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.
期刊：
International Journal of Environmental Technology and Management,2024年27(4-6):400-414 ISSN：1466-2132
作者机构：
[Ye He] School of Civil Engineering, Hunan City University, Yiyang, 413000, China
关键词：
river safety remediation;ecological environment;qualitative assessment;analytic hierarchy;evaluation metrics
摘要：
In order to achieve the accuracy of ecological environment quality assessment under river safety regulation, this article conducts research on the construction method of a qualitative evaluation model for ecological environment quality. Firstly, construct an evaluation system and establish the main framework for qualitative evaluation of ecological environment quality. Secondly, the analytic hierarchy process was used to determine the criteria layer indicators, and 18 evaluation indicators were selected for the indicator layer. Thirdly, the information entropy redundancy is determined based on the entropy method, and the index weight is calculated. Finally, establish a comprehensive evaluation index, determine specific scoring standards for each indicator state, match different scoring levels based on the scores, and complete the construction of an ecological environment quality assessment model to achieve accurate evaluation of ecological environment quality. By combining the average score of each region and the average score of each indicator, it can be concluded that the final score of the ecological environment quality assessment in the study area is 70.97 points, which belongs to a good level. This indicates that the overall ecological environment quality of the region is in a good state after river safety renovation.
摘要：
为了研究使用矩形钢管连接的新型全预制冷弯薄壁型钢复合墙体的抗侧性能,设计了6个足尺试件,并进行了水平低周往复加载试验,分析了龙骨间距、覆面板类型、单面或双面覆板等因素对新型复合墙体试件抗侧性能的影响.新型墙体的覆面板为OSB板与硅晶钙板.试验结果表明:使用矩形钢管连接的新型复合墙体具有良好的整体抗震性能;单面或双面覆板对墙体抗侧性能影响显著,双面覆板的新型复合墙体的屈服荷载约为单面覆板新型复合墙体的2倍;龙骨间距和覆面板材料对墙体抗侧性能的影响相对较小.在试验基础上,使用OpenSEES软件建立了试验墙体的有限元分析模型,并针对矩形钢管壁厚、周边螺钉间距取值进行了参数分析.参数分析结果表明,矩形钢管连接件壁厚取值推荐为2.5 mm,周边螺钉间距推荐取50～100 mm.
摘要：
Degradation of bond strength due to corrosion of steel strands is of great importance for serviceability of prestressed concrete structures. An analytical model is proposed to demonstrate the effect of corrosion of steel strand on reduction of bond strength. Corrosion expansion force generated by steel strand corrosion before and after corrosion cracking is firstly estimated. Then, the reduced gripping effect of the concrete, change of friction coefficient between the corroded strand and reduction force on the bearing face are considered in calculating the pre-rib extrusion force. Finally, the enhancement of bond strength due to transverse confinement of stirrups is considered and the ultimate bond strength of corroded steel strand is calculated. Comparison of results between the prediction and experimental result shows the proposed model can be used to reasonably evaluate the bond strength. The prediction result of the bond strength model is affected by the degree of strand corrosion, but almost not by the drawing method.
摘要：
A damage detection method based on the quadratic correlation function of strain responses (QCoS) and pattern matching degree (PMD) is proposed in the present study. For this method, only QCoS is calculated in time domain by strain responses, and there is no need for modal parameter extraction and analytical model of structures. It is proved that QCoS is the function of modal parameters of structures, such as natural frequency, mode shape and damping ratio. Numerical simulations of a simply supported steel beam are analyzed for illustrating the effect of excitation position, reference point and damage level on QCoS, respectively. The results show that QCoS is sensitive to local damage in the structure and robust to measurement noise. Therefore, QCoSs are used to construct the damage feature vector. The damage detection is performed by comparing the damage feature vectors before and after the structural damage. Three simply supported aluminum beams are tested in the laboratory to demonstrate the effectiveness and practicability of the proposed method.
