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Numerical analysis of the influence of the contact boundary condition and specimen geometry on concrete compressive strength

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Procedia Structural Integrity 2023年 47卷 261-267页

作者： Caroline Bremm Luísa Inda Leandro Ferreira Friedrich Sabrina Vantadori Ignacio Iturrioz Luis Kosteski Engineering Post Graduation Program Federal University of Pampa Av. Tiaraju 810 Alegrete 97546-550 Brazil Civil Engineering Graduate Program Federal University of Pampa Av. Tiaraju 810 Alegrete 97546-550 Brazil Program of Mechanical Pos-Graduation Federal University of Rio Grande do Sul Sarmento Leite 425 Porto Alegre 90040-060 Brazil Department of Engineering & Architecture University of Parma Parco Area delle Scienze 181/A 43124 Parma Italy

In the present paper, the influence of the contact boundary condition and specimen geometry on the concrete compressive strength is numerically investigated by using a version of the Lattice Discrete Element Method (LDEM), implemented on Abaqus/Explicit. More precisely, two types of contact boundary conditions are considered and, for each of them, three different slenderness levels (height/width ratio - h/b) are analyzed (that is, h/b = 0.5, 1.0, and 2.0) by considering a square cross-section. Moreover, for h/b = 2.0, a circular cross-section is also examined. Two models are developed: one by using the LDEM and the other by using a hybrid model, combining Finite Elements and LDEs. The results show that both the boundary conditions and the sample geometry influence the axial compressive strength.

关键词： Abaqus concrete compressive strength Lattice Discrete Element Method (LDEM)

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Study of Machine Learning Techniques for Damage Identification in a Beam 10th

Study of Machine Learning Techniques for Damage Identifica...

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10th International Conference on Wave Mechanics and Vibrations, WMVC 2022

作者： da Silva Coelho, Jefferson de Sousa, Amanda Aryda Silva Rodrigues Machado, Marcela Rodrigues Dutkiewicz, Maciej Department of Mechanical Engineering University of Brasília Campus Universitário Darcy Ribeiro Faculdade de Tecnologia - Asa Norte DF Brasília Brazil Post-Graduate Program - Integrity of Engineering Materials University of Brasília Campus Universitário Darcy Ribeiro Faculdade de Tecnologia - Asa Norte DF Brasília70910-900 Brazil Faculty of Civil Environmental Engineering and Architecture University of Science and Technology Bydgoszcz85-796 Poland

ISBN: (纸本)9783031157578

Damage is defined as any change to the material, geometry or boundary condition that can modify the structure’s properties or response. In the past, damage identification was performed through periodical inspection, non-destructive testing/non-destructive evaluation, or visual observation. Structural health monitoring (SHM) has emerged to transition from offline damage identification to near real-time and online damage assessment. Hence, SHM is a damage detection strategy to monitor a structure for a period using a series of continuous measurement devices, which then collect the system’s characteristics and subsequently perform statistical analysis to assess the current circumstances and health of the structure. One of the first steps for the study of SHM is damage detection followed by monitoring. Machine Learning (ML) techniques can be used to develop viable algorithms to make potential predictions. ML algorithms are therefore providing the tools needed to enhance the capabilities of SHM systems and provide intelligent solutions to past challenges. Preliminary studies have reviewed that the extension of ML into SHM has dramatically increased the system’s capabilities, providing innovative solutions to different research challenges. This work conducts a study of the use of ML to identify damage in a beam and discuss the challenge of usage, performance and implementation of each technique. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Decision trees

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Variability of Middle East springtime dust events between 2011 and 2022

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AIR QUALITY ATMOSPHERE AND HEALTH 2024年第6期17卷 1341-1360页

