期刊：
Water Supply,2023年23(9):3761–3774. ISSN：1606-9749
通讯作者：
Qian, DY
作者机构：
[Cao, Yanmin] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Hunan, Peoples R China.;[Qian, Dongyue] Tianjin Acad Water Transportat Engn, Minist Transport, Tianjin 300456, Peoples R China.;[Wang, Chongyu] Hunan Water Planning & Design Inst Co Ltd, Changsha 410008, Hunan, Peoples R China.
通讯机构：
[Qian, DY ] T;Tianjin Acad Water Transportat Engn, Minist Transport, Tianjin 300456, Peoples R China.
关键词：
contribution rate;cross city driving force;water quality factor;Xiang River Basin
摘要：
Based on the monthly monitoring data of 16 water quality monitoring stations in the Xiang River Basin from 1990 to 2020, the Mann-Kendall test was used to analyze dissolved oxygen, 5-day biochemical oxygen demand, permanganate index, total phosphorus, ammonia nitrogen, cadmium, arsenic, and hexavalent chromium. The changing trend of nine indicators, including the stepwise regression method, was used to determine the cross city driving force of each water quality index, and the contribution rate (weight) of each driving force was obtained by principal component analysis. The research results show that (1) agriculture in Yongzhou is the main driving force, and its contribution rate is 67.2%; (2) urbanization has a greater impact on the driving process of the water environment in the Xiang River Basin, and its contribution rate is as follows: Changsha (83%) > Hengyang (80.7%) > Pingxiang (63.7%) > Chenzhou (60.9%) > Xiangtan (57.4%) > Zhuzhou (50%) > Loudi (48.5%); (3) the urbanization of Zhuzhou City and Loudi City's urban sewage discharge not only has an impact on the city's water environment, but also drives the water environment in the downstream Xiangtan area. The research results can provide a basis and reference for the study of water environmental governance in the basin.
期刊：
Energy Science & Engineering,2023年11(9):3185-3203 ISSN：2050-0505
通讯作者：
Wang, G
作者机构：
[Liu, Ronghua; Chen, Yong; Wang, Pengfei] Hunan Univ Sci & Technol, Sch Resource & Environm & Safety Engn, Xiangtan, Hunan, Peoples R China.;[Liu, Ronghua; Chen, Yong; Wang, Pengfei] Work Safety Key Lab Prevent & Control Gas & Roof D, Xiangtan, Hunan, Peoples R China.;[Wu, Jiaokun; Chen, Yong] Natl Key Lab Gas Disaster Detecting Preventing & E, Chongqing, Peoples R China.;[Wu, Jiaokun; Chen, Yong] China Coal Technol Engn Grp Chongqing Res Inst, Chongqing, Peoples R China.;[Wang, Gang; Chen, Yong] Shandong Univ Sci & Technol, State Key Lab Strata Intelligent Control & Green M, Qingdao, Peoples R China.
通讯机构：
[Wang, G ] S;Shandong Univ Sci & Technol, State Key Lab Strata Intelligent Control & Green M, 579, Qianwangang Rd, Qingdao 266590, Shandong, Peoples R China.;Shandong Univ Sci & Technol, Minist Sci & Technol, 579, Qianwangang Rd, Qingdao 266590, Shandong, Peoples R China.
