作者：
Xie, Lan;He, Guojing;Wang, Alice Xiaodong;Crocetti, Roberto;Shen, Lian;...
期刊：
Journal of Bridge Engineering,2023年28(1):04022125 ISSN：1084-0702
通讯作者：
Guojing He
作者机构：
[Shen, Lian; Xie, Lan] Changsha Univ, Coll Civil Engn, 98 Hongshan Rd, Changsha 410022, Hunan, Peoples R China.;[He, Guojing] Cent South Univ Forestry & Technol, Dept Civil Engn & Mech, 498 Shaoshan Rd, Changsha 410004, Hunan, Peoples R China.;[Wang, Alice Xiaodong] Laval Univ, Quebec City, PQ G1V 0A6, Canada.;[Crocetti, Roberto] KTH Royal Inst Technol, Dept Civil & Architectural Engn, S-10044 Stockholm, Sweden.;[Tang, Xiao] Changsha Urban Construct Secondary Vocat Sch, Dept Civil Engn, 500 Xilong Rd, Changsha 410126, Hunan, Peoples R China.
通讯机构：
[Guojing He] P;Professor, Dept. of Civil Engineering and Mechanics, Central South Univ. of Forestry and Technology, 498 Shaoshan Rd., Changsha, Hunan 410004, China
摘要：
The hysteretic behavior of bolt connections in a timber-concrete composite (TCC) bridge was investigated. Six identical TCC specimens were designed with bolted connections and subjected to reversed cyclic loading tests. The failure modes, energy dissipation capacity, stiffness degradation, strength degradation, and hysteretic responses of the specimens were evaluated. The experimental results indicate that the predominant failure mode was a dual-hinge mechanism in the bolts of the TCC specimens. The TCC specimens exhibited satisfactory energy dissipation and achieved a mean ductility factor of 6.76. A finite-element model was developed to simulate the cyclic response of the tested TCC specimens. The simulated data are in good agreement with the experimental data. The experimental and numerical results reported are useful for the development of design guidelines for TCC bridges with bolted connections.
摘要：
In order to further improve the performance of bio-asphalt, because of its poor high-temperature performance, another biomass material, diatomaceous earth, was employed as a composite modifier, and a composite-modified asphalt was made to increase the high-temperature performance of bio-asphalt. The optimal preparation parameters of a rapeseed heavy oil-diatomaceous earth composite-modified asphalt were identified by employing an orthogonal test design. Based on the laboratory test, the physical properties, rheological properties, and microscopic properties of the asphalt were evaluated correspondingly by utilising matrix asphalt, rapeseed heavy oil-modified asphalt, and diatomaceous earth-modified asphalt as the control group. The results of the orthogonal test analysis showed that the optimum preparation parameters of the rapeseed heavy oil-diatomaceous earth composite-modified asphalt were 8% rapeseed heavy oil, 5% diatomaceous earth, a shear period of 35 min, and a shear rate of 2500 r/min. The addition of rapeseed heavy oil improved the fatigue resistance and low-temperature performance of the asphalt, but, at the same time, the asphalt penetration increased, the softening point and viscosity decreased, and the high-temperature rutting resistance decreased. Compared with the matrix asphalt, the viscosity of the rapeseed heavy oil-diatomaceous earth composite-modified asphalt at 135 degrees C rose by 23.2%. The rutting factor G*/sin delta increased by 45.5%, 15.6%, 17.6%, 29.8%, and 22.0%, while the fatigue factor G*center dot sin delta increased by 41.9%, 14.2%, 16.7%, 19.4%, and 23.1%, respectively, in the high-temperature rheological properties test temperature interval from 52 degrees C to 76 degrees C. The creep stiffness S fell by 16.2%, 36.1%, and 25.2%, while the creep rate m rose by 25.8%, 52.9%, and 13.4%, respectively, in the low-temperature rheological performance test temperature interval from -24 degrees C to -12 degrees C. Therefore, diatomaceous earth may effectively counteract the softening effect of the rapeseed heavy oil on the matrix asphalt and may raise the strength level and permanent deformation resistance of the composite-modified asphalt with only partial loss of fatigue resistance. The matrix asphalt, rapeseed oil, and diatomaceous earth exhibited high compatibility. The integration of rapeseed oil and diatomaceous earth largely did not modify the chemical properties of asphalt, and it was able to maintain the qualities of asphalt itself. Rapeseed heavy oil and diatomaceous earth on the thermal stability of the matrix asphalt has the opposite effect. The reorganisation component of diatomaceous earth on the colloidal structure of asphalt is conducive to the stabilisation of the nature of the asphalt, which can significantly improve the temperature stability of asphalt.
