+Advanced Search
  • Volume 48,Issue 9,2021 Table of Contents
    Select All
    Display Type: |
    • Analysis and Prediction of Wind-induced Response of Willow

      2021, 48(9).

      Abstract (349) HTML (0) PDF 1.99 M (556) Comment (0) Favorites

      Abstract:In order to investigate the distribution law of wind-induced acceleration response at various heights of the trunk,different time distances and different wind speeds,field measurements were made on the front wind field and trunk acceleration response of a single willow tree. The results show that there are significant differences between the probability distribution characteristics of wind-induced tree trunk acceleration response and wind-downwind pulsating wind speed. The wind-downwind pulsating wind speed approximates the Gaussian distribution,and the probability distribution of wind-downwind acceleration response of tree trunk is a sharp non-Gaussian probability distribution. The wind-induced response of willow is a process of forced vibration. The generalized Pareto extremum algorithm was used to calculate the extremum acceleration response. When the distance was 180 s,the correlation between the mean wind speed in front of the tree and the extremum acceleration response in the downwind direction was the highest. The response of extreme acceleration at different height of the trunk under different mean wind speed in the front of the tree was analyzed and predicted by fitting. It was found that the downwind extreme acceleration of the trunk had a quadratic nonlinear relationship with the mean wind speed in the front of the tree. The study of wind-induced response characteristics of willow is of great significance to the study of wind resistance of tress.

    • Creep Model for Anchor-soil Interface Considering Shear Stress and Soil Dry Density

      2021, 48(9):1-9.

      Abstract (287) HTML (0) PDF 1.81 M (461) Comment (0) Favorites

      Abstract:In geotechnical anchorage engineering,the soil density has a influence on the shear creep behavior of anchor-soil interface. A special device for preparing the element anchor specimens in drilling method was designed and made to investigate the influence of soil dry density on anchor-soil interface shear creep behavior. Several specimens with different soil dry densities were prepared by using this device. Creep loads were applied by incremental step using a self-designed anchor - soil interface shear creep testing system. A cluster of interface shear creep curves in various stress levels for those specimens with different soil dry densities was obtained by T-K Tan's method. Anchor-soil interface long-term shear strengths in different soil dry densities were obtained by the isochronal curves method. Creep curves under partial stress levels of each specimen were selected and translated into isochronal curves. Creep models for each different soil dry density specimen considering shear stress were established by regression analysis for those isochronous curves using a hyperbolic model. The creep model for the anchor-soil interface considering the effect of shear stress and soil dry density was obtained by establishing an empirical relationship between creep model parameters and soil dry density finally. The prediction results show that the proposed creep model has good accuracy for both participated and no participated creep curves in modeling.

    • Failure Mode and Calculation Method of Ultimate Bearing Capacity of a Single Stone Column in Soft Soil under Vertical Loading

      2021, 48(9):10-19.

      Abstract (289) HTML (0) PDF 2.72 M (467) Comment (0) Favorites

      Abstract:The finite difference method is used to numerically simulate the complete bearing and failure process of a single stone column under vertical loading in soft soil. The plastic hardening constitutive model considering volumetric strain interception is used to simulate the stone column,which can well reflect the nonlinear dilatancy mechanical behavior of the stone column and the resulting column-soil interaction. The bulging deformation of the stone column,the evolution of soil stress acting on the stone column,the failure modes and the corresponding typical p-s curves are analyzed. The overall shear failure mode assumed by the traditional formula is only applicable to soils with high stiffness,while the local shear failure mode is more common in soft soils. Therefore,based on the theory of circular hole expansion in elastoplastic media,the calculation formula of ultimate bearing capacity of single stone column considering the column bulging deformation and the soil stiffness is derived. The formula is verified by the numerical simulation solution. The bearing mechanism and failure mode of the single stone column in soft soil are systematically studied,which provides a theoretical foundation for further study on the bearing mechanism of composite ground reinforced with stone columns.

