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7th Asia-Pacific Conference on FRP in structures, APFIS 2019

作者： Fabbri, M. Yu, Q.Q. Gao, R.X. Key Laboratory of Performance Evolution and Control for Engineering Structures Ministry of Education Tongji University Shanghai200092 China Department of Structural Engineering Tongji University Shanghai200092 China Department of Architecture University of Bologna Ravenna48121 Italy

ISBN: (纸本)9780648752899

Carbon fibre-reinforced polymer (CFRP) materials have high strength-to-weight ratio, good resistance to fatigue and corrosion, and ease of installation, which is demonstrated great potential in fatigue strengthening of defected steel components. Currently, much research has been performed to investigate the effect of environmental attack on the CFRP strengthening system. However, in most studies, the specimens were first well cured in room condition for two weeks and then placed in harsh conditions. The potential risk of the exposure at the curing stage of the adhesive has not been well understood. This paper presents an experimental study on the fatigue behaviour of CFRP strengthened steel plates. The specimens were exposed to marine atmosphere for 6 weeks and tested by fatigue loading, with special focus on the influence during the curing stage of the structural epoxy. This study extends the understanding of the environmental durability of CFRP bonded steel plates and provides some useful suggestions for the strengthening technique. © APFIS 2019. All right reserved.

关键词： Fatigue of materials

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Investigation of gold mine tailings as supplementary cementitious material: performance and carbon footprint

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Journal of Cleaner Production 2025年 518卷

作者： Zhao, Zengfeng Ji, Chenyuan Wang, Jin Zhu, Lei Wang, Dongxing Tošić, Nikola Department of Structural Engineering College of Civil Engineering Tongji University Shanghai200092 China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai200092 China Huludao Bajia Mining Co. Ltd Huludao125000 China Department of Geological Resource and Geological Engineering College of Geosciences China University of Petroleum Beijing102249 China School of Civil Engineering Wuhan University Wuhan430072 China Civil and Environmental Engineering Department Universitat Politècnica de Catalunya Barcelona08034 Spain

This study investigates the potential of using gold mining tailing sludge to produce low-carbon mortar through physical grinding and calcination treatments. Tailing sludge was ground for 20 min to produce tailing powder (WKN), which was then calcined at 750 °C to obtain calcined tailing powder (CWKN). The effects of substituting cement with WKN and CWKN on the workability, strength, and durability of mortar were evaluated. Results show the density of mortar decreases with increase of tailing substitution rate. The CWKN-based mortar requires higher water demand (additional superplasticizer was used to ensure similar flowability) and increase the density of mortar at fresh state compared to the WKN-based mortar. Using WKN significantly reduces the compressive strength of mortar after 28 days (with a 43.9 % drop at 30 % replacement). In contrast, CWKN exhibits pozzolanic activity, with only a 9 % strength reduction at 20 % substitution compared with the reference one (a 34.4 % strength improvement over the case of WKN). CWKN-based mortar has a higher electric flux and carbonation depth, which is due to higher reactivity of CWKN than that of WKN. Life cycle assessment indicates that 30 % WKN reduces CO2 emissions by 156.7 kg/m3, while 20 % CWKN achieves the best unit strength carbon emission, reducing emissions by 1.05 kg CO2-eq./m3/MPa compared to pure cement-based mortar. The study highlights that the aluminum content in mortar significantly affects its properties, which is due to the formation of calcium-aluminate-silicate-hydrate gels. This study demonstrates that recycling gold tailings sludge can effectively address industrial waste issues while significantly reducing carbon emissions of mortars. © 2025 Elsevier Ltd

关键词： Compressive strength

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Transport properties of p-type CaMg_(2)Bi_(2) thermoelectrics

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Journal of Materiomics 2019年第4期5卷 567-573页

