Abstract:By introducing the stochastic ground motion model based on the probability density evolution method, the exceedance probability of engineering structures at different peak ground acceleration in a certain site and period can be assessed and presented, and the key problem of selecting the ground motion in seismic fragility assessment can be solved. Furthermore, when the structures encounter the earthquake ground motion in a different exceedance probability, the basal amplitude parameter of the stochastic ground motion model will be increased to calculate the failure probability of engineering structures at each limit state, which is consistent to the increment dynamic analysis of the seismic fragility analysis. The research that assigns the probability to the measurement of the ground motion intensity for the seismic fragility curves avoids the difference between the different methodologies used in the seismic fragility analysis. The proposed methodology should integrate with the total probability decision framework of performance based earthquake engineering to provide a solid theoretical foundation for the seismic probabilistic safety assessment of engineering structures.

Abstract:Since wind induced internal pressure of a building with a large opening is usually caused by rolling viscous turbulent fluid and Bernoulli equation cannot be applied to this situation completely,a new governing equation for wind induced internal pressure with a single opening was derived using the boundary layer theory and the mixing length theory. Using the standard four order Runge Kutta numerical method to solve internal pressure governing equation,the influence of the energy loss coefficient on the calculation results of the proposed equation was analyzed and the calculation results of the proposed equation was compared with those of empirical formula.The results show that the internal pressure of the energy dissipation is caused by the turbulent diffusion term. Moreover, the physical meaning of the energy dissipation of the opening is further clarified.

Abstract:The wind pressure distribution characteristics on two panel and three panel billboards supported by single column were studied with wind tunnel model tests. The distribution characteristics of mean and fluctuating wind pressure coefficients in different wind directions, the influences of different wind directions on mean and fluctuating wind pressure coefficients and the frequency domain characteristics of the fluctuating wind pressure of typical pressure taps on the surfaces of the panels were discussed. The results show that the absolute values of mean wind pressure coefficients on each panel decrease with the increase of wind direction; the absolute values of mean wind pressure coefficients and fluctuating wind pressure coefficients near the edge of leeward panels are larger than those on the interior areas of leeward panels; either the superimposition or offset of the wind pressure exists on both surfaces of a single panel in various approaching directions; the main frequency of fluctuating wind pressure spectra of the outside surface of windward panel is lower than that of internal surface of leeward panel, and so is the energy. In comparison ,the bandwidth of fluctuating wind pressure spectra of internal surfaces of panels are wider and the energies are lower; the local wind pressure coefficients on the surfaces of panels are greatly influenced by the columns of billboards.

Abstract:In order to study the shear crack and the tensile shear stirrup dowel action of high strength concrete (HSC) after elevated temperatures, two Z shaped HSC specimens were cast. After being exposed to 200°C, 400°C and 800°C, the push off tests of specimens were conducted to study the effect of the elevated temperature and the concrete strength on the shear crack. The dowel action model was developed based on the beam on elastic foundation theory, and the dowel shear stress between HSC and stirrup after elevated temperatures was calculated in combination with the measured crack width and crack slip. The results show that except for an exposed temperature of 200°C, the crack peak deformation (crack peak width and crack peak slip) increases with the increase of temperature. As the strength of concrete (at any temperature) increases, the peak crack deformation decreases. The dowel shear stress of the stirrup exhibits a linear relationship with the crack slip, and the dowel shear stiffness reduces as the exposed temperature rises and increases as the concrete strength increases. The dowel shear stress increases as the exposed temperature rises and reduces as the concrete strength increases.

Abstract:In order to study the improving mechanical behavior of composite girder on the hogging moment zone with post combined prestressed concrete slab, especially on the concrete cracking property in this range, two composite girders, one being common composite girder and the other composite girder with post combined prestressed concrete slab, were designed and fabricated, on which static tests were conducted. The main mechanical behaviors including girder deformation, strain distribution, concrete cracks, relative slip between steel and concrete, bearing capacity etc were tested. The testing results show that the load for initial concrete cracking and that for serviceability limit state of composite girder with post combined prestressed concrete are 3.87 times and 5.38 times of those of common composite girder respectively, which indicates that adopting post combined prestressed concrete slab for composite girder can significantly improve the resistance cracking ability in the negative zone of composite girder.

