Abstract:In this paper, incremental dynamic analysis was used to investigate the effects of higher modes on seismic reposes of tall piers. Firstly the limitation of current design method focusing on conventional bridges was presented. Then the seismic performance of tall piers was investigated by incremental dynamic analysis method. The results show that with the contributions of higher modes of massive piers, multiple plastic zones are formed along the pier height under strong earthquake. The ultimate displacement at the pier top cannot be estimated by methods in current design codes, and the displacement varies outofphase with the curvature at the pier bottom. Further, the distribution patterns of shear force and bending moment along pier height are more complex than the linear and triangular distributions of conventional piers. Finally, some improvements for seismic design of tall piers are proposed.

Abstract:In order to study the fatigue property and the repair method of butt welds in folded Ushaped steel rib of composite bridge deck, a composite deck specimen has been tested twice, an original state and a repaired state, for fatigue character research in this paper. In first test, the specimen used butt welds without backing plate on the connection of the Ushaped ribs was loaded repetitively until a crack appeared. Then the butt welds with backing plate were applied to repair the fatigue crack. And after that, the second fatigue test was carried until the new weld crack appearing. The fatigue failure mode of composite bridge deck, fatigue strength of butt weld for folded Ushaped ribs, repair method of fatigue crack and the fatigue property after reinforcement were tested carefully. The results show that butt welds without backing plate are the vulnerable position of the composite bridge deck under cyclic loading, and fatigue crack appeared in this position first. Adopting butt welds with backing plate to repair the cracked welds is an effective reinforcement method.

Abstract:In order to reveal more information and understanding on behavior and failure mechanisms of high strength steel Q690 endplate connection after fire, a fullscale experimental study has been carried out after cooling down from fire temperature 550°C. Further, their behavior was compared with the provisions of Eurocode 3 and the test results obtained from the experimental study on the high strength steel endplate connections without fire exposure. The research shows that the failure mode of high strength steel Q690 endplate connection after fire is bolt failure with yielding of the flange, and their rotation capacity is sufficient. What is more, using accurate postfire mechanical properties, the component method which Eurocode 3 proposed based on connections made of mild steels can be used to calculate the plastic resistance and to predict the failure mode of high strength steel endplate connections after fire, but it is not suit to predict their stiffness. Furthermore, they can regain more than 90% of its original load bearing capacity after cooling down from fire temperature 550 °C. Moreover, a series of formulations are presented for judging the failure mode of high strength steel endplate connections post fire.

Abstract:Uniaxial tensile tests of Q420 steel at different strain rates (0.001288 s-1) were carried out to study strain rate effect on mechanical properties by INSTRON and Zwick/Roell HTM5020 testing machine. The experimental results show that Q420 steel is sensitive to strain rates, with strain hardening characteristic changing along strain rates. Finite element (FE) modeling of these tensile tests is developed to reversely extrapolate the true stressstrain relationship of Q420 steel beyond necking, using LSDYNA of ANSYS. The simulation results show that the true stressstrain relationships of Q420 steel transform from powerlaw Ludwik model to exponential Voce model with the increasing strain rate. To get a fine dynamic constitutive model, a modified H/VR model is established by introducing a new strain rate sensitivity function into the H/VR constitutive model, where Wagoner rate law is replaced by the dynamic increase factor of the CowperSymonds model. The results show that the modified H/V–R model fits the experimental data well and captures strain hardening at high strain accurately as well as the variation of strain hardening with strain rate.

Abstract:Determination of mechanical parameters of rock mass is very important for the design and optimization in rock engineering. It is difficult to get the mechanical parameters of rock mass by filed or lab tests, hence the method to determine macro mechanical parameters of jointed rock mass using numerical experiment is presented in this paper. Firstly, jointed rock mass are discretized into rock and joints; then determine their mechanical parameters by lab test; after that, assemble the rock and joints to form rock mass; finally get the mechanical parameters of rock mass using numerical experiments. This method is applied in expressway project in Guizhou province. The optimization analysis of rock mass parameters for rock slope is conducted. The effects of specimen size, anisotropy, mechanical parameters of rock and joints on the macro parameters of rock mass are studied. The numerical test method provides a new idea for determination and optimization of mechanical parameters for jointed rock mass in engineering.