摘要：
Void is an important manifestation of the strength of asphalt mixture, but few studies have focused on the change of voids during the compaction of asphalt mixtures. The voids of SMA-13 and OGFC-13 were selected as the research objects, and the compaction process of the asphalt mixture was analyzed based on different compaction degree specimens in lab through gyratory compactor. Firstly, CT scanning was used to extract the void structure of the asphalt mixture at different degrees. Secondly, based on the 26-connectivity algorithm, the connected voids and closed voids of asphalt mixture were extracted, and the volume and particle size distribution were analyzed. Thirdly, the gradation of voids was analyzed by the two-parameter Weibull function, and the morphological characteristics of voids were analyzed by roundness, sphericity, and abundance. The results showed that the distribution of cross -section voids ratio and the number of voids of the SMA-13 was more uniform than that of OGFC-13. The characteristic parameters of two-parameter Weibull function showed that with the increase of specimen density, the three-dimensional void size became smaller and smaller, and the void size distribution became more and more uniform. The sphericity and roundness of the voids of SMA-13 and OGFC-13 were less affected by the compaction degree, and the void abundance of the OGFC-13 gradation asphalt mixture was greatly affected. For the connectivity of voids, the closed void volume of OGFC-13 increased with the increase of compaction degree, but the maximum proportion of closed voids in the total void volume does not exceed 10% during the compaction process. For the gradation SMA-13, the compaction degree of 90%similar to 93% was the boundary interval of connected voids from existence to nonexistence, which may be a critical interval for forming skeleton strength during the compaction process.
关键词：
Metro train;building vibration;secondary noise;numerical analysis;vibration control
摘要：
With the rapid development of urban rail transit, the environmental vibration and secondary noise induced by metro train operation have become increasingly serious, posing stricter requirements on the vibration and secondary noise of sensitive building office (SBO) and sensitive building school (SBS). To predict and control the vibrations and secondary noise in sensitive buildings along the metro line induced by metro train operations. A prediction method for the vibration and secondary noise of sensitive buildings along the metro line during metro train operation has been proposed. The sub-model of train-track system coupled dynamics and the sub-model of track-tunnel-soil-building system dynamics are included. The influence of metro train operation on the vibration and secondary noise of SBO and SBS is studied. The influence of the distance between the metro line and the building on the vibration and secondary noise of the sensitive building is discussed, and an effective control scheme of vibration and secondary noise is proposed. Results show that the vibration frequencies of the SBS and the SBO caused by the metro train operation are concentrated at about 8[Formula: see text]Hz and 63[Formula: see text]Hz. The vibration below the second floor of SBO caused by the metro train operation exceeds the limit, and the secondary noise below the third floor of SBS exceeds the limit. The secondary noise inside the building of each floor of SBO exceeded the limit. Using secondary noise to evaluate the environmental impact of metro train operations is more stringent than relying solely on vibration assessments. secondary noise is recommended in engineering to assess the impact of metro train operation on sensitive buildings along line. Combined with vibration, secondary noise and construction requirements, SBS and SBO are recommended to be no less than 72[Formula: see text]m and 74[Formula: see text]m away from the metro line, respectively.
摘要：
To accurately predict the peak dilation angle of rock discontinuities, a hybrid data-driven model based on the improved sparrow search algorithm is proposed. The main influencing features such as normal stress, basic friction angle, uniaxial compressive strength and three-dimensional roughness parameters are used as the inputs of the model, and the peak dilation angle is used as the output of the model. The coefficient of determination (R2), mean absolute error (MAE), root mean square error (RMSE), and mean absolute percentage error (MAPE) are introduced to evaluate the prediction performance of the proposed model and compare its performance with existing classical models. Then, the effect of different normalization methods on data-driven model is discussed. Finally, the shapley additive explanations (SHAP) method is adopted to explain the contribution and relative importance of each input feature. The results indicate that the proposed model can well describe the complex nonlinear relationship between influencing features and peak dilatation angle. Compared with classical models, the proposed model has the highest accuracy and the smallest error. R2, MAE, RMSE and MAPE are 0.966, 1.029, 1.184 and 3.99 % respectively. SHAP results show that normal stress and uniaxial compressive strength are the most important input features for predicting peak dilation angle. Compared with mean normalization method and arc-tangent normalization method, the min-max normalization method is more suitable as a pre-processing method for the proposed model.
