摘要：
Electrically conductive cementitious composites (ECCCs) have become a significant research interest in structural health monitoring. The use of graphite in ECCCs can significantly improve their electrical performance, however, with unsatisfactory friction resistance because of the graphite's smooth microsurfaces. Slag can be incorporated with graphites into ECCCs to achieve good performance in both of mechanical resistance and electrical conductivity. This study investigated the impact of graphite and slag on the electrical and mechanical behaviors of ECCCs. Two hundred and eighty ECCC specimens were prepared with two different types of slags and with various conductivity ingredient fractions and curing times. The specimens were tested for compressive strength, flexural strength, and electrical resistance. It was concluded the 4% graphite content in ECCCs can significantly enhance electrical conductivity with moderate decrease in compressive and flexural strengths. Slags were found to improve both electrical conductivity and mechanical properties of ECCCs. The best results could be obtained with optimized contents of steel slag, blast furnace slag, and graphite. Finally, the microstructural mechanisms of the ECCC specimens were analyzed using scanning electron microscope (SEM) for graphite and slag. Variable sensitivity analysis was performed to allow for optimization of ingredient contents. (C) 2021 Elsevier Ltd. All rights reserved.
摘要：
This paper presents an optimization algorithm for band-gap maximization aimed at designing the porosity of a cementitious composite. Numerical analysis revealed the relationship between the composite porosity and band structure. With the utilization of gravels as the main aggregate, microbeads and a vesicant were also mixed to produce the porous cementitious composite, where correlative experiments were conducted on the mixture proportion. Digital microscope images were applied to evaluate the micro-construction details of the composite. The acoustic performance of the porous concrete was tested by an impedance tube. The results show that the maximum sound absorption coefficient of the phononic crystal composed of 4 mm gravels and surrounding microbeads can reach 90%. The frequency corresponding to the peak value is 1490 Hz, which is consistent with the frequency range of the band gap from theoretical derivation and simulation analysis. This developed methodology is expected to be applied to the design of cementitious structures to achieve sound absorption performance enhancement.
通讯机构：
[Shimin Zhu] K;Key Laboratory of Building Safety and Energy Efficiency of the Ministry of Education, Hunan University, Changsha 410082, PR China<&wdkj&>College of Civil Engineering, Hunan University, Changsha, Hunan 410082, PR China
关键词：
Grouted anchors;Laterite;Load transfer behavior;Merchant model;Time effect
期刊：
Journal of Applied Geophysics,2021年186:104273 ISSN：0926-9851
通讯作者：
Liang Zhang
作者机构：
[Zhang, Liang; Zhang, Sheng] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preve, Yiyang 413000, Hunan, Peoples R China.;[Zhang, Liang; Zhang, Sheng] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Hunan, Peoples R China.;[Ling, Tonghua; Yu, Bin; Huang, Fu] Changsha Univ Sci & Technol, Sch Civil Engn, Changsha 410114, Hunan, Peoples R China.
通讯机构：
[Liang Zhang] H;Hunan Engineering Research Center of Structural Safety and Disaster Prevention for Urban Underground Infrastructure, Hunan City University, Yiyang, Hunan 413000, China<&wdkj&>College of Civil Engineering, Hunan City University, Yiyang, Hunan 413000, China
摘要：
To reduce the shielding effect of strong jamming signals such as direct waves and multiple echoes on the effective signals in ground penetrating radar (GPR) images and effectively improve the GPR image resolution, a method to remove strong interference signals in GPR that combines the wavelet transform and F-K filtering is proposed. First, we choose a biorthogonal wavelet basis that matches the waveform of GPR signal, and an original GPR image is decomposed into subimages of different frequency bands based on the optimal wavelet basis. Second, according to the difference in the distribution of the effective signals and the strong interference of different subsignal images in the wavenumber domain, different bandpass filters are designed to accurately separate the effective signals and strong interference, and the subimages are reconstructed after the interference being removed. The processing of the forward simulated and measured GPR images shows that the combined method of wavelet transform and F-K filtering can produce different F-K filters according to the characteristics of different subsignal images and accurately process the image, suppressing the strong interference and retaining the effective signals to the greatest extent. Compared to the results of the predictive deconvolution method and the conventional F-K method, the cavity reflection in the image processed by the proposed method is more obvious, the coaxial signal is continuous and clear, and the image resolution is improved, which proves the feasibility and effectiveness of this method in separating strong interference waves. (C) 2021 Elsevier B.V. All rights reserved.