作者： Broomandi, Parya Galan-Madruga, David Satyanaga, Alfrendo Hamidi, Mehdi Ledari, Dorna Gholamzade Fathian, Aram Sarvestan, Rasoul Janatian, Nasime Jahanbakhshi, Ali Bagheri, Mehdi Karaca, Ferhat Al-Dousari, Ali Kim, Jong Ryeol Nazarbayev Univ Sch Engn & Digital Sci Dept Civil & Environm Engn Kabanbay Batyr Ave 53 Nur Sultan 010000 Kazakhstan Nazarbayev Univ Sch Engn & Digital Sci Dept Elect & Comp Engn Kabanbay Batyr Ave 53 Nur Sultan 010000 Kazakhstan Hlth Inst Carlos III Natl Ctr Environm Hlth Dept Atmospher Pollut Ctra Majadahonda Pozuelo Km 2-2 Madrid 28220 Spain Babol Noshirvani Univ Technol Fac Civil Engn Babol Iran Univ Tehran Sch Civil Engn Tehran Iran Rhein Westfal TH Aachen Neotecton & Nat Hazards Inst Aachen Germany Res Inst Earth Sci UNESCO Chair Coastal Geo Hazard Anal Tehran Iran Univ Calgary Dept Geosci Water Sediment Hazards & Earth Surface Dynam Water Calgary AB Canada Hakim Sabzevari Univ Fac Geog & Environm Sci Dept Climatol Sabzevar Iran Delft Univ Technol Fac Civil Engn & Geosci Dept Geosci & Engn Stevinweg 1 NL-2628 CN Delft Netherlands Tallinn Univ Technol Taltech Dept Marine Syst Div Modelling & Remote Sensing Tallinn Estonia Loughborough Univ Sch Architecture Bldg & Civil Engn Loughborough England Nazarbayev Univ Environm & Resource Efficiency Cluster EREC Kabanbay Batyr Ave 53 Nur Sultan 010000 Kazakhstan Kuwait Inst Sci Res Environm & Life Sci Res Ctr Crisis Decis Support Program Kuwait Kuwait

The Middle East frontal sand and dust storms (SDS) occur in non-summer seasons, and represent an important phenomenon of this region's climate. Among the mentioned type, spring SDS are the most common. Trend analysis was used in the current study to investigate the spatial-temporal variability of springtime dust events in the Middle East using synoptic station observation from 2011 to 2022. The plausible changes in some controlling factors of dust activity at selected important dust sources in the Middle East were also studied during this time period. Our results showed a statistically significant spike in springtime dust events across the Middle East, particularly in May 2022. To evaluate the relative importance of controlling factors, the applied feature of importance analysis using random forest (RF) showed the higher relative importance of topsoil layer wetness, surface soil temperature, and surface wind speed in dust activity over the Middle East between 2011 and 2022. Long-term trend analysis of topsoil moisture and temperature, using the Mann-Kendall trend test, showed a decrease in soil moisture and an increase in soil temperature in some selected important dust sources in the Middle East. Moreover, our predictions using ARIMA models showed a high tendency to dust activities in selected major dust origins (domain 2 and domain 5) with a statistically significant increase (p-value < 0.05) between 2023 and 2029. Observed spatial and temporal changes within SDS hotspots can act as the first step to build up for the first time an SDS precise intensity scale, as well as establishing an SDS early warning system in future.

关键词： Sand and dust storms Drought Soil moisture Soil temperature Mann-Kendall trend test ARIMA model the Middle East

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Evaluation of the effect on the permanent tooth germ and the adjacent teeth by finite element impact analysis in the traumatized primary tooth

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INTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY 2024年第6期34卷 822-831页

作者： Kurt, Ayca Yaylaci, Murat Dizdar, Ayberk Naralan, Muhammed Enes Yaylaci, Ecren Uzun Ozturk, Sevval Cakir, Binali Recep Tayyip Erdogan Univ Fac Dent Dept Pediat Dent Rize Turkiye Recep Tayyip Erdogan Univ Biomed Engn MSc Program Rize Turkiye Recep Tayyip Erdogan Univ Fac Engn & Architecture Dept Civil Engn Rize Turkiye Recep Tayyip Erdogan Univ Turgut Kiran Maritime Fac Rize Turkiye Kocaeli Univ Dept Biomed Engn Kocaeli Turkiye Recep Tayyip Erdogan Univ Fac Dent Dept Oral & Maxillofacial Radiol Rize Turkiye Recep Tayyip Erdogan Univ Technol Transfer Off Rize Turkiye Ataturk Univ Dept Oral & Dentomaxillofacial Radiol Fac Dent Erzurum Turkiye Recep Tayyip Erdogan Univ Fac Dent Dept Pedodont Rize Turkiye

BackgroundOne of the primary concerns in the paediatric emergencies is traumatic dental *** study aimed to create trauma in primary teeth and reveal its effects finite element ***-dimensional models were created using cone-beam computed tomography images, representing a maxillary primary central incisor. An impact force moving at a speed of 10 m/s was simulated on the labial tooth surface in two directions: buccal and *** stress and deformation experienced in the adjacent tooth due to the primary tooth were higher than those generated in the permanent tooth. Forces applied in the incisal direction resulted in higher levels of stress and deformation in the permanent tooth germ. The difference between the stress and deformation values in primary teeth in the forces applied in the buccal and incisal directions is 21% and 75%, respectively;in the permanent tooth germ, this difference was 233% and 100%, *** on the findings of this study, it is crucial to thoroughly evaluate not only the affected primary tooth but also the adjacent teeth and the permanent tooth germ in traumatic dental injuries. This comprehensive examination allows for the anticipation and management of potential long-term problems.