关键词：
degree of metamorphism;gas desorption;pore volume;primary coal;specific surface area
摘要：
Exploring the pore and gas desorption characteristics of primary coal with different degrees of metamorphism. Abstract Pore difference characteristics and adsorption/desorption experiments of primary coal with different degrees were explored to study the characteristics of pore structure and gas desorption. The results show that the pore volume increases with the increase in the degree of metamorphism. In primary coal with different degrees of metamorphism, the distribution of micropores, small pores, and medium‐sized pores (by volume) is WY < PM < CY. The distribution of large pore volume and visible pore volume was WY > PM > CY. According to the pore volume distribution law of different metamorphic primary coals, the average pore diameters of WY, PM, and CY were 68.40, 45.60, and 30.50 nm, respectively. The porosity and specific surface area of primary coal with different degrees of metamorphism show a distribution pattern such that WY > PM > CY. For large pore and visible pore, the pore volumes of WY, PM, and CY coal were 0.0785, 0.0587, and 0.0300 mL/g, respectively, and the proportions were 81.86%, 74.49%, and 55.25%, respectively. The porosity of WY, PM, and CY were 11.57%, 9.03%, and 6.57%, respectively, and the specific surface areas were 6.917, 5.826, and 5.611 cm3/g. According to the desorption characteristics of coal bodies with different metamorphic degrees at different time nodes found that the gas desorption at different time nodes shows similar changes under the same adsorption equilibrium pressure. The higher the degree of coal metamorphism, the greater the amount of gas desorption, and the faster the desorption amplitude. The desorption intensity of WY coal is significantly higher than that of PM and CY coal with the increase of desorption time which also verifies the measurement results of pore structure and adsorption constant.
摘要：
The vacuum preloading method effectively strengthens soft soil foundations with vertical drainage, which produces a smear effect when laying sand drains. Meanwhile, the seepage of pore water and soil deformation during consolidation exhibit nonlinear characteristics. Therefore, based on Gibson's 1D large-strain consolidation theory, this paper developed a more generalized large-strain radical consolidation model of sand-drained soft foundations under free-strain assumptions. In this system, the double logarithmic compression permeability relationships for soft soils with large-strain properties, the variation in the radical permeability coefficient in the smear zone, and the effect of the non-Darcy flow were all included. Then, the partial differential control equations were numerically solved by the finite difference method and validated with existing radical consolidation test results and derived analytical solutions. Finally, the influences of relevant model parameters on consolidation are discussed. The analysis shows that the greater the maximum dimensionless vacuum negative pressure P0, the faster the consolidation rate of sand-drained foundations. Meanwhile, the decrease in the negative pressure transfer coefficient k1 will result in a decreasing final settlement amount. Moreover, the consolidation rate of sand-drained foundations is slower considering the non-Darcy flow, but the final settlement is unaffected.
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.
关键词：
finite difference time domain (FDTD);reverse time migration (RTM);finite difference time domain reverse time migration (FDTD-RTM);wavelet multi-resolution analysis;super-resolution reconstruction method
摘要：
The finite difference time domain (FDTD) method was used to solve the Maxwell's equation to obtain the reverse time migration (RTM) of ground penetrating radar (GPR) signals, namely, the FDTD-RTM. In order to ensure that the correct numerical solution of iterative calculation was achieved, it was necessary to obtain high-resolution signals, which greatly limits the applicability of FDTD-RTM in engineering. Based on the characteristics of wavelet multi-resolution analysis, this study proposed a super-resolution signal reconstruction method to improve signal resolution, with the view to completely solving the problem of FDTD-RTM limitation caused by insufficient signal sampling using GPR. The results of electromagnetic simulation showed that the signals reconstructed by the above method were highly similar to the signals sampled with the same resolution. On this basis, reverse time migration electromagnetic simulation and physical model tests were designed. The results of both experiments showed that the under-sampled GPR signals could achieve FDTD-RTM following super-resolution reconstruction, and that the migration imaging results of the target were basically consistent with the design scheme. The signal super-resolution reconstruction method based on the wavelet theory was thus shown to successfully achieve the overall application of FDTD-RTM in GPR signal analysis.
摘要：
Reasonable assessment of corrosion initiation probability in existing reinforced concrete structures is an important premise for ensuring the safety and durability of such structures. In this paper, a simplified dual time-dependent chloride diffusion model considering the load effect is established and verified by comparing its results with the experimental data. Then, a modelling method of imprecise random fields is developed. In addition, a novel probabilistic analysis method of corrosion initiation in existing RC structures with imprecise random fields is proposed. The case analysis results show that the corrosion resistance of existing structures will be overestimated without considering the effect of imprecise random fields. In comparison, the upper bound of cumulative probability of corrosion initiation is 2.29 times of that using the existing deterministic method in this case. Parametric analyses show that the imprecise random field of concrete cover (Cd) has the greatest effect on the cumulative probability of corrosion initiation, followed by initial surface chloride concentration (Cs) and chloride diffusion coefficient (Da). Compared with the interval coefficient of variation and correlation length, the cumulative probability of corrosion initiation is more sensitive to the interval mean, especially the interval mean of Cd. Additionally, the effect of interval correlation length of Cs is sequentially greater than that of Cd and Da.
