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An on-site evaluation method for corrosion degradation of in-service cable wires by image histogram matching 11

An on-site evaluation method for corrosion degradation of in...

11th International Workshop on Structural Health Monitoring 2017: Real-Time Material State Awareness and Data-Driven Safety Assurance, IWSHM 2017

作者： Xu, Yang Li, Shunlong Li, Hui Gu, Chenyu Li, Xinbin Chen, Xiaowei Qiao, Weidong Key Lab of Intelligent Disaster Mitigation Ministry of Industrial and Information Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters Ministry of Industry and Information Technology Harbin150090 China Key Lab of Structures Dynamic Behavior and Control Ministry of Education Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China School of Transportation Science and Engineering Harbin Institute of Technology Harbin150090 China

ISBN: (纸本)9781605953304

This paper proposes a novel non-destructive method by image histogram matching to evaluate the corrosion degradation of cable wires in service quantitatively. Artificial accelerated salt spray test is adopted to simulate the corrosion environment, and adequate RGB images are taken by a consumer-grade camera to cover the whole information of corroded surface for each specimen under different corrosion periods. Histogram distribution analysis is applied to study the concentrated modes of RGB images, and joint Gaussian distribution is fitted to capture location parameters. Timevariant models of the location parameters are regressed and then the mechanical properties are learnt by tensile and fatigue tests. Once the features of RGB corrosion images of steel wires are matched to the proposed time-variant models, the corresponding corrosion degree and mechanical properties can be estimated. The proposed method is meaningful for the on-site evaluation of cable wires in service with no need to carry on corrosion and mechanical degradation tests after replacing cables.

关键词： Graphic methods

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Evaluation of residual mechanical properties of steel fiber-reinforced reactive powder concrete after exposure to high temperature using nondestructive testing

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Procedia Engineering 2017年 210卷 588-596页

作者： Xiaomeng Hou Muhammad Abid Wenzhong Zheng Ghulam Qadir Waqar Key Lab of Structures Dynamic Behavior and Control Ministry of Education Harbin Institute of Technology Harbin 150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin 150090 China

Reactive powder concrete (RPC) is classified as ultra-high performance concrete, owing to its superior strength, excellent durability and high fracture energy. However, RPC may also be severely affected by devastating fire exposures. This paper presents the variations in residual mechanical properties of RPC after exposure to high temperature. The strength of RPC after cooling was also assessed by nondestructive tests (NDTs). The ultrasonic pulse velocity (UPV) method and resonance frequency (RF) method were used. The samples were subjected to the target temperature of 120℃, 300℃, 500℃, 700℃ and 900℃. The heating was continued for further 3 hours so that steady state condition was achieved. The available equations have been used for determination of dynamic elastic modulus of RPC using UPV and RF measurements. The residual mechanical properties, RF and UPV were plotted as a function of temperature. The result shows that the residual strength increases from room temperature to 300℃. However, above 300℃, it’s decreasing gradually. Various comparisons have been made between residual mechanical strength versus UPV and RF measurements. Relationships have been proposed among residual mechanical properties versus NDTs values. These relationships can be employed for post-fire strength assessment of RPC structures.

关键词： Reactive powder concrete high temperature residual mechanical properties ultrasonic pulse velocity resonance frequency

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Water transport properties for unsaturated cement-based materials

Water transport properties for unsaturated cement-based mate...

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第三届中国国际复合材料科技大会

作者： Chunsheng Zhou Wei Wang Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry and Information Technology Harbin Institute of Technology

The durability performance of cement-based material is actually and mostly determined by the penetration process of deleterious agents and possible chemical and physical reactions between them, where water always plays an important role. In addition, the transport properties of other agents also depend seriously on the water content. It is rather essential to understand the distribution of water and its transport in partially saturated cement-based materials, which are facilitated herein through low-field nuclear magnetic resonance(NMR) technique and gas permeability testing on partially saturated white cement mortar specimens. It is found that most water is stored in inter-layer pores when it is equilibrated with relative humidity below 75%. Due to the marked contraction or swelling of interlayer pores during drying or wetting, the gel pores and inter-hydrate pores are greatly changed while the overall porosity is little altered. At totally drying state, the pore structure of cement-based material becomes obviously coarser, making the gas permeability remarkably larger than water permeability by as large as 2-3 orders of magnitudes. The intrinsic gas permeability obtained on partially saturated specimens reveals that, both the permeability to water and gas depend nonlinearly on the water content, which are well characterized by the models we suggested. Not only the water saturation degree but also the induced pore structure evolution should be incorporated when modelling the transport of water.

关键词： Durability permeability pore structure saturation degree low-field NMR

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Experimental study on pore structure and chloride ion diffusion of negative temperature cement-based materials

Experimental study on pore structure and chloride ion diffus...