    • Experimental Study on Horizontal Bearing Characteristics of Tripod-bucket Foundation in Sand

      2021, 48(9):20-29.

      Abstract (486) HTML (0) PDF 3.45 M (447) Comment (0) Favorites

      Abstract:Based on a series of small-scale model tests,the bearing characteristics of suction tripod-bucket foundation under horizontal loads are studied,and the effects of the length diameter ratio,load direction and spacing of suction caisson are investigated. The test parameters include three different aspect ratios (length/diameter),three load directions and three caisson spacing conditions. According to the test results,the characteristics of the load-displacement curve for the tripod-bucket foundation under various working conditions are different. Under the same caisson weight and different spacing conditions,increasing the aspect ratio is beneficial to improve the horizontal bearing capacity. However,before the foundation loses stability,the caisson with a larger aspect ratio results in greater horizontal displacement. The change of load direction has a significant influence on the joint working area of the suction tripod-bucket foundation. When the load direction is 0 degree,the corresponding joint working effect area is the largest,which provides the most benefit to the horizontal bearing capacity of the foundation. On the other hand,when the load direction is 60 degrees,the joint working effect between the caisson and soil is the weakest,resulting in the smallest horizontal bearing capacity. Under the same size and load direction conditions,with the increase of caisson spacing,the bearing capacity increases in different degrees. And the larger the ratio of length to diameter is,the more obvious the increase of bearing capacity is.

    • Experimental Study on Shaking Table Test under Structure Coupling Action of Integrated Underground Station with Soil and Upper Cover

      2021, 48(9):30-42.

      Abstract (405) HTML (0) PDF 7.26 M (356) Comment (0) Favorites

      Abstract:In order to study the seismic response law of the subway station structure with integrated superstructure,based on the above ground underground integrated structure system of rail transit and single subway station structure system,the shaking table test of silty sand was carried out. The seismic response of subway station structure is studied from the acceleration and strain,and the results are compared with each other. The results show that: 1) with the increase of seismic intensity,the acceleration peak of soil and the structure increases gradually,while the acceleration amplification coefficient decreases gradually. The variation law of acceleration along the buried depth is related to the type of ground motion; 2) with the increase of seismic intensity,the amplitude of tensile strain of the integrated superstructure gradually increases. In the model,the amplitude of tensile strain at the end of the column is the largest,followed by the side wall,and the floor shows the smallest value. 3) The acceleration and strain of the integrated subway station structure are smaller than that of the single subway station structure,while the acceleration variation law is similar. With the increase of seismic intensity,the difference of strain amplitude gradually increases,while the difference increase show the gradual decrease and converge trend.

    • Deep Learning for Preprocessing of Measured Settlement Data

      2021, 48(9):43-51.

      Abstract (296) HTML (0) PDF 1.52 M (517) Comment (0) Favorites

      Abstract:Based on Long Short Term Memory (LSTM) in deep learning,a new method for preprocessing the measured settlement data is proposed by building a Seq2Seq model. Seq2Seq can automatically learn the law of settlement development by observing a large number of effective measuring point data,and can recalculate the settlement of abnormal measuring points after training is completed,which can effectively avoid the interference of abnormal data on the subsequent settlement prediction. Taking the actual measured settlement data in multiple areas of an airport as the background,the reliability of the model was verified by comparing the calculated settlement value of the Seq2Seq model with the measured values. Combined with parametric analysis such as hyperparameters and data sets,the influencing factors on improving model learning ability are studied. The research results show that,under the condition that the training set selects 40 measurement points and the test set selects 15,the average error of the model recalculated value and the measured value in the whole process is 3 cm. When the training set and data features are increased and the deviation between the training set and the test set is reduced,the accuracy of the model is significantly improved and the error is reduced to 2 cm.

    • Split Grouting Test and Application of Foundation Reinforcement in Collapsible Loess Area in Northwest China

      2021, 48(9):52-60.