作者机构：
[Peng, Zhigao; Peng, ZG; Deng, Zongwei; Feng, Haoxiong; Xiao, Ming] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;[Liu, Shenggui] China Univ Min & Technol Beijing, Sch Mech & Civil Engn, Beijing 100083, Peoples R China.;[Peng, Zhigao; Peng, ZG] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.
通讯机构：
[Peng, ZG ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.
摘要：
Under specific conditions, moisture in natural coal seams can be adsorbed in the pores of the coal matrix, reducing the amount of methane adsorption sites and the effective area of the transport channels. This makes the prediction and evaluation of permeability in CBM exploitation more challenging. In this paper, we developed an apparent permeability model of coalbed methane coupling viscous flow, Knudsen diffusion, and surface diffusion which considers the effects of adsorbed gas and moisture in the pores of the coal matrix on the permeability evolution. The predicted data of the present model are compared with those of other models, and the results show good agreement, verifying the accuracy of the model. The model was employed to study the apparent permeability evolution characteristics of coalbed methane under different pressure and pore size distribution conditions. The main findings are as follows: (1) moisture content increases with saturation, with a slower increase for smaller porosities and an accelerated non-linear increase for porosities greater than 0.1. (2) Gas adsorption in pores decreases permeability, further weakened by moisture adsorption under high pressure but negligible at pressures below 1 MPa. (3) Higher water saturation weakens gas transport capacity, especially with pore sizes smaller than 10 nm. (4) The non-Darcy effect weakens with higher initial porosity, and neglecting moisture adsorption may significantly deviate from actual values in modeling methane transport in coal seams. The present permeability model can capture the transport characteristics of CBM in moist coal seams more realistically and is more applicable for predicting and evaluating the gas transport performance under dynamic variations of pressure, pore size, and moisture. The results in this paper can explain the transport behavior of gas in moist, tight, porous media and also provide a foundation for coalbed methane permeability evaluation.
通讯机构：
[Jianxin Peng ] P;Professor, Key Laboratory of Bridge Engineering Safety Control by Department of Education, School of Civil Engineering, Changsha University of Science and Technology, Changsha, Hunan, China (corresponding author: [email protected])
摘要：
A test was carried out to study the interface shear strength between carbonated concrete substrate and self-compacting concrete (SCC) overlay. One hundred and fourteen Z-type specimens were designed and subjected to direct shear tests. The influence of four interface treatment methods, three strengthening schemes and SCC strength on interface shear strength were discussed. Two coefficients considering the influence of interface treatment method and strengthening scheme on interface shear strength between carbonated concrete and SCC were developed. The results show that interface shear strength is affected not only by SCC strength but also by the strengthening scheme for the same interface treatment method, which increases with the increase of overlay strength for the same interface treatment method and strengthening scheme. The position of groove has little influence on interface shear strength for grooved specimens. Implanting steel bar is the most effective way to improve interface shear strength. When the carbonation time is around 60 days, the interface shear strength is increased by about 17%. The theoretical interface shear strength obtained by the developed model agreed well with tested values. The mean ratio of tested interface shear strength to theoretical strength is 0.86.