作者机构：
[Huang, Guoping] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;[Wang, Hui] Ningbo Univ, Sch Civil & Environm Engn, Ningbo 315000, Peoples R China.;[Shi, Feiting] Yancheng Inst Technol, Engn Dept, Yancheng 224051, Peoples R China.
通讯机构：
[Hui Wang] S;School of Civil and Environmental Engineering, Ningbo University, Ningbo 315000, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
salt freeze-thaw cycles;carbonation;quick hardening;sulphoaluminate cement-based;basalt fibers
摘要：
The effect of salt freeze-thaw cycles coupled with carbonation on the mechanical performance of quick hardening sulphoaluminate cement-based reactive powder concrete combined with basalt fibers was investigated. The ratios of basalt fibers in sulphoaluminate cement-based reactive powder concrete (SAC-RPC) were 1%, 2%, 3% and 4% by the volume of concrete. The mechanical strengths (compressive strength, flexural strength and bonding strength) of SAC-RPC were investigated after curing for 5 h, 1 d, 14 d and 28 d, respectively. Meanwhile, the mechanical strengths of resultant concrete were detected, when different NaCl freeze-thaw cycles and carbonation were adopted. Results showed that the addition of basalt fibers could effectively improve the mechanical strengths, especially the flexural strength of SAC-RPC. The dosage of 3.0% was the threshold value affected mechanical strengths. The flexural, compressive and bonding strengths of SAC-RPC were higher than 8.53 MPa, 34 MPa and 3.21 MPa, respectively. The mass loss and mechanical strengths loss of SAC-RPC increased in the form of quadratic function with the increasing number of NaCl freeze-thaw cycles and varied in the form of quadratic decreasing function. Meanwhile, the effect of carbonation on the mechanical strengths of SAC-RPC can be ignored. Additionally, the coupling effect of salt freeze-thaw cycles and carbonation could accelerate the attenuation of concrete strength. The mechanical strengths loss demonstrated a decreased quadratic function with the increasing volume of basalt fibers.
摘要：
The classical Fourier heat conduction theory as well as the widely used Fick's diffusion law predicts an infinite wave velocity. This is physically unrealistic. By generalizing the classical Fourier's and Fick's laws, this paper presents a hyperbolic diffusion law to apply heat and moisture coupling. The transient response of the hygro-thermo-elastic field in infinitely long hollow cylinders subjected to sudden heat and moisture shock on the inner and outer surfaces is studied. With the aid of the Laplace transform and the decoupling technique, the closed-form solutions of temperature, moisture, elastic displacement and stresses are determined respectively. The analytical results show that the thermal and moisture relaxation time effect between temperature and moisture is significant for composites. Compared with the classic counterpart, the finite hygrothermal wave speed of the pipe is achieved and decreases with the relaxation time rising. The temperature, moisture, elastic displacement and stresses are calculated. Numerical results are displayed graphically to show the influence of the phase lag of heat/moisture flux on the response of the hygro-thermo-elastic fields. Non-Fourier and non-Fick effects are remarkable between the classic model and hyperbolic hygrothermal coupling model. Some drawbacks induced by the classical Fourier's and Fick's laws are averted.
作者：
Li, Miao;Huang, Tian Li*;Liao, Jin Jin;Zhong, Jian;Zhong, Ji Wei
期刊：
LATIN AMERICAN JOURNAL OF SOLIDS AND STRUCTURES,2020年17(5) ISSN：1679-7825
通讯作者：
Huang, Tian Li
作者机构：
[Li, Miao] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.;[Huang, Tian Li; Liao, Jin Jin; Zhong, Jian; Li, Miao] Cent South Univ, Sch Civil Engn, Changsha 410075, Peoples R China.;[Zhong, Ji Wei] Wuhan Bridge Sci Res Inst Ltd, Wuhan 430034, Peoples R China.
通讯机构：
[Huang, Tian Li] C;Cent South Univ, Sch Civil Engn, Changsha 410075, Peoples R China.
关键词：
Weigh in motion;Urban highway bridge;Vehicle load model;Gauss distribution;Fatigue vehicle load model
摘要：
Abstract With the rapid development of China's economy, many long-span bridges have been built and put into service. Vehicle load has been changing year by year in terms of the gross vehicle weight (GVW), the wheelbase and the traffic volume, especially the overload of heavy vehicles, which is a major challenge to the safety and durability of bridges. It is necessary to establish the vehicle load model through the measured traffic data for actual traffic conditions of the given bridge. In this study, the weigh-in-motion (WIM) data collected from an operational long-span urban highway bridge located in Wuhan, China, were used to analyze the statistical characteristics of vehicle loads. On the basis of the types of vehicles, (1) Considering the double or multimodal Gauss distribution characteristics of the GVW, the expectation maximization (EM) algorithm was used to estimate the statistical parameters of the Gauss distribution; (2) The generalized extreme value distribution (GEV) was used to develop the statistical model of the vehicle load extreme value; (3) The vehicle load extreme values in the design reference period of the urban highway bridge were estimated by the extreme value type I distribution; (4) According to the axle weight and the axle spacing, a statistical fatigue vehicle load model for the small and medium span urban highway bridges located in Wuhan, China was presented based on the Miner linear accumulated damage hypothesis and the effective fatigue damage principle.