To accurately predict the peak dilation angle of rock discontinuities, a hybrid data-driven model based on the improved sparrow search algorithm is proposed. The main influencing features such as normal stress, basic friction angle, uniaxial compressive strength and three-dimensional roughness parameters are used as the inputs of the model, and the peak dilation angle is used as the output of the model. The coefficient of determination (R2), mean absolute error (MAE), root mean square error (RMSE), and mean absolute percentage error (MAPE) are introduced to evaluate the prediction performance of the proposed model and compare its performance with existing classical models. Then, the effect of different normalization methods on data-driven model is discussed. Finally, the shapley additive explanations (SHAP) method is adopted to explain the contribution and relative importance of each input feature. The results indicate that the proposed model can well describe the complex nonlinear relationship between influencing features and peak dilatation angle. Compared with classical models, the proposed model has the highest accuracy and the smallest error. R2, MAE, RMSE and MAPE are 0.966, 1.029, 1.184 and 3.99 % respectively. SHAP results show that normal stress and uniaxial compressive strength are the most important input features for predicting peak dilation angle. Compared with mean normalization method and arc-tangent normalization method, the min-max normalization method is more suitable as a pre-processing method for the proposed model.
摘要：
A comprehensive literature review on pre-stressed concrete beams subjected to corrosion reveals that most experimental studies are on rectangular sections even though T-shaped and box sections are more widely used in engineering practice with post-tensioned prestress, in particular for heavy structures like bridges. In this paper, five post-tensioned T-shaped beams were prepared, four of which were subjected to accelerated corrosion, and then all the beams were subjected to the four-point bending test. Special attention was directed to the cracking propagation and failure patterns, load-deflection, load-strain of concrete and steel strand, ductility and flexural capacity of the test beams. The experimental results show that the flexural behavior of the test beams deteriorates with the corrosion degree of prestressed strands, especially when the corrosion degree exceeds 2 %. When the corrosion degree is 8.42 %, the failure pattern of crushing of compressed concrete is changed to the rupture of the wires. The corrosion effects on the load-strain of steel strands depend on corrosion loss, strand position and loading stress state. Corrosion of steel strands reduces the compressive strain of concrete at the same compression position and the ultimate strain of the prestressed strands at the position of beam end. Finally, a numerical model is proposed, which can provide accurate and effective predictions of the failure pattern and flexural capacity of the corroded post-tensioned T-shaped beam.
A comprehensive literature review on pre-stressed concrete beams subjected to corrosion reveals that most experimental studies are on rectangular sections even though T-shaped and box sections are more widely used in engineering practice with post-tensioned prestress, in particular for heavy structures like bridges. In this paper, five post-tensioned T-shaped beams were prepared, four of which were subjected to accelerated corrosion, and then all the beams were subjected to the four-point bending test. Special attention was directed to the cracking propagation and failure patterns, load-deflection, load-strain of concrete and steel strand, ductility and flexural capacity of the test beams. The experimental results show that the flexural behavior of the test beams deteriorates with the corrosion degree of prestressed strands, especially when the corrosion degree exceeds 2 %. When the corrosion degree is 8.42 %, the failure pattern of crushing of compressed concrete is changed to the rupture of the wires. The corrosion effects on the load-strain of steel strands depend on corrosion loss, strand position and loading stress state. Corrosion of steel strands reduces the compressive strain of concrete at the same compression position and the ultimate strain of the prestressed strands at the position of beam end. Finally, a numerical model is proposed, which can provide accurate and effective predictions of the failure pattern and flexural capacity of the corroded post-tensioned T-shaped beam.
