Abstract:The reasonable laying of colored pavement at the entrance of highway tunnel is significantly important for improving visual warning and ensuring driving safety. Based on the traffic characteristics at the entrance of the highway tunnel， the current common laying types of colored pavement at the entrance of the tunnel are summarized after a large number of investigations. According to the requirements of speed transition， and based on the model of driving perception-behavior， perspective principle， and the flash rate principle， the design suggestions of colored pavement laying position， length， and stripe spacing are given. From the perspective of brightness transition， two methods of increasing safety distance and theoretical verification of design scheme are proposed. Finally， starting from the laying requirements of the color pavement at the entrance of the tunnel， the main problems faced by the current colored pavement design at the entrance of the tunnel are discussed in order to provide reference for the design and further research of colored pavement scheme.

Abstract:In order to clarify the research and application status of landscape in tunnel engineering， the landscape elements of tunnel entrance were systematically sorted out， the specific expressions of landscape elements were analyzed and corresponding design recommendations were proposed. The results show that the type of tunnel portal determines the overall style of the landscape of tunnel entrance. The overall performance of portal decoration， texture， color， brightness， line type， etc. has a great influence on the landscape effects of portal appearance.The darkened and softened portal wall may reduce the light reflection， decrease tunnel entrance brightness， and relieve portal oppression. Greening at the entrance can restore the ecology and beautify the environment through ecological protection and planting. The light-absorbing ability and low reflectivity of plants may reduce the light at the entrance. The greening creates a comfortable driving environment， which is currently the mainstream of highway tunnel landscape design. The guiding system such as entrance nameplates， sketch buildings， and colored pavements has an information-oriented function. Through reasonable settings of shape， color， location， and style， the sight-inducing function can be correctly used to improve drivers’ attention. The landscape design at the entrance that considers the regional culture and the coordination with the surrounding environment can relieve drivers’ psychological tension and improve safety and comfort.

Abstract:The segment joint of shield tunnel is the weak link of the whole lining structure. The joint opening displacement exceeding limit can easily lead to different degrees of damage and destruction to the structure. Aimed at the problem of large deformation between shield tunnel rings， a non-constant resistance and slip anchor joint is proposed in this paper. Based on the finite element software ABAQUS， a three-dimensional refined numerical model of joint-segment is established. Considering the influence factors such as segment thickness， segment strength and segment axial force， the shear performance and failure mechanism of joint-segment structure are studied in depth. The results show that the segment strength has little effect on the shear stiffness and structural damage of the joint-segment structure. At different axial forces， the segment damage and the stress distribution of the sleeve rod are inconsistent. With the gradual increase of the axial force， the friction force also increases and shares part of the shear force， resulting in a corresponding decrease in the damage of the segment， while the damage degree of the sleeve rod is relatively increased. When the segment is thin， it is difficult to give full play to the mechanical properties of the joint， and even cracks， appear on the inner surface of the segment， which will affect the safety of the lining structure. The research results of this paper can provide technical reference for the design and processing of new joints.

Abstract:Based on the stress-strain results of triaxial test， the strength parameters of cohesive soil were obtained. A Drucker-Prager （D-P） criterion-based simulation method for Mohr-Coulomb （M-C） cohesive soil is then established according to the Drucker-Prager condition equivalence. The ‘Gap Constraint Method’ is applied to simulate the influence of the supporting time on the soil mechanical behavior. The influence of stratum parameters and construction characteristics on stratum mechanical behavior and support reaction force of shield tunnel in cohesive soil is finally discussed by using the proposed numerical calculation methods. It can be found that he radius of plastic zone and support reaction force of surrounding rock have a linear relationship with the cohesion， the internal friction angle and the tunnel diameter. The radius of the plastic zone and the supporting reaction decreased significantly with the increase of cohesion and internal friction angle， and the influence of the internal friction angle is more distinct. When the tunnel diameter increases from 6 m to 14 m， the radius of plastic zone increases by about 210 %， and the support reaction increases by about 230 %. The lateral pressure coefficient will significantly affect the shape， the range， and the distribution of the plastic zone after excavation. The plastic zone gradually increases and the support reaction force gradually decreases with the extension of support time. When the released displacement exceeds by 40 % of the total displacement， both the increase and the decrease tend to mitigate. Taking the engineering practice in this paper as an example， when the stratum moisture content is controlled between 8 % and 15 %， the stratum convergence is about 20 % of the total displacement， the stratum self-supporting ability can be fully exerted to reduce the support reaction.

