关键词：
CFRP;ECC;Anchorage;Bond performance;Single shear test
摘要：
The problem of low material utilization caused by premature interface debonding is prevalent in carbon fiber-reinforced polymer (CFRP)-reinforced concrete structures. In this study, the influence of anchors on the bonding and behavior of the FRP-engineered cementitious composite (ECC) layer and concrete interface was analyzed. A total of 42 single shear tests were performed to investigate the interface–bond behavior between the FRP-ECC layer and concrete under static load in case of anchor reinforcement. The variables mainly include the matrix type, anchor location, anchor spacing, and number of anchors. The results show that the anchor can increase the interfacial load-carrying capacity up to 85%; the maximum slip value of the interface can also be enhanced. Furthermore, the influence of the location, spacing, and number of anchors on the interface bonding performance is closely related to the effective bonding length and post-anchor bond length. The effective bonding length is 400 mm based on the strain distribution calculation and analysis. The test results provide valuable information for FRP anchor reinforcement in FRP-ECC composite layer-reinforced concrete structures.
摘要：
The sustainable development of the construction industry necessitates the utilization of multipurpose Cement Composites (CC). Therefore, the integration of nanomaterials has the potential to provide CC that exhibits superior performance and possesses several functionalities. Hence, the use of Carbon Nanotubes (CNTs) inside the concrete cementitious sector holds significant potential for implementing effective solutions toward creating a sustainable ecosystem characterized by versatile attributes. Nevertheless, the prediction of the characteristics of these composites is a significant challenge owing to their complex composite structure and non-linear response. Furthermore, the process of designing and executing experimental trials on diverse samples and across various age groups is arduous, time-consuming, and financially burdensome. There is currently a dearth of a predictive model capable of estimating the compressive strength of concrete including nanoparticles. The utilization of such models is of significant importance in the project and study of Reinforced Concrete (RC) structures including nanoparticles. Three machine learning algorithms, including Gene Expression Programming (GEP), Gradient Boosting (GB), and Extreme Gradient Boosting (XGB), were utilized in this study to forecast the Compressive Strength (CS) of nanocomposites that incorporate CNTs. The evaluation of the models' reliability was conducted by the utilization of cross-validation with K-folding and subsequent statistical error analysis. According to the results of the coefficient of determination (R2), the XGB model achieved the highest R2 value (0.95), while the GB model and GEP model both earned R2 values of 0.94. Furthermore, the validation method for the models included the implementation of statistical analysis and k-fold cross-validation. Therefore, the XGB model exhibited much lower values for statistical metrics compared to the GEP and GB models. In addition, a GEP empirical equation and a Graphical User Interface (GUI) have been created for practical applications in predicting the strength of concrete. This streamlines the procedure and provides a valuable instrument for harnessing the model's potential in the field of civil engineering. Furthermore, the use of Shapley analysis is conducted to assess the predominant factors in concrete prediction. The findings of this research indicate that the curing time, type of cement, and water-to-cement ratio significantly influence the properties of CNT-based concrete composites.
通讯机构：
[Fu, G ] C;Changsha Univ Sci & Technol, Sch Civil Engn, Dept Mech, Changsha, Peoples R China.
关键词：
local-global buckling;piezoelectric cylindrical shells;stepped thickness;buckling control;Hamiltonian system
摘要：
The Hamiltonian system is utilized to establish an accurate buckling solution model for piezoelectric material cylindrical shells with stepped thickness. The critical loads and nonuniform buckling modes are obtained by finding the symplectic eigenvalues and eigensolutions of the Hamiltonian equation. The results show that the transition between local buckling and global buckling can be controlled by an applied voltage. These findings can provide a novel method to control the buckling deformation range and symmetry of cylindrical shells.
