期刊：
Theoretical and Applied Fracture Mechanics,2023年127:104065 ISSN：0167-8442
通讯作者：
Zhang, K
作者机构：
[Zhang, Ke; Li, Na; Zhang, K] Kunming Univ Sci & Technol, Fac Civil Engn & Mech, Kunming 650500, Yunnan, Peoples R China.;[Zhang, Ke] Kunming Univ Sci & Technol, Fac Elect Power Engn, Kunming 650500, Yunnan, Peoples R China.;[Bao, Rui] China Nonferrous Met Ind Co Ltd, Kunming Prospecting Design Inst, Kunming 650051, Yunnan, Peoples R China.;[Fan, Wenchen] Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Zhang, K ] K;Kunming Univ Sci & Technol, Fac Civil Engn & Mech, Kunming 650500, Yunnan, Peoples R China.
关键词：
Fractured rock mass;Sand 3D printing;Digital image correlation method;Mechanical properties;Anisotropy
摘要：
A complex fracture distribution in a rock mass makes the preparation of a physical sample with fracture networks an important problem in rock mechanics testing. As sand 3D printing offers outstanding advantages in the fabrication of complex structures, it is used in this study. There are a number of 3D printed samples with fracture networks at different rotation angles were prepared. In terms of low dispersion in the geometric and mechanical properties, the possibility of using 3D printing sand samples to reproduce fractured rock mass with high precision was verified. The fracture behavior and the mechanical anisotropy of fractured rock masses were quantitatively analyzed by uniaxial compression testing and digital image correlation method. Dispersion measure of the strain field was proposed as a method for identifying crack initiation, and the variation mechanism of the proposed measure was interpreted. By calculating the displacement vector distribution, it is found that the strain-softening behavior is related to the rock block interlocking. The fractured rock masses exhibit post-peak strain-softening behavior, and the mechanical property (& sigma;i, UCS and E) and crack coalescence pattern show obvious anisotropic characteristics. The results show that 3D printing and DIC provide convenience for the quantitative characterization of fracture behavior and mechanical anisotropy of complex fractured rock mass.
摘要：
Cracking damage of the sheathing wallboards in screw connections is the typical failure mode of cold formed steel (CFS) structures under seismic effects, which limits the shear capacity and weakens the hysteretic performance of CFS structures. To improve the shear performance of CFS-sheathing screw connections, a novel screw connection with carbon fiber reinforced polymer (CFRP) reinforcement is proposed in this paper. Cyclic tests were conducted on a total of 26 sets of screw connections with different configurations and wall sheathings, and the effects on the failure modes and shear performance of the connections with and without CFRP reinforcement were investigated. The strengthening effects of the sheathing material, panel thickness and end distance on the shear properties of the connections were discussed. The results indicated that (1) except for specimens with 15 mm end distance, CFRP reinforcement can effectively avoid brittle cracking failure of the connections, and the failure mode tended to ductile failure of the bearing and pull-through damage. (2) in addition to the stiffness, the shear strength, deformation capacity, ductility and energy dissipation capacity of CFRP-strengthened connections are significantly enhanced. The effect of CFRP on the shear performance improvement of connections sheathed with gypsum board (GWB) and magnesium glass board (MgO) is greater than that of oriented strand board (OSB), and the strengthening effect is not significantly influenced by the board thickness. A toughness evaluation method for CFRP-strengthened connections was proposed, and the design formulae for the shear strength of the CFRP-strengthened screw connections were recommended based on the load resistance factor design (LRFD) method and allowable strength design (ASD) method.