关键词： deformation finite element method permanent tooth germ primary teeth stress traumatic dental injury

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Mechano-responsive hydrogel for direct stem cell manufacturing to therapy

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Bioactive Materials 2023年第6期24卷 387-400页

作者： Yufeng Shou Ling Liu Qimin Liu Zhicheng Le Khang Leng Lee Hua Li Xianlei Li Dion Zhanyun Koh Yuwen Wang Tong Ming Liu Zheng Yang Chwee Teck Lim Christine Cheung Andy Tay Department of Biomedical Engineering National University of Singapore117583Singapore Institute for Health Innovation&Technology National University of Singapore117599Singapore School of Civil Engineering and Architecture Wuhan University of Technology430070WuhanChina NUS Tissue Engineering Program National University of Singapore117510Singapore Lee Kong Chian School of Medicine Nanyang Technological University636921Singapore School of Mechanical and Aerospace Engineering Nanyang Technological University639798Singapore Institute of Molecular and Cell Biology Agency for ScienceTechnology and Research(A*STAR)138648Singapore Department of Orthopaedic Surgery Yong Loo Lin School of MedicineNational University of Singapore119288Singapore Mechanobiology Institute National University of Singapore117411Singapore

Bone marrow-derived mesenchymal stem cell(MSC)is one of the most actively studied cell types due to its regenerative potential and immunomodulatory *** cell expansion methods using 2D tissue culture plates and 2.5D microcarriers in bioreactors can generate large cell numbers,but they compromise stem cell potency and lack mechanical preconditioning to prepare MSC for physiological loading expected in *** overcome these challenges,in this work,we describe a 3D dynamic hydrogel using magneto-stimulation for direct MSC manufacturing to *** our technology,we found that dynamic mechanical stimulation(DMS)enhanced matrix-integrinβ1 interactions which induced MSCs spreading and *** addition,DMS could modulate MSC biofunctions including directing MSC differentiation into specific lineages and boosting paracrine activities(e.g.,growth factor secretion)through YAP nuclear localization and FAK-ERK *** our magnetic hydrogel,complex procedures from MSC manufacturing to final clinical use,can be integrated into one single platform,and we believe this‘all-in-one’technology could offer a paradigm shift to existing standards in MSC therapy.

关键词： Mesenchymal stem cell Dynamic mechanical stimulation Magnetic hydrogel Stem cell manufacturing Cell therapy

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Durable Pet Air Filter Based on a Biomimetic Surface Functionalization Method for Formaldehyde Degradation and Aerosol Filtration

SSRN

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SSRN 2024年

作者： Li, Yunhe He, Weidong Shen, Ruiqing Zhou, Xiaotong Liu, Jingxian Filter Test Center School of Resources and Civil Engineering Northeastern University NO. 3-11 Wenhua Road Heping District Liaoning Shenyang110819 China Fire Protection & Safety Engineering Technology Program College of Engineering Architecture and Technology Oklahoma State University StillwaterOK74078 United States

Currently, most air filters, such as polyester (PET) fiber non-woven fabric, only have a single function of particulate filtration. However, the removal of substances harmful to human health, such as volatile organic compounds (VOCs) and bacteria, is becoming increasingly important in indoor air purification. Herein, based on the biomimetic surface functionalization properties of polydopamine (PDA) and the photocatalytic degradation of organic matter and the antibacterial effect of RGO (reduced graphene oxide)-TiO2, a multifunctional PET/PET-PDA-RGO-TiO2(P/PPRT) filter with a sandwich structure was prepared for formaldehyde degradation, aerosol filtration, and bactericidal operation. When the preparation concentrations of DA (dopamine), GO (graphene oxide), and TiO2 solutions are 2 g/L, 0.05 g/L, and 20 g/L, respectively, P/PP2R0.05T20 maintains optimal performance of photocatalytic reaction kinetics and reaches a formaldehyde degradation rate of higher than 79% within 300 min in the 7th cycle of usage. Compared with the base subtracts, P/PP2R0.05T20 has the highest filtration efficiency of 88.57% to 99.18% for 0.3 to 10 µm particles, respectively, and has a filtration efficiency of higher than 74% for 0.3 µm particles in the 7th cycles of usage. The quality factor of P/PP2R0.05T20 is improved significantly due to the sandwich structure. The effect of loaded particulate on the catalyst on photocatalytic degradation of formaldehyde was also studied. It was found that the photocatalytic formaldehyde degradation rate of P/PP2R0.05T20 is about 81.8% within 300 min under different A2 particulate load content. In addition, P/PP2R0.05T20 has a bioaerosol removal rate of higher than 99% against Escherichia coli. This study provides a practical approach to preparing a multifunctional air filter with the performance of aerosol filtration, photocatalytic degradation of formaldehyde, and bactericidal function using PET non-woven fabric. © 2024, The Authors. All rights reserved.