摘要：
Self-stressing steel tube concrete is a novel composite structure created by substituting ordinary concrete with self-stressing expansion concrete within a steel tube. Compared to regular steel tube concrete, self-stressing steel tube concrete structures can overcome the limitation that ordinary steel tube concrete is prone to voids. Many engineering studies have shown that these structures are prone to fatigue damage at the welded joints of steel tubes under repeated loads. Factors such as welding residual stress, welding defects, and stress concentration contribute to this susceptibility, which could potentially lead to catastrophic accidents. In this study, fatigue tests and finite element analysis were conducted on self-stressed concrete-filled steel tube joints of DY-type joints. The fatigue behavior of the joints under alternating loads was investigated through experiments and validated with the finite element analysis results. The impact of concrete's self-stress on joint fatigue performance was examined, including the stress concentration factor (SCF) and geometric parameters such as the ratio of the branch pipe outer diameter to the main pipe outer diameter, the ratio of the main pipe's outer radius to its wall thickness, the ratio of the branch pipe wall thickness to the main pipe, and the correlation between the angle of the main pipe and the branch pipe. The research results show that the node can withstand 2 million alternating loads without failure under a fatigue stress amplitude of 47.2 MPa. Additionally, the fatigue life of the test model under variable amplitude loads is converted into that under constant amplitude loads. The fatigue life of the node indicates that it can withstand 4.16 million cycles under the given fatigue amplitude before fatigue cracks appear. Additionally, variations in geometric parameters can impact the fatigue life of the node, but do not lead to changes in the initiation position of fatigue cracks. Moreover, as self-stress increases, the fatigue performance of the tube node will decrease, although the effect of self-stress on the stress distribution around the weld is minimal.
Self-stressing steel tube concrete is a novel composite structure created by substituting ordinary concrete with self-stressing expansion concrete within a steel tube. Compared to regular steel tube concrete, self-stressing steel tube concrete structures can overcome the limitation that ordinary steel tube concrete is prone to voids. Many engineering studies have shown that these structures are prone to fatigue damage at the welded joints of steel tubes under repeated loads. Factors such as welding residual stress, welding defects, and stress concentration contribute to this susceptibility, which could potentially lead to catastrophic accidents. In this study, fatigue tests and finite element analysis were conducted on self-stressed concrete-filled steel tube joints of DY-type joints. The fatigue behavior of the joints under alternating loads was investigated through experiments and validated with the finite element analysis results. The impact of concrete's self-stress on joint fatigue performance was examined, including the stress concentration factor (SCF) and geometric parameters such as the ratio of the branch pipe outer diameter to the main pipe outer diameter, the ratio of the main pipe's outer radius to its wall thickness, the ratio of the branch pipe wall thickness to the main pipe, and the correlation between the angle of the main pipe and the branch pipe. The research results show that the node can withstand 2 million alternating loads without failure under a fatigue stress amplitude of 47.2 MPa. Additionally, the fatigue life of the test model under variable amplitude loads is converted into that under constant amplitude loads. The fatigue life of the node indicates that it can withstand 4.16 million cycles under the given fatigue amplitude before fatigue cracks appear. Additionally, variations in geometric parameters can impact the fatigue life of the node, but do not lead to changes in the initiation position of fatigue cracks. Moreover, as self-stress increases, the fatigue performance of the tube node will decrease, although the effect of self-stress on the stress distribution around the weld is minimal.
作者机构：
[Wu, Yuexing; Wang, Xinzhong] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.;[Fan, Yonghui; Fan, YH; Shi, Jun; Wu, Yuexing; Luo, Chao] Chongqing Jiaotong Univ, State Key Lab Mt Bridge & Tunnel Engn, Chongqing 400074, Peoples R China.;[Wang, Xiangchuan] Huasheng Testing Technol Co Ltd, Chongqing 400039, Peoples R China.
