Abstract:

In order to deeply reveal the force transmission and damage mechanism of column-to-drilled-shaft connections， detailed finite element simulation of exist experimental test was conducted， and force transmission and damage mechanism were analyzed. After verification of finite element models， the effect of shear-span ratio， embedment depth， connection diameter-to-column diameter ratio and pile transverse reinforcement ratio on seismic performance of column-to-drilled-shaft connections was studied by numerical simulation. Results indicate that proposed finite element models can adequately replicate the mechanical behavior of column-to-drilled-shaft connection. The damage of connection region is presented as pile stirrup yielding induced by horizontal compression from embedment pier segment. Additionally， the connection strength increases with the increasing of shear-span ratio， connection diameter-to-column diameter ratio， embedment depth and pile transverse reinforcement ratio.

Abstract:

This paper develops a complete data-exchange technology based on IFC standard for various types of steel structures. On the one hand， the complete geometric information and additional attributes of the steel structure model can be derived， so that the universal construction BIM software can parse the model and edit the parameterized components. On the other hand， the complete information can be imported to mainstream detailing design software for steel structures named Tekla， then structure model can be regenerated based on these obtained information， from which the secondary edit as well as the construction drawing can be achieved. Verified by engineering Applications， this technology enhances the integrity of information transfer and the quality of model transformation when applied to BIM data-exchange of steel structure， avoiding repeated modeling in different design stages and improving design efficiency greatly.

Abstract:

Stiffened deep mixed columns （SDMCs） can effectively increase bearing capacity， reduce settlement and enhance stability when they are used to improve soft soil. Currently， the researches on SDMCs have been mainly focused on the engineering properties of SDMC under vertical loading， leaving a gap in improving understanding of failure mode of SDMC under embankment load as well as its calculation approach. This paper conducted a series of 1g gravity scale-reduced model tests， including embankments supported by natural soft soil， deep mixed （DM） column-reinforced soil， and SDMC-reinforced soil. The instability of embankments supported by different foundations were analyzed through a comparison of deformation of embankment， stresses on column head and soil， strains in column， and failure modes of column. The applicability of the existing stability calculation methods were assessed. The results showed that the SDCM columns effectively restrained the soil deformation， namely， its settlement on the embankment crest and the ground heaving outside the embankment were approximately 61% to 71%， and 12% to 46% of those in the model test with DM columns， leading to a significantly enhancement on the global stability of the embankment. The SDCM columns failed progressively， and it may have failure modes of compression， a combination of compression and bending， and bending， depending on the column positions under embankment and column stiffness. The slip plane did not exactly go through the broken positions of column. The equivalent shear strength method had applicability to the stability analysis of SDMC-supported embankment as compared with other methods considered in this study.

Abstract:

Reinforcement corrosion has been one of the major causes of degradation of reinforced concrete structures. Identifying the internal damage signals of corroded RC structures will provide a theoretical basis for structural health monitoring of existing buildings. This study investigated the effect of steel corrosion on the flexural characteristics of RC beams at the microscopic crack level using acoustic emission （AE） technique. The rise time/peak amplitude （R/A）， ringing count/duration （AF） and improved b （I_b） values of the acoustic emission signal were calculated for reflecting the changes in cracking patterns and damage modes of corroded RC beams. The results show that the ultimate load capacity of rusted reinforced concrete beams decreases significantly with the increase of reinforcement corrosion rate. there is a good correspondence between acoustic emission signal and concrete damage， and the damage process of the specimen can be divided into three damage stages： initial damage stage， damage evolution stage， and sustained damage growth stage. Besides， the trend of b-value curve can reflect the formation and development of cracks. Moreover，with the increase of load， the proportion of shear cracks in the specimen gradually increases， and the higher the degree of corrosion of the specimen in the sustained damage stage， the higher the proportion of shear cracks.

