期刊：
Structural Engineering and Mechanics,2024年91(3):239-250 ISSN：1225-4568
通讯作者：
Gong, BB
作者机构：
[Gong, Binbin] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;[Gong, Binbin] Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.;[Li, Hao] CCCC Third Highway Engn Co Ltd, Beijing 100102, Peoples R China.
通讯机构：
[Gong, BB ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.
关键词：
cracks;fracture behavior;reinforced concrete;rigid body spring model;Voronoi diagram
摘要：
With the aim to provide better predication about fracture behavior, a numerical simulating strategy based on the rigid spring model is proposed for reinforced concrete (RC) structures in this study. According to the proposed strategy, concrete is partitioned into a series of irregular rigid blocks based on the Voronoi diagram, which are connected by interface springs. Steel bars are simulated by bar elements, and the bond slip element is defined at bar element nodes to describe the interaction between reinforcement and concrete. A concrete damage evolution model based on the separation criterion is adopted to describe the weakening process of interface spring between adjacent blocks, while a nonlinear bond slip model is introduced to simulate the synergy behaviour of reinforced steel bars and concrete. In the damage evolution model of concrete, the influence of compressive stress perpendicular to the interface on the shear strength is considered. To check the effectiveness and applicability of the proposed modelling, experimental and numerical studies about a simply- supported RC beam and the two- notched concrete plates in Nooru-Mohamed's- Mohamed's experiment are conducted, and the grid sensitivity are investigated.
作者：
Wang, Xinzhong;Li, Linshu;Xiang, Yi;Wu, Yuexing;Wei, Mei
期刊：
Frontiers in Materials,2024年10 ISSN：2296-8016
通讯作者：
Wang, XZ
作者机构：
[Li, Linshu; Wang, XZ; Wang, Xinzhong; Wu, Yuexing; Xiang, Yi] Hunan City Univ, Sch Civil Engn, Yiyang, Peoples R China.;[Wei, Mei] Hunan Arts & Crafts Vocat Coll, Sch Digital Arts, Yiyang, Peoples R China.
通讯机构：
[Wang, XZ ] H;Hunan City Univ, Sch Civil Engn, Yiyang, Peoples R China.
关键词：
concrete-filled steel tube;basalt fiber;short columns;finite element analysis;bearing capacity;ductility coefficient
摘要：
<jats:p>With rapid economic and social development, both concrete-filled steel tube (CFST) composite structures and basalt fiber (BF) have been widely applied in the field of civil engineering. To investigate the laws and characteristics of the influence of chopped BF on the mechanical properties of CFST columns and further promote the application of BF in CFST structures, the axial compressive bearing capacity test of 18 CFST short columns was carried out, and the influence of BF of different lengths on their structural mechanical properties was analyzed. The test results were compared with the theoretical calculation results and the finite element analysis results to verify the reasonableness of the test results. The results reveal that the axial compressive bearing capacity of the CFST short column after adding BF is significantly improved compared to the ordinary CFST short column, in which the bearing capacity and the ductility coefficient are increased by approximately 8.1% and 31.6%, respectively, on average. In addition, changing the length of BF has less effect on the bearing capacity of CFST short columns, the rate of increase in bearing capacity decreases with an increase in the steel ratio of CFST, and the coefficient of ductility increases with the increase in the steel ratio.</jats:p>
期刊：
International Journal of Structural Stability and Dynamics,2024年 ISSN：0219-4554
通讯作者：
Wang, L
作者机构：
[Wu, Yuexing; Wang, Xinzhong] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.;[Chen, Zhaowei; Wu, Yuexing; Zhou, Jianting] Tunnel Engn Chongqing Jiaotong Univ, State Key Lab Mt Bridge, Chongqing 400074, Peoples R China.;[Zhang, Jinquan] Minist Transport, Res Inst Highways, R China, Beijing 100088, Peoples R China.;[Wang, Lang] Southeast Univ, Sch Civil Engn, Nanjing 211189, Peoples R China.
通讯机构：
[Wang, L ] S;Southeast Univ, Sch Civil Engn, Nanjing 211189, Peoples R China.
关键词：
Long-span cable-stayed bridges;bridge system excitation;train-track-bridge dynamic interaction;mapping relationship
摘要：
Urban rail transit is rapidly evolving, with long-span cable-stayed bridges becoming increasingly popular among engineers because of their adaptability. However, as the operation time of bridges with tracks increases, the combined effects of repeated wheel loads and various bridge system excitations, including temperature changes and shrinkage-creep, gradually alter the alignment of the main beam. Similarly, the track structure on the bridge deck also undergoes vertical displacement, leading to corresponding degradation in rail alignment. This study applies singular function theory and verifies its effectiveness in bridge mechanical analysis. For the steel spring floating plate track cable-stayed bridge system, the mapping relationship between the deformation of the bridge's main beam and the track's deformation under bridge system excitation is derived, integrating singular function theory with the theory of train-track-bridge dynamic interaction. By analyzing the force transfer mechanism of the track-bridge system under system excitation, this research examines the effects of different excitations on the coupled dynamic response of the train-track-bridge. These findings suggest that system excitations increase the dynamic response of the train-track-bridge system, which is crucial for improving the durability and reliability of urban rail transit infrastructure.