摘要：
Water immersion significantly influences the mechanical characteristics of rock materials, with the degradation of these properties often leading to engineering hazards. Understanding the micro mechanism of rock-water interaction is crucial when evaluating the mechanical behavior of a rock mass. A series of multiscale tests were conducted to investigate the micro and macro behaviors of Plagioclase amphibolite, sourced from Gansu, China, under water immersion conditions. The results indicated that the micro particles transitioned from a flake-dispersed structure in a dry state to floc clusters after 20 days of immersion. The surface micro morphology was analyzed using a laser scanning machine, revealing a transformation from a smooth state to roughness, attributed to the emergence and swelling of numerous micro humps. The evolution of parameters such as the standard deviation of the height distribution (Sq), profile area ratio(Sdr), and the root mean square of the first derivative of surface (Sdq) demonstrated that the rock expanded uniformly, with the micro grains swelling to varying degrees. NMR-based porosity testing suggested an exponential increase in damage, leading to the interconnectedness of newly formed micro-pores with neighboring ones due to water immersion. Ultimately, the water-induced porosity doubled compared to the original porosity. Additionally, the axial swelling rate exhibited a corre-sponding increase in tandem with the growth in porosity, with an average value of 0.141 %. Finally, linear functions were established between uniaxial compressive strength, elastic modulus, and axial swelling rate. These findings offer a comprehensive understanding of the multiscale evolution characteristics of Plagioclase amphibolite under water intrusion.
作者机构：
[Zhang, Ke; Xu, Yi; Zhang, Kai; Zhang, K] Kunming Univ Sci & Technol, Fac Civil Engn & Mech, Kunming 650500, Yunnan, Peoples R China.;[Zhang, Ke; Zhang, Kai; Zhang, K] Kunming Univ Sci & Technol, Fac Elect Power Engn, Kunming 650500, Yunnan, Peoples R China.;[Bao, Rui] Kunming Prospecting Design Inst China Nonferrous M, Kunming 650051, Yunnan, Peoples R China.;[Fan, Wenchen] Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Zhang, K ] K;Kunming Univ Sci & Technol, Fac Civil Engn & Mech, Kunming 650500, Yunnan, Peoples R China.;Kunming Univ Sci & Technol, Fac Elect Power Engn, Kunming 650500, Yunnan, Peoples R China.
摘要：
A deep knowledge of the failure mechanisms and early warning of dangerous rocks is an important issue in geological disaster prevention and reduction. This study focuses on the failure analysis of dangerous rocks from a laboratory scale, whose models are prepared by 3D printing (3DP) technology. The frozen-thawing test (FTT) is performed to reproduce the failure processes of toppling and falling types dangerous rocks. In addition, the digital image correlation (DIC) technique is applied to detect the deformation characteristics of dangerous rock models during the tests. The relative displacements along the structural plane and the displacement vectors on the dangerous rock surface are further extracted to quantitatively reveal the failure mechanism from a fine-view perspective. It is found that the toppling type dangerous rock is dominated by the rotational failure, while the falling type dangerous rock is dominated by tensile‒shear failure. Furthermore, a DIC-based early warning method is proposed for identifying the precursors of dangerous rock instability from a laboratory perspective. The results provide an important application and reference value for the study of dangerous rock prevention and reduction.
作者：
Deng Yulong;Ding Ke;Ouyang Chunsheng;Luo Yingshe;Tu Yu;...
期刊：
Results in Engineering,2023年17:100837 ISSN：2590-1230
通讯作者：
Ding Ke<&wdkj&>Ouyang Chunsheng
作者机构：
Hunan Province Key Laboratory of Engineering Rheology, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China;College of Civil Engineering, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China;[Tu Yu; Fu Jianyi; Wang Wei] Hunan Institute of Traffic Engineering, Hengyang, 421000, China;[Du Yaguang] Wuhan Municipal Engineering Design & Research Institute Co., Ltd., Wuhan, Hubei, 430015, China;[Deng Yulong; Ding Ke] Hunan Province Key Laboratory of Engineering Rheology, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China<&wdkj&>College of Civil Engineering, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China
通讯机构：
[Ding Ke; Ouyang Chunsheng] H;Hunan Province Key Laboratory of Engineering Rheology, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China<&wdkj&>College of Civil Engineering, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China<&wdkj&>Hunan Institute of Traffic Engineering, Hengyang, 421000, China<&wdkj&>Hunan Province Key Laboratory of Engineering Rheology, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China<&wdkj&>College of Civil Engineering, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China
摘要：
As a common structural form, thin plates are widely used in civil engineering. Since the thin plate needs to face harsh work conditions, the damage inevitably to be accumulated, thus affecting the stability and safety of the application components. Therefore, it is of great application significance to quantify and characterize the damage of thin plates. However, the raw images produced by current inspection techniques such as Ultrasonic immersion C-scan technology, Metal sheet Lamb wave inspection technology, etc applied to thin plates usually bring various noises and imperfections during the reception, encoding, and transmission. In this paper, wavelet transform and Curvelet transform are used to denoise the detected noise image. First, we outline the numerical implementation of two newly developed multi-scale representation systems. Curvelet transform is a new multi-scale transform based on wavelet transform after 1999. The purpose of this paper is to analyze the influence of wavelet and Curvelet transform on image denoising. These methods can also be applied to the problem of image restoration from noisy images, and the effects of denoising on images are compared. The results show that the Curvelet transform can accurately identify the damage location for the thin plate damage degree, damage range, strip damage, and multiple damage conditions, and its energy focusing is better than that of the wavelet transform in each type of thin plate damage.
