRAN is used to rewrite the model file information and reduce the number of model elements and nodes while boosting modeling and computational efficiency. Implicit lever and column elements are introduced to simulate anchors with and without asphalt coatings, respectively, and appropriate stiffness matrices and iterative FE calculation formulas are derived. The resulting FE model is used to simulate the anchoring system. Results show that the asphalt coating technique reduces the surrounding rock wall’s damage zone and increases anchor stresses inside deep rock masses. This can improve the rock mass mechanical characteristics near the anchors and increase the stabilities of the surrounding rock and the safety crane girder. The proposed calculation and grid re-meshing method shows good adaptability and practicality, and can serve as a reference for similar FE analysis processes.

Migration of Alkali and Alkaline Earth Metallic Species and Structure Analysis of Sawdust Pyrolysis Biochar

( Yijun Zhao ),( Dongdong Feng ),( Yu Zhang ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.5

In order to resolve the AAEM species migration routes and the interaction relationship between biochar structure and AAEM species during biomass pyrolysis, experiments were performed in an entrained flow reactor with N2 at 500~900 oC. ICP-AES, XPS and SEM-EDX were used to examine content and distribution of AAEM species and the physicochemical structures of biochar. The results show that at 500~700 °C, the precipitation rate of AAEM species is relatively high. At high temperature (>700 °C), the AAEM species continue to migrate from interior to exterior, but little precipitation from biochar surface. And the migration of AAEM species is mainly realized by the C-O bond as the carrier medium. The AAEM species on biochar surface are mainly Na, Mg and Ca (<700 °C), while changing to K, Mg and Ca (≥700 °C). From 500 °C to 900 °C, the biochar particle morphology gradually changes from fibers to porous structures, finally to molten particles. At 700~900 °C, Ca element is obviously enriched on the molten edge of the biochar porous structures.

Memetic Two-echelon Vehicle Routing Optimization Based on Q Learning Theory and Differential Evolution Algorithm

Liu Dongdong,Liu Kai,Wang Feng,Han Bo,Zhao Zhengping,Tan Fuxiao,Niu Lei 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.8

In allusion to such problems as low accuracy and long convergence time in traditional two-echelon vehicle routing optimization algorithm, a Memetic algorithm (QDEMA) based on Q learning theory and differential evolution is proposed in this article to solve above problems. Firstly, it is necessary to research the two-echelon vehicle routing optimization problem and adopt the optimal segmentation method to obtain the relatively reasonable distribution plan for the first-echelon SDVRP problem in order to accordingly determine the distribution quantity of the transfer stations; secondly, the second-echelon MDVRP distribution scheme is solved to obtain the total distance and the total number of the distribution vehicles for the two-echelon optimization problem; thirdly, in allusion to the solution of the second-echelon MDVRP distribution scheme, Q learning theory and the differential evaluation algorithm are adopted to design new Memetic algorithm in order to globally optimize MDVRP distribution scheme; finally, the simulation experiment is carried out to verify the algorithm effectiveness.

Discrete Particle Swarm Optimization Algorithm in Flexible Hybrid Flow Shop Scheduling

Liu Dongdong,Liu Kai,Zhao Zhengping Han Bo,Zhang Yan 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.10

Traditional flexible flow shop scheduling cannot adapt to the work processes with existence of parallel machines, and blocks or limits the processes with no-wait constraints. Firstly, according to the problem in NWBFFSSP, which minimizes the maximum time used in the flow shop, an optimal solving model has been designed to realize the flexible flow shop scheduling with multi constraints; besides, for the distribution of machinery is improved, Finally, in the solving process, a real-time release priority strategy has been proposed to determine processing machine for each work piece. Furthermore, a methodology to detect work piece conflicts has been introduced while the conflicts are then eliminated by a kind of right moving strategy based on the maximum difference. The experimental results verify the effectiveness and feasibility of the proposed algorithm.

Structural Evaluation of Torsional Rigidity of New FRP–Aluminum Space Truss Bridge with Rigid Transverse Braces

Le Zhu,Dongdong Zhang,Fei Shao,Qian Xu,Qilin Zhao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.7

