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2020 fib Symposium: Concrete structures for Resilient Society

作者： Fang, Jing Jiang, Chao Gu, Xiang-Lin Key Laboratory of Performance Evolution and Control of Engineering Structures of Ministry of Education Tongji University Shanghai China Department of Structural Engineering College of Civil Engineering Tongji University Shanghai China

ISBN: (纸本)9782940643042

Concrete bridges usually undergo repeated vehicle or train loads which will cause fatigue growth of micro-cracks of concrete and hence accelerate the penetration of chloride ions into concrete. In this paper, a multi-scale method is proposed to characterize the effect of fatigue damage on the chloride diffusivity of concrete. First, concrete is considered as a two-phase composite material composed of mortar and coarse aggregates. Residual strain of concrete is used to characterize the effects of fatigue loads and the generalized self-consistent model is implemented to determine residual strains of aggregates and surrounding mortar in concrete. The fatigue damage of concrete is then assumed to reside in both the damaged mortar matrix and the cracked/crushed zones between the damaged mortar matrix and coarse aggregates. Furthermore, through elastic mechanical analysis, the volume of cracked/crushed zone is estimated as a function of residual strain of concrete caused by fatigue loads. Then the fatigue-damaged concrete is further considered as a three-phase composite material composed of coarse aggregates, damaged mortar matrix and cracked/crushed zone between them. With the specific chloride diffusion coefficients of all three components reported by the literature and their respective volume fractions calculated by the authors, the chloride diffusion coefficient of fatigue damaged concrete can be calculated by the generalized self-consistent scheme. Several chloride penetration tests on fatigue damaged concrete are collected to validate the proposed chloride diffusion coefficient model. It is found that the predicted values of chloride diffusion coefficient in fatigue damaged concrete are in acceptable agreement with those reported by experimental results. In summary, the proposed model of chloride diffusion coefficient in fatigue damaged concrete will contribute to more accurate predictions for chloride ion penetration into concrete in bridges. Moreover, the multi-sc

关键词： Fatigue damage

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Determining Moist-Based Ventilation Rates for Residential Buildings with Low-Infiltration in China: A Preliminary Discussion 1

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11th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC 2019

作者： Tang, Shengyi Ye, Wei Su, Xing Zhang, Xu School of Mechanical Engineering Tongji University Shanghai200092 China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai200092 China

ISBN: (数字)9789811395208

ISBN: (纸本)9789811395192

There is a growing concern over whether ventilation rates (VRs) for building are health-based. For example, moisture-related problems, e.g., molds and mites, can pose adverse health effects on occupants. However, ventilation-induced moist indoors is an overlooked issue in China. In this paper, the effects of VRs, as well as typical building characteristics, on indoor humidity levels were investigated using EnergyPlus. 1008 residential models (with low infiltration, and various ventilation and climate scenarios) were simulated. Generally-agreed non-healthy humidity levels were used to analyze health risks. The results showed that, first, buildings in two hot summer zones were at risk of high indoor humidity, while buildings in two cold zones might experience higher risks of low humidity. Second, higher the VRs, higher the risk of low humidity in cold zones, and higher the risk of dampness in hot summer zones. Third, it can be easier to be more humid indoors for small-size, top-floor, or north orientation residences in China. © 2020, Springer Nature Singapore Pte Ltd.

关键词： Ventilation

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Numerical study on axial loading performance of grouted connections

Numerical study on axial loading performance of grouted conn...