作者： Cheng Sun Xuemin Shi Liangtao Zheng Bo Chen Wen Li Interdisciplinary Materials Research Center School of Materials Science and EngineeringTongji Univ.4800 Caoan Rd.Shanghai201804China School of Materials Science and Engineering Tongji Univ.4800 Caoan Rd.Shanghai201804China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji Univ.1239 Siping Rd.Shanghai200092China

Due to the complex crystal structure for low lattice thermal conductivity and the tunable valence bands for superior electronic performance,CaAl_(2)Si_(2)-structured AB_(2)C_(2) Zintl compounds have been frequently proven as promising p-type thermoelectric *** this work,thermoelectric properties of CaMg_(2)Bi_(2) are systematically investigated in a broad carrier concentration(10^(18)-10^(20) cm^(-3))through Agdoping for comprehensively evaluating its potential for thermoelectric *** broad carrier concentration enables a well assessment of the carrier transport properties by single parabolic band with acoustic phonon scattering and a revelation of the carrier transport by multiple valence orbitals when the carrier concentration higher than ~2×10^(19) cm^(-3),leading to a significant enhancement in electronic *** the help of additional point defect phonon scattering introduced by BaMg_(2)Bi_(2)-alloying,a reduction in lattice thermal conductivity in the entire temperature range and the lowest one of ~0.7 W/m-K are achieved,leading to a 100% enhancement in average *** addition to the contribution of a multiband *** work not only demonstrates CaMg_(2)Bi_(2) as a promising thermoelectric material,but also provides a well understanding of its underlying material physics.

关键词： Thermoelectric CaMg_(2)Bi_(2) Carrier concentration Band manipulation

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Experimental and numerical study of macro-cell corrosion between crossed steel bars 6

Experimental and numerical study of macro-cell corrosion bet...

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6th International Conference on Durability of Concrete structures, ICDCS 2018

作者： Dong, Z. Gu, X.L. Jin, Z.H. Key Laboratory of Performance Evolution and Control for Engineering Structures Ministry of Education College of Civil Engineering Tongji University Shanghai China

ISBN: (纸本)1849953945

Reinforcing steel bars embedded in concrete are always intersected with each other to form rebar mesh or three-dimensional steel cage. The present study aims to investigate the phenomenon of severe corrosion observed at stirrups or some intersections of steel rebar mesh, which has not been well studied before. Macrocell corrosion between crossed steel bars was considered to be the major cause for this phenomenon. In this regard, crossed steel bars were divided into intersected zone (IZ) and non-intersected zone (NIZ). The macrocell current at the face-to-face IZ was calculated by Ohm's law. A one-dimensional model based on transmission line method was employed to obtain the distribution of macro-cell current on the NIZ juxtaposed to the IZ. Experiments of steel bars in aqueous solutions and concrete were undertaken to verify the numerical model. The results demonstrated a good match between experiments and numerical model. It was also shown that the distribution of macro-cell current on the non-intersected areas was influenced by the resistivity of electrolyte. Based on the corrosion rate model presented in this study, the severe corrosion observed at stirrups or some intersection zones of rebar mesh can be explained and quantified. © ICDCS 2018. All rights reserved.

关键词： Concrete buildings

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Model uncertainty of externally bonded CFRP-to-steel joints 9

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9th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil engineering, CICE 2018

作者： Yu, Q.Q. Zhang, D.M. Gu, X.L. Huang, H.W. Key Laboratory of Performance Evolution and Control for Engineering Structures Ministry of Education China Tongji University Department of Structural Engineering China

ISBN: (纸本)9780000000002

This paper presents a study of the model factor Ε for bond strength model of carbon fibre-reinforced polymer (CFRP)-to-steel joints, which is defined as the ratio of tested bond strength to the predicted result by the models. A total of 402 single/double-lap shear tests of externally-bonded joints were collected to evaluate the statistics of Ε and two frequently used models in literature were compared. Specimens with cohesive failure, adhesion failure, CFRP delamination as well as combined failure were included. The statistics of Ε indicate a high level of both the mean value and coefficient of variation (COV). It was found that the model factors of the models with a relatively high COV value (larger than 0.3) were not random, but heavily dependent on the input parameters. © INTER-NOISE 2019 MADRID - 48th International Congress and Exhibition on Noise control engineering. All rights reserved.