摘要：
为研究节段超高性能混凝土(Ultra-High Performance Concrete,UHPC)装配式桥梁干接缝的直接剪切性能,基于有限元分析理论,在通用有限元分析软件(ABAQUS)中建模分析UHPC干接缝,得到了...展开更多 为研究节段超高性能混凝土(Ultra-High Performance Concrete,UHPC)装配式桥梁干接缝的直接剪切性能,基于有限元分析理论,在通用有限元分析软件(ABAQUS)中建模分析UHPC干接缝,得到了UHPC接缝在直剪荷载作用下的受力性能;利用已有试验数据对美国国家公路(American Association of State Highway and Transportation Officials,AASHTO)节段桥梁设计规范及多位学者所提出的UHPC干接缝抗剪承载力计算公式进行适用性及准确性评价;同时结合收集的实测数据拟合得到UHPC干接缝直剪承载力公式。结果表明,基于混凝土塑性损伤理论的ABAQUS计算模型可以较好模拟UHPC干接缝的直剪受力特征,各个模型试验结果与有限元结果的比值的平均值为0.970,变异系数为0.107;基于普通混凝土结构的美国AASHTO公式和西班牙ATEP公式不能准确预测UHPC干接缝的抗剪承载力,计算结果偏于不安全;前期学者提出的UHPC接缝计算公式预测结果偏保守,经济性较差;该研究给出的计算公式预测准确,可为实际节段UHPC装配式桥梁的接缝设计与计算提供参考。收起
关键词：
Structural optimization;Confined polyhedral pipeline;Stability;Pressure and thermal fields;Configuration factor
摘要：
This paper investigates the structural optimization of a polyhedral composite subsea pipeline (cylinder) under pressure and thermal fields. The pipeline is confined tightly and deforms inward when it is subjected to external loadings. The interface is frictionless between the pipeline and its surrounding medium. Based on the above assumptions, thin-walled shell principles, and an admissible displacement function, the potential energy of a pipeline per unit length is obtained explicitly by simplifying the radius and bending rigidity. After taking the first derivative of the potential energy, two equilibrium equations are obtained. By combining these two equations, the critical buckling pressure of the polyhedral pipeline is expressed analytically with the inclusion of the temperature effects. Then, the present analytical study is compared with other numerical and experimental results, and excellent agreements are reached. A configuration factor is defined as the buckling pressure between the polyhedral and circular pipeline. Finally, parametric studies show the configuration factor decreases with the increase of thickness-to-radius ratio, the increase of the number of sides, and the increase of the temperature variation, respectively. Therefore, a polyhedral pipeline with a low thickness-to-radius ratio is recommended in engineering practices since it may reduce the material cost.
摘要：
Recent years saw tremendous developments of data-driven modeling in various engineering fields. As for the contact modeling between complex surfaces, the utilization of neural networks successfully eliminates the limitations encountered by the traditional physics-based contact modeling strategy. However, contrary to its increasingly extensive applications, very little attention has been paid to the role of network hyper-parameters in reducing the model redundancy and improving its training efficiency. In this work, a novel neural network considering link switches has been presented for the data-driven modeling of complex con-tact phenomena. In order to further boost its prediction performance, genetic algorithm (GA) is employed for the optimal settings of relevant hyper-parameters. An indoor exper-imental setup is utilized to demonstrate the effectiveness of the presented methodology. Comprehensive comparisons with the base models indicate the superiorities of the established locally-connected-neural-network-based contact force model for complex geometries.
作者机构：
[Y. Q. Han] School of Civil Engineering, Central South University, Changsha, People’s Republic of China;[X. L. Peng] School of Civil Engineering, Changsha University of Science and Technology, Changsha, People’s Republic of China
通讯机构：
[X. L. Peng] S;School of Civil Engineering, Changsha University of Science and Technology, Changsha, People’s Republic of China
摘要：
Some arms of nanorobots display L-shaped structures. The transverse free bending vibration of an L-shaped cantilever nanobeam carrying a tip nanoparticle is investigated. Based on the nonlocal elasticity, the nonlocal parameter is introduced to capture the size effect of the mechanical behavior of the cantilever–mass system. The frequency equation is deduced analytically. Exact resonance frequencies of the L-shaped nanocantilever–mass system are numerically evaluated and compared with their corresponding values of the macro-scale L-shaped cantilever–mass system. The numerical results show that the nonlocal parameter declines the resonance frequencies. If removing the nonlocal parameter, our results reduce to the resonance frequencies of transverse bending vibration of L-shaped cantilevers with an attached tip mass. The effects of the nonlocal parameter, the ratio of the attached mass to the structure mass, the length ratio of two members of the L-shaped cantilever–mass system on the resonance frequencies are analyzed.