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International fib Symposium on Concrete structures for resilient society, 2020

作者： Cao, Chengcheng Chen, Tao Zhang, Chihai Fang, Qi Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai200092 China Department of Structural Engineering Tongji University Shanghai200092 China

ISBN: (纸本)9782940643042

With the rapid increase in demand for offshore wind power, the offshore wind power industry has gradually shown a trend of wind farms moving toward the further offshore. Meanwhile, the size of offshore wind turbines has become larger. Grouted connections (GCs) as an important joining method attaching the pile and the substructure for offshore wind turbines whose diameter is continuously increased and the strength of the material used is improved constantly. Previous studies on low-strength and small-scale GCs have failed to meet current engineering needs. Therefore, it is necessary to further investigate GCs. In this study, the finite element method is used to analyse how the interface transfer strength, ultimate bearing capacity and ductility of the grouted connections affected by radial stiffness, ratio of height to space and ratio of length to diameter. Results suggest that the interface transfer strength and the ultimate bearing capacity increase with increasing radial stiffness and ratio of height to space. Although increasing the ratio of length to diameter can increase the ultimate bearing capacity, the interface transfer strength is rather reduced, so it is uneconomical to increase the bearing capacity by increasing the ratio of length to diameter. In addition, increasing the radial stiffness can effectively improve the ductility of the structure, but increasing the ratio of height to space and the ratio of length to diameter is disadvantageous for the ductility of the structure. The research results have important reference value for practical engineering design. © fédération internationale du béton (fib).

关键词： Finite element method

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Numerical simulations on buoyancy-driven plumes from various sphere-attached heating sources 16

Numerical simulations on buoyancy-driven plumes from various...

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16th Conference of the International Society of Indoor Air Quality and Climate: Creative and Smart Solutions for Better Built Environments, Indoor Air 2020

作者： Zhao, Wenxuan Ye, Wei Zhang, Xu School of Mechanical Engineering Tongji University Shanghai201804 China Key Laboratory of Performance Evolution and Control for Engineering Structures Ministry of Education Tongji University Shanghai200092 China

ISBN: (纸本)9781713823605

A spherical scientific facility is under construction, during which high-temperature buoyancy-driven plume would be released from surfaces. However, there is still knowledge gap on the temperature distributions for plumes along the sphere. In this paper, CFD simulations were employed to analyse the temperature profiles of the plumes from sphere-attached sources with various intensity and location. The results showed that, first, the buoyancy-driven plumes exhibited different flow patterns from that of the conventional sources, and source-attached location on the sphere has a great effect on the thermal environment. Second, dimensionless excess temperature t*(τ,θ ) of the plumes along the sphere were approximately the same when temperature ranging from 80-300 ℃. Third, temperature distributions on the radial sections did not fully conform to the Gaussian distribution during the developing period. The simulation can be useful in developing ventilation for heating sources on spherical surfaces. © 2020 16th Conference of the International Society of Indoor Air Quality and Climate: Creative and Smart Solutions for Better Built Environments, Indoor Air 2020. All rights reserved.

关键词： Computational fluid dynamics

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Corrosion behavior on titanium alloys as octg in oil fields 3rd

Corrosion behavior on titanium alloys as octg in oil fields

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3rd International Conference on Materials Science and Industrial Applications, MSIA 2021

作者： Wang, Xinyu Zhu, Shidong Liu, Qiang Fu, Anqing Li, Jinling School of Materials Science and Engineering Xi'an Shiyou University Xi'an710065 China State Key Laboratory for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials CNPC Tubular Goods Research Institute Xi'an710077 China School of Chemistry & Chemical Engineering Shaanxi Province Key Laboratory of Environmental Pollution Control and Reservoir Protection Technology of Oilfields Xi'an Shiyou University Xi'an710065 China

ISBN: (纸本)9783035738056

Titanium alloys have been taken as Oil Country Tubular Goods (OCTG) owing to their higher strength, and better corrosion resistance, but there are some problems in their application process. The corrosion types of titanium alloys were emphatically discussed, and corrosion mechanism was analyzed in this paper. The results showed that the main corrosion type of titanium alloys in hydrochloric acid was pitting, and the surface roughness of titanium alloys could affect it. The critical current density of titanium alloys in phosphoric acid was closely related to temperature and phosphoric acid concentration. The passivation of titanium alloys could be carried out by the growing oxide film at low current density, to achieve the higher stability of passivating film in the concentrated sulfuric acid. Titanium alloys suffered from more serious corrosion in the CO2containing completion fluid environment than that in the CO2-containing formation water environment. H2S would cause electrochemical corrosion and stress corrosion of titanium alloy pipe, leading to hydrogen embrittlement and even cracking of OCTG. Passivating film was the key to corrosion resistance of titanium alloys, and its composition would change with the depth of the film, presenting N-type. The dynamic corrosion of titanium alloys was mainly controlled by charge transfer. © 2021 Trans Tech Publications Ltd, Switzerland.

