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SSRN 2023年

作者： Luo, Liang Shi, Jun Wang, Jianan Qu, Yiwen Dai, Bin School of Civil Engineering Central South University Changsha410075 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China

Expanding the application of defective recycled aggregates (RA) to ultra-high performance concrete (UHPC), it is necessary to modify them with nano-silica (NS) in conjunction with steel fibers (SF), and it is worthwhile to investigate the bending behavior under the typical characteristics of this new *** study investigates the flexural performance of recycled aggregate ultra-high-performance concrete (RA-UHPC) using a four-point bending test and analyzes the influence of RA substitution rates (0%, 50%, and 100%), SF content (0%, 1%, and 2%), and NS content (0%, 1%, 3%, and 5%) on its flexural toughness and microstructure. Additionally, digital image correlation (DIC) technology was employed to capture crack evolution during the test, and SEM microstructural analysis was used to elucidate the flexural mechanism of this fiber-nano composite concrete. The results show that the load-deflection curves of specimens without SF exhibit initial linear-elastic growth, followed by a sharp decrease in load after the peak without a distinct descending stage. In contrast, specimens with SF display three typical stages, with a smoother and flatter descending stage. The cross-distributed SF enhances post-peak ductility, transforming the failure behavior from quasi-brittle to ductile. Increasing SF content significantly enhances the flexural strength and toughness of the specimens, while an increase in RA substitution rate and NS content results in a slight reduction in flexural strength (fp). The changes in residual strength observed through both methods are consistent, with almost no residual strength in the brittle failure specimens. Moreover, DIC technology, relying on precise image capture, can predict crack positions before the peak load is reached. Finally, the microstructural analysis in SEM is combined to illustrate the flexural mechanism of this fiber-nanocomposite concrete. © 2023, The Authors. All rights reserved.

关键词： Image correlation

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Functional outlier detection for density-valued data with application to robustify distribution to distribution regression

arXiv

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arXiv 2021年

作者： Lei, Xinyi Chen, Zhicheng Li, Hui Key Lab of Intelligent Disaster Mitigation of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China

Distributional data analysis, concerned with statistical analysis and modeling for data objects consisting of random probability density functions (PDFs) in the framework of functional data analysis (FDA), has received considerable interest in recent years. However, many important aspects remain unexplored, such as outlier detection and robustness. Existing functional outlier detection methods are mainly used for ordinary functional data and usually perform poorly when applied to PDFs. To fill this gap, this study focuses on PDF-valued outlier detection, as well as its application in robust distributional regression. Similar to ordinary functional data, detecting the shape outlier masked by the "curve net’’ formed by the bulk of the PDFs is the major challenge in PDF-outlier detection. To this end, we propose a tree-structured transformation system for feature extraction as well as converting the shape outliers to easily detectable magnitude outliers, relevant outlier detectors are designed for the specific transformed data. A multiple detection strategy is also proposed to account for detection uncertainties and to combine different detectors to form a more reliable detection tool. Moreover, we propose a distributional-regression-based approach for detecting the abnormal associations of PDF-valued two-tuples. As a specific application, the proposed outlier detection methods are applied to robustify a distribution-to-distribution regression method, and we develop a robust estimator for the regression operator by downweighting the detected outliers. The proposed methods are validated and evaluated by extensive simulation studies or real data applications. Relevant comparative studies demonstrate the superiority of the developed outlier detection method with other competitors in distributional outlier detection. © 2021, CC BY.

关键词： Statistics

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Fragility-based probabilistic seismic safety assessment of RC frame structures with infilled masonry walls

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Tumu Gongcheng Xuebao/China Civil Engineering Journal 2014年 47卷 260-265页

作者： Yu, Xiaohui Li, Yanjun Lu, Dagang Jia, Mingming Fan, Feng Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Jinan University Jinan250022 China

A suit of real ground motion records are selected as inputs. The empirical thresholds provided by the Chinese seismic design code are adopted as the definitions of the concerned limit states. Then the seismic fragility analysis is conducted for the three-story, five-story and ten-story RC frames with and without infilled masonry walls. The limit state failure probabilities and the damage state failure probabilities conditioned on the frequent earthquake, the design-based earthquake and the major earthquake are calculated. As compared to the results from the RC bare frames we can find that the infilled masonry walls can effectively reduce the failure probability of the RC frame structures under various earthquakes and can consequently promote the safety levels against earthquake.

