Abstract:With the developments of past 30 years, people working in the civil engineering area have stand on an very important historical node: to establish the third generation design theory of structures. This paper briefly addresses the historic clues of the first and second generations of structural design theory and discusses the basic contradictions associated with the second generation of structural design theory. The characteristics typically featured by the third generation of structural design theory is then illustrated and basic framework are proposed as well. It is point out that the theory of solid mechanics, the modern numerical computational methods and probability density evolution theory consist of the three milestones of the third generation design theory of structures. The primary objective of the third generation of structural design theory is to achieve the global reliability design of structures in its life cycle such that a scientific quantification description can be drawn upon the global safety and service reliability of engineering structures. Ongoing work towards completely building up the third generation of structural design theory is outlined.

Abstract:A cable seismic isolation system was proposed for long span continuous girder bridges in deep water. A method was presented for obataining the ground motion acceleration of different excitation points which based on the recorded ground motion arrays itself considering the spatial variability at the same time. Compared with the conventional system and the feeble fixed system, the seismic isolation effectivity of cable seisimc isolation system was studied when the spatial variability of ground motions was considered, and the effect of earthquake induced hydrodynamic pressure on the seismic response of deep-water bridges was discussed. The results indicate that the deep-water continuous girder bridges with cable-sliding friction aseismic bearing have remarkable isolation performance, and this bearing is sensitive to the spatially varying earthquake ground motions including wave-passage, incoherence and site-response effect. The effect of hydrodynamic pressure on the seismic response of bridges in deep water is different, considering the spatial variability of ground motions relative to a uniform excitation, which is also changed with apparent wave velocity, incoherence coefficient, local site condition when wave-passage, incoherence and site-reponse effect are considered. Therefore, this can provide a certain criterion of reference for seismic design of long-span deep-water bridges.

Abstract:Based on detailed analysis of material properties of recycled aggregate concrete (RAC) and the differences between the nonlinear behavior of RAC and those of normal concrete, key points about elastic-plastic analysis on RAC structures, including selecting the proper analysis software, constitutive relation model and structure modeling were discussed. Then the elastic-plastic analysis on one RAC frame-shear wall high-rise demonstration project was undertaken, while the analysis result were compared with that of normal concrete structures. The analysis result demonstrates that when the recycled coarse aggregate (RCA) replacement ratio is lower than 30%, although the relative elastic-plastic drift angle of RAC structures is larger than that of normal concrete structures, it can still meet the requirements of “no-collapsing with rarely-met intensity earthquake”. The energy dissipation due to structural elastic-plastic deformation and hysteretic stiffness degradation of RAC structure accounts for 32.8% of the total energy, which decreases by 9.6% from the corresponding normal concrete structure. According to the performance of the components, it can be concluded that the high-rise RAC frame-shear wall structure conforms the concepts for the seismic design such as “strong column-weak beam” and “strong wall-weak coupling beam”.

Abstract:Traditional viscous damping wall (VDW) needs large wall area to provide large damping force. In order to solve this problem, a viscous damping wall with displacement amplification lever (VDW-DAL) was proposed. Hysteretic experiment of traditional VDW and VDW-DAL specimens was carried out to verify the amplification effect of VDW-DAL. After adding displacement amplification factor into damping force formula of traditional VDW, a new damping force formula for VDW-DAL was obtained and it fit well with the experimental results. The slip phenomenon of hysteretic curves caused by gap was simulated and the effect of gap ratio on energy dissipation reducing rate was analyzed by theoretical derivation.