期刊：
Mathematical Problems in Engineering,2020年2020 ISSN：1024-123X
通讯作者：
Li, Yongsuo
作者机构：
[Yao, Qi; Liang, Xiaoqiang; Zhang, Sheng; Hu, Da; Li, Yongsuo] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.;[Hu, Da] Cent South Univ, Minist Educ, Key Lab Metallogen Predict Nonferrous Met & Geol, Changsha 410083, Peoples R China.;[Wu, Youping] PowerChian Zhongnan Engn Co Ltd, Changsha 410014, Peoples R China.
通讯机构：
[Li, Yongsuo] H;Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.
摘要：
The primary purpose of this paper is to analyze and predict the ground settlement law of large-span rectangular shield frame bridge jacking project, to provide a reference for the optimization design and safe construction of similar projects. In this paper, combined with the jacking project of ultra-shallow buried soft soil layer rectangular shield frame bridge, through the on-site monitoring, the settlement deformation law of the longitudinal and transverse sections of the expressway pavement during the jacking construction process is discussed, and the reasons for the large settlement and rebound are analyzed. The basic laws of the road surface settlement with time are summarized. Based on the Kriging spatiotemporal prediction model, the road surface settlement is predicted. The research shows that the transverse settlement trough of the pavement caused by the rectangular shield frame bridge's jacking construction is stable within 15 m-20 m on both sides toward the axis and symmetrical along the coordinate axis and the alignment roughly conforms to the normal distribution. The influence range of settlement trough becomes greater and greater with shield jacking, and the final settlement curve is W-shaped. After comparing the predicted curve with the measured road settlement curve, we found that the two curves are in good agreement, and the prediction result of the Kriging spatiotemporal prediction model is valid, which can reflect the process of road deformation development during the jacking process of the shield.
摘要：
Sandstone-mudstone particle mixture (SMPM) is one of the main materials, which has been widely used for filling in and around reservoirs for water conservation projects. During the periodic rising and falling of the water level, the fill material for the embankments, dam, and other waterfront features will also undergo drainage-saturation cycles. The deformation and coefficient of lateral pressure at rest K-0 may be affected by periodic saturation. In this study, a device is modified for testing the K-0 for gravel-soil under periodic saturation. In order to investigate the effects of periodic saturation on K-0, a series of experiments were performed for SMPM under different vertical stress and saturation cycling. K-0(N) values of SMPM containing 20% mudstone particles under periodic saturation were obtained. The results shows that the K-0(N) initially increased, but eventually reached a stable value with the increasing number of periodic saturation cycles. The magnitude of the coefficient increment was also found to be related to the stress condition. K-0(N) is a logarithmic function of the saturation cycling time. By calculating K-0(N) with the proposed empirical formula, the deformation and stress distribution of the SMPM filler in waterfront engineering works can be calculated with greater precision.
关键词：
sandstone;cyclic wetting and drying;P-wave velocity;acoustic wave parameters and resistivity (AWPR) testing;cumulative damage
摘要：
This paper carries out cyclic wetting and drying experiments on the sandstones from the bank slope of an inland port, and explores the deterioration features and acoustic wave parameters and resistivity (AWPR) of the sandstone. The variations in P-wave velocity, attenuation coefficient, nonlinear coefficient, resistivity, and other indices with the cycle number were discussed in details. Then, the correlations between P-wave velocity, resistivity, and physical-mechanical indices were analyzed based on the experimental results. Through the analysis on instantaneous damage analysis, a cumulative damage model was proposed, in the light of the AWPR. The results show that: the evolution of sandstone resistivity can accurately reflect the deterioration features of the sandstone under cyclic wetting and drying, providing a desirable tool to characterize rock strength deterioration and internal damage changes. Taking cycle number into account, the proposed theoretical model for cumulative damage can derive the damage and deterioration of sandstone excellently. By this model, the AWPR at any moment can be acquired in real time on site, which is convenient for engineering application.