摘要：
In slope ecological restoration projects, reinforcing soil and promoting vegetation growth are essential measures. Guest soil spraying technology can be used to backfill modified soil and vegetation seeds onto the slope surface, resulting in successful ecological restoration. The use of organic polymer modifiers to reinforce soil has several benefits, such as high strength, effective results, and low pollution levels. Organic polymer soil modifiers can be divided into two categories: synthetic polymer modifiers and biopolymer modifiers. This paper provides a thorough review of the properties and interaction mechanisms of two types of polymer modifiers in soil consolidation. The properties of organic polymer modifiers make them applicable in soil and vegetation engineering on slopes. These modifiers can enhance soil mechanics, infiltration, and erosion resistance and promote vegetation growth. Therefore, the suitability of organic polymer modifiers for soil and vegetation engineering on slopes is demonstrated by their properties and potential for improvement in key areas. Furthermore, challenges and future prospects for slope protection technology using organic polymer modifiers are suggested.
通讯机构：
[Chen, AJ ] C;Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Peoples R China.
关键词：
Glued laminated timber truss;Synergy of forces;Bolted connections with steel splints;Parametric analysis;Height-to-span ratio;Thickness-to-diameter ratio
摘要：
In order to deeply understand the mechanical performance of glued-laminated timber trusses connected by steel-plates and bolts, two groups of truss specimens were designed and fabricated by changing the connection forms of the nodes, while maintaining the height and span of the trusses unchanged. Each group of truss specimens was subjected to the mid-span load. At the same time, finite element numerical analysis was conducted on the tested trusses. Based on the agreement between the experimental and numerical simulation results, the influence of the parameters of thickness-to-diameter ratio and height-to-span ratio on the mechanical performance of these trusses was explored. The research results show that both types of node connections in the glued-laminated timber trusses have good bearing capacity. The main failure modes are the splitting of the diagonal web members at the mid-span node and the crushing failure of the bolt holes. The HJ-C type truss, which has the upper and lower chord members connected, exhibits better ductility, greater stiffness, and better structural synergy in load-bearing capacity. As the thickness-to-diameter ratio increases, the form of the bolts at the truss failure gradually changes from being straight to yielding. The optimal thickness-to-diameter ratio is 8.3. As the height-to-span ratio decreases, the initial stiffness and ultimate load-bearing capacity of the truss show a decreasing trend. The truss exhibits better mechanical performance when the height-to-span ratio is 1/4.
摘要：
Glulam beams connected with steel splints and bolts (GBSBs) are subjected to cyclic reciprocating dynamic loads in practice, which eventually leads to damage accumulation and structure failure. In order to promote the development of GBSBs, an experimental study was carried out, and theoretical analysis of the fatigue behavior of GBSBs was conducted. Three static load test beams and six fatigue test beams were designed and fabricated, taking into account the different stress levels and fatigue limit loads. Theoretical analysis of the data, linear regression analysis, and electron microscopy analysis of the material were carried out. The test results show that the GBSBs have good fatigue properties and that fatigue damage mainly occurs near the loading point. As the number of load cycles increases, the mid-span deflection and strain of the beam increase by a significant amount, and linear degradation of the stiffness occurs. In addition, a linear regression analysis of the amplitude of the fatigue load and the fatigue life was carried out, resulting in a fatigue limit load of 0.5435 Fu.