关键词： Volatile organic compounds

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Proposition of a Clay Brick with Reduced Thickness and High Fire Resistance by Means of Numerical and Experimental Analysis

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JOURNAL OF MATERIALS IN civil ENGINEERING 2023年第9期35卷 04023320-04023320页

作者： Lima, F. Christ, R. Bolina, F. Tutikian, B. F. Univ Vale Rio Dos Sinos UNISINOS Grad Program Architecture & Urbanism Ave Unisinos 950 BR-93022750 Sao Leopoldo Rio Grande Do S Brazil Univ Costa Dept Civil & Environm Calle 58 55-66 Barranquilla 080002 Colombia Univ Vale Rio Dos Sinos UNISINOS Inst Tecnol Desempenho & Construcao Civil itt Perf Ave Unisinos 950 BR-93022750 Sao Leopoldo Rio Grande Do S Brazil

Clay brick masonry is a construction system used worldwide due to its economy and technical viability. While its behavior when subjected to high temperatures is relatively well known, civilian construction has evolved and introduced lighter and more slender elements with no assessment of the potential decrease in performance. This study sought to develop a clay brick masonry system of reduced thickness and high fire resistance. In order to accomplish this objective, heat transfer in bricks of different geometries was analyzed with a finite element numerical model calibrated with experimental data. A wall sample was constructed in real scale with the optimum geometry obtained from the numerical analysis and evaluated experimentally. Results showed a satisfactory agreement between the model and experimental wall sample and produced a possible nonload-bearing compartmentalization system of reduced thickness with a 180 min fire resistance rating.

关键词： Clay brick masonry Fire safety Shaft Computational model

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Circular concrete-filled double skin steel tubes under concentric compression: Tests and FEA parametric study

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COMPOSITE STRUCTURES 2023年第1期309卷

作者： Yilmaz, Berika C. Cihan Binbir, Ergun Guzelbulut, Cem Yildirim, Hasan Celik, Oguz C. Istanbul Tech Univ Grad Sch MS Environm Control & Construct Technol Program Istanbul Turkiye Istanbul Tech Univ ITiO Grad Sch Struct Engn Program TR-34485 Istanbul Turkiye Univ Tokyo Sch Engn Dept Syst Innovat Tokyo Japan Istanbul Tech Univ Dept Civil Engn TR-34485 Istanbul Turkiye Istanbul Tech Univ Dept Architecture Struct & Earthquake Engn Div TR-34437 Istanbul Turkiye

Both experimental and numerical investigations are performed to determine complete inelastic behavior of circular concrete filled double skin steel tubes (CFDSTs) with different compositions. In the experimental part, 8 circular tubes including 2 DSTs (double skin steel tubes without infill) and 6 CFDSTs are tested under concentric axial compression to failure. Presence/absence of infill concrete, hollow ratio (X = 0.47 --0.70), and concrete type (plain, polypropylene and steel fibers added) are the parameters. To cover more parameters such as further hollow ratios, inner and outer tube thicknesses, a numerical work is added. AISC 360-16 and Eurocode 4 (EC4) are employed to evaluate their applicability for CFDSTs. Results show that the hollow ratio and outer/inner tube slendernesses (D/t) have a significant impact on the behavior. Experimental and numerical results reveal that, independent of the concrete composition (i.e. with or without any fibers) and hollow section ratio, concrete infill has significantly improved axial strength (up to 86 %) and ductility (up to 314 %) by delaying local buckling. Polypropylene and steel fibers improve the overall behavior with an enhanced displacement ductility and energy absorbtion. CFDSTs with smaller hollow ratios (say 0.47 or smaller) present much better inelastic behavior mainly from the enhanced confinement effect.