通讯机构：
[Fan, YH ] C;Chongqing Jiaotong Univ, State Key Lab Mt Bridge & Tunnel Engn, Chongqing 400074, Peoples R China.
关键词：
concrete-filled steel tube arch bridge;ultimate span;strain energy minimization method;finite element analysis;response surface method
摘要：
In order to study the ultimate span of a concrete-filled steel tube (CFST) arch bridge, taking the structural strength, stiffness, and stability as the limiting conditions, the finite element analysis method is adopted to carry out research on the influence law of a single parameter of the pipe diameter, wall thickness, and cross-section height on the ultimate span of the arch axial shape. The result is used as a sample point to determine the ultimate span of the CFST arch bridge under multifactor coupling based on the response surface method. The finite element method is used to check the strength, stiffness, stability, number of segments and maximum lifting weight, steel content rate, and steel pipe concrete constraint effect coefficient of the CFST arch bridge under the ultimate span diameter. The results show that, when analyzed using a single parameter, the ultimate span diameter of the CFST arch bridge increases with the increase in the steel pipe diameter and the cross-section height, and then decreases. Moreover, it increases with the increase in the wall thickness of the steel pipe, and the CFST arch bridge reaches the ultimate span with the increase in the steel pipe wall thickness. When the pipe diameter is 1.38 m, the CFST arch bridge reaches the ultimate span; according to a multi-parameter coupling analysis, when the pipe diameter is 1.49 m, wall thickness is 37 mm, and cross-section height is 17 m, the CFST arch bridge reaches the ultimate span of 821 m, which meets all of the limiting conditions, and, at this point, the arch axial coefficient is 1.2. The results of the finite element calculation show that the structural strength, prior to the stiffness, stability, and other limitations, just reaches the critical value of the limiting conditions.
作者机构：
[Xie, Zhongliang; Cai, Yuehui; Hu, Huanxiao; Chu, Aikun; Lu, Yufan; Gan, Benqing] Minist Educ, Key Lab Metallogen Predict Nonferrous Met & Geol E, Changsha 410083, Peoples R China.;[Xie, Zhongliang; Cai, Yuehui; Hu, Huanxiao; Chu, Aikun; Lu, Yufan; Gan, Benqing] Cent South Univ, Sch Geosci & Info Phys, Changsha 410083, Peoples R China.;[Deng, Chao] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.
通讯机构：
[Deng, C ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.
关键词：
Compaction;Concrete construction;Diffusion;Fracture;Grouting;Mortar;Soils;Stresses;Diffusion modes;Displacement field;Grouting in homogeneous sand;Grout–soil interaction effect;Interaction effect;Soil interaction;Stress field;Temporal variation;Water to cement (binder) ratios;Water-to-cement ratios;Sand
摘要：
Due to the unique characteristics of sandy soil layers, there is often a coupling effect of multiple grout diffusion patterns in the grouting process, and different slurry diffusion modes may lead to different responses of soil structures. In this study, laboratory grouting model tests were conducted with homogeneous sand under different water-to-cement (w/c) ratios to reveal the temporal variations in grouting pressure, soil stress fields, and displacement fields during the grout diffusion process. The results show that, during the grouting process in the fine sand layer, the grout mainly exhibited a compaction–splitting diffusion mode. The farther away from the grouting center, the more pronounced the hysteresis effect of soil pressure caused by grout diffusion. Meanwhile, as the w/c ratio increased, the diffusion mode between the slurry and the soil was in a transitional state. At w/c > 1.2, the primary pattern changed from the fracture–compaction pattern to the permeation–fracture–compaction pattern and fracture–permeation pattern. And the overall trend of the grouting pressure curve was similar under all of the w/c ratio conditions, showing a trend of increasing to the maximum value of the pressure first and then decreasing. With the increase in the water–cement ratio, the overall value of the grouting pressure curve showed a decreasing trend, the pressure value increased more slowly with time before reaching the maximum value, and the more obvious the influence of water–cement ratio was when w/c > 1.2. Additionally, the surface displacement also exhibited an overall decreasing trend, and it had no obvious lifting value under the condition of w/c = 1.6.