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第三届中国国际复合材料科技大会

作者： Guan Xinchun Bai Shuai Li Hui Ou Jinping Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology

The early frost may cause serious injury to the internal pore structure of concrete, and hence has a strong influence on the impermeability and mechanical properties of concrete. In this paper, the chloride ion diffusion coefficient of different frozen level and different kind negative temperature cement-based materials was studied. The pore structures of those negative temperature cement-based materials was studied by fractal theory. The correlation between chloride ion diffusion coefficient and fractal dimension was discussed. Experimental results show that the pore structure of negative temperature cement-based materials possesses fractal characteristics and fractal dimension has good correlation with chloride ion diffusion coefficient. The results can provide a reference to application of negative temperature concrete.

关键词： Cement-based materials Negative temperature concrete Pore structure Fractal Chloride diffusion

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Study on the effect of ground motion direction on the response of engineering structure

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Earthquake Engineering and Engineering Vibration 2016年第4期15卷 649-656页

作者： Sun Menghan Fan Feng Sun Baitao Zhi Xudong Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology School of Civil Engineering Harbin Institute of Technology Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration

Due to the randomness of earthquake wave magnitude and direction, and the uncertain direction of strong axis and weak axis in the construction of engineering structures, the effect of the direction of ground motion on a structure are studied herein. Ground motion records usually contain three vertical ground motion data, which are obtained by sensors arranged in accordance with the EW （East -West） direction, NS （South- North） direction and perpendicular to the surface （z） direction, referring to the construction standard of seismic stations. The seismic records in the EW and NS directions are converted to Cartesian coordinates in accordance with the rotation of θ = 0°-180°, and consequently, a countless group of new ground motion time histories are obtained. Then, the characteristics of the ground motion time history and response spectrum of each group were studied, resulting in the following observations：（1） the peak and phase of ground motion are changed with the rotation of direction θ, so that the direction θ of the maximum peak ground motion can be determined; （2） response spectrum values of each group of ground motions change along with the direction θ, and their peak, predominant period and declining curve are also different as the changes occur; then, the angle θ in the direction of the maximum peak value or the widest predominant period can be determined; and （3） the seismic response of structures with different directions of ground motion inputs has been analyzed under the same earthquake record, and the results show the difference. For some ground motion records, such as the Taft seismic wave, these differences are significant. Next, the Lushan middle school gymnasium structure was analyzed and the calculation was checked using the proposed method, where the internal force of the upper space truss varied from 25% to 28%. The research results presented herein can be used for reference in choosing the ground motion when checking the actual damage to struct

关键词： direction of grotmd motion structure effect coordinate transformation response spectrum

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LQD-RKHS-based distribution-to-distribution regression methodology for restoring the probability distributions of missing SHM data

arXiv

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arXiv 2018年

作者： Chen, Zhicheng Bao, Yuequan Li, Hui Spencer, Billie F. Key Lab of Intelligent Disaster Mitigation of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin China Key Lab of Structures Dynamic Behaviour and Control of the Ministry of Education Harbin Institute of Technology Harbin China School of Civil Engineering Harbin Institute of Technology Harbin China Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign UrbanaIL United States Department of Civil and Environmental Engineering University of Illinois at Urbana - Champaign UrbanaIL United States

Data loss is a critical problem in structural health monitoring (SHM). Probability distributions play a highly important role in many applications. Improving the quality of distribution estimations made using incomplete samples is highly important. Missing samples can be compensated for by applying conventional missing data restoration methods;however, ensuring that restored samples roughly follow underlying distributions of true missing data remains a challenge. Another strategy involves directly restoring the probability density function (PDF) for a sensor when samples are missing by leveraging distribution information from another sensor with complete data using distribution regression techniques;existing methods include the conventional distribution-to-distribution regression (DDR) and distribution-to-warping function regression (DWR) methods. Due to constraints on PDFs and warping functions, the regression functions of both methods are estimated from the Nadaraya-Watson kernel estimator with relatively low degrees of precision. This article proposes a new indirect distribution-to-distribution regression method in the context of functional data analysis for restoring distributions of missing SHM data. PDFs are transformed to ordinary functions residing in a Hilbert space via the newly proposed log-quantile-density (LQD) transformation;the regression for distributions is realized in the transformed space via a functional regression model constructed based on the theory of Reproducing Kernel Hilbert Space (RKHS), corresponding result is subsequently mapped back to the density space through the inverse LQD transformation. Test results using field monitoring data indicate that the new method significantly outperforms conventional methods in general cases;however, in extrapolation cases, the new method is inferior to the distribution-to-warping function regression method. Copyright © 2018, The Authors. All rights reserved.