      Abstract (366) HTML (0) PDF 2.02 M (337) Comment (0) Favorites

      Abstract:In order to verify the effectiveness and practicability of splitting grouting reinforcement method in treating collapsible loess foundation in northwest China,and to guide the safety construction,firstly,the split grouting field experiment was carried out on the site where the reinforced building is located. After 56 days,static load tests were carried out on the natural foundation and the grouting composite foundation. On this basis,a 30-day immersion test was carried out to collect the raw data such as grouting micrographs,bearing capacity and collapsibility. According to the test results,combined with the on-site building,the same materials and test methods were used to correct the tilting and reinforce the building. The results showed that: under the condition that the maximum pressure of primary grouting was 0.3 MPa and the maximum pressure of secondary grouting was 0.6 MPa,the method of split grouting with steel tube with mass ratio 1 ∶ 1 cement slurry and split grouting in two layers showed a good splitting effect. The bearing capacity of the loess foundation strengthened by splitting grouting method was nearly three times higher than that of the original foundation,which greatly improved the engineering properties of the loess. After grouting,more than 67% loess collapsibility could be effectively eliminated. The building underwent uniform settlement and had good stability. In addition,a new settlement calculation method based on pile-soil stress ratio for composite foundation with small pile diameter was proposed.

    • Static Responses of Unevenly Supported Ballastless Track under Self-weight Loads

      2021, 48(9):61-69.

      Abstract (471) HTML (0) PDF 1.69 M (308) Comment (0) Favorites

      Abstract:To evaluate the deterioration problem of geometry and stress states for the ballastless track caused by the uneven subgrade settlement of high-speed railway,a 3D FEM model of the CRTS ΙΙ type ballastless track-subgrade system was established in this paper. A total of 64 types of differential settlements were simulated (with wavelengths of 5~40 m and amplitudes of 5~40 mm). Based on the flexibility of the concrete base,quantitatively characterizing method for the geometry mapping and stress level of the track structure was proposed. The results show that the mapping characteristics of the track structure are mainly determined by the flexibility of the concrete base. When the settlement wavelength is less than 15 m or the wavelength is between 15~20 m with the settlement amplitude greater than 15 mm,the subgrade and track are separated due to uncoordinated deformation. The increase of the track structure deformation leads to the development of additional tension stresses in the concrete structure and the subgrade contact stresses,which are prone to approach or exceed their allowable strength and results in damaged failure. Meanwhile,an increase of the modulus and thickness of the concrete base is not significant for improving the smoothness of the rail surface. On the contrary,it increases the track tensile stress and the subgrade contact stress.

    • Study on Interface Interaction Between Graphene Oxide Modified Asphalt and Surface Anisotropic Aggregate

      2021, 48(9):70-78.

      Abstract (270) HTML (0) PDF 3.48 M (509) Comment (0) Favorites

      Abstract:In this study,the interfacial adhesion properties of graphene oxide(GO) modified asphalt to surface anisotropic aggregates were investigated at atomic scale in dry and water intrusion environments. Molecular dynamics simulation was used to study the molecular interaction between GO modified 12 component asphalt and the anisotropic crystal planes of typical weak alkali aggregate,calcite,and acid aggregate,α-quartz,respectively. On the basis of verifying that the density and thermodynamic parameters of the model are reasonable,the distribution and concentration of asphalt components and GO on the aggregate surface are characterized by Radial Distribution Function and Relative concentration Profile. In addition,the adhesion energy was used to calculate the difference of the adhesion performance of GO modified asphalt aggregate interface under different conditions. The results show that GO molecules,due to their large specific surface area and active sites of surface modification,are more concentrated in the interface between asphalt and aggregate than other components of asphalt. Combined with different surface atomic density and ionic activity of minerals,GO modified asphalt can significantly improve the adhesion between asphalt and aggregate in both dry and water intrusion environments. Due to the high loading of Si atoms on the surface of GO molecules,GO modified asphalt has stronger bond strength with quartz (an acidic aggregate) such as calcite (an alkaline aggregate).

    • Transfer Matrix Method for Calculating Deformation of Jointed Pipeline

      2021, 48(9):79-87.