Abstract:A 1∶20 scale model of a typical mid span concrete cable stayed bridge was designed, constructed and tested on 4 shake tables in longitudinal and transverse directions, respectively, first with minor excitations of Chi Chi wave and then with site specific artificial wave. The destructive behavior was observed with much severe transverse shaking of site specific artificial wave. The experimental results showed that the bridge responses which were excited by the long period Chi Chi wave were larger under longitudinal earthquake input, but the structure responses which were excited by Chi Chi wave and site specific artificial wave were similar under transverse earthquake input because the two wave spectrum characteristics concerned were basically identical. Under the transverse site specific artificial wave input with PGA approaching 1.3g, the upper beams of the tower were obviously damaged including the fracture of longitudinal reinforcement and concrete spalling in a large area, which formed the plastic hinges between the upper tower column and the tower upper beam, therefore the tower base were effectively protected owing to this weakened framing effect.

Abstract:To construct a risk assessment system of durability failure for large span hybrid girder cable stayed bridge, new definitions related to durability failure risk were proposed from an assessment view based on the analysis of existing concepts of durability and risk. Considering the long time span of durability, risk factors which have long term effect were identified through investigation and consultation, thus the durability failure risk factor database of large span hybrid girder cable stayed bridge was built. Combining expert investigation method, fuzzy comprehensive evaluation method and analytic hierarchy process, the fussy analytic hierarchy process based on professor research was studied to assess the risk of durability failure. Introducing the analysis of importance rate to risk assessment of durability failure, durability failure risk importance analysis was proposed which can assess the impact on top risk event of bottom risk factors. Based on a certain Changjiang Bridge, the foregoing risk assessment system was practiced and the feasibility was proved, providing reference to security operation and preventive maintenance for large span hybrid girder.

Abstract:The strength in heat affected zone of welded aluminum alloy decreases sharply. One of the effective measures is to use CFRP sheets for reinforcement. A shear experiment of 37 double lap joints of aluminum alloy reinforced with CFRP sheets, including specimens with different CFPR bond length, bond width, bond layers, single layer thickness and bond form, was conducted. Failure modes, bond mechanism between CFRP sheets and aluminum alloy, and strain distribution were studied. Besides, effective bond length and ultimate load calculation formulas of the double lap joint were proposed.

Abstract:Taking amasonryand reinforced soil composite retaining wall of Hubei Shifang(Shiyan to Fangxian) Expressway as the research object, using the geotechnical centrifuge model test, the deformation characteristics and the soil pressure distribution of the combined retaining wall was studied, and the effects of reinforcement modulus, length and vertical spacing of reinforcement on the composite retaining wall was investigated. It is found out that the lower masonry retaining wall and the upper reinforced earth retaining wall have obvious mutual influences, the introversion of masonry retaining wall occurs under the load of upper reinforced soil wall, and the introversion of masonry wall further increases the horizontal displacement of the upper part of reinforced soil retaining wall and makes the pressure distribution more uneven at the bottom. Increasing the geogrid modulus, increasing reinforced length and reducing reinforcement spacing are more conducive to the control of the deformation of reinforced soil retaining wall. The earth pressure in reinforced soil and the horizontal earth pressure behind retaining wall, which are impacted by reinforced parameters, are smaller than the theoretical value. The wall top settlement of composite retaining wall occurs mainly in the construction period, and measures should be taken to strengthen the construction quality control and ensure the compactness of soil.

Abstract:For the double row arrangement of freezing pipes in artificial ground freezing, Bakholdin gave an analytical solution to the steady state temperature field. However, the solution only aimed at the inline and general staggered arrangements, which could not meet practical requirements. For irregular arrangements of freezing pipes in engineering practice, in this paper, a generalized analytical solution to the steady state temperature field of double row pipe freezing was proposed. First, based on the separability of boundary conditions for harmonic equations, a special single row pipe freezing problem was solved by superposition of the Bakholdin’s single row pipe solution and the linear temperature field solution. Then, the generalized analytical solution to the steady state temperature field was derived for double row pipe freezing in irregular arrangements according to the special single row pipe solution. Comparison of the analytical solution with the numerical thermal analysis shows that the analytical solution is precise enough, and the experimental results of physical model indicates that the analytical solution meets the accuracy requirement in engineering.

Abstract:To study the influence of axle load on asphalt pavement rutting, large amounts of highway axle load data around China were collected and analyzed. Then, the shear stress of pavements under three different axle types was analyzed, based on which the method to convert axle load spectrum of various axles to one standard axle was established and the collected load data were processed. The contribution of axle load at each level to pavement rutting was calculated and the rutting spectrums with axle load spectrums of typical provinces were plotted. The influence of different axle load on pavement rutting was studied using the processed data. It is found that the influence can be divided into three levels: for the standard axle load which is less than 10 tons, the pavements resist the deformation very well; for those between 10 to 15 tons, the pavements resist deformation well; for those bigger than 15 tons, the pavements resist the deformation poorly. Then the relationship between shear strength and standard axle load was studied, it is found out that using modified asphalt which has high shear strength can alleviate the rutting problem.