关键词： Uncertainty analysis

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Data-driven parametric design of additively manufactured hybrid lattice structure for stiffness and wide-band damping performance

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Additive Manufacturing Frontiers 2025年第2期4卷

作者： Li, Chenyang Yuan, Shangqin Zhang, Han Li, Shaoying Li, Xinyue Zhu, Jihong State IJR Center of Aerospace Design and Additive Manufacturing School of Mechanical Engineering Northwestern Polytechnical University Xi'an 710072 China Key Laboratory of Metal High-Performance Additive Manufacturing and Innovative Design MIIT China Northwestern Polytechnical University Xi'an 710072 China Institute of Intelligence Material and Structure Unmanned System Research Institute Northwestern Polytechnical University Xi'an 710072 China Aircraft Strength Research Institute of China Xi'an 710065 China Modern Control Technology Research Institute Xi'an 710065 China

The outstanding comprehensive mechanical properties of newly developed hybrid lattice structures make them useful in engineering applications for bearing multiple mechanical loads. Additive-manufacturing technologies make it possible to fabricate these highly spatially programmable structures and greatly enhance the freedom in their design. However, traditional analytical methods do not sufficiently reflect the actual vibration-damping mechanism of lattice structures and are limited by their high computational cost. In this study, a hybrid lattice structure consisting of various cells was designed based on quasi-static and vibration experiments. Subsequently, a novel parametric design method based on a data-driven approach was developed for hybrid lattices with engineered properties. The response surface method was adopted to define the sensitive optimization target. A prediction model for the lattice geometric parameters and vibration properties was established using a backpropagation neural network. Then, it was integrated into the genetic algorithm to create the optimal hybrid lattice with varying geometric features and the required wide-band vibration-damping characteristics. Validation experiments were conducted, demonstrating that the optimized hybrid lattice can achieve the target properties. In addition, the data-driven parametric design method can reduce computation time and be widely applied to complex structural designs when analytical and empirical solutions are unavailable. © 2025 The Author(s)

关键词： Data-driven Hybrid lattice structure Machine-learning method Wide-band damping

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How does the control logic influence the establishment of a data-driven chiller model?

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Journal of Physics: Conference Series 2021年第1期2006卷

作者： Shunian Qiu Zhenhai Li Ruikai He Jiajie Li Zhengwei Li School of Mechanical Engineering Tongji University Shanghai Shanghai 201804 China China Academy of Building Research Beijing Beijing 100013 China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai Shanghai 201804 China

The modelling of chiller performance is critical for chiller optimal control, and fault detection and diagnosis (FDD). Different kinds of chiller models including sophisticated mechanistic models (white-box models), purely data-driven models (black-box models like artificial neural networks, ANN), and semi-physical models (grey-box models like empirical equations) have been proposed and tested. Due to the development of machine learning techniques, data-driven models have become more popular recently. The performance of the established data-driven model (accuracy, robustness, generalization) could significantly affect the model application. To enhance the model performance, a lot of studies have been carried out on investigating and modifying the model structure. However, the influence of the data quality on model training has not been sufficiently studied. When adopting historical data to train models, the data distribution is highly correlated to the control logic. So how does the control logic influence the establishment of data-driven chiller models by affecting the data distribution? In this study, experiments are conducted on an air-cooled chiller under model-free stochastic control to acquire rich and variable operational dataset; then the dataset is grouped into three corresponding to different chiller control logics. Finally, three models trained by three training datasets are evaluated, and the results suggest that when establishing data-driven chiller models, preliminary stochastic operation is cost-effective to acquire rich data for robust chiller modelling.