      Abstract (487) HTML (0) PDF 1.29 M (318) Comment (0) Favorites

      Abstract:Excavation of subway tunnels often causes additional deformation or even damage of adjacent underground pipelines. The jointed pipeline can be regarded as a beam on an elastic foundation. The joints were simplified as "free hinge" and "spring hinge". Based on Winkler's foundation model,a governing differential equation for calculating the pipeline deformation was given and solved by the transfer matrix method. The field matrix for pipeline sections and the point matrix for pipeline joints were derived,and the linear equations for unknown boundary values of the differential equation were obtained. Case calculation and centrifugal model test were conducted and in-situ data were collected. Through comparing the calculation results of this paper with these of finite element method,as well as with in-situ data and test results,the correctness of the calculation model and the transfer matrix method was verified. Parametric analysis of the factors influencing pipeline deformation was carried out. The results show that the worst situation for joint deformation is that the tunnel centerline is right below the joint. The relative rotation angle of the free hinge is hardly affected by the foundation coefficient in the soil stratum. Therefore,the pipeline with a free hinge is easy to have a large relative rotation angle. The peak value of the relative rotation angle appears when the length of the pipeline segment is times of the width coefficient of the settlement trough. The limit of the normalized relative rotation angle is 1.1. This limit can be used as a conservative estimate of the normalized relative rotation angle in the case of a shortage of design data.

    • Prediction of Compressive Strength of CFRP-confined Concrete Columns Based on BP Neural Network

      2021, 48(9):88-97.

      Abstract (300) HTML (0) PDF 1.18 M (451) Comment (0) Favorites

      Abstract:In order to study the predictive ability of BP neural network on compressive strength of CFRP-confined concrete and the output performance of neural network model,this paper establishes a BP neural network prediction model for the compressive strength of CFRP-confined concrete based on a large number of experimental data. The influence of data combinations on the prediction accuracy of the neural network model is investigated. Based on the theory of neural network,the high-precision BP network model is generated into general formulas and simplified formulas for application convenience,and the prediction results of the neural network models and the empirical formulas are compared and discussed. The analysis results show that: BP neural network can well mine the data information of the input and output parameters and obtain a prediction model with high accuracy; compared with the traditional regression models,the simple linear equation derived by using purelin instead of sigmoid as the transfer function only adds a constant term,and the average value of prediction result/test result is 1.011,and the coefficient of variation is 0.112,showing a higher prediction accuracy and stability.

    • Fire Following Earthquake Simulation Analysis Considering of Fire Door Fragility

      2021, 48(9):98-107.

      Abstract (173) HTML (0) PDF 2.25 M (320) Comment (0) Favorites

      Abstract:Post-earthquake fire simulation technology based on BIM was discussed to quantitatively evaluate the impact of fire door damage on the fire temperature distribution. Three seismic waves consistent with the site type and its seismic design group were selected to analyze the nonlinear structure of the 9-story Benchmark steel structure model,and the inter-story displacement angle was used as the evaluation index of the non-structural component door damage,combined with the door vulnerability curve of FEMA P-58 to establish the door damage model. Then,using the fire door damage model obtained by BIM,the information model of the fire was quickly and accurately established. The Pyrosim was imported to simulate and analyze its impact on the fire temperature distribution,and the real temperature field distribution based on the correlation between the burning substance and the fire location was obtained. The results show that the increase in the number of door damages directly affects the temperature of the frame columns,and the larger the number,the higher the temperature of the frame columns; except for the fire and unburned fire compartments,the temperature of frame columns in other fire compartments with regard to door damage is significantly higher than that without considering door damage,with a maximum of 483.98 ℃. When the fire is located at different layers,the number of frame columns that reach the temperature boundary value of each layer is different.

    • Study on Shear Resistance of Cold-formed Thin-walled Steel Grouting Wall with Intermediate Support

      2021, 48(9):108-128.