Abstract:In order to explore the crystallization behavior and differences in the drainage pipe， this paper， in combination with field research and the crystallization blockage theory conducted physical model tests to explore the crystallization law in the drainage pipe of six drainage pipe materials， nano-coating and silica phosphorus crystal scale inhibitor. The results show that the flow rate is the dominating factor in pipe improvement， At a small flow rate， there is little difference in improvement between different materials and nano-coating， thus the crystallization amount are very large. When it comes to the high flow rate， the crystallization of each condition is pretty low， and the order of crystallization amount from small to large is nano-coating， polytetrafluoroethylene （PTFE）， polyethylene （PE）， polypropylene （PPR）， double-wall corrugated pipe （HDPE）， polyvinyl chloride （PVC）， steel pipe and silicon phosphorus crystal. The material with a low surface energy and a large contact angle has a certain preventive effect on crystallization under the high flow rate condition. Gravity deposition dominates the crystalline material under the low flow rate condition and promotes heterogeneous nucleation， while deposition under the high flow rate condition is closely related to the material properties of the pipe， and the exfoliation effect is absolutely dominant.

Abstract:To explore the influence of offshore tide on the mechanical response of the retaining structure of foundation pit， the dynamic water level boundary input method is adopted to analyze the attenuation law of groundwater seepage under the action of tides at different amplitudes. Based on the measured groundwater level data near the retaining structure， the inversion method for tidal groundwater level amplitude at the numerical model boundary is established， and the mechanical response of the retaining structure of foundation pit under the action of tidal groundwater at different amplitudes are then studied. This study indicates that with the help of the inversion method for tidal groundwater level amplitude based on the attenuation law of groundwater seepage， the boundary groundwater level required for the small-scale regional numerical analysis of the foundation pit can be obtained without considering the geological information of the actual offshore area in detail， which has a good application value in the analysis of the tidal effect on offshore engineering. The direct contact area between the sea-side retaining structure and the strong permeable layer and the drilled grouting pile in the pit-in-pit are more affected by the cosine tidal waves， with the horizontal lateral swing of these two parts showing a ‘sinusoidal-cosine similarly’ change rule with time. However， due to the self-collaborative deformation and the effect of pore pressure loads with different phases in other strata， the lateral time-history curves of the back-sea side retaining structure and the other regions of the seaside retaining structure show an asymmetric ‘irregular groove’ change rule. Under the action of tide， the lateral displacement amplitude of the retaining wall at the back of the sea gradually decreases with the increase of depth， but the lateral displacement amplitude， the bending moment increment distribution and the internal bracing axial force of the retaining wall at the sea side are closely related to the permeability of the stratum. Especially in the structural design of the project affected by large tide， the maximum lateral displacement position and bending moment peak position of the static working condition should be avoided to coincide with the position of the strong permeable layer as far as possible.

Abstract:The reliability of structural inspection and monitoring data is the key basis for understanding the operation state of the structure and providing maintenance decisions. The structural data are usually acquired by manual inspection or sensors， whose quality is difficult to be verified. As a result， there is a lack of an effective approach for data audit， the accuracy and credibility of manual monitoring data cannot be effectively tested， which may affect infrastructure management and structure operation. Therefore， a bridge health monitoring data audit method is proposed based on Benford’s law， and two typical experiments of crack length data and accelerator data are employed and analyzed. The results indicate that Benford’s law has a good adaptability in structural data audit and it can effectively identify the data characteristics， reflecting the abnormal data.