Abstract:A dynamic auto regression model based on the time series analysis with Kalman filter was proposed for pavement condition prediction. Existing prediction models could not be applied to Chinese airports due to the incomplete monitoring data and the complexity to be updated. The time series model was first established based on the pavement condition index (PCI) data of the airport in eastern China. Then Kalman filter algorithm was utilized to update the models. By the comparison with the actual monitoring data, the prediction models are proven to be reliable in Chinese airports. The predictions of the dynamic auto regression model are more accurate than the auto regression model despite the incomplete monitoring data.

Abstract:In order to investigate the pavement performance of cement stabilized municipal solid waste incineration bottom ash aggregate (BAA) and crushed stones, natural aggregate were replaced by BAA (0 9.5 mm) with different percentages to prepare the mixture. Then the performance including compaction characteristic, unconfined compressive strength, splitting strength, compressive modulus of resilience, shrink characteristic and frost resistance was tested. The results show that BAA increases the optimum waster and decreases the maximum density of the mixture. The unconfined compressive strength, the splitting strength, the compressive modulus of resilience and the frost resistance of the mixture contained BAA are lower than those of the control mixture. The use of BAA increases the long term dry shrinkage strain of the specimens, while decreases the sensitivity to water loss. Moreover, when the dosage of BAA does not exceed 30% of the aggregates, both the temperature shrinkage strain of the specimens and the sensitivity to temperature can be decreased. Based on the performance analysis, it is recommended that the dosage of BAA is 20% to 30%.

Abstract:The Bayesian based potential for safety improvement method identifies signalized intersection hotspots using the difference between the Bayesian posteriors of crash number and the expected crash number for similar sites which are obtained from the regression model. As the difference increases, the potential for safety improvement increases. In addition, the Bayesian method combines clues from both the observed crash frequency of a specific site and the expected crash number for similar sites to estimate the crash number which can overcome the problem associated with the fluctuation of observed crashes. Based on signalized crash data at intersections in Shanghai, the full Bayesian based potential for safety improvement method is compared with the crash frequency method, the empirical Bayesian method, the full Bayes method and the empirical Bayesian based potential for safety improvement method. The results show that the proposed full Bayesian potential for safety improvement is superior to other methods.

Abstract:A communication based train control(CBTC) system testing method based on computer virtualization was proposed to solve the bottleneck in the traditional system testing due to the constraints of physical hardware environment. The CBTC system virtualization testing platform was built with the computer virtualization technology, which can simulate the real hardware environment. Then an adaptive testing case reduction and optimal scheduler algorithm based on this platform was designed to reduce the number of the testing cases on the premise of guaranteeing the testing coverage, and the system testing time can be decreased through optimizing the execution sequence of the testing cases. For the CBTC system of Shenzhen metro line 2, an experiment was conducted to compare with the traditional testing method. The experiment shows that the proposed method can reduce approximately 45% of the number of testing cases, and decrease approximately 33% of the testing time. So the system testing efficiency is improved.

Abstract:Considering different contribution rates to station riderships (in this essay, it means exit and enter ridership) of population within different distance to the station, it is necessary to classify population into different circle groups according to their distance to the station as a variable of the forecasting model. Population variable in circle group has been certified by partial correlation analysis and at the same time, other significant factors influencing station ridership have been obtained. Because of the irrationality of linear multi variable regression, the back propagation neural networks forecasting model has been built to reflect the high non linear relation between the independent variable and dependent variable. The case study indicates that the forecasting model based on population variable in circle group and BP neural networks significantly precedes other models and meanwhile, it is real time. Based on the above model, the contribution rate model of population in different circle groups to station ridership has been built, where any background variable of the station has been known. The result of the contribution model also indicates the forecasting model based on population variable in circle groups and BP neural network can better reflect the relationship between station ridership and all the factors influencing the riderships.

Abstract:In this paper, rice husk mortar made from rice husk and cement was prepared and the effect of two pretreatment processes, including water soaking and saturated lime water soaking, on the properties of rice husk mortar were studied. The results indicate that the mechanical properties of rice husk mortar made from pretreated rice husk were significantly higher than that made from untreated rice husk. The saturated lime water soaking pretreatment method is better than the water soaking method. The hydration heat peak and heat release in 3 days of rice husk mortar made from saturated lime water soaking is the highest. This paper also analyzes the change of surface functional groups of rice husk by infrared spectrum. The results show that after pretreatment the hemicellulose absorption peak reduces and the aliphatic absorption peak disappears on rice husk surface.