      Abstract (392) HTML (0) PDF 3.40 M (495) Comment (0) Favorites

      Abstract:In order to improve the shear bearing capacity and lateral stiffness of C-shaped cold-formed thin-walled steel structure,a new type of Z-shaped cold-formed thin-walled steel grouting wall with intermediate support is proposed. Based on cyclic loading experiment,the wall model is established by ABAQUS finite element software. Then,the accuracy of the model is verified through three aspects,namely,the wall failure characteristics,load-displacement curve and the maximum shear bearing capacity of the wall. The influence of Z-shaped diagonal brace,steel thickness,transverse brace and vertical load on the shear performance of the wall is analyzed. The results show that the shear bearing capacity of the wall is mainly provided by three parts: Z-shaped diagonal brace,filler material and inner wall panel;the wall panel,filler material and steel frame are mutually constrained and work together; Z-shaped diagonal brace can effectively improve the shear bearing capacity of the wall,which is especially obvious in the empty frame wall; with the increase of steel thickness,the shear bearing capacity of the wall gradually increases,but the influence decreases with increase of the steel thickness; the transverse keel and vertical load have little influence on the shear bearing capacity of the wall; with the increase of vertical load,the shear bearing capacity of the wall reduces,but the reduce range is small; the shear bearing capacity calculation formula that is applicable to the new type of cold-formed thin-walled steel grouting wall with intermediate support is deduced,and the key points of the wall structure are put forward.

    • Experimental Investigation on Corroded Cold-formed Thin-walled C-shaped Steels Short Columns under Axial Compression

      2021, 48(9):129-137.

      Abstract (390) HTML (0) PDF 1.61 M (404) Comment (0) Favorites

      Abstract:This paper studies the influence of corrosion on the bearing capacity of cold-formed thin-walled C-shaped steel short columns under axial compression. Through the monotonic tensile test of the plate,the mechanical property degradation law of the corroded cold-formed thin-walled steel plate was studied. Five corroded cold-formed thin-walled columns were subjected to axial compression test. Failure mode,deformation characteristics and bearing capacity of the columns were analyzed. The calculation method of the ultimate load was discussed. The experimental results show that the yield platform of corroded steel becomes shorter or even disappears,and its yield strength decreases linearly with the increase of corrosion rates. The failure mode of the corroded C-shaped short column under axial compression is local buckling failure of the web,but local buckling occurs mostly at the weakest part of the web. The ultimate load decreases linearly with the increase of the average thickness loss rate. The effective width method and the direct strength method,considering the degradation of the mechanical properties of the corroded steel and thickness reduction,can predict the ultimate load of the C-shaped steel short columns under axial compression. However,the modified direct strength method is closer to the test results,and the modified effective width method is more conservative.

    • Fine Modeling of Coupled Vibration of Highway Bridge under Vehicle Loading and Verification Analysis

      2021, 48(9):138-146.

      Abstract (275) HTML (0) PDF 3.42 M (278) Comment (0) Favorites

      Abstract:In the existing coupling vibration analysis of vehicle bridge,the influence of vehicle dynamic characteristics and flexible tire on the vehicle bridge coupling vibration response can not be accurately considered. In order to further study the influence of pneumatic tire pressure on vehicle bridge coupling vibration,the linear elastic rubber material is used to simulate the tire and define the air pressure in the tire based on LS-DYNA program. Combined with the structural parameters of the commonly used heavy-duty three-axle vehicle,the dynamic characteristics of the vehicle suspension system are simulated by using the spring damping element,beam and shell element,and a three-dimensional vehicle model is established. Based on the test results of the real bridge and the response surface method,a high-precision finite element bridge model is obtained. The vehicle subsystem and the bridge subsystem are coupled together to form the explicit vehicle bridge coupling vibration analysis model through the contact algorithm built in the explicit solution program LS-DYNA. The correctness of the method is verified by comparing the calculation results with the measured results,and the influence of tire pressure on bridge vibration is analyzed.

    • Response Analysis of High-speed Railway Bridge-rail System Subjected to Near-fault Pulse-type Earthquake

      2021, 48(9):147-154.