摘要：
Live load of moving vehicles has a very important effect on the fatigue life of suspension bridges, which causes not only vertical deformation but also longitudinal deformation. In this study, a general analytical formulation for analyzing the quasistatic longitudinal displacement of suspension bridges under vertical live loads is developed, and the underlying deformation mechanism is revealed. First, the analytical vertical and longitudinal deformation equations for the single main cable subjected to live loads are formulated considering the geometric nonlinearity. Then, the relation of longitudinal displacements between the stiffening girder and the main cable for a single-span suspension bridge is established through analyzing the geometric configuration of deformed deck-suspender segment and imposing the null longitudinal force condition. The relation is further modified to incorporate the effect of central buckles (CBs). Compared with the finite-element (FE) prediction, the proposed analytical solution is quite accurate for both concentrated and distributed loads. It is found that the coupling of vertical and longitudinal displacement of main cables and the longitudinal constraint between the cables and girder, are responsible for the longitudinal displacement of the girder. The effects of sag-to-span ratio, CB, and inclined suspenders are studied. The longitudinal displacement of the girder can be reduced by about 20% when the sag-to-span ratio is varied from 1/9 to 1/11, and the CB with proper stiffness is more effective in reducing the longitudinal displacements. The proposed formulation can be conveniently applied for parameter optimization in the preliminary design stage so as to avoid tedious repetitive FE analysis.
期刊：
Mechanics Based Design of Structures and Machines,2023年51(6):3004-3025 ISSN：1539-7734
通讯作者：
Xian-Fang Li
作者机构：
[Zhang, Xue-Yang; Peng, Yi; Li, Xian-Fang] Cent South Univ, Sch Civil Engn, Changsha 410075, Peoples R China.;[Peng, Yi] Hunan City Univ, Sch Civil Engn, Yiyang, Peoples R China.
通讯机构：
[Xian-Fang Li] S;School of Civil Engineering, Central South University, Changsha, PR China
关键词：
Heat-moisture coupling;convective boundary;non-Fourier effect;hygrothermal stresses;phase lag
摘要：
In this article, by considering the Dufour effect and Soret effect, a hygrothermal coupling model based on phase delay of heat and moisture fluxes is established for convective surfaces. The convective surfaces are described by Robin boundary conditions. The Dirichlet boundary conditions (prescribed temperature and moisture on the surfaces) and Neumann boundary conditions (prescribed heat and moisture fluxes) are two extreme cases of the Robin conditions. Using Laplace transform, the effects of different relaxation times and moist-heat coupling on the temperature, moisture, and stress of the hollow cylinder are analyzed from two aspects of time and space. For convective boundary, the dependence of temperature, moisture, and stress on the phase lag of heat and moisture fluxes is examined. The results show that the temperature and moisture distributions along with the hygrothermal stress fields exhibit different behaviors, depending on the coefficient of Robin condition.
作者机构：
[Liang, Xiaoqiang; Yang, Xian; Hu, Da; Li, Yongsuo; Hu, D] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.;[Yi, Shun; Liang, Xiaoqiang; Yang, Xian; Hu, Da; Hu, Yongjia; Hu, D] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;[Hu, Da; Hu, D] Power China Zhongnan Engn Co Ltd, Hunan Prov Key Lab Key Technol Hydropower Dev, Changsha 410014, Peoples R China.
通讯机构：
[Hu, D ] H;Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;Power China Zhongnan Engn Co Ltd, Hunan Prov Key Lab Key Technol Hydropower Dev, Changsha 410014, Peoples R China.
摘要：
To provide theoretical support for the safety control of rectangular pipe jacking tunnels crossing an existing expressway, a method for predicting the surface settlement of a rectangular pipe jacking tunnel is proposed in this study. Therefore, based on the high approximation of the BP neural network to any function under the multiparameter input, the PSO-BP mixed prediction model of the ground subsidence of the ultrashallow buried large section rectangular pipe jacking tunnel is established by taking into account the adaptive mutation method, adopting the improved particle swarm optimization (IPSO) algorithm with adaptive inertia weight and mutation particles in the later stage to determine the optimal hyperparameters of the prediction model. Through the case study of an ultrashallow large cross-section rectangular pipe jacking tunnel, this algorithm is compared with the traditional algorithm and combined with field monitoring data for analysis and prediction. The prediction results show that compared with the traditional BP neural network prediction model, AWPSO-BP model and PWPSO-BP model, the improved PSO-BP mixed prediction model shows a more stable prediction effect when the change in surface subsidence is gentle and the concavity and convexity are large. The predicted subsidence value is close to the actual value, and the accuracy and robustness of the prediction are significantly improved.