关键词： Titanium alloys

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Experimental study on the synergistic lateral resistance of CLT walls and tension-only braced frames

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engineering structures 2025年 339卷

作者： Gao, Yuan Song, Xiao-bin Department of Structural Engineering Tongji University Shanghai200092 China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai200092 China

To enhance the lateral performance of glulam frame structures, a beam-through steel-timber hybrid structure is proposed, featured by the synergistic lateral resistance of CLT walls and tension-only braces. Low-cycle reversed loading tests were conducted on two composite frames consisting of the CLT wall and tension-only braced frame to investigate the synergistic lateral resistance mechanism between these components. The test results indicated that the failure of the components of the composite frame started with the tensile yielding of the tension-only bracing, the cracking at the ends of the glulam columns, and followed by failure of the CLT wall's hold-down connections. The tension-only bracing was mainly active during the elastic stage of the composite frame, providing no less than 70 % of the lateral resistance, while the CLT wall became more critical in the elastic-plastic stage of the composite frame, contributing more than 55 % of the lateral resistance. © 2025 Elsevier Ltd

关键词： Timber

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A generalised, multi-phase-field theory for dissolution-driven stress corrosion cracking and hydrogen embrittlement

arXiv

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arXiv 2022年

作者： Cui, Chuanjie Ma, Rujin Martínez-Pañeda, Emilio Department of Civil and Environmental Engineering Imperial College London LondonSW7 2AZ United Kingdom College of Civil Engineering Tongji University Shanghai200092 China Key Laboratory of Performance Evolution and Control for Engineering Structures Tongji University Shanghai200092 China

We present a phase field-based electro-chemo-mechanical formulation for modelling mechanics-enhanced corrosion and hydrogen-assisted cracking in elastic-plastic solids. A multi-phase-field approach is used to present, for the first time, a general framework for stress corrosion cracking, incorporating both anodic dissolution and hydrogen embrittlement mechanisms. We numerically implement our theory using the finite element method and defining as primary kinematic variables the displacement components, the phase field corrosion order parameter, the metal ion concentration, the phase field fracture order parameter and the hydrogen concentration. Representative case studies are addressed to showcase the predictive capabilities of the model in various materials and environments, attaining a promising agreement with benchmark tests and experimental observations. We show that the generalised formulation presented can capture, as a function of the environment, the interplay between anodic dissolution- and hydrogen-driven failure mechanisms;including the transition from one to the other, their synergistic action and their individual occurrence. Such a generalised framework can bring new insight into environment-material interactions and the understanding of stress corrosion cracking, as demonstrated here by providing the first simulation results for Gruhl’s seminal experiments. Copyright © 2022, The Authors. All rights reserved.

关键词： Fracture mechanics

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Simulations on Pressure Characteristics of Low-Flow Rate Water Circulating System Based on Porous Media Model 1

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11th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC 2019

作者： Xue, Yu Zhao, Wenxuan Ye, Wei Wu, Chao Zhang, Xu School of Mechanical Engineering Tongji University Shanghai201804 China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University 1239 Siping Road Shanghai200092 China