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Bond Behavior Between Seawater Sea-sand Recycled Aggregate Concrete and Glass-Fiber-Reinforced Polymer Bars

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Tongji Daxue Xuebao/Journal of Tongji University 2018年第7期46卷 884-890and971页

作者： Xiao, Jianzhuang Liao, Qingxiang Zhang, Qingtian Qiang, Chengbing Liu, Xian College of Civil Engineering Tongji University Shanghai200092 China Key Laboratory of Performance Evolution and Control for Engineering Structures Ministry of Education Tongji University Shanghai200092 China

The standard cube pull-out tests were conducted to study the bond behavior between the ribbed glass-fiber-reinforced polymer (GFRP) bars and concrete made with different raw materials and different strengths. The results showed that the use of recycled coarse aggregate (RCA) decreased the bond strength while seawater sea-sand (SS) had nominal effect on that of concrete. Different concretes shared similar bond stress-slip curve. Similar with natural aggregate concrete (NAC), the bond strength between seawater sea-sand recycled aggregate concrete (SSRAC) and the ribbed GFRP bars improved with the increase of compressive strength of concrete. Furthermore, four bond stress-slip models were selected to fit the experimental curves and the results showed that all the four models fitted the experimental curves well and the model proposed by Malvar had the highest coefficient of determination. © 2018, Editorial Department of Journal of Tongji University. All right reserved.

关键词： Compressive strength

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Experiment and Analysis of Thermal Conductivity of Marine Concrete with Different Composition

Experiment and Analysis of Thermal Conductivity of Marine Co...

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作者： Qingzhang Zhang Shuanzhu Tian Kangzong Li Zhongyuan Li College of Civil Engineering and Architecture Henan University of Technology Key Laboratory of Performance Evolution and Control for Engineering Structures(Tongji University) Ministry of Education

The thermal conductivity and porosity of marine concrete with different composition were measured by transient plane heat source *** effects of aggregate volume fraction,sand ratio and water-cement ratio on thermal conductivity of marine concrete were *** the analysis of these factors and the comparison with other scholars,it is found that the thermal conductivity of marine concrete increases with the increase of aggregate volume fraction,decreases with the increase of sand ratio and water-cement ratio.

关键词： Experiment and Analysis of Thermal Conductivity of Marine Concrete with Different Composition

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Experimental investigation on thermal insulation performance of air interlayer under an impinging jet at high temperature

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IOP Conference Series: Materials Science and engineering 2019年第3期609卷

作者： Jian Cai Wei Ye Chengqiang Zhi Yixiang Huang Xu Zhang School of Mechanical Engineering Tongji University Shanghai 200092 China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai 200092 China

Air interlayers are widely used in building envelope to reduce heat transfer between indoor and outdoor environments. However, it is less common to apply to industrial processes in confined spaces, especially when the heating source is at high temperature with high velocity. In this paper, a special structure with air interlayer between two plates for thermal insulation was derived from an industrial manufacturing application. The effects of the interlayer on heat transfer was investigated under an impinging jet at high temperature. An experimental mock-up was designed to produce high temperature (~ 500 °C) impinging gas jet with relative stable high velocity (~56 m/s) at the nozzle exit. The impingement surface of the test structure was covered with a 2mm thick stainless-steel plate at a distance of 5mm, which formed a horizontal air insulation layer. Benchmark test was also conducted after the removal of the stainless-steel layer. In each case, a standard procedure within a duration of 30 min was applied to minimize the variations of testing conditions. The temperatures at both inner and outer surfaces of the structure, as well as the temperatures from inside and outside the air interlayer, were measured by thermocouples. In addition, an analytical model to account for the effects of air insulation was proposed to compared with experiments. The results showed that, the air interlayer can reduce the highest temperatures for about 48 °C. The temperature difference at the end of the experiment was about 30 °C. The analytical model was in good agreement with the experimental data and the maximum difference was ~6.5 °C.

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