通讯机构：
[Zhefeng Liu] S;School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>Author to whom correspondence should be addressed.
摘要：
In order to understand the seismic damage assessment of reinforced concrete column members, the coupling relationship between the capacity degradation and the accumulated hysteretic energy and the displacement history was considered. The energy-based damage index under the random variable amplitude loading history was proposed. On the basis of preliminary research, the corresponding relationship between the damage index and the construction member parameters and seismic parameters was established, the damage mechanism was analyzed according to the damage index, and then the performance-based design process was proposed. It was found that increase in the stirrup ratio can slow down the damage, and the slowing effect was initially fast and then slows. When the reinforcement ratio is doubled, the damage index decreased by 0.063. The longer the earthquake duration was, the more serious the damage was, and this phenomenon was more obvious when the ductility coefficient was larger. With the increase in the ductility coefficient, the damage continuously increased. Therefore, it is an effective way to decrease the damage by controlling the ductility coefficient. Among all the influencing factors, the fundamental period and seismic intensity contributed more significantly to the damage indicators. When the damage index (performance objective) was determined, the target stirrup ratio can be obtained according to the proposed performance design process, that is, this design process can be used in the performance-based design. The design method based on damage index can make up for the deficiency that the design method based on the ductility coefficient does not consider the earthquake duration.
摘要：
Corrosion can accelerate the deterioration of the mechanical properties of orthotropic steel bridge decks (OSBDs), seriously affecting the service safety of steel bridges. In this paper, thirty Q345C steel and four OSBD specimens with various corrosion levels are designed to investigate the effect of corrosion on the static behavior of OSBDs. Then, corrosion damage and its influence on mechanical properties are explored by static loading experiments. The constitutive model for Q345C steel is built considering the impact of corrosion. Finally, a numerical analysis considering geometric initial defects is employed to compare the effect of corrosion location on bearing capacity degradation. It is observed from the tested results that the corrosion led to the failure mode of Q345C steel changing from plastic failure to brittle failure. The ultimate bearing capacity of specimens with a local corrosion rate of 7.92%, 12.05%, and 16.24% decreased by 11.08%, 14.45%, and 17.82%, respectively. Corrosion leads to stress concentration in the top plate area, causing local instability of the structure. The degradation degree of the bearing capacity of the top plate is greater than that of the U-rib corrosion corresponding to the same corrosion conditions.
作者机构：
[Chen, Yi; Xue, Yanghao; Zhao, Changjie; Liu, Chang] Guizhou Univ, Sch Civil Engn, Guiyang 550025, Guizhou, Peoples R China.;[Rao, Junying; Rao, JY] Guizhou Univ, Res Ctr Space Struct, Guiyang 550025, Guizhou, Peoples R China.;[Chen, Yi; Xue, Yanghao; Zhao, Changjie; Liu, Chang] Guizhou Prov Key Lab Rock & Soil Mech & Engn Safe, Guiyang 550025, Guizhou, Peoples R China.;[Yin, Quan] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Hunan, Peoples R China.
通讯机构：
[Rao, JY ] G;Guizhou Univ, Res Ctr Space Struct, Guiyang 550025, Guizhou, Peoples R China.
摘要：
To investigate the mechanical properties of fractured dolomite, this study analyzed the fracture characteristics (dip angle, length, position, quantity) using the Pearson coefficient and MIC coefficient. Subsequently, the data pertaining to fracture characteristics is preprocessed using a third-degree polynomial, and a three-classification strategy is implemented to improve the logistic regression algorithm to establish the strength prediction model of fractured dolomite. Furthermore, the significance order of the impact of fracture characteristics on rock strength was determined using the numerical simulation software PFC3D, and the dip angle effect was explained from the perspective of internal fracture propagation within the rock. The results show that: (1) When the regularization coefficient λ = 10,000, the algorithm has the highest prediction accuracy and the strongest model generalization ability. (2) The numerical simulation analysis software PFC3D can accurately invert rock failure process and characteristics, and the order of influence of fracture characteristics on rock strength is dip angle > length > position.