Abstract:In order to check the performance of the new type of composite bridge deck proposed in this paper under the wheel load and test its performance in the second system of the bridge deck, and also to compare it with the performance of the common bridge deck, 3 different types of bridge deck are designed and fabricated. One is concrete bridge deck, another is orthotropic steel bridge deck, and the third is composite bridge deck with concrete slab and orthotropic steel plate with U-shape stiffener. Static load test is conducted on these specimens to investigate the cracking behavior of concrete in the negative moment zone and measure the deformation and the strains in different locations on the decks. The result proves that the local stress level of the composite bridge deck acted by the vehicle load is lower than that of the orthotropic steel bridge deck. The composite bridge deck has a high fatigue strength and wheel-load resisting strength. The bearing capacity of orthotropic composite deck in the second system of the bridge deck is 1.42 times and 0.97 times that of the concrete deck and orthotropic deck respectively. The bearing capacity of composite is almost equal to that of orthotropic steel bridge deck with half the amount of steel.

Abstract:To investigate the load transfer mechanism of hybrid girder joint with cells and bearing plate, a theoretical model was established to calculate this hybrid structure, based on the method of continuous elastic interlayer. This model considered the slip effect between concrete and steel, and the local press effect of the bearing plate. By comparing the calculation results of this theoretical model and a finite element model, and analyzing its affecting factors, the following conclusions were obtained. The discrepancy of accumulated axial deformation between steel and concrete works as a main reason of the fact that the maximum shear force of its connectors occurs at the end of the hybrid joint, far away from the rear bearing-plate. And this maximum shear force will experience a trend of first increase, then decrease and finally approaching to an invariable value, if the length of joint grows. Increasing the stiffness of the connector will lead to the increase of its maximum value, but in a relatively lower level. Increasing the axial rigidity of concrete or decreasing the axial rigidity of steel will both lead to the decrease of connectors’ shear force.

Abstract:The superimposed shear wall is a new assembly-type RC structure, now the superimposed shear walls are applied to medium and low-rise buildings in China. The shearing performances of adhesive interface is crucial in developing a monolithic action for superimposed shear wall; Different types of connecting reinforcement at the interface also influence the shearing performances, there has been no experimental study on the mechanical behavior of adhesive interface. The shearing performances of adhesive interface under different types of connecting reinforcement were analyzed through six double-superimposed specimens. The results showed that shear failure of the interface was the cause of failure of double-superimposed specimens, but the crack formation and development in the two interface was not in synch, the double-superimposed specimen kept good integrity until cracks began to appear. The failure of non-reinforced specimens was brittle, during the process of failure, the improved specimens in which the type of connecting reinforcement is stirrup taken on better ductility than the traditional ones in which the type of connecting reinforcement is truss bar; The ultimate shear strength of the interface was determined by adhesion of interface, shear-friction and dowel action of shear reinforcement, however, adhesion of interface had been destroyed in a certain extent under the limit state, the ultimate bearing capacity of double-superimposed specimens was not simply by summarizations of maximum of three parts.

Abstract:In order to obtain behavior and failure mechanisms of high strength steel endplate connections in fire, full-scale tests on 7 joints were conducted at elevated temperature 550℃ under steady state fire condition. The connection specimens included 4 high strength steel endplate connections and 3 mild steel endplate connections. The endplate thickness and the endplate material are the focus of the parametric study. In order to compare, corresponding tests at ambient temperature were carried out as well. Moreover, the current provisions of Eurocode 3 were validated with experimental results. It is found that a proper thinner high strength steel endplate can improve the rotation capacity of connection both at ambient temperature and in fire, and simultaneously achieve similar moment resistance with a mild steel endplate connection, which guarantees the safety of an entire steel structure.