关键词： Concrete-filled Double Skin Steel Tubes Ultimate Strength Compression Behavior Ductility Polypropylene and Steel Fiber-Reinforced Concrete

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Hydropower Advantages over Batteries in Energy Storage of Off-Grid Systems: A Case Study

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ENERGIES 2023年第17期16卷 6309-6309页

作者： Guruprasad, Prajwal S. M. Quaranta, Emanuele Coronado-Hernandez, Oscar E. Ramos, Helena M. Inst Super Tecn Energy Technol Dual Degree Program P-1049001 Lisbon Portugal Karlsruhe Inst Technol CERIS IST P-1049001 Lisbon Portugal European Commiss Joint Res Ctr I-21027 Ispra Italy Univ Tecnol Bolivar Fac Ingn Cartagena 131001 Colombia Univ Lisbon Dept Civil Engn Architecture & Environm Civil Engn Res & Innovat Sustainabil CERIS Inst Super Tecn P-1049001 Lisbon Portugal

Microgrids are decentralized power production systems, where the energy production and consumption are very close to each other. Microgrids generally exploit renewable energy sources, encountering a problem of storage, as the power production from solar and wind is intermittent. This research presents a new integrated methodology and discusses a comparison of batteries and pumped storage hydropower (PSH) as energy storage systems with the integration of wind and solar PV energy sources, which are the major upcoming technologies in the renewable energy sector. We implemented the simulator and optimizer model (HOMER), which develops energy availability usage to obtain optimized renewable energy integration in the microgrid, showing its economic added value. Two scenarios are run with this model-one considers batteries as an energy storage technology and the other considers PSH-in order to obtain the best economic and technical results for the analyzed microgrid. The economic analysis showed a lower net present cost (NPC) and levelized cost of energy (LCOE) for the microgrid with PSH. The results showed that the microgrid with the storage of PSH was economical, with an NPC of 45.8 Meuro and an LCOE of 0.379 euro/kWh, in comparison with the scenario with batteries, which had an NPC of 95.2 Meuro and an LCOE of 0.786 euro/kWh. The role of storage was understood by differentiating the data into different seasons, using a Python model. Furthermore, a sensitivity analysis was conducted by varying the capital cost multiplier of solar PV and wind turbines to obtain the best optimal economic solutions.

关键词： hydropower energy storage pumped storage hydropower (PSH) batteries net present cost (NPC) levelized cost of energy (LCOE) microgrids

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Quantifying Outdoor Cooling Effects of Vertical Green System on Mean Radiant Temperature

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SSRN 2023年

作者： Kim, Eun Sub Yun, Seok Hwan Lee, Dong Kun Kim, Na Youn Piao, Zheng Gang Kim, Sang Hyuck Park, Seunghwan Interdisciplinary Program in Landscape Architecture Seoul National University Seoul08826 Korea Republic of Integrated Major in Smart City Global Convergence Program Seoul National University Seoul08826 Korea Republic of Specialized Graduate School of Intelligent Eco-Science 4 Dept. of Landscape Architecture Seoul National University Seoul08826 Korea Republic of Department of Landscape Architecture and Rural System Engineering Seoul National University Seoul08826 Korea Republic of Department of Building Energy Research Korea Institute of Civil Engineering and Building Technology Goyang10223 Korea Republic of

Vertical green systems (VGS) are expected to mitigate outdoor heat stress through a transpiration cooling effect. There is a lack of knowledge on how VGS influence outdoor thermal comfort, particularly focusing on energy flux. This study quantifies the outdoor cooling effects of VGS, and distinguishes the energy flux between them and outdoor urban spaces. In addition, we discuss their cooling efficiency. Outdoor experiments were conducted during the hot summer period on building facades in city. Our study on VGS focused on the measurement of climatic variables, surface temperatures of plant leaves (Fatsia japonica), net radiation, and estimating transpiration and evaporation. The surface temperature of VGS were up to 4.3 °C higher than those of high albedo walls, while the reflected radiations (short and long-wave radiation) were 120 w/m2 lower than albedo walls during the day. The mean radiant temperature (MRT) of VGS was 3.02 °C lower than the high albedo wall during daytime, except in the case of shaded areas (0.45 °C). We confirmed that the cooling efficiency of transpiration was 7.38 times more effective than evaporation from soil without plants. Therefore, VGS is efficient in terms of long-term heat reduction and can be an effective strategy to mitigate outdoor heat stress. © 2023, The Authors. All rights reserved.

关键词： Transpiration

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