Abstract:Based on a model of convex polyhedron ballast, a method for evaluation of the particle size is proposed under the condition of minimal shadow area of it. By contrast with the evaluation methods of particle volume and minimum bounding square perpendicular to the principal axis of minimum moment of inertia, a detailed analysis of the abovementioned method is carried out. Then the particle size of ballast particle is evaluated through using it. By establishing the accumulation masse of ballast particles with single and broad particle size distribution, the influence of different particle size distributions on the ballast settlement is analyzed. The results show that the proposed evaluation method in this paper provides a more accurate evaluation for the particle size of ballast particle. When the initial packing density of ballast is 1.55 g?m-3, the value of accumulated settlement of sleeper with broad particle size distribution is less than the one with single particle size distribution. And the value of accumulated settlement of sleeper with a large particle size is greater than the one with a small particle size.

Abstract:It is found that optimal backcalculation point may be exist during the modulus backcalculation in the three layers structure of asphalt pavement. Through a large number of modulus backcalculation confirmed the existence of the optimal balckcalculation point and found the position of the optimal backcalculation point, try to explain the inevitability of existence of the optimal backcalculation point in theoretically. The writer compares the backcalculation method with domestic and foreign modulus backcalculation method through precision and efficiency, it is confirmed that the backcalculation method using optimal backcalculation point, precision and efficiency of this method are all very high which make the possible of massive modulus backcalculation.

Abstract:Based on the urban transportation demand, the paper studied the optimization multiple services approach of bus frequency and bus seats associating with urban transit to transport passengers. For the operation characteristics of a bus corridor, the paper presents a bilevel model for optimization of a bus corridor. The upper optimizing model of minimizes the costs in terms of waiting time, invehicle travel time and operator cost. The models then determine which of these services should be offered at what frequencies and with number of vehicles. The lower model is traditional stochastic user equilibrium(SUE) model. The sequential quadratic programming(SQP) algorithm is developed for constructing optimal approach and proved the ability to find the optimal solution. An application of the models to the case shows that the optimizing models are practical and effective for satisfying the demand of passengers and improving the operating efficiency of bus transit system.

Abstract:This research analyzes bicycle maneuvers in 92 escooterpassingbicycle events collected from two shared bicycle paths in Shanghai. The results show that an overtaken bicyclist may experience three phases in a passing event: a normal riding phase, an overtaking effect phase in which the bicyclist is under the escooter’s pressure, and a transitional phase of adjusting the bicycle’s maneuvers. In the overtaking effect phase, the bicycle’s acceleration will fluctuate more sharply but less uniformly than in the normal riding phase. The start time and the length of the overtaking effect phase differ between different types of passing events, and they also differ based on the bicycle’s longitudinal and lateral movements. A safety evaluation model is proposed to assess the overtaken bicycle’s safety in these events. The model indicates that, on average, the negative effect of an adjacent passing event on the overtaken bicycle’s safety is five times as much as that of a free passing event. A field test shows that the model can accurately reveal bicyclists’ actual sense of safety during the overtaking, with an accuracy of 87.05%.

Abstract:This paper embarks from the elaborating management of small and mediumsized Railway transport service provider, combines with the enterprise features, establishes an elaborating management system of small and mediumsized Railway transport service provider that can describe the relationship among variables. The model remedies many defects, thus it is reasonable to measure the influence of variable factors. Then, the paper taking transport branch of China Railway No.X Group Co., Ltd as an example, using the survey data verify the effectiveness of the proposed model, and the key factors that influences its refinement system management performance are found.