摘要：
The loading intermittence duo to the time interval between adjacent passing trains is conducive to improving the dynamic stability of railway subgrade, but this intermittence effect is always ignored in existing experimental studies on the dynamic characteristics of subgrade fillers in which a continuous cyclic loading method was adopted to simulate the long-term train-induced loading on subgrade. This paper aims to study the backbone curves of subgrade silty filler under intermittent train-induced loading, considering the time interval between adjacent passing trains. By conducting a series of intermittent cyclic triaxial tests on silty filler, the backbone curves of each loading stage were constructed, and the effects of loading intermittence on the backbone curves were elaborated. The experiment results indicate that the loading intermittence enhances the resistance of subgrade silty filler to the dynamic loading and is conducive to the upward deviation of the backbone curves. The loading intermittence could effectively increase the ultimate value of dynamic stress amplitude that the silty filler could bear under cyclic loading, but has little effect on the maximum/initial resilient modulus. The backbone curves increase approximately linear under the states of plastic shakedown and plastic creep, but show significant nonlinearity after including the incremental collapse samples. Hyperbolic models for backbone curves such as H-D model and its improvement model could be adopted to characterize the backbone curves of silty filler under intermittent loading, and the normalization of H-D model was also discussed to integrate the influencing factors (i.e., moisture content and confining pressure) of the backbone curves.
通讯机构：
[Zhao, B ] C;Changsha Univ Sci & Technol, Sch Civil Engn, Changsha 410004, Peoples R China.
关键词：
ultra-high-performance concrete;steel fiber;fracture phase field method;tensile strength;strengthening mechanism;crack surface energy
摘要：
The engineering optimization of ultra-high strength concrete (UHPC) requires urgent exploration of the strengthening mechanism of steel fiber in UHPC and the establishment of an effective simulation model. In this study, we propose a new fracture phase field model that considers the fracture energy of the interface between steel fiber and UHPC matrix. The model is utilized to conduct uniaxial tensile numerical simulations of 3D UHPC incorporating steel fibers, and a comparative experiment is conducted to validate the proposed model. The results display a notable agreement between the simulation and experiment. It is found that the tensile strength and residual strength of UHPC increase with steel fiber volume content and decrease with steel fiber diameter. The inclusion of steel fibers in UHPC results in more intricate crack patterns during the fracture process. The above results can be attributed to the debonding occurring at the interface between the steel fiber and the UHPC matrix which dissipates additional energy and thus enhances the UHPC. This work establishes a theoretical foundation for UHPC performance design and the development of effective simulation methods.
通讯机构：
[Wang, L ] C;Changsha Univ Sci & Technol, Sch Civil Engn, Changsha 410114, Peoples R China.
关键词：
Global reliability;DPIM;Failure mode;Target reliability index;Cable-stayed bridge
摘要：
This study presents an approach to analyzing the dynamic global reliability of cable-stayed bridges using the direct probability integral method. The analysis considers the degradation of resistance in the concrete main beam, tower, and cables, as well as the time-varying nature of the load effect. Six types of limit state functions for failure modes are established, including bending failure of the beam, static torsional failure of the beam, wind vibration failure of the beam, transverse buckling failure of the tower, longitudinal strength failure of the tower, and strength failure of the stay cable due to fretting fatigue and corrosion. A time-dependent extreme value mapping is constructed in the time domain, then the joint probability density integral equation of time-varying extreme value mapping of multiple performance functions is established. According to the mean and variance of random variables in the evaluation reference period, the direct probability integral method with Heaviside function (DPIM-H) is employed to solve the equation, and the dynamic global reliability index of cable-stayed bridge is obtained. As an example, the Brotonne cable-stayed bridge's global reliability is analyzed, and the reasonable value of the global target reliability index is studied considering the structural performance degradation.