作者机构：
[Yang, Xin] Cent South Univ Forestry & Technol, Bangor Coll, Changsha 410004, Peoples R China.;[Long, Jiangping] Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Peoples R China.
通讯机构：
[Xin Yang] B;Bangor College, Central South University of Forestry and Technology, Changsha 410004, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
collapse mode;upper bound theorem;support pressure;failure probability
摘要：
Based on the kinematics-based upper bound theorem and reliability theory, the stability of deep tunnel roofs in nonlinear Hoek-Brown media is investigated. The performance functions of rectangular and circular tunnels are proposed according to the roof collapse mode, respectively, with support pressure and pore water pressure being considered. With the proposed performance function of the rectangular tunnels, the first-order reliability method is utilized to perform reliability analysis. The rock strength parameters are regarded as random variables following the normal or lognormal distribution. To assess the validity of the obtained results, reliability indexes for different support pressure values are calculated and compared with solutions using the response surface method and Monte-Carlo simulation. The agreement shows that the first-order reliability method effectively evaluates the reliability index with the proposed performance function. Sensitivity analysis is performed to throw light on the significance of different random variables, and the impact of the variation coefficient on reliability indexes is discussed. For circular tunnels, MCS is utilized to evaluate the roof stability with the proposed performance function. The influences of the support pressure on the reliability index and the corresponding design points are investigated. The parametric study shows that the normal distribution of random variables has more influence on the failure probability than that of the lognormal distribution. However, the difference between the two distributions is small. sigma(t) is the major factor that influences the reliability index compared to the B and r(u). The supporting pressure for circular tunnels is smaller than that of rectangular tunnels when a target reliability index of 2.5 (failure probability equals 0.62%) is given.
期刊：
Fatigue & Fracture of Engineering Materials & Structures,2023年46(5):1775-1791 ISSN：8756-758X
通讯作者：
Zhang, Ke(zhangke@kust.edu.cn)
作者机构：
[Zhang, Ke; Zhang, Kai] Kunming Univ Sci & Technol, Fac Civil Engn & Mech, Kunming, Peoples R China.;[Zhang, Ke] Kunming Univ Sci & Technol, Fac Elect Power Engn, Kunming, Peoples R China.;[Bao, Rui] China Nonferrous Met Ind Co Ltd, Dept Sci & Technol, Kunming Prospecting Design Inst, Kunming, Peoples R China.;[Fan, Wenchen] Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha, Peoples R China.;[Xie, Jianbin] Yunnan Univ, Dept Civil Engn, Kunming, Peoples R China.
通讯机构：
[Ke Zhang; Ke Zhang Ke Zhang Ke Zhang] F;Faculty of Civil Engineering and Mechanics, Kunming University of Science and Technology, Kunming, China<&wdkj&>Faculty of Electric Power Engineering, Kunming University of Science and Technology, Kunming, China
关键词：
crack initiation and propagation;debonding mechanism;digital image correlation (DIC);inclusion;rock mechanics
通讯机构：
[Jue Liu] S;School of Civil Engineering, Central South University of Forestry and Technology, Changsha 410004, China<&wdkj&>Hunan Province Key Laboratory of Engineering Rheology, Central South University of Forestry and Technology, Changsha 410004, China<&wdkj&>Author to whom correspondence should be addressed.