Abstract:The effects of sulfates on the adsorption and dispersing properties of cement paste of polycarboxylate (PCE) superplasticizer were studied. The effects of sulfates on the hydration process of cement paste were systematically investigated through isothermal calorimetry as well as scanning electron microscope (SEM). The results show that the addition of sulfates reduces the adsorption of PCE on cement particles and hence impairs the dispersing capability of PCE. Among the sulfates, alkali sulfates (Na2SO4 and K2SO4) most significantly influence the dispersing capability of PCE, while the poorly soluble CaSO4?2H2O slightly influences the dispersing capability of PCE. A small amount of sulfates retards induction period, promotes the maximum hydration rate, and increases the heat evolution rate due to the transformation from ettringite (AFt) to mono calcium aluminate (AFm). A high amount of sulfates significantly advances the maximum hydration rate peak at acceleration period, promotes the formation of AFt, and impairs the formation of hydrated calcium aluminate (CAH). Among the sulfates, the addition of MgSO4 greatly retards the hydration heat peak at acceleration period and significantly promotes the transformation from AFt to AFm. After cement paste is hardened, a large number of filamentous hydrated sulphoaluminate phases are present due to the addition of MgSO4, because MgSO4 greatly retards the hydration process and slows the nucleation and precipitation of hydration products.

Abstract:Belitecalcium sulfoaluminateferrite (BCSAF) cement clinker was prepared from clay, bauxite and calcium carbonate. The influence that the mineral composition has on the compressive strength of cement paste was then analyzed. Boron was doped as a stabilizer, and the effects that Boron has on clinker calcination and hydration were investigated. The structure and composition of the BCSAF clinker was analyzed based on Xray powder diffraction, scanning electron microscopy, and thermal analysis. The results demonstrate that the earlyage strength of the cement paste depends mostly on the hydration of calcium sulfoaluminate, and that belite hydration makes great contributions to the lateage strength development. Ferrite is beneficial to the mass transfer during calcination. However, when the ferrite content is too high, the activity of belite tends to decrease. The doping of Boron, on one hand, helps to stabilize the belite at the α’ polymorph, improving the hydration activity of BCSAF cement at early ages. On the other hand, it prompts the chemical reactions during the clinker calcination, and reduces the formation of the transient product, gehlenite. As a result, the compressive strength of the cement paste at 3 d age is improved due to the Boron doping.

Abstract:A series of polycarboxylate superplasticizers (PCEs) with different functional groups were synthesized through free radical polymerization. The adsorption behavior as well as dispersing capability of these PCEs was investigated. In addition, the effects of these PCEs on cement hydration process were systematically studied through isothermal calarimetry and Xray diffraction(XRD). The results show that PCE with acylamino groups most significantly depresses the dispersing capability due to highly decreased adsorption amount on cement particles, while PCEs with ester function groups rarely influence the dispersing capability. PCEs with sulfonic groups exhibit enhanced adsorption behavior. The introduction of ester groups or AMPS into PCE backbones remarkably hinders the induction period of cement paste, in comparison with reference PCE (P(PEG1AA4)) (the molar ratio of side chains to negative ions is 1:4), while the introduction of sulfonic groups into PCE molecules improves the maximum hydration heat evolution rate at acceleration period. At early ages, PCEs inplanted with sufonic groups, acylamino groups, or ester groups promotes the hydration process in comparison with reference PCEs (P(PEG1AA4)). However, at 28 days, cement paste added with reference PCE (P(PEG1AA4)) exceeds that with other PCEs in cement hydration degree.

Abstract:Acrylic coating containing alkaline earth metallic carbonates material and single, twocomponent polyurethane coating are made out. Three functional fillers——glass microbead, ceramic microbead and titanium dioxide's modification effect on the above two emulsion coatings' properties of reflective heatinsulation is systematically studied. The results of experiments indicate that the modification effect on acrylic coating is optimal when the dosage of glass microbead and ceramic microbead is respectively 8% and 10%. In addition, the absorptivity of polyurethane coating can be reduced about 38% through compounding three kinds of microbeads. Functional filler's modification effect on polyurethane coating is obviously better than that of acrylic coating.

Abstract:Established simulation model of membrane humidification to research humidifier characteristics in the process of heat and mass transfer. And an analysis was made of the effect of structural parameter and gas parameter in this process. The main conclusions are as follows: Increased pressure in wetside will lead an increase of water vapor molecules osmotic amount. The dryside pressure increases, while the amount of water molecule penetration would reduce. And in another aspects, effects of gas humidity on water vapor molecules osmotic amount is similar to that of pressure. The heat and mass transfer performance of counter flow layout is better than that of downstream layout, so which the former is preferred on flow channel layout choice.