Abstract:

To account for the non-uniform frost heave deformation at different directions and freezing depths caused by the unidirectional freezing and the radial freezing temperature gradient of tunnel surrounding rock in cold regions， this study introduces the radial freezing temperature Tr and the non-uniform frost heave coefficient k in parallel and vertical freezing directions to characterize the non-uniform frost heave of the rock mass. Theoretical derivations establish an analytical solution for frost heave force in cold region tunnels， followed by a case study and analysis of influencing factors. The research reveals that neglecting the impact of freezing temperature gradient leads to a significantly overestimated frost heave force. Considering the influence of freezing temperature gradient effectively enhances the reliability of frost heave force calculations. The frost heave force， when influenced by freezing temperature gradient， increases logarithmically with the growth of the non-uniform frost heave coefficient k. Additionally， it decreases linearly with the increase in the elastic modulus ratio E_Ⅱ/E_Ⅲ of frozen and unfrozen surrounding rock， with larger EⅡ/EⅢ requiring a higher critical value of k to generate frost heave force. Furthermore， tunnel frost heave force increases with the enlargement of the frozen surrounding rock's outer radius， the elastic modulus of the unfrozen surrounding rock， and field stress. Conversely， it gradually decreases with the increase in the inner radius of the lining and the frost heave coefficient per unit temperature of the frozen surrounding rock.

Abstract:

Nature coarse aggregate （NCA） and recycled coarse aggregate （RCA） concrete were prepared using coarse aggregates with particle sizes ranged from 4.75mm-10 mm， and their printability as a 3D printing ink was comparatively evaluated. The effects of different curing conditions on the anisotropic mechanical properties of 3D printed concrete after hardening were also explored. The experimental results show that compared with NCA， the full replacement of RCA can accelerate the loss of workability of the printing ink. Through the scientific regulation of the mix ratio， the printable ink can still maintain printability after 10 min of resting， which can be increased to 20 min under continuous printing. Compared to standard curing， the 7d strength loss of natural and recycled specimens under natural curing is 19.84% and 20.13%， respectively. The relationship between the anisotropic compressive strengths was X-axis （print direction） > Z-axis （stacking direction） > Y-axis （drive shaft direction， vertical X-axis）. The Y-axis compressive strengths of the natural and recycled printed specimens were 83.41% and 84.27% of the X-axis， showed significant anisotropy at 28d of standard curing. Finally， the formation mechanism of anisotropy by aggregate type and 3D printing interlayer properties was elucidated from the micro viewpoint.

Abstract:

Nature-based coastal ecological restoration and protection has attracted increasing attention. In terms of physical experiments on the effects of coastal vegetation on hydrodynamics and sediment transport， the description method of vegetation including classification， material selection and characterization was introduced. The field structure， wave damping and flow resistance under the influence of vegetation were reviewed. Sediment transport aspects such as distribution of suspended sediment concentration， sediment resuspension， deposition and erosion patterns were discussed. Finally， future research prospects were presented.

Abstract:

The major achievements of intelligent compaction measurement value （ICMV） are systematically summarized in this paper. The following contents of ICMV are discussed： development history， calculation mechanisms， advantages and disadvantages， filler applicability and influencing factors between ICMV and in-situ test values. The analysis indicates that there are the matching mechanisms between ICMV and subgrade materials and ICMV should be selected according to these mechanisms to improve the detection effect. During the fitting analysis， the types of subgrade ICMV and in-situ measurement values should be considered comprehensively to determine the influencing factors， so as to avoid the redundancy or the loss of regression features. Since some features have nonlinear effects on labels， it is not recommended to use linear models to predict the labels of intelligent compacted data. In view of the above problems， specific suggestions， including matching relationship between ICMV and materials， the importance of influence factors and the selection strategies of regression algorithms， are presented here in order to serve as references for the future research and application of ICMV.

Abstract:

For detachable precast cement concrete pavement， a joint with clamping ring connected dowel bar is proposed. Based on expounding its structural characteristics and basic parameters， the deflection load transfer coefficient and deflection difference are selected as indexes， and the finite element method is used to analyze the influence of the parameters of the lower opening groove， the transmission rod， and the clamping ring on the load transfer ability of the joint with clamping ring connected dowel bar. Meanwhile， the varying regularity of the elements and the interface stress of the clamping ring connected dowel bar joint is analyzed， and reasonable structural parameters are obtained. Furthermore， the load transfer performance of the clamping ring connected dowel bar is evaluated by indoor full-scale test. The results show that the load transfer capacity of the proposed joint with clamping ring connected dowel bar meets the requirements， which has certain engineering practical value.