Abstract:To assess the applicability of an auto-generated grid system named snappyHexMesh grid in large eddy simulation， the simulation results of the flow around a circular cylinder at an Re of 3 900 and a square cylinder at an Re of 22 000 based on both the snappyHexMesh grid system and the artificial grid system were compared in this paper. By configuring suitable computational domains and setting proper numerical schemes， both the snappyHexMesh grid and the artificial grid system show good numerical stability during each simulation process. The comparison of the numerical results using different grid systems with the experimental data shows that using the snappyHexMesh grid can enhance the numerical efficiency； the flow around a circular cylinder is sensitive to the change of the grid system， and the snappyHexMesh grid with different densities will significantly affect the aerodynamic characteristics and the flow structures in the wake of a circular cylinder； the flow around a square cylinder can be accurately reproduced using snappyHexMesh grid system， and the snappyHexMesh grid system has a better applicability in large eddy simulation of the flow around a square cylinder than that of a circular cylinder.

Abstract:For railway bridges， the increase of span will lead to the decrease of bridge stiffness and the overrun of beam end angle， which limits the development of super long-span high-speed railway bridges. In order to break through this bottleneck， a super long-span new truss bridge is proposed. The structural system has good mechanical properties and its stiffness is much higher than that of the arch bridge， which is especially suitable for railway bridges. In the new system truss bridge， inclined rods with a large stiffness are set at the angle of the truss to effectively restrain the line displacement of the main girder， and double trusses are set in the middle as well as triangular trusses are set on both sides， so that the structure has a better flexural capacity， stiffness， and stability. In addition， the bridge is mainly steel structure， which can be prefabricated and assembled， Therefore the construction is convenient and fast. The structural form and mechanics principle of the new truss bridge are described. By using the finite element software Midas/ Civil， the structure of a 650 m half through span reduction truss bridge is analyzed and studied. The results show that the strength， vertical stiffness， beam end angle， stability， integrity， and dynamic characteristics of the half through span reduction truss bridge satisfy the requirements， and it has better mechanical properties and economy than the traditional arch bridge.

Abstract:In order to explore the influence of different layouts of welding stud on the shrinkage of steel-ultra-high performance concrete （UHPC） composite bridge slabs， a full-scale segmental composite bridge slab shrinkage monitoring test with a welding stud spacing of 200 mm and 300 mm under normal temperature curing conditions was conducted. Finite element analysis software was used to simulate the shrinkage of the test model. based on which， the parametric analysis of the shrinkage of the composite bridge deck at different welding stud spacing was performed. The test monitoring results show that the initial setting time of UHPC in the test is about 17 hours. The UHPC shrinkage in the edge area of the steel-UHPC composite bridge deck is larger than that in the central area. The maximum shrinkage in the first 72 hours is about 450×10^－6. When the stud spacing increases from 200 mm to 300 mm， the UHPC is weakened by the overall restraint， the restraint effect of the steel plate decreases， and the maximum compressive strain is reduced by about 51.6 %. The restraint effect of the reinforcing steel is strengthened， and the maximum compressive strain value increases by about 42.9 %. The finite element analysis shows that the strain difference at the interface between UHPC and the end of the steel plate increases by 20.9 %， and the shear stress of the welding stud at the maximum slippage increases by 64.7 %. The parametric analysis shows that when the stud spacing increases from 100 mm to 400 mm， the UHPC tensile stress in the mid-span decreases by 3.7 %. The compressive stress of the steel plate in the mid-span decreases by 17.8 %， and the compressive stress of the steel bar increases by 86.3 %. The above results show that the increase of the welding stud spacing weakens the combined effect between steel and UHPC， and at the same time causes the distribution of the secondary internal force of the structure. The secondary internal force between UHPC and the steel structure decreases， the restraining effect of the steel bars increases， and the compressive stress increases. Properly increasing the stud spacing can reduce the UHPC tensile stress and the secondary internal force of the steel structure caused by shrinkage， but it is necessary to pay attention to the weakening of the combined effect on the mechanical properties.

Abstract:In order to study the structural behavior of reinforced concrete beam-column joints and the changing rules of the constraints between them at elevated temperatures， thermal-load coupling tests on reinforced concrete frame beams were conducted. Based on the test， the VULCAN program is adopted to conduct the numerical analysis of the fire response of the frame beam subjected to high temperature alone， the beam-column subjected to high temperature at the same time， and the beam-column joint moment-rotation relationship at a constant load. The results show that the end restraint strength of reinforced concrete frame beams decreases with the increase of temperature. The peak value of the rotational angle at the beam-column joint has a certain delay compared to the peak value of the restraint moment.