关键词： Earthquakes

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Cathode Potential Regulates the Microbiome Assembly and Function in Electrostimulated Bio- Dechlorination System

SSRN

引用

SSRN 2022年

作者： Li, Zhi-Ling Cao, Di Shi, Ke Liang, Bin Zhu, Zhongli Liu, Wenzong Nan, Jun Sun, Kai Wang, Ai-Jie State Key Laboratory of Urban Water Resources and Environment School of Environment Harbin Institute of Technology Harbin150090 China Shenzhen518055 China Key Lab of Structures Dynamic Behavior and Control of China Ministry of Education School of Civil Engineering Harbin Institute of Technology Harbin150090 China

Mechanism of microbiome assembly and function driven by cathode potential in electro-stimulated microbial reductive dechlorination system remain poorly understood. Here, core microbiome structure, interaction, function and assembly regulating by cathode potential were investigated in a 2,4,6-trichlorophenol bio-dechlorination system. The highest dechlorination rate(24.30μM/d)was observed under-0.36Vwith phenol as a major end metabolite, while, lower (-0.56V) or higher (0.04Vor-0.16V)potentials resulted in 1.3~3.8 times decreased of dechlorination kinetic constant. The lower the cathode potential, the higher the generated CH4 , revealing cathode participated in hydrogenotrophic methanogenesis. Taxonomic and functional structure of core microbiome significantly shifted within groups of -0.36V and -0.56V, with dechlorinators ( Desulfitobacteriu , Dehalobacter ), fermenters ( norank_f_Propionibacteriaceae , Dysgonomonas )and cathode-utilizing methanogen ( Methanosarcina ) highly enriched, and the more positive interactions between functional genera were found. The lowest number of nodes and links and the highest positive correlations were observed among constructed sub-networks classified by function, revealing simplified and strengthened cooperation of functional genera driven by group of -0.36 V. Cathode potential plays one important driver controlling core microbiome assembly, and the low potentials drove the assembly of major dechlorinating, methanogenic and electro-active genera to be more deterministic, while, the major fermenting genera were mostly governed by stochastic processes. © 2022, The Authors. All rights reserved.

关键词： Dechlorination

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Mechanical Properties and Microstructure of Ultra-High-Performance Concrete Containing Recycled Aggregates Co-Modified with Steel Fibres and Nanosilica after Exposure to Elevated Temperatures

SSRN

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SSRN 2023年

作者： Sun, Hang Luo, Liang Yuan, Huan Li, Xi Key Lab of Structures Dynamic Behavior and Control The Ministry of Education Harbin Institute of Technology Harbin150090 China School of Transportation and Science Engineering Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China

This study explores the mechanical properties and microstructure of ultra-high-performance concrete with recycled aggregates (UHPC-RA) enhanced by nanosilica (NS) and steel fibers (SF) at elevated temperatures. Thirty-six mixtures, varying in RA replacement rates, SF, and NS content, were prepared and tested for compressive strength, splitting tensile strength, and elastic modulus. Microstructural analyses included SEM morphology, XRD composition, pore size distribution, thermal conductivity, and elemental distribution studies. Results show temperature-induced changes, including SF oxidation and spalling, causing brittle failures due to weakened cementitious matrix and ITZ bonding. Moisture evaporation and hydration product decomposition lead to mass loss. Compressive strength initially increases and then decreases with rising temperatures, while overall splitting tensile strength decreases. Deterioration in UHPC-RA's microstructure is main reason for macroscopic mechanical property degradation. Linear relationships between compressive and splitting tensile strength were established. SEM and XRD confirmed that NS particles contribute to the conversion of CH to C-S-H gels. © 2023, The Authors. All rights reserved.

关键词： Steel fibers

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Efficient single-grid and multi-grid solvers for real-space orbital-free density functional theory

arXiv

引用

arXiv 2022年

作者： Bu, Ling-Ze Wang, Wei School of Civil Engineering Harbin Institute of Technology Harbin150090 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

To improve the computational efficiencies of the real-space orbital-free density functional theory, this work develops a new single-grid solver by directly providing the closed-form solution to the inner iteration and using an improved bisection method to accelerate the line search process in the outer iteration, and extended the single-grid solver to a multi-grid solver. Numerical examples show that the proposed single-grid solver can improve the computational efficiencies by two orders of magnitude comparing with the methods in the literature and the multi-grid solver can improve the computational efficiencies even once for the cases where high-resolution electron densities are needed. © 2022, CC BY-NC-SA.