Abstract:

During the mechanical cleaning operation on ballast bed， backfilling ballast in batches would lead to a layered and uneven ballast distribution. To reveal the effect of uneven ballast distribution on the mechanical properties， the simulation model of ballast bed was generated based on the basic principle of discrete element method. Then three kinds of ballast layering distributed conditions were simulated in the model， the uniform distribution， "large upper and small lower" distribution and "small upper and large lower" distribution， respectively. And the mechanical characteristics of ballast bed during the tamping operation and the stabilizing operation were analyzed. The results show that the uneven ballast distribution has impact on the mechanical properties of ballast bed. The compactness of ballast bed is less affected， while the vertical stiffness and the lateral resistance are obviously affected. During the tamping operation， the "small upper and large lower" ballast distribution is most conducive to improve the vertical stiffness. While during the stabilizing operation， the "large upper and small lower" ballast distribution is most conducive to improve the transverse resistance. The flow of ballast particles is an important factor to improve the vertical stiffness and the lateral resistance of ballast bed.

Abstract:

To analyze the speed and reliability characteristics of trams under manual driving conditions in sections， wheel odometer data was used to calculate the characteristic indexes in acceleration， cruise， braking and intersection section， and influence mechanism of manual driving decision on each index was proposed. Multi-factor regression model and probability distribution model of section running speed are established. The results indicate that driver can not achieve full acceleration and deceleration due to the fuzzy control of manual driving； the contribution of terminal speed and braking coefficient to section running speed accounts for 57%， which is important for driving behavior optimization； the section running speed conforms to Gaussian mixture distribution（GMM） with high deviation rate to the common green wave bandwidth，resulting in low time reliability of tram lines.

Abstract:

The production of kitchen waste has increased rapidly with the implementation of garbage classification in China. However， the low utilization rate of biogas， low added value of products and high cost of biogas slurry treatment led to poor economic benefits of the mainstream anaerobic digestion project， which promoted the utilization technology of kitchen waste to be upgraded. Organic acids prepared in the anaerobic fermentation of organic matter are widely used， among which acetic acid can be used as basic raw material in pharmaceutical and chemical industries. In recent years， the demand of bio-based acetic acid is increasing， due to energy crisis， raw material scarcity and environmental problems. Acetic acid prepared by fermentation of kitchen waste might provide a new way for high-value utilization of organic solid waste and low-carbon energy transformation. In this paper， the biological metabolic mechanism， the influences of different parameters and the reinforcement strategies of acetic acid production in organic waste anaerobic fermentation treatment were expounded， so as to provide references for the practical engineering application of anaerobic acetic acid production of kitchen waste.

Abstract:

Recent studies show that an applied electric field can significantly alter the evaporation process and evaporation rate of pure water. In order to investigate the effect of the applied electric field on the microstructure and evaporation properties of high salt solutions， molecular dynamics simulations （MD） were adopted to simulate pure water and LiCl， KCl and CaCl₂ salt solutions in parallel （x-direction） and perpendicular （z-direction） directions to the liquid. Based on the simulation results， the influence of the electric field on the evaporation speed， the orientation of water molecules， hydrogen bonding and hydrated ions was analyzed， and the motion of different ions in the solution under the electric field was detected and compared. The electric field in the x-direction can significantly increase the proportion of free water molecules in the salt solution. When the electric field in the x-direction modulates from 0 to 0.3 v·nm^-1， the proportion of free water molecules in LiCl， KCl and CaCl₂ solutions augment by 48%， 38% and 56% respectively， effectively enhancing the evaporation rate of the high-salt solution.

Abstract:

Microfluidic paper-based analysis devices （μ-PADs） have received extensive attention in the fields of environmental detection and analytical chemistry due to their low cost and green technology. The μ-PADs-based fluorescence detection technique is highly sensitive and easy to operate， which shows special advantages in on-site rapid detection. In recent years， researchers worldwide have developed deeper into this field. In this paper， the manufacturing methods of μ-PADs are introduced， followed by the discussion of fluorescence detection mechanisms. Then， the research status and application potential of μ-PADs-based fluorescence sensing technology for environmental pollutant detection are analyzed and summarized， and the future development trends and applications are prospected.