Abstract:Shaking table tests are designed and performed on high-rise frame structures considering pile-soil dynamic interaction system and a frame structure model on fixed-base condition with the 1：6 scaling factor in this paper to study the influence mechanism of pile-soil interaction on the dynamic characteristics of high-rise structures on soft soil foundation. The layered shear box is used to simulate the boundary of soil. The mixture of sawdust and sand is adopted as the foundation soil， and the superstructure is a 12-story reinforced concrete frame structure. The foundation adopts the 3 × 3 pile group foundation. By comparing the structural dynamic characteristics of the soil structure interaction （SSI） frame model and the fixed-base model， the influence law of the SSI effect on the high-rise frame structure in this test is summarized. The soil has a significant filtering effect on ground motion. It mainly amplifies the vibration near the fundamental frequency of the soil， and the amplification amplitude decreases with the strengthening of ground motion. The soil amplifies the peak acceleration in minor earthquakes and reduces the peak acceleration in major earthquakes. The frequency of the structure in the SSI system decreases and the damping ratio increases. The structural damage in the SSI system appears later and develops more slowly than that of the fixed-base structure. At the frequency of soil， the vibration mode of SSI system is significantly affected by the soil， and its vibration mode amplitude distribution is obviously different from that of the fixed-base structure. The vibration mode of the SSI system far away from the soil frequency is consistent with that of the fixed-base model.

Abstract:In order to better control the mixture gradation and obtain the best road performance， the fractal characteristics of the gradation of cold-recycled mixtures （CRM） and the characteristics of reclaimed asphalt pavement（RAP） false aggregates are studied in this paper， which involves the selection of six representative gradation curves within the standard gradation range. Further， the particle size distribution function is established with the help of the fractal geometry theory and the fractal dimension of composite gradation （D）， the fractal dimension of coarse aggregate gradation （D_C）， and the fractal dimension of fine aggregate gradation （D_F） are obtained. The correlation between the fractal dimension and dry splitting strength， freeze-thaw splitting strength ratio（TSR）， dynamic stability， and maximum tensile bending strain of the CRM is analyzed. Subsequently， a road performance prediction model of the CRM based on the fractal dimension of gradation is established. Finally， by analyzing the influence of the variability of the gradation on the performance of the CRM， the gradation control method of the CRM considering the influence of false aggregates is proposed. The results indicate that the particle size distribution and gradation of the CRM can be quantitatively described by the fractal dimension so as to reflect the road performance of the CRM. Based on the performance prediction model of the fractal dimension， the road performance of the CRM can be well predicted， and the relative error between the predicted and measured values is basically within 15 %. When the variance of gradation change rate before and after extraction （D_V） > 85 or gradation change value before and after extraction （V_a） > 3.6， the high-temperature resistance of the CRM should be improved by adding a new coarse aggregate or adjusting the gradation curve closer to the lower limit.

Abstract:According to the designed profiles of wing and nose rails at the No. 18 high-speed single-way turnout， the rolling contact fatigue （RCF） crack initiation in nose rail was predicted by the coexistence prediction method of RCF crack initiation and wear growth considering the impact load and material plastic deformation caused by the wheel load transfer from wing rail to nose rail when the train passes the turnout to side and reverse direction. The analysis shows that the worst position at the nose rail is the part with a top width of 35~40 mm at which the impact load caused by wheel load transferring is the largest. There would be plastic deformation at rail surface of this part under impact load which would reduce the material stress and strain obviously until the plastic deformation reaches a stable state with a certain number of wheel cycles. At that time， the maximum plastic deformation is 0.087 5~ 0.092 5 mm， which would prolong the （RCF） crack initiation. The maximum fatigue damage in the nose rail is at the rail subsurface. The RCF crack initiation positions for the nose rail at top width of 35 mm and 40 mm are 1.2 and 1.5 mm below rail surface vertically， 4~5 mm and 1~2 mm from rail center towards gauge side horizontally respectively. Moreover， the RCF crack initiation life are 1.63 ×10⁶ and 3.97 ×10⁶ tones at these two positions respectively.