期刊：
Construction and Building Materials,2024年421:135710 ISSN：0950-0618
通讯作者：
Weiwei Han<&wdkj&>Hui Peng
作者机构：
National-Local Joint Laboratory of Engineering Technology for Long-term Performance enhancement of Bridges in Southern District(Changsha University of Science & Technology), Changsha, Hunan 410114, China;School of Civil Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China;School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China;[Yigang Lv] National-Local Joint Laboratory of Engineering Technology for Long-term Performance enhancement of Bridges in Southern District(Changsha University of Science & Technology),Changsha, Hunan 410114,China<&wdkj&>School of Civil Engineering, Changsha University of Science and Technology,Changsha, Hunan 410114,China;[Jinghang Zhang; Miao Su; Xianliang He; Hui Peng] School of Civil Engineering, Changsha University of Science and Technology,Changsha, Hunan 410114,China
通讯机构：
[Weiwei Han; Hui Peng] S;School of Civil Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China<&wdkj&>School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China
摘要：
To clarify the bond performance between steel rebar and ultrahigh performance concrete containing coarse aggregates (UHPC-CA), a total of 33 pull out specimens was cast. The effects of coarse aggregate particle size, coarse aggregate content, and steel fiber content on the failure modes and bond stress-slip curves of the specimens were studied. Based on the virtual crack model, considering the tensile contribution of steel fibers and the bridging effect of coarse aggregates, a model for the bond strength between UHPC-CA and steel rebar was established. The research findings indicated that there was a corresponding matching relationship between coarse aggregate particle size and the spacing of steel rebar ribs. In the 5–8 mm particle size group, the specimens showed 7.95% and 9.01% increases in bond strength compared to the 3–5 mm and 8–10 mm particle size groups, respectively. When the coarse aggregate content of UHPC-CA was 20%, the bond strength was the highest, increasing by 11.39% compared to specimens without coarse aggregates. The bond strength first increased and then decreased with increasing steel fiber content. Excessive steel fiber content could lead to the clustering of steel fibers, reducing the effective number of steel fibers contributing to toughening. The calculated results from the established bond strength model were compared with experimental and literature results, yielding an average ratio of 0.993 and a standard deviation of 0.166. This model effectively predicts the bond strength between UHPC-CA and steel rebar.
通讯机构：
[Wen, W ] C;Changsha Univ Sci & Technol, Sch Civil Engn, Changsha 410114, Peoples R China.
关键词：
Disintegrated carbonaceous mudstone;Triaxial test;Numerical simulation;Discrete element method
摘要：
The paper aims to study the mechanical characteristics of disintegrated carbonaceous mudstone in a triaxial stress state from a micro-perspective of particles. Based on the discrete element method (DEM), a spherical-polymer (SP) model that includes three different types of the particles (triangle-like, rectangle-like, and sphere) was proposed and combined the error diagram with R2 to analyze the difference between the SP model and Ball-Ball (BB) model. Meanwhile, a sensitive analysis of micro-mechanical characteristics was carried out, which quantitatively described the sensitivity of different parameters according to stress-strain curves. The processes of deformation and failure for the disintegrated carbonaceous mudstone were finally analyzed based on the displacement diagram of the particle according to the energy theory. The results suggest that the SP model could better reflect the mechanical characteristics of disintegrated carbonaceous mudstone, for the SP models, the correlation coefficient (R2) range was larger than the BB model. From the sensitivity analysis of parameters, the decreasing rate of initial deformation modulus was 56-66% as the stiffness ratio was modified when fixing other factors. The peak strength correlated well with the tensile-shear strength ratio, stiffness ratio, and friction coefficient. The modification of abnormal-shaped particles' volume fraction ratio could affect the peak shear strength significantly. For the disintegrated carbonaceous mudstone, the processes of deformation and failure were discussed by energy transference which particle elements go from a low-energy state to a high-energy state.