摘要：
In the light of the shielding effect of the strong reflection signal generated by the steel bars and the inhomogeneous of concrete materials on the weak signal in the tunnel lining detection, a high-resolution GPR image processing method of biorthogonal wavelet energy entropy in different time windows is proposed. Wavelet analysis has the characteristics of multiresolution, and wavelet entropy can represent the energy distribution characteristics of signals in different time windows with different scales. Firstly, the discrete biorthogonal wavelet transform is applied to decompose the original GPR image into subimages with different frequencies and different spatial local changes. Secondly, appropriate time windows are selected for wavelet entropy adaptive threshold processing of each subimage in the light of the different amplitude ratio of effective signal to strong interference in each subimage, and finally the reconstructed image after removing the strong reflection is spectrally whitened. Both the forward simulations and actual measurement results show that the method can effectively remove strong reflection interference, clear weak signals, and maintain the continuity of the reflection events, and compared to the conventional pulse deconvolution, predictive deconvolution and wavelet entropy methods with the same time window, this method has a more thorough interference removal effect, and the effective signal performance is more obvious, which proves the effectiveness and accuracy of the proposed method in improving the resolution of GPR image and highlighting weak signal.
作者机构：
[Peng, Zhigao; Peng, ZG; Feng, Haoxiong; Xiao, Ming] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;[Peng, Zhigao; Peng, ZG] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Hunan, Peoples R China.;[Liu, Shenggui] Univ Min & Technol Beijing, Sch Mech & Civil Engn, Beijing 100083, Peoples R China.;[Long, Yanqing] Hunan Tunnel Engn Co LTD, Yiyang 413000, Peoples R China.
通讯机构：
[Peng, ZG ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Hunan, Peoples R China.
摘要：
The occurrence of coalbed methane adsorption-desorption hysteresis has been widely observed, but a unified understanding of its mechanism is lacking, and the factors affecting its degree are unclear. This study introduces a microscale LB model for gas diffusion-adsorption-desorption in porous media that also accounts for the adsorption-desorption hysteresis effect. The accuracy of the model has been validated using previous experimental data, and the primary controlling factors of adsorption-desorption hysteresis were analyzed. The findings are as follows: (1) In the process of methane diffusion-adsorption-desorption, Knudsen diffusion dominates in micro- and mesopores, while viscous flow prevails in macropores; our model can adaptively adjust gas transport regimes across a broad range of pore sizes and pressures. (2) The desorption amount and rate are close relative to the correction factors α and β. A higher α value corresponds to greater initial adsorption as well as longer desorption time, whereas a lower β value implies weaker desorption capacity and a slower desorption rate. (3) Pore size can affect gas diffusion-adsorption-desorption kinetics, where larger pore size corresponds to efficient gas diffusivity; when r < 10 nm, the desorption process is mainly controlled by the desorption rate. Overall, this study has offered new insights into the mechanism behind methane adsorption-desorption hysteresis at the microscale, identified primary controlling factors of methane diffusion-adsorption-desorption process, and provided a foundation for numerical simulations and experiments related to the adsorption-desorption hysteresis.
摘要：
To investigate the reasonable range of the inclination angle of arch ribs, a spatial finite element method was employed based on a concrete-filled steel tube (CFST) basket-handle through an arch bridge with a span of 360 m. A spatial finite element model was established using Midas/Civil software, which was verified with actual bridge data. The effects of different arch rib inclination angles were investigated under static loads. The structural natural frequencies, linear elastic stability coefficients, internal forces, and displacements were comprehensively considered to determine the reasonable range of the inclination angle. The results show that when the inclination angle ranges between 8 & DEG; and 10 & DEG;, the first, third, and sixth natural frequencies of the structure are increased. It effectively improves the lateral and torsional stiffness of the arch ribs while ensuring optimal out-of-plane stability of the arch ribs. Compared with the parallel arch, the stability is improved by 20.2%. The effects of angle variation on displacement and internal force of the arch ribs were not significant. Considering all indicators, the optimal range of the inclination angle for the arch ribs of 300-m-level highway CFST arch bridges is suggested to be 8 similar to 10 & DEG;.