Abstract:This paper proposes an intelligent perception method for detecting delamination of cement emulsified asphalt （CA） mortar in slab tracks based on the structure-borne sound signals collected by trackside acoustic sensors. A vehicle-track-bridge coupled vibration calculation model and an acoustic-vibration coupling analysis model are established to simulate the vibration and acoustic radiation response of the slab tracks and bridge structures under the dynamic loads caused by passing trains. The influence of CA mortar delamination on the vibration and acoustic radiation response is analyzed. By using simulated acoustic data and support vector machines （SVM）， binary and multi-class classification recognition of 15 types of CA mortar delamination are implemented. The results show that compared with displacement response， acceleration response and acoustic radiation response are more sensitive to CA mortar delamination. The classification performance of the binary SVM model varies for different measurement points， but the accuracy can generally reach over 85 %. The classification accuracy of the binary SVM model trained based on the sound pressure data at a specific measurement point decreases by 10 % to 30 % for unknown measurement points compared with that for the specific measurement points. The fusion of multi-point position data can improve the accuracy of multi-class classification recognition.

Abstract:Aimed at the dependence of hazards of the autonomous driving system （ADS） and scenarios， a method for identifying hazards of the safety of the intended functionality （SOTIF） at the vehicle level is proposed based on the finite state machine （FSM）. First， the elements constituting hazardous events are specified. Then the FSM is adopted to abstract the ADS in combination with vehicle states and the operational environment. Finally， by identifying the conflicts between vehicle states and the operational environment， hazardous events of the ADS related to the SOTIF are systematically identified， which overcomes the overdependence on expert knowledge. The proposed method is applied to identify hazardous events on an SAE L3 autonomous vehicle to verify its effectiveness. The results show that compared with the system theoretic process analysis （STPA） method， the FSM model contains more detailed and systematic environmental information and the elements constituting the hazardous events are directly provided by the FSM model， which supports systematic identification of hazardous events.

Abstract:The velocimetry algorithm of the traditional global navigation satellite system（GNSS） considers the fact that the Doppler measurement value is the projection of the relative motion velocity of the receiver and GNSS satellites along the line of sight direction， without considering the influence of light travel time. As a result， there is a small systematic deviation， and the velocity estimation accuracy is not high， limiting its application in the field of precision velocity determination. In this paper， based on the velocimetry algorithm of the traditional GNSS， a first-order to third-order integral Doppler interpolation algorithm is proposed. The instantaneous Doppler is used to replace the average Doppler， and the accuracy of velocity determination using second-order interpolated integral Doppler is improved by three orders of magnitude compared with the accuracy of velocity determination using average Doppler. Besides， the influence of light travel time is considered， and the Doppler deviation caused by the inconsistency of receiving and transmitting time is corrected， and the correction algorithms in the earth inertial coordinate system （ECI） and in the earth fixed coordinate system （ECEF） are given respectively. The experimental results show that the systematic deviation is eliminated， and the root mean square （RMS） of three-dimensional velocity error is reduced to 3.3 mm·s^-1， which can meet the application requirements of high-precision velocity determination.

Abstract:When the attribute value of the existing failure mode and effect analysis （FMEA） method is the intuitionistic fuzzy number and the risk degree is measured by deterministic distance operator， it is difficult for evaluation experts to accurately describe the related uncertainty problems. Therefore， first an intuitionistic fuzzy hybrid Euclidean distance interval number （IFHEDIN） operator and its excellent properties are proposed based on the study of the ordered weighted distance operator， the theory of interval number and the sorting method of interval number. Then， the uncertain IFHEDIN operator is constructed to improve the FMEA method so as to analyze the reliability of failure modes of products or systems， and to calculate and rank the risk levels at the same time. Finally， the effectiveness， the reliability and accuracy of the proposed approach are verified by the risk analysis and evaluation of failure mode in the actual hospital radiation tumor treatment process， which provides decision-making support for relevant medical diagnosis managers to deal with and control risks.