作者机构：
[Peng, Wenzhe] Chinese Acad Sci, Inst Rock & Soil Mech, State Key Lab Geomech & Geotech Engn, Wuhan, Peoples R China.;[Peng, Wenzhe; Zhao, Minghua; Zhou, Shuai; Zhang, Ling] Hunan Univ, Coll Civil Engn, Changsha, Peoples R China.;[Zhu, Qin] Changsha Univ Sci & Technol, Coll Civil Engn, Changsha, Peoples R China.;[Peng, Wenzhe; Peng, WZ] Chinese Acad Sci, Inst Rock & Soil Mech, State Key Lab Geomech & Geotech Engn, Wuhan 430071, Peoples R China.
通讯机构：
[Peng, WZ ] C;Chinese Acad Sci, Inst Rock & Soil Mech, State Key Lab Geomech & Geotech Engn, Wuhan 430071, Peoples R China.
关键词：
Large-diameter monopile;vertical bearing capacity;void;marine clay;reduction coefficient;finite element limit analysis
摘要：
This study utilizes the finite element limit analysis (FELA) method to numerically investigate the effect of single and dual voids on the vertical bearing capacity of nearshore large-diameter monopiles in marine clay. After validating the numerical model, numerous numerical analyses in predicting the behavior of the pile-void system were conducted under different geometric parameters of pile and void, different pile-void distances, and different undrained shear strengths. These numerical results can be expressed in the form of design charts for vertical capacity reduction coefficients, which can facilitate a quick and straightforward assessment of pile capacity considering single and dual voids by multiplying the capacity without voids by respective coefficients. In addition, the numerical results can further give the contours of the plastic multiplier of the pile-void system which can be used to graphically conclude several representative failure modes. In short, this study intuitively illustrates the void effect on the pile vertical bearing capacity (including failure mode) and shows the significant differences between the cases with single and dual voids.
摘要：
Cracks are one of the most common pavement surface diseases. Timely repair of these cracks is imperative to prevent a substantial reduction in the pavement's service life. However, the persistent challenges in crack segmentation arise from factors such as thin and shallow crack characteristics, a cluttered background, and foreground distractors. In response to these challenges, a dual-path network for pavement crack segmentation is introduced, leveraging a synergistic combination of Convolutional Neural Network (CNN) and transformer. First, the proposed approach involves a lightweight CNN encoder for local feature extraction and a novel transformer encoder integrating a fully convolutional high-low frequency attention (FCHiLo) mechanism and an efficient feedforward network for global feature extraction. Second, a complementary fusion module (CFM) is introduced to aggregate intermediate features extracted from both encoders. The multi-scale fusion outputs are systematically conveyed to the decoder, facilitating gradual image recovery and segmentation result acquisition. Evaluation on three publicly available datasets-DeepCrack, CrackForest, and CrackTree 260-affirms the superior performance of the proposed network compared to ten established models.
摘要：
Thin-walled structures are commonly used in the design of mechanical systems, and their flexible dynamic problems are the frontiers in engineering research. In this paper, a flexible multibody system modeling method based on the shell theory is firstly developed for the dynamics of ammunition manipulator with thin-walled structure. We obtained the kinematic equation of the Reissner-Mindlin shell structure based on the floating frame of reference formulation. The coupling of membrane deformation and bending deformation with rigid motion is integrated in the proposed model, which is the characteristic of Reissner-Mindlin shell different from solid structure. In order to overcome membrane-locking and shear-locking problems in shell element simulation, an edge-center based strain smoothing - discrete shear gap (ECSS-DSG) element is introduced. The ECSS-DSG method achieves better membrane and bending behavior, as well as effectively overcoming shear-locking. Accordingly, the ECSS-DSG shows better performance in the structural analysis. Based on these works, the parameters of the ammunition manipulator model are identified by combining with experimental results. Subsequently, the prediction of model dynamic response under various working conditions is verified, which shows its excellent robustness. Our research can not only provide theoretical support for the further study of the ammunition manipulator, but also provide reference for the study of the dynamics of multibody system with thin wall structure.