Abstract:The aim of this paper is to prepare dual low communion fatty acids phase change materials (PCM) with lauric acid (LA) and myristic acid (MA), according to the calculation results of low eutectic phase transition point theory. Using the vacuum absorption method, a eutectic mixture of lauric acid and myristic acid was incorporated with expanded perlite (EP), and the phase change aggregates were encapsulated with appropriate encapsulations. The cross section of phase change aggregate was observed using field emission scanning electron microscopy (SEM). It was discovered that the fatty acids were absorbed into the porous particle inside and adhered to the wall of perlite pore, and the fatty acids steadily existed in the space encircled by paraffin and expanded perlite inside wall. The LA MA eutectic mixture as PCM was confined in the porous EP by a mass fraction of 200%, and it demonstrated that paraffin was effective to encapsulate the LA MA/EP composite aggregates by a mass fraction of 60%, with less than 3% mass loss after the thermal cycle test, and just 4% mass loss after being soaked into the alkali solution. More PCMs can lead to a decrease of effective heat value, a longer temperature delay and a greater cooling extent. The physical and mechanical performances of the PCMs based mortar board can meet the requirements of the standards of building insulation mortar.

Abstract:Based on the description of nonlinear factors, the eight degrees of freedom of EV was built. Under the sin usoidal road excitation, the responses to the model was obtained, then, the bifurcation diagram, the Poincaré section and the largest Lyapunov exponent were studied. The results indicate that the chaos exists in the system. The evolution through periodic, quasi periodic into the chaotic motions are discovered. Suspension deflections of the special point in the bifurcation diagram were studied. It is found that it could reflect the dynamic behavior of system using the changes of suspension deflections.

Abstract:It is difficult to estimate the vehicle sideslip angle which is a very important indicator of automotive lateral movement. In order to estimate the sideslip angle accurately, the kinematics direct integral method, the estimation methods based on extended Kalman filter and the extended Luenberger observer were developed in this paper. Then, the three developed sideslip angle estimation methods were adjusted and validated in several typical testing conditions in simulation, with a certain intensity of noise. The characteristics and the adaptability of different methods were also analyzed. The kinematics direct integral method cannot estimate accurately in long time range, but can swiftly show the tendency of the change of sideslip angle in extreme conditions; The extended Kalman filter can generally estimate very well, but it usually overestimates in some dynamic conditions; The extended Luenberger observer can also estimate well, but it often underestimates in some conditions.

Abstract:In order to improve the crashworthiness and simultaneously achieve the lightweight goal, a design method was proposed for an aluminum bumper. A crashworthiness simulation model was established first and topology optimization was conducted based on hybrid cellular automata (HCA). The material distribution from topology optimization was used to generate H shaped cross section. Base on the Kriging modeling technique, size optimization was executed to acquire the optimal sectional dimension. The final result demonstrates that the proposed method is able to provide a reasonable cross sectional shape and size of the bumper, and to improve the crashworthiness of the bumper beam and to achieve a lightweight design.

Abstract:Coordinate transformation is the essence of registration between airborne and terrestrial LiDAR system. The traditional coordinate transformation needs to obtain several common points and calculate the model parameters by those points. However, common points are hard to select in terrestrial and airborne point cloud due to different platforms and discrete sample mode. Taking building profile features as objects, a features constraint registration method was proposed in this paper to achieve the registration between point clouds and topographic maps. First, the feature line and feature plane of building facades were obtained from airborne and terrestrial point cloud separately. After being projected to the horizontal, the plane transformational parameters were calculated according to the relationship between model parameters and feature parameters. Next, the vertical parameter were computed by slicing the top layer of point cloud and elevation of the control points. Finally, the method was verified by a case study in Shanghai Ocean Aquarium.

Abstract:The concept of risk chain is put forward, and a novel approach was proposed for assessing schedule risks. First, in order to find out the interrelationships among risks, the evaluation information provided by a panel of experts was analyzed by an objectifying process; secondly, a risk interaction network was established based on the identified interrelationships, and the method to divide a risk interaction network into some unattached risk chains was explained; thirdly, a formula was provided to assess the various risk chains, according to obtained parameters from a simulation process taking the information of project schedule and properties of risk chains into consideration. Finally, a numerical example was analyzed to illustrate the feasibility and effectiveness of the proposed approach.

Abstract:This paper obtains the information of users’ behaviors of social media through the questionnaire survey on We Chat. It attempts to construct a theoretical model in combinination of the UTAUT model, the perceived risk theory, the media richness theory and uses and gratifications theory, in order to analyzes factors influencing the users’ behavior of social media. The analysis based on structural equation model using SPSS and AMOS software shows that, the proposed model is effective in explaining the users’ behavior of social media. The result means that, technology acceptance, content resources and use gratifications have a positive impact on the users’ behavior of social media, while perceived risk has a negative one.