Abstract:Based on a stoichiometric gasoline direct injection (GDI) vehicle certified to China V emission standards, the particulate mass, particulate number, and the composition of particle emissions during New European driving cycle (NEDC) with different start conditions (cold start at 25 ℃, hot start at 25 ℃ and cold start at 5 ℃) was investigated. The results show that particulate mass，number and copositions are significantly affected by start conditions i.e. the GDI vehicle bring higher particulate mass and number emission when cold start at 5 ℃, 81 percent of total carbon (TC) is organic carbon (OC) when cold start at 25 ℃, OC percentage changes little when hot start, but decreases 15 percent at 5 ℃. Soluble organic fractions (SOF) are mainly composed of fatty acids and alkanes, SOF components change little when hot start, but PAHs fractions increase 24 times at 5 ℃; Fatty acids are mainly composed of C16:0 and C18, start conditions and ambient temperature have little effect on fatty acids components; Alkane are mainly composed of C24H50、C25H52、C26H54 and C27H56, alkane components change little when hot start, but change greatly at 5 ℃; PAHs are mainly composed of middlering PAHs and highring PAHs, and these fractions changed greatly when hot start at 25 ℃ and cold start at 5 ℃.

Abstract:In this paper, taking the whole parallel flow minichannel evaporator including four processes as the reach model, study the effects of structure factors (the relative position of the import and export pipe with the header; the combined altitudes between flat tube and header) on evaporator flow distribution. Introducing three dimensionless parameters (P′in, P′out, H) to indicate that three relative positional relationship, the calculation results show that when P′in=0.591, P′out=0.402, H=0.239, the uniformity of the refrigerant flow distribution is preferably.Considering the influence of the three structural parameters, an optimized structure was obtained, making the uniformity of flow distribution greatly improved, unevenness decreased 20% than the initial structure.

Abstract:In order to improve the door stiffness and simultaneously achieve the lightweight goal ,the sinking rigidity and mass of the tailedweld bank door were proposed as optimization objectives based on the door sinking stiffness conditions and window frame stiffness conditions, sampling points were obtained by using optimal latin hypercube, and the approximated system, including the door sinking stiffness, window frame stiffness and plastic deformation, was constructed by kriging model while the mass was fitted by response surface model. Nondominated sorting genetic algorithmII (NSGAII) genetic algorithm was used for multiobjective optimization, a pareto optimal solution set is gained, to verify this optimization solution, and eventually get the ideal optimization results.

Abstract:An analytical model was proposed to estimate the production rate of seriesparallel production line. Each machine has both operation dependent failure (ODF) and time dependent failure (TDF). Machine states include operation, ODF, TDF and ODF&TDF. First, the machine states space and transition relations were defined. The twoworkstation line performance evaluation method was established based on discrete state Markov chain, and this method was used as a building block of the decomposition method. The whole line production rate was estimated through iterative calculation of the decomposition method. In order to improve the efficiency, a set of parallel machines were replaced with an equivalent machine. Several numerical examples and an actual production line case were carried out to demonstrate the accuracy and efficiency of the proposed method.

Abstract:Taking painting velocity, spray gun standoff and trajectory pitch as optimization objectives, establishing film thickness distribution model for trajectory planning on curved surfaces. Considering the surfaces to be painted, setting film thickness uniformity as optimization goal, using particle swarm optimization(PSO) algorithm to optimize the objects. Fitting the surfaces with nonuniform rational Bspline(NURBS), generating painting passes by NURBS control points. Combining optimal objects with painting passes, the trajectory for painting process on curved surface can be obtained finally. By analyzing the results of painting simulation on prow, planar, concave, convex and S type surface, the validity and effectiveness of offline trajectory planning method for spray painting robot were verified.

Abstract:wostep modulusbased matrix splitting algorithms are proposed to solve weakly nonlinear complementarity problems. Convergence theory is established when the system matrix is either positive definite or an H+matrix. Moreover, the choice of the parameters for twostep modulusbased successive overrelaxation methods is also discussed. Numerical experiments show that the proposed methods are efficient and better than the modulusbased matrix splitting methods in aspects of iteration steps and CPU time.

Abstract:An implicit double discretization method is developed for pricing European and American options under Merton's jumpdiffusion model. Stability of the method is discussed. Numerical experiments show that the proposed method is effective and robust, and has advantages over the explicit scheme.