摘要：
Field tunnel monitoring of stresses and strains is of critical importance for understanding the interaction behavior of twin tunnels, but it is rarely done for projects of twin box jacking tunnels. In this study, the optical frequency domain reflectometer (OFDR) sensing technique was employed to conduct field monitoring for a project of twin box jacking tunnels with a small spacing (5.4 m), a shallow minimum cover depth (4.39 m), a large cross-section (9.8 m × 5.9 m), and a long jacking distance (215.9 m) crossing the Beijing-Hangzhou Grand Canal. A scheme of laying circumferential and axial “W” shaped optical fibers was proposed to monitor the accumulated vertical misalignment and rotation of tunnel. Results indicate that small spacing could cause more significant compressive strains in the earlier constructed tunnel, and the maximum compression positions were in the crown and the wall near the second tunnel. In addition, the rotation angle decreased with the increment of tunnel spacing, when the spacing was lower than one times the box width. In the end, an axial monitoring scheme was discussed to evaluate the tunnel opening, and a horizontal misalignment scheme was derived to accomplish the full monitoring of tunnel misalignment in three directions.
Field tunnel monitoring of stresses and strains is of critical importance for understanding the interaction behavior of twin tunnels, but it is rarely done for projects of twin box jacking tunnels. In this study, the optical frequency domain reflectometer (OFDR) sensing technique was employed to conduct field monitoring for a project of twin box jacking tunnels with a small spacing (5.4 m), a shallow minimum cover depth (4.39 m), a large cross-section (9.8 m × 5.9 m), and a long jacking distance (215.9 m) crossing the Beijing-Hangzhou Grand Canal. A scheme of laying circumferential and axial “W” shaped optical fibers was proposed to monitor the accumulated vertical misalignment and rotation of tunnel. Results indicate that small spacing could cause more significant compressive strains in the earlier constructed tunnel, and the maximum compression positions were in the crown and the wall near the second tunnel. In addition, the rotation angle decreased with the increment of tunnel spacing, when the spacing was lower than one times the box width. In the end, an axial monitoring scheme was discussed to evaluate the tunnel opening, and a horizontal misalignment scheme was derived to accomplish the full monitoring of tunnel misalignment in three directions.
通讯机构：
[He, Y ] C;Changsha Univ Sci & Technol, Sch Civil Engn, Changsha 410114, Peoples R China.
关键词：
Bridge engineering;Load bearing capacity;Support vector machine;Genetic algorithm;Finite element model
摘要：
Existing reinforced concrete (RC) bridges are subjected to environmental erosion and vehicle loads. It is becoming an urgent problem to evaluate the safety condition of bridge structures combining inspection data with artificial intelligence methods. This paper proposes a data-driven capacity assessment framework for existing RC bridges. The load capacity limit state (LCLS) and serviceability limit state (SLS) prediction model are established based on the proposed information fusion machine learning model. The genetic algorithm (GA) optimized support vector machine (SVM) learner is established to capture the relationship between the feature variables and the LSLS or SLS. Forty-five samples are obtained by static and dynamic simulation of the ANSYS models. Five-dimensional parameters are adopted as the key input parameters of the model, including the maximum dynamic deflection, crack opening ratio, and crack normal damage ratio at midspan, 1/4 span, and 3/4 span. The Shapley additive explanations method is proposed to conduct parameters sensitivity analysis. The results show that the GA-SVM regression algorithm in LCLS and SLS reduction factor prediction is better than the artificial neural network (ANN) model. The crack opening ratio is the most critical parameter that can considerably affect the outcomes of the LCLS and SLS prediction.