Abstract:A 3D finite element model has been established to investigate the influences of various factors on the longitudinal mechanical behavior of special-shaped shield tunnel structure comprehensively. The results show that: the overall displacement along the longitudinal direction of special-shaped shield tunnel is downward, and the displacement curve can be represented by a cubic polynomial; the longitudinal effective rigidity ratio initially decreases and then increases with the magnitude of the transverse effective rigidity ratio; the effect of transverse effective rigidity ratio on the longitudinal stiffness is minor, and the recommended design value is 0.65; the longitudinal effective rigidity ratio decreases with the increasing depth under both staggered joint assembling and straight joint assembling conditions; the longitudinal reinforcing effect leads to a larger longitudinal stiffness for staggered-jointed structure than that for straight-jointed structure in soft ground; the coefficient of subgrade reaction has the most evident impact on the longitudinal effective rigidity ratio, which increases linearly with the growth of the coefficient of subgrade reaction; the amount of the longitudinal pre-tightening stress of bolts also leads to a linear increasing trend of the longitudinal effective rigidity ratio, but the impact is not obvious. Finally, a simplified analytical model based on the measured value of the opening amount of the ring seam has been proposed to determine the longitudinal equivalent rigidity and the longitudinal effective rigidity ratios. The effectiveness of the model has been verified by comparing the predicted values with results of the numerical calculations.

Abstract:When freezing method is used in connecting passage in the subway, the structural of soft soil will be weaker because of freezing and thawing.And in the permafrost melting process, dissipation rate of pore water is so slower that leads to the soil has initial consolidation in the early subway operation,and then causing differential settlement by the long-term subway loading.In this paper, regarding the freezing temperature and the initial consolidation of the soil as influence factors.Through the dynamic triaxial test ,study the regular pattern of pore water pressure under subway cyclic loading . According experimental data, the established a model of dynamic pore pressure accumulation experimental which considers the freezing temperature and the initial consolidation . Study has shown that: freezing and thawing action will change the internal particle connection and pore structure of soil, and the dynamic pore water pressure accumulation rate of frozen-thawed soil becomes faster under cyclic loading; the lower the freezing temperature, the pore pressure of frozen-thawed soil develops faster with higher times of vibration , and the larger stable pore pressure value is in final; the initial consolidation of thawing soil has a greater impact on the pore water pressure, the higher the initial consolidation means the slower the development of pore water pressure and the smaller stable value;the coupling effect of freezing at low temperature and low initial degree of consolidation exacerbates accumulation of pore pressure of frozen-thawed soil , and it further soften the structure of soil.

Abstract:In order to improve the learning and analysis level of vehicle’s motion patterns, considering the characteristics of trajectories and the requirements of trajectory modeling, a modeling method for trajectories was proposed. This method consisted of two parts, which were trajectory fuzzy clustering and path modeling. Firstly, the improved Hausdorff distance was extended and used to measure the geometrical similarity between trajectories, and the improved fuzzy C-means trajectory clustering algorithm was further established to realize the clustering of vehicle trajectories. Based on the results of trajectory clustering, the path models based on discrete state were established and the Corresponding trajectory anomaly detection algorithm was proposed. Finally, the experimental results in the real scene verified the applicability and validity of the proposed method .

Abstract:A traffic state identification method for intersections is proposed based on detection data with a low frequency from detection on the mid of the urban roads which is applied for urban interrupted flow in medium and small cities of our country. At first, the relationship between occupation, volume and traffic state is analyzed under different parameters of circumstances based on simulation data and a method of curve fitting is proposed to build the boundaries of different traffic state. Then the functional relationship of coefficients of boundaries functions with environment variables is fit out which is later applied to general ones. The methods above is verified by simulation data with the identification rate of over 80%, and empirical data with the identification rate of over 75% , with severe mistake rates less than 2.1%.

Abstract:As the research focus in international snow and ice field, snow-depth prediction of snowdrift on highway still has not been well solved. Based on meteorological data provided by automatic weather stations installed along the anti snow corridor on White Snow Mountain and meteorological bureau, index values of four factors (snowfall, air temperature, wind speed and humidity) which have influence on snow depth of snowdrift on highway are extracted and prediction model of snow depth of snowdrift on highway based on BP Neural Network is established. 199 sets of data during five snowfall in study area are used to train network and establish model, then use 20 sets of data to validate the model. Validation results show relative error of accumulated snow-depth predictions in 20 hours is less than 10% and 85% of relative error of snow-depth predictions is less than 20%. Therefore, the model has strong generalization ability and high accuracy. Sensitivity analysis of snowfall, air temperature, wind speed and humidity indicates that snow depth is directly proportional to snowfall and inversely proportional to other three factors, wherein snowfall has the greatest impact on snowdepth, followed by wind speed, humidity minimum.