ISBN: (数字)9789811395284

ISBN: (纸本)9789811395277

A spherical experimental device is placed in an underground cylindrical laboratory hall, and the surface is covered with ~17,510 photomultiplier tubes (PMTs) for detecting radiation signals. Since the device is placed underground for a long time, an effective water circulation is required to remove radon and algae to ensure stable operation. In this paper, the pressure distribution characteristics of water in the PMT region are studied. The PMT areas of the device are simplified into a porous media. Two models, i.e., a vertical-flow and a horizontal-flow model, were established to obtain the coefficient of resistance using CFD. In addition, the relationship between the pressure difference and the water entry parameters in the porous media is also studied. The results show that the resistance coefficients of single-layer PMT and two-layer PMT are similar in the vertical direction. However, the resistance coefficient of two-layer PMT in the horizontal direction is smaller than that of the single-layer PMT. Another simplified 2D model was also proposed to further study the effect of the simplified porous media on the overall flow. Overall, when the water inlet velocity is smaller, and the angle of inclination of the inlet is larger, the fluid is more likely to pass through the PMT areas, and the pressure distribution in the PMT areas can be more uniform. © 2020, Springer Nature Singapore Pte Ltd.

关键词： Porous materials

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Monitoring Based Intelligent Perception and Prediction of Vortex-Induced Vibration of Long-Span Bridges: Methodology and Application

SSRN

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SSRN 2023年

作者： Dan, Danhui Yu, Xuewen Li, Houjin Zeng, Gang Guan, Hua School 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 Zhejiang Zhoushan Sea Crossing Bridge Co. Ltd. Zhoushan316031 China Tongji University Room 708 Bridge Building T1239 Siping Road Shanghai China

With the continuous breakthrough in span and the application of lightweight and high-strength materials, bridge structures become increasingly flexible, highlighting the issue of wind-induced vibrations. Wherein vortex-induced vibration (VIV) occurs under frequent wind conditions and is difficult to avoid entirely. This paper focuses on the intelligent perception and prediction of bridge VIV and presents a systemic solution that includes the contents of (a) Real-time identification of VIV based on the features of structural responses;(b) Online tracking of structural state parameters when VIV occurs;(c) Assessment of driving comfort and safety during VIV based on vibration level and field of view;(d) Prediction of VIV driven by data rules and dynamical model. The technical framework covers the aspects of prediction, identification, tracking, and evaluation of VIV, which can provide timely data support for bridge management and maintenance. The proposed methods are verified through the VIV events of two long-span suspension bridges. And some of them have been applied to construct a VIV monitoring system for one of the bridges. © 2023, The Authors. All rights reserved.

关键词： Structural health monitoring

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Force-displacement relationship modelling of masonry infilled walls with openings in hinged steel frames

Research Square

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Research Square 2021年

作者： Zuo, Haoran Zhang, Weiping Wang, Baotong Gu, Xianglin The Hong Kong Polytechnic University Hong Kong Key Laboratory of Performance Evolution and Control for Engineering Structures Ministry of Education Tongji University Shanghai200092 China

Seismic behaviour of masonry infilled frames has attracted extensive attentions from researchers, and it was found that infills normally experienced a diagonal compression under lateral loading. Infill was therefore assumed as an equivalent diagonal strut in structural response estimations of infilled frames, and a force-displacement curve was adopted to describe the mechanical properties of the strut. However, the influences of infill aspect ratio, vertical load acting on the surrounding frames, and opening were not systematically addressed in establishing the force-displacement relationship of infills. To investigate the effects of these influential parameters on the lateral responses of infilled walls including initial stiffness and strength, detailed three-dimensional finite element (FE) models of masonry infilled hinged steel frames are developed in ABAQUS in the present study, and a wide parametric study with respect to various aspect ratios, vertical loads, and opening sizes and locations is performed. A generalized force-displacement relationship model of infilled walls is proposed based on regression analyses of numerical results. The efficacy of the proposed model is examined by using the existing experimental test results, and it shows that the model can accurately predict the lateral stiffness and load carrying capacity of infilled walls and thus has great potential applications in structural designs and analyses for masonry infilled steel frames. © 2021, CC BY.

关键词： Aspect ratio

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