通讯机构：
[Xiao, M ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Hunan, Peoples R China.
摘要：
This paper investigates the implementation of a Multi-Objective Optimization technique for improving public transportation route planning in the setting of smart cities. Recognizing the difficulties of urban mobility, our technique incorporates a variety of criteria, including traffic patterns, cost-effectiveness, and environmental impact, to create an efficient route design system. The research applies complex algorithms to overcome the issues present in existing route planning procedures, using real-world data sources such as GPS data and traffic reports. We illustrate the efficacy of our strategy in boosting time efficiency, lowering costs, and decreasing environmental footprints via extensive case studies. The assessment measures used emphasise the suggested system’s advantages over current techniques. The debate digs into the larger implications for smart city development, recognising limits and providing possibilities for further study. This study adds vital insights and practical answers to the developing subject of smart city transportation, providing a solid basis for the continuing growth of urban mobility.
通讯机构：
[Yu, J ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.
摘要：
Bike-sharing has a significant impact on commuters' rational planning of their travel times, which can lead to an advance or delay in the peak passenger flow of the subway system during the morning peak. To explore the impact of bike-sharing on subway commuters' choices of departure times, we developed a departure time choice model considering the effect of bike-sharing. This model considers both constant and linear marginal-activity utility and compares it with traditional departure time choice models. Research indicates that within the timeframe that ensures on-time arrival at work, models not accounting for bike-sharing services underestimate both the departure rate and the total number of commuters compared to actual figures. Specifically, under the constant marginal-activity utility, about 6.76% of commuters actually choose to depart earlier, while under the linear marginal-activity utility, this figure is 6.91%. Conversely, during the departure timeframes that lead to late arrival at work, the traditional model overestimates both the departure rate and total number of commuters. Finally, through case analysis, we further revealed the dynamic relationship between commuter departure rates, commuting fatigue, and number of bike-sharing and calculated the actual commuting costs for different proportions of bike-sharing. The results indicate that when the number of bike-sharing reaches 30% of the commuting demand, it can maximally reduce the commuting costs for commuters by approximately 23.32%. These findings offer a crucial basis for optimizing management strategies for morning peak subway commuting.
摘要：
<jats:p>Bamboo contains water-soluble saccharides and carboxylic acid which have an anticoagulation effect on Portland cement, and the anticoagulation ingredients can directly influence the hydration reaction extent. Hydration product varieties and hydration product-bamboo shaving binding interfaces of the Portland cement, and finally the mechanical properties of bamboo cement particle boards. In this paper, bamboo shavings are pretreated by carbonizing treatment, hydro-thermal treatment and alkali treatment; high performance liquid chromatography is adopted to analyze the influences of three different pretreatment methods on contents of water-soluble saccharides and carboxylic acid in the bamboo shavings; a Fourier infrared spectrometer and an X-ray diffractometer are respectively utilized to analyze the characteristic peak changes and crystallization property changes of chemical ingredients of the bamboo shavings before and after the three types of pretreatment. This paper discusses effects of three types of pretreatment methods in eliminating water-soluble saccharides and carboxylic acid in the bamboo shavings. Bamboo Portland cement particle boards was prepared using bamboo shavings, which are pretreated in three ways, and influences and mechanisms of different pretreatment methods on properties of the bamboo Portland cement particle boards were studied. Research indicates that the mechanical properties of the Portland cement particle board prepared from bamboo shavings pretreated with 3 % NaOH solution are superior to requirements of qualified products and superior products specified in the Standard.</jats:p>
摘要：
An innovative anchorage technology named load distributive compression anchor (LDCA) has recently been employed in a multitude of geotechnical engineering. The anchoring structure comprises multiple anchor bodies, thereby overcoming the bearing defects associated with conventional load-concentrated anchors and providing superior bearing performance. The complex structural configuration of LDCA considerably complicates the process of load-transfer theoretical modeling. A lack of relevant studies from theoretical solution perspective is yet evident in previous works. In this paper, a theoretical model was proposed for the load-transfer analyses of LDCA, of which the soil-anchor interface mechanical behavior was specially characterized by a disturbed state concept (DSC)-based nonlinear model. The mechanical simulation for the connections in different anchor bodies was incorporated into the theoretical analysis framework through the utilization of finite difference method. Three groups of 3D finite element (FE) models were established to simulate the load-transfer behaviors of LDCAs with different numbers of anchor bodies. The theoretical calculations agree well with the FE numerical results and the in-situ pullout test data, thereby confirming the applicability of the load-transfer theoretical model. The axial force and interface shear stress distributions, as well as the bearing capacity for LDCAs, were discussed based on theoretical calculations and FE simulations. Sensitivity analysis of several key design parameters was conducted to investigate their effects on the bearing capacity of LDCAs. The findings achieved in this study can provide insights into the understanding of the load-transfer behaviors of LDCA, and contribute to the bearing performance evaluation.