Abstract:

A comparative analysis was conducted to evaluate four feature-selection algorithms in the context of diagnosing air handling unit （AHU） faults using deep belief network （DBN） with poor-data. The results indicate that the feature subset filtered by the maximum correlation minimum redundancy algorithm exhibits superior performance in terms of diagnostic accuracy and stability. Subsequently， a fault diagnosis model was developed by integrating DBN into a self-training framework， and a case study was performed to validate its efficacy. The findings demonstrate that the diagnosis accuracy of DBN self-training model can be improved by up to 19.5% than that of pure DBN. Furthermore， two self-training pseudo-label sampling strategies， namely uniform sampling and proportional sampling， were proposed. While both strategies contribute to increased diagnostic accuracy with a reduction in sampling number， the maximum difference observed among different sampling numbers is 3.42%. Notably， the uniform sampling strategy consistently outperforms the proportional sampling strategy， with a maximum accuracy difference of 1.39% across all scenarios with poor-data， which indicates that， in situations where the fault labels are seriously lacking， the uniform sampling strategy with the smaller sampling number is beneficial to improve the diagnosis performance of DBN self-training model.

Abstract:

To efficiently clean industrial time series with the characteristics of periodicity， a streaming data cleaning system was first designed using distributed components. The system employs Mosquitto for data gathering， Flume for connection， and Kafka for the buffer， which provides benefits of high throughput and a large buffer. The data cleaning component serves as the core of the system. Then， a periodic time series cleaning algorithm was proposed based on a constraint model. Integrating the characteristics of temporality， periodicity， and physical meaning， the methods of periodic detection and data slicing were added to the original speed constraint algorithm， so as to solve the distortion problem of the original algorithm and improve the availability to deal with periodic data. Finally， the effectiveness of the system and the improved algorithm was verified using a tunnel boring machine data set as a case study.

Abstract:

The intelligent brake test system's core is to establish the first vehicle brake pressure control model for different marshaling trains. A mathematical model of the first train tube in different marshaling trains is established based on the aerodynamic equation. The model takes into account the influence of the filling and exhaust of other vehicles on the tube pressure change of the first train. The brake valve's effective cross-sectional area is designed， calculated， and tested in a simulation using the established mathematical model. This provides a theoretical basis and technical guidance for developing new brake valves， as well as improving or repairing existing ones. To verify the accuracy of the model， test data obtained from the train brake test bench is compared and analyzed with the simulation results. The initial inflation data of the first train tube in long groups and the common brake pressure data were predicted and obtained.

Abstract:

In order to reveal the thermal comfort characteristics and heating energy consumption demand of residents in winter under the effect of personal comfort systems （PCS）， this paper takes Hangzhou as the object. By means of questionnaire survey and on-site measurement， the thermal comfort characteristics under various typical thermal environment regulation methods， such as opening windows， shading， using air conditioning and PCS， and indoor hourly temperature and energy consumption are simulated. The results show that the neutral temperatures of “no equipment + sitting”， “air conditioning + sittin”， “PCS+ sitting”，“no equipment + housework”， “air conditioning + housework” and “PCS+ housework” in winter are 17.3， 18.8， 16.4， 15.7， 15.7， 13.9℃ respectively. A comfortable temperature range respectively is 14.3 to 20.3 ℃， 17.1 to 20.5 ℃， 14.4 to 18.4 ℃， 13.7 to 17.8 ℃， 13.3 to 18.1 ℃， 11.0 to 16.9 ℃. The indoor thermal comfort level in winter is greatly affected by behavioral patterns. The proportion of comfortable time in the living room is 43.74%~80.21%， and the proportion of comfortable time in the bedroom is more than 70%. When air conditioning and PCS are used for heating， the energy intensity of a typical building is 1.28kWh·m^-2 in early and late winter and 13.06kWh·m^-2 in severe winter.