期刊：
Remote Sensing of Environment,2023年295:113643 ISSN：0034-4257
通讯作者：
Liu, GX
作者机构：
[Zhu, Jun] Changsha Univ Sci & Technol, Sch Traff & Transportat Engn, Dept Surveying Engn, Changsha, Peoples R China.;[Ding, Xiaoli; Liu, Guanxin] Hong Kong Polytech Univ, Fac Construct & Environm, Dept Land Surveying & Geoinformat, Hong Kong, Peoples R China.;[Zhao, Rong] Cent South Univ Forestry & Technol, Sch Civil Engn, Dept Surveying Engn, Changsha, Peoples R China.;[Fu, Haiqiang] Cent South Univ, Sch Geosci & Info Phys, Dept Geomatics Sci & Technol, Changsha, Peoples R China.
通讯机构：
[Liu, GX ] H;Hong Kong Polytech Univ, Fac Construct & Environm, Dept Land Surveying & Geoinformat, Hong Kong, Peoples R China.
关键词：
Penetration depth;Desert area;Hematite;Kufra Basin;Random forests model
摘要：
Penetration depth of synthetic aperture radar (SAR) signals over a desert is a key parameter to understand the internal properties of the desert. Existing approaches for obtaining the penetration depth require good quality interferometric SAR (InSAR) data of very short temporal and long spatial baselines. Such data are often difficult to obtain in a highly dynamic desert. We propose a new machine learning (ML) based approach for inverting penetration depth of SAR signals over large desert areas by jointly using InSAR, polarimetric SAR (PolSAR) and optical remote sensing data. First, SAR scattering parameters and terrain properties are determined based on PolSAR and Landsat 5 TM multispectral data and a DEM. The penetration depth of SAR signals over a small desert area is obtained based on methods such as using a scattering model. A random forest model is then used to establish the relationship between the SAR scattering parameters and site features, and the penetration depth, and then is used to derive the penetration depth over a large desert area. The approach is applied to calculate the penetration depth of ALOS-1 PALSAR L-band signals for a large part of the Kufra Basin, an area of about 60, 000 km2. The penetration depths of four types of typical landforms in area (i.e., sandy plains, paleochannels, rocks and man-made features) are discussed in relation to the geological and climatic conditions. The average signal penetration depths over the paleochannels, sandy plains, and rocks and man-made features are 2.84 m, 1.97 m, 1.21 m, respectively. It is found that the backscattering coefficient, dielectric constant, surface roughness and mineral composition are the most important parameters in determining the signal penetration depths. An interesting point is that the existence of hematite in the sand can increase the dielectric dissipation of the sand medium and shorten the signal penetration depth.
摘要：
In this study, a novel three-dimensional semi-rigid steel joint with a channel steel component is proposed, in which the channel steel component is connected to the column flange through a hybrid connection of bolts and welds along the minor axis. The design of the minor axis connection in this study had no weakening effect on the column web, and it was more convenient and easier to attach the additional channel steel component than the additional plates to the column flanges by welding. In order to investigate the static behaviour and seismic performance of the proposed novel three-dimensional semi-rigid steel joint with a channel steel component and to evaluate the interaction between both axes, numerical analyses were conducted systematically. The finite element (FE) models are firstly calibrated against the experimental results in order to get accurate results, and then the rotating characteristics, joint moment capacity, joint stiffness, ductility and energy dissipation capacity of the proposed novel semi-rigid steel joints were analysed under ten loading cases along the major and minor axes. The results indicate that the proposed novel semi-rigid steel joint has good energy dissipation capacity and deformation performance. Loading in the major-axis direction has almost no influence on the ultimate joint moment capacity but has some influence on the initial stiffness, ductility, stiffness degradation and energy dissipation ability of the proposed novel semi-rigid steel joint along the minor axis. In addition, the modified moment-rotation (M-theta) hysteretic model for the proposed novel semi-rigid steel joint is capable of effectively characterising its hysteretic behaviours, which can provide a reference for practical applications.