      Abstract (357) HTML (0) PDF 1.05 M (347) Comment (0) Favorites

      Abstract:To study the dynamic response law of high-speed railway bridge-rail system subjected to the action of near-fault impulse earthquake, an 8×32.7 m high-speed railway simply supported box girder bridge is taken as an example for the simple-supported beam form structure most commonly used on high-speed railway line. A bridge-rail model considering the interaction between simply supported beams and CRTS I type slab ballastless track is established. The effects of near-fault ground pulses with rupture front pulses,sliding pulses,and pulse-free near-fault on the bridge-rail system are discussed,as well as the changes of bridge-rail system dynamic response when fastener resistance changes. The results show that the stress and deformation rules of the track under the action of the three pulse types of ground motion are consistent. The pulse-type ground motion increases the track stress and displacement by about 20% when compared with the pulse-free ground motion. Compared with the track system,the pier is more sensitive to the type of pulse. Under the action of pulse and slip pulse before the rupture,the maximum displacement of the pier top is increased by 106.6% and 148.6%,respectively,when compared with the non-pulse ground motion. The bending moment of the pier bottom and the shear force are also increased significantly,and the impact of the pulse type on the bridge structure should be considered in the seismic design of high-speed railway bridges. When the longitudinal resistance of the fastener is increased from 5 kN/group to 15 kN/group,the maximum displacement of the pier top is reduced by 10%,but the peak stress and displacement of the track are about twice the original values.

    • Numerical Study of Robust Time-delay Compensation Method for Real-time Hybrid Simulation

      2021, 48(9):155-162.

      Abstract (420) HTML (0) PDF 1.21 M (417) Comment (0) Favorites

      Abstract:To address the problem that the variable time delay seriously affects the stability and accuracy of the real-time hybrid simulation(RTHS),a robust time-delay compensation method was studied. A feedback controller based on H∞ robust control method of mixed sensitivity was designed to stabilize the dynamics of the testing system,while the polynomial extrapolation method was employed to compensate for the time-delay. The proposed method was applied to a linear Benchmark problem. To further investigate the performance of the proposed method,virtual RTHSs were carried out with linear and nonlinear physical substructure(PS) employing linear and nonlinear models of the loading system. The results showed the measured displacements were almost identical to the desired displacements. Compared with the existing method,RTHS with the robust time-delay compensation method had a smaller error. For nonlinear PS,the root-mean-square error(RMSE) and peak error(PE) were both between 0.6% and 1.5%,and the probability of RMSE greater than 10% and PE greater than 6% was far less than 0.05. The study demonstrated that the robust delay compensation method can improve the accuracy of RTHS greatly and behavior strong robustness.

    • Study on Anti-permeability Mechanism of PFRC under Preloading

      2021, 48(9):163-172.

      Abstract (245) HTML (0) PDF 2.48 M (278) Comment (0) Favorites

      Abstract:To study the anti-permeability mechanism of polypropylene fiber reinforced concrete (PFRC) under preloading,one type of coarse polypropylene fiber and two types of fine polypropylene fibers were selected to add into concrete. The diffusion coefficient of chloride ion of hybrid PFRC under five different preloading levels was analyzed by chloride diffusion coefficient test. The mercury intrusion porosimetry (MIP) and the scanning electron microscopy (SEM) were used to investigate the effect of fiber hybridization and preloading level on the micropore structure and permeability of concrete. The test results showed that the chloride diffusion coefficient of PFRC specimen A8 under five preloading levels decreased by 93.9%,90.8%,77.5%,63.5% and 66.5%,respectively,all of which have the largest reduction,indicating that the anti-chloride ion permeability of hybrid PFRC was superior to plain concrete and the concrete reinforced with one kind of fiber. Moreover,multi-scale fiber hybridization with coarse and fine fibers can form a three-dimensional spatial network structure,resulting in a synergistic effect at different levels,and the anti-permeability of concrete under different loading levels was effectively improved.

Journal Browsing
The current ranking