摘要：
To investigate the regeneration mechanisms of rejuvenated asphalt mixtures, molecular simulation techniques were employed to research virgin and aged asphalt's fusion characteristics and interface mechanical properties. The blended zone was identified based on relative density distribution, and a molecular-scale calculation method for the Degree of binder Blended (DOB) between virgin and aged asphalt was proposed. Finally, the influence of DOB on the mechanical properties of the asphalt-aggregate interface was evaluated through interface pull-out tests. The results revealed that the proposed molecular-scale DOB calculation method effectively assessed the blending effectiveness between virgin and aged asphalt. Higher degrees of asphalt aging made it more challenging for aged asphalt to fuse with virgin asphalt, while elevated temperatures facilitated diffusion fusion between them. Under tensile loading, initial cracks were primarily initiated from the rejuvenated asphalt's blended zone. This region represented the weakest area within the interface system and was prone to fracture under load. The increase in DOB significantly improved the interfacial properties of recycled asphalt, with the increase in DOB the interfacial tensile strength increased by 4%-14% and the fracture energy increased by 10%- 19%. However, this enhancement effect diminished with an increased degree of asphalt aging. At the molecular scale, increasing DOB improved the interface strength and deformation resistance of rejuvenated asphalt. The molecular simulation results provide theoretical guidance for evaluating the fusion degree of aged asphalt in RAP materials and determining the utilization efficiency of aged asphalt.
摘要：
The microstructure, mineral composition, total organic carbon content, etc., of gas shale are crucial parameters for shale reservoirs, which can directly/indirectly affect shale brittleness, fracturing effect, adsorption ability and production efficiency. The study proposed a workflow to characterize the physical and mechanical parameters of Lower Silurian Longmaxi shale outcrop samples extracted from the favorable block in Changning, Sichuan, southwest China. This study elaborated on the influence of these physical and mechanical characteristics and proposed a corresponding brittleness index on shale extraction. In addition, it put forward corresponding suggestions for development and risk control. For a better understanding the mechanisms of shale gas storage and production, XRD, XRF, SEM, low temperature Nitrogen adsorption method, nuclear magnetic resonance and other measurements were employed to analyze and study the mineral composition, microstructure, and adsorption performance of shale. The results demonstrated that the pores of shale are mainly slit pores; there are diverse pore types in shale, mainly including intergranular pores, mineral particle dissolution pores, and internal pores of organic matter; The samples with relatively low porosity also noticeably exhibit ultra-low permeability, and the nanopore structure is remarkably significant, with distribution primarily in range of 5–237 nm. Finally, a brittleness index considering the influence of water content and the mechanical properties was proposed, and the coupling interaction of various minerals components and mechanical properties on the brittleness index can more objectively reflect the brittleness characteristics of deep shale formation.
关键词：
Asphalt mixture;Mesoscopic analysis;Skeleton evolution;Aggregate contact;Particle movement;Discrete element method
摘要：
The aggregate skeleton is the intrinsic core of asphalt mixtures for load transfer, which is quite different under various gradations. For evaluating the loading characteristics of the aggregate skeleton, this research combined the 3D blue -ray scanning technology and discrete element method (DEM) to establish the numerical models of different graded asphalt mixtures considering the real aggregate morphology. A linear parallel bond model was used to simulate the adhesion effect of asphalt, and the uniaxial compression numerical simulation was verified by indoor tests. In addition, the contact force, contact number, anisotropy, and rotation angle were used to evaluate the aggregate skeleton evolution under uniaxial compression loading. Furthermore, the contribution of each grade aggregate in the gradation to the skeleton structure was analyzed. Results show that the average contact force is higher in large -size aggregates above 9.5 mm, which exhibit greater load transfer efficiency. Moreover, 4.75-9.5 mm size aggregates combine the functions of bearing and filling, and its role is significantly affected by the gradation. It is also found that the internal skeleton structure can be optimized and adjusted under stress. The contact numbers of different graded mixtures follow a close decrease, and the strong contacts are mostly provided by coarse aggregates above 4.75 mm. The anisotropy development of aggregate skeleton contact force is induced by the stress, and the deviator fabric of asphalt mixtures show a good linear positive correlation with the uniaxial compressive strength (UCS). Besides, fine aggregates exhibit greater cumulative rotation angle and instability effect, it is feasible to detect asphalt mixture deformation by the rotation angle of particles.