Abstract:Subgrade fillers in the vicinity of bridge abutments are very difficult to be well compact. And the material of subgrade fillers is inhomogeneous. As a result the variability of subgrade stiffness is observed. Focusing on the effect of the key uncertainties on the dynamic properties and the safety evaluation of the dynamic design of the transition zone, and based on the theory of the railway system dynamics, a plane strain finite-infinite element model is employed to investigate the system dynamics of a subgrade-bridge transition zone. In this model, the vertical force coupling for the rail and the substructure is achieved by modifying the fastening spring stiffness matrix and the infinite element method is employed to prevent the wave reflection on boundaries. With this model and the stochastic finite element method based on the Latin hypercube sampling method, The influence of the parameter variability of subgrade stiffness on dynamic response of vehicle-track coupling system in the transition zone is investigated. The results indicate that the influence of the variability of subgrade stiffness on the rail vertical dynamic displacement is greater than that of the wheel-rail contact force and the acceleration of the vehicle body. The dynamic response of transition zone is more sensitive to the parameter variability of the filler in the transition zone than that of the subgrade surface layer. Dynamic response data deviate from normality, and at the 95% confidence level, the maximum value of the acceleration of the vehicle body and the wheel-rail force approximately obey the Weibull distribution. While the data distribution of the maximum value of the rail vertical dynamic displacement presents obvious “high peak and thick tail”, and it is easy to appear the abnormal large value. In order to reduce the vertical dynamic displacement of the rail and facilitate the construction quality control, the subgrade stiffness of the transition section should be improved. The maximum value of the rail vertical dynamic displacement is selected as the safety evaluation index of the dynamic design of the transition zone and the result reveals that the fuzzy failure probability of the current design is 0.00045 and the design is safe.

Abstract:Based on vehicle with brake by wire system (BBW), this paper proposed a new yaw stability optimized control strategy. Two degrees of freedom vehicle model was used as reference model, and proportional integral (PI) control algorithm was used to derive the additional yaw moment. According to the additional yaw moment and the steering wheel angle, the driver’s intention and the actual driving characteristics of vehicle were recognized. This paper distributed the additional yaw moment to every wheel based on the method combining the Pseudo Inverse method and mathematical programming approach. Within brake by wire system, the master cylinder fixed frequency pressure-regulating method was used to follow the target wheel cylinder pressure. The results of hardware-in-loop (HIL) test show that this control strategy can ensure the yaw stability of vehicle effectively on the road surface with high or low adhesion coefficient.

Abstract:The low-speed maglev train presented by national maglev transportation engineering R&D center was regarded as the research object. The design of magnetic suspension control (MSC) system under disturbance, nonlinear and time variant was discussed. Firstly, the nonlinear dynamic model of the MSC system was derived and the simulation platform of the MSC system was established. Next, the linear PD control law was designed. The simulation results show its performance depended on parameters and its robust was weak. An improved sliding mode controller was developed to improve the robustness by utilizing exponential reaching law and variable boundary layer. The Lyapunov method was employed to prove its stability. The sufficient simulations show that the presented control method had good dynamic performance, high control accuracy and strong robustness without chattering. Finally, the experiment verified the effectiveness of the improved sliding mode controller.

Abstract:In this paper a simulation strategy based on the coupling finite element analyse and multi-body dynamics has been proposed for the collision analyse between a city tram and an oblique obstacle. This simulation strategy is suitable for railway vehicles in terms of collision simulation、crashworthy design and structural optimisation. According to the simulation results the impact angle has been identified as the most determinate factor during the collision between a city tram and an oblique obstacle. With the increased impact angle, the derailment risk of the collided city tram rise significantly. In order to avoid the derailment the maximum impact angle should be reduced to 25°. Besides that, the derailment risk of the collided city tram is also affected by the friction coefficient between wheel and rail. The reduced friction coefficient due to bad weather decreases the wheel-rail forces against the lateral motion of wheel sets. As a result, the collided city tram is more likely to derail.