关键词： Computational efficiency

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Compressive Strength Evaluation of Concrete Confined With Spiral Stirrups by Using Adaptive Neuro-fuzzy Inference System (ANFIS)

Research Square

引用

Research Square 2021年

作者： Chang, Wei Zheng, Wenzhong Key lab of Structures Dynamic Behavior and Control Ministry of Education Harbin Institute of Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China

The compressive strength of concrete confined with spiral stirrups was an important parameter to evaluate the load-bearing capacity of concrete columns. The confinement provided by spiral stirrups let concrete under the triaxial compression state and improved the compressive strength of concrete. However, the relationships between concrete and stirrups were complex and the existing prediction models for evaluating the compressive strength of confined concrete were various. In this paper, an adaptive neural-fazzy inferenxe system (ANFIS) model was developed to evaluate the compressive strength of concrete confined with stirrups. A set of 231 experimental results of concrete confined with spiral stirrups were collected from the previous studies to establish a reliable database. The investigated parameters included the aspect ratio of specimens, the diameter, spacing, yield strength, and volumetric ratio of stirrups, the ratio of longitudinal reinforcement, and the compressive strength of concrete. The results showed that the ANFIS model predicted the compressive strength of confined concrete accurately. By comparing with existing models, the proposed ANFIS model had high applicable and reliability. The effects of the investigated parameters on the compressive strength of concrete were analyzed based on the proposed ANFIS model. © 2021, CC BY.

关键词： Compressive strength

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Convective meta-thermal concentration for ultrahigh efficient Stirling engine with waste heat and cold utilization

arXiv

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arXiv 2023年

作者： Zhou, Xinchen Xu, Xiang Ouyang, Xiaoping Huang, Jiping Fudan University Shanghai200433 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters the Ministry of Industry and Information Technology Key Lab of Structures Dynamic Behavior and Control the Ministry of Education Harbin Institute of Technology Harbin150090 China School of Materials Science and Engineering Xiangtan University Xiangtan411105 China

The Stirling engine, which possesses external combustion characteristics, a simple structure, and high theoretical thermal efficiency, has excellent potential for utilizing finite waste heat and cold resources. However, practical applications of this technology suffered from thermal inefficiency due to the discontinuity and instability of waste resources. Despite advances in energy storage technology, temperature variations in the heat-exchanging fluids at the hot and cold ends of the Stirling engine remained significant obstacles. In this work, convective meta-thermal concentration (CMTC) was introduced between the heating (cooling) fluids and the hot (cold) end of the Stirling engine, employing alternating isotropic materials with high and low thermal conductivities. It was demonstrated that CMTC effectively enhanced the temperature difference between the hot and cold ends, leading to a remarkable improvement in Stirling engine efficiency. Particularly, when the Stirling engine efficiency tended to zero due to the limited availab.lity of waste heat and cold resources, CMTC overcame this limitation, surpassing existing optimization technology. Further analysis under various operating conditions showed that CMTC achieved a significant thermal efficiency improvement of up to 1460%. This work expanded the application of thermal metamaterials to heat engine systems, offering an exciting avenue for sustainable energy utilization. Copyright © 2023, The Authors. All rights reserved.

关键词： Waste heat

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Influence of FPB on seismic performance of single-layer reticulated domes under vertical earthquakes

引用

Tumu Gongcheng Xuebao/China Civil Engineering Journal 2014年 47卷 181-185页

作者： Kong, Dewen Fan, Feng Zhi, Xudong Sun, Menghan Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Harbin Institute of Technology Harbin150090 China

As an effective base isolation device, friction pendulum bearings (FPB) were finely modeled and applied in the K8 single-layer reticulated domes in this paper. First, influence of friction pendulum bearings was analyzed on the seismic performance of single-layer spherical reticulated shell from two aspects, the peak acceleration and earthquake energy. Moreover, the seismic performance of structure with FPB was studied under different ground motion intensities from three aspects, the dynamic stress, the nodal acceleration, and the vertical relative displacement of nodes. The result showed that the peak vertical acceleration was reduced and a part of earthquake energy was isolated by using FPBs. Under the different ground motion intensities, the seismic effect of a K8 single-layer spherical reticulated shell structure with FPB was similar.

关键词： Earthquakes

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Experimental and Numerical Studies of Compressive Strength of 3d Printed Concrete Considering Interlayer Bonding Performance

SSRN

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SSRN 2023年

作者： Tang, Boyang Yan, Jiachuan Han, Xiaoyu Lin, Yini Fan, Feng Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China

This paper studied the compressive properties of 3D printed concrete and analyzed their influencing factors, including layer thickness and printing time interval. The investigation also explored the impact of inter-layer and inter-bar bonding properties on concrete's compressive strength by examining key factors. The findings revealed that compressive strength decreases as layer thickness decreases and printing time interval increases. Moreover, interlayer tensile and shear strength decrease with longer printing time intervals, while the anisotropic mechanical properties of 3D printed concrete become more pronounced as the number of printed layers increases. The study employed cohesive elements to numerically simulate the compressive strength of concrete specimens with varying number of layers and interlayer intervals. Parametric analysis was conducted to investigate bonding layer failure under different loading directions, and damage modes were analyzed. Finally, an empirical equation for predicting the compressive strength of 3D printed concrete was proposed and validated using experimental data. © 2023, The Authors. All rights reserved.

关键词： Compressive strength

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