关键词： Probability distributions

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Long term mechanical properties of alkali activated slag

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IOP Conference Series: Materials Science and Engineering 2018年第1期292卷

作者： J Zhu W Z Zheng Z Z Xu Y F Leng C Z Qin College of Civil Engineering and Architecture Harbin University of Science and Technology Harbin 150080 Key Lab of Structures Dynamic Behavior and Control of the Ministry Education Harbin Institute of Technology Harbin 150090

This article reports a study on the microstructural and long-term mechanical properties of the alkali activated slag up to 180 days, and cement paste is studied as the comparison. The mechanical properties including compressive strength, flexural strength, axis tensile strength and splitting tensile strength are analyzed. The results showed that the alkali activated slag had higher compressive and tensile strength, Slag is activated by potassium silicate (K2SiO3) and sodium hydroxide (NaOH) solutions for attaining silicate modulus of 1 using 12 potassium silicate and 5.35% sodium hydroxide. The volume dosage of water is 35% and 42%. The results indicate that alkali activated slag is a kind of rapid hardening and early strength cementitious material with excellent long-term mechanical properties. Single row of holes block compressive strength, single-hole block compressive strength and standard solid brick compressive strength basically meet engineering requirements. The microstructures of alkali activated slag are studied by X-ray diffraction (XRD). The hydration products of alkali-activated slag are assured as hydrated calcium silicate and hydrated calcium aluminate.

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Effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material

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IOP Conference Series: Materials Science and Engineering 2018年第1期292卷

作者： J Zhu W Z Zheng C Z Qin Z Z Xu Y Q Wu College of Civil Engineering and Architecture Harbin University of Science and Technology Harbin 150080 Key Lab of Structures Dynamic Behavior and Control of the Ministry Education Harbin Institute of Technology Harbin 150090

The effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material (AASCM) is studied. The research contents include: fiber type (plant fiber, polypropylene fiber), fiber content, mechanical property index, tensile stress-strain relationship curve, treating time. The test results showed that the compressive strength of two fibers reinforced AASCM was about 90 ~ 110MPa, and the tensile strength was about 3 ~ 5MPa. The reinforcement effect of polypropylene fiber is superior to that of plant fiber, and the mechanical properties of polypropylene fiber reinforced AASCM are superior to those of plant fiber, According to the comparison of SEM pictures, the plant fiber and polypropylene fiber are both closely bound with the matrix, and the transition zones are complete and close. Thus, it is proved that plant fiber and polypropylene fiber delay the crack extension and enhance the ductility of AASCM.

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Multi-species ionic transport model for concrete coupling ion-cement hydrate interactions into Nernst-Planck equation

Multi-species ionic transport model for concrete coupling io...

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第三届中国国际复合材料科技大会

作者： Bingbing Guo Yi Hong Guofu Qiao Jinping Ou Key Lab of Structures Dynamic Behavior and Control (Harbin Institute of Technology) Ministry of Education School of Civil Engineering Harbin Institute of Technology Centre for Composite Material and Structure Harbin Institute of Technology

Reinforced concrete(RC) structures are widely used in civil engineering, but the ingress of chloride ions is one of the major factors that deteriorate the durability of RC structures. Thus, many numerical models have been reported to study the mass transport of cement-based material in the previous papers. However, most of these models did not consider the interactions between ions in the pore solution and the cement hydrate or considered the interactions by modifying the diffusion coefficients. This research presents a multi-species ionic transport model for concrete that couples ion-cement hydrate interactions into Nernst-Planck equation. Firstly, a two-phase FEM concrete geometric model that included mortar phase and coarse aggregate phase was built. Moreover, the surface complexation model and the phase-equilibrium model were used to simulate the ion-cement hydrate interactions, and Nernst-Planck equation was used to simulate the effect of the driving forces of the concentration and electric field gradients in the concrete, which were conducted by using PHREEQC code and COMSOL, respectively. Then, the interactive interface that coupled the ion-cement hydrate interactions and Nernst-Planck equation was established by using MATlab language. Finally, the results of the numerical multi-species ionic transport model for concrete were verified by the experimental data published in the previous paper.

关键词： concrete multi-species transport model ion-cement hydrate interactions Nernst-Planck equation

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Effects of Rice Husk Ash on Strength and Permeability of Ultra-high Performance Concrete

Effects of Rice Husk Ash on Strength and Permeability of Ult...

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第九届水泥混凝土国际会议

作者： Huanghuang HUANG Xiaojian Gao Guangshuai Han School of Civil Engineering Harbin Institute of Technology Key Lab of Structure Dynamic Behavior and Control(Harbin Institute of Technology).Ministry of Education

This paper aims to investigate the effects of rice husk ash(RHA) on strength and penneability of ultra-high performance concrete(UHPC).The RHA was manufactured by calcining rice husk at temperature of 500 "C and incorporated in UHPC mixture to replace different ratio of SF by *** every mixture,fluidity,compressive and flexural strength,permeability before and after loading and pore structure were measured at different curing *** results show that the addition of RHA can enhance the compressive strength of UHPC at 3,28 and 120 days and refine the pore structure of UHPC measured by MIP method at 3 and 28 *** can also improve the permeability of UHPC before exposure to *** vertical loading or lateral loading,samples incorporated RHA behave better anti-permeability than the control mixture when the loading does not exceed 70%of load ***,RHA may bring about an increase in permeability of UHPC when being subjected to very high levels of loading(above80%).

关键词： Ultra-high performance concrete Rice husk ash Strength development Permeability Loading

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