A unique fiber-reinforced polymer (FRP)–aluminum spatial truss structure with upper I-type, transverse beam braces was developed for deployable bridging, yielding the operational advantages of bestraddled erection bridges. Experimental testing and numerical simulation were performed to evaluate the torsional rigidity of a fabricated cantilever, full-scale experimental structure. The predictions obtained based on a computational finite element model were strongly consistent with the experimental results. Moreover, a numerical decomposition and reconstruction procedure was employed to understand the load-bearing mechanism of the structure. The results demonstrated that the improved transverse braces possessed adequate capacity for providing sufficient rigidity and lateral stability to the complete twin-treadway structure under torsion. The torsional center of the improved structure was located at the axis of symmetry of the twin-treadway bridge deck. The representative torsional rigidity of the twin-treadway module was approximately 87.5 kN·m2/degree. Compared to the original construction, the improved structure exhibited only minor discrepancies regarding the torsional rigidity, and consistent characteristics in terms of the load-bearing mechanism. The torsional rigidity of the improved twin-treadway structure was primarily generated by the vertical bending rigidities of its two parallel single treadways through the rigid transverse braces. This significant finding specifically pertains to the unique twin-treadway hybrid bridge. The results presented in this work are expected to provide valuable insights, which could, in turn, lead to further the development of similar lightweight structural systems.

Time-Delay and Amplitude Modified BP Imaging Algorithm of Multiple Targets for UWB Through-the-Wall Radar Imaging

( Huamei Zhang ),( Dongdong Li ),( Jinlong Zhao ),( Haitao Wang ) 한국정보처리학회 2017 Journal of information processing systems Vol.13 No.4

In order to solve the undetected probability of multiple targets in ultra-wideband (UWB) through-the-wall radar imaging (TWRI), a time-delay and amplitude modified back projection (BP) algorithm is proposed. The refraction point is found by Fermat`s principle in the presence of a wall, and the time-delay is correctly compensated. On this basis, transmission loss of the electromagnetic wave, the absorption loss of the refraction wave, and the diffusion loss of the spherical wave are analyzed in detail. Amplitude compensation is deduced and tested on a model with a single-layer wall. The simulating results by finite difference time domain (FDTD) show that it is effective in increasing the scattering intensity of the targets behind the wall. Compensation for the diffusion loss in the spherical wave also plays a main role. Additionally, the two-layer wall model is simulated. Then, the calculating time and the imaging quality are compared between a singlelayer wall model and a two-layer wall model. The results illustrate the performance of the time-delay and amplitude-modified BP algorithm with multiple targets and multiple-layer walls of UWB TWRI.

Simultaneous desulfurization and denitrogenation of model fuels by polyethylene glycol-modified resorcinol/formaldehyde resin-derived carbon spheres

Jie Wen,Dongdong Zhao,Yingying Lu,Jing Huang,Yanping Li,Hui Zhang,Airong Li 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.7

A series of resorcinol/formaldehyde (RF) resin-derived carbon spheres modified by polyethylene glycol (PEG) were prepared. The effects of PEG addition time during hydrothermal treatment and molecular weight on the pore structure, surface acidic groups, particle size, and adsorption performances of the obtained spherical activated carbons were investigated. Two types of model fuel containing indole, quinoline, and dibenzothiophene (DBT) as target adsorbates were prepared to evaluate the adsorption performances of the spheres, which increased in the order of DBT<quinoline<indole. Hydrogen bonding may be critical in the removal of indole. Both the surface area and oxygen- containing functional groups influenced the adsorption capacity, with the latter significantly influenced by PEG addition time. PEG addition during the RF resin cross-linking stage sharply reduced the total concentration of acidic groups on the carbon sphere surfaces. The adsorption thermodynamics and kinetics of nitrogen and sulfur compounds were also investigated. The adsorption isotherms of all S/N species were of the Freundlich type at 25 oC. The pseudo-second-order rate equation well described the adsorption kinetics. Both external diffusion and intra-particle diffusion controlled the rate of adsorption.

Time-Delay and Amplitude Modified BP Imaging Algorithm of Multiple Targets for UWB Through-the-Wall Radar Imaging

Zhang, Huamei,Li, Dongdong,Zhao, Jinlong,Wang, Haitao Korea Information Processing Society 2017 Journal of information processing systems Vol.13 No.4

In order to solve the undetected probability of multiple targets in ultra-wideband (UWB) through-the-wall radar imaging (TWRI), a time-delay and amplitude modified back projection (BP) algorithm is proposed. The refraction point is found by Fermat's principle in the presence of a wall, and the time-delay is correctly compensated. On this basis, transmission loss of the electromagnetic wave, the absorption loss of the refraction wave, and the diffusion loss of the spherical wave are analyzed in detail. Amplitude compensation is deduced and tested on a model with a single-layer wall. The simulating results by finite difference time domain (FDTD) show that it is effective in increasing the scattering intensity of the targets behind the wall. Compensation for the diffusion loss in the spherical wave also plays a main role. Additionally, the two-layer wall model is simulated. Then, the calculating time and the imaging quality are compared between a single-layer wall model and a two-layer wall model. The results illustrate the performance of the time-delay and amplitude-modified BP algorithm with multiple targets and multiple-layer walls of UWB TWRI.