Abstract:Experimental study on the effects of Ar-O2 atmosphere on ion current characteristic of natural gas in an SI engine was conducted. Engine fueled by natural gas was modified base on an inline two-cylinder diesel engine. Air was replaced by oxygen and argon (with higher specific heat ratio) mixture as engine intake gas. Results show that the ion current strength increase significantly under Ar-O2 atmosphere compared with air. When argon percentage is 79% or lower, the eigenvalue of ion current is corresponding very well with combustion characteristics calculated by pressure. Ion current can detect knock reliably, but it is insensitive to knock’s intensity.

Abstract:Dynamic characteristics, generation mechanism and inhibition measure of manual transmission gear rattle were analyzed systematically by specialized bench test and vehicle experiment. Firstly, experimental condition and sensor layout of manual transmission gear rattle were designed and considerations for specific experimental operation and data postprocessing were clarified. Secondly, characteristics measurement of the original clutch damper was implemented on a special test bench, and vehicle experiments of manual transmission gear rattle were conducted on two steady conditions including idling and creeping condition. Finally, clutch damper parameters optimization was proposed to inhibit severe gear rattle phenomenon and then it was validated by vehicle experiments. The research achievements would contribute to improving clutch damper products and solving gear rattle problem in the engineering practice.

Abstract:Firstly, two adjacent shuttle louvers were taken as the research object, the new model employed analytical method to analysis the fraction of beam radiation passing directly through the louvers, specular reflection fraction of beam radiation using the number and direction of reflection based on ray-tracing method, and net-radiation method was used to analysis diffuse reflection fraction. Secondly， based on the model analysis, the calculating program of solar direct radiation was developed with the MATLAB software to describe the shape, size, tilt angle and surface optical properties of shuttle louvers. Finally, the errors of the traditional calculation methods were analyzed , and found that “flat hypothesis ” model would overvalued results of solar transmission, especially when the opening is directly?facing?the incident beam radiation. And the relative error is 5% or more for the rest situation.

Abstract:Abstract: An image texture analysis method integrated Gabor filter and Gray-level co-occurrence matrix is used to extract the texture features of marine magnetic anomalies. Using OKMS clustering algorithm realized magnetic anomaly field partition of different texture features .The model test and actual application results show that image texture analysis method integrated Gabor filter and Gray-level co-occurrence matrix can effectively extract the texture characteristics information of magnetic anomalies. The partition results of Caroline Marine magnetic anomaly show that Caroline plate magnetic anomaly can be divided into 11 areas, partition results coincide well with strip magnetic anomaly areas and magmatic activity areas,and this method provides a reference for processing and interpretation of magnetic anomaly

Abstract:Morphological evolution downstream of tidal barrage is sensitive to regulation engineering project. A set of methodology integrating verified tidal current model, sediment transport model and morphological evolution model was set up to quantify the influences of different stages of regulation engineering project in the Shuanglong Estuary on currents and morphological evolution. Results indicate that the changes of currents and morphological evolution are closely associated with partially deepened-widened channel and increased tidal influx. In general, increased wetted area in the upper estuary has intensified the asymmetry of flood-ebb current velocity and even induces recirculating flow. While fully regulation over the estuary with a fixed slope will increase tidal current velocity significantly and relieve the asymmetry of flood-ebb current velocity as well. Though increased tidal influx at the estuary acts a positive factor washing out the sediment in lower channel, sediment deposition occurs in widened section of the estuary due to the decreasing tidal current velocity, especially in recirculating flow region. Therefore, for enhancing the function of regulation project, releasing water from upper barriers and dredging regularly are also needed.