Abstract:The flow simulated in a wind tunnel is different from that in the free stream of the atmosphere in reality because of the existence of tunnel walls. In certain conditions, large blockage ratios will seriously distort the flow around the building models and the aerodynamics of the building models. Therefore, errors will exist in test results. However, structural wind engineering researchers have paid a little attention to blockage effects. Firstly, this paper briefly introduces the mechanism of blockage effects and concludes the characteristics of the flow and the aerodynamics of buildings under the blockage. Secondly, the main factors which influence the blockage effects are summarized including inflow characteristics, the shape, the number and the arrangement of buildings, etc. Furthermore, the blockage correction methods involved with wind tunnel tests and numerical simulation are reviewed, and the limitation of the blockage ratio is listed from classic works. Finally, some recommendations for future studies are proposed.

Abstract:Based on the mechanism of snowdrift and the characteristics of snow redistribution on roofs, a numerical simulation method about snowdrift on roofs was proposed with consideration of repose angle of snow. Then, the snow redistribution on a flat roof was simulated by the method. The effect of repose angle of snow on the characteristics of flow field around flat roof was also analyzed. Finally, the numerical results of snow redistribution were compared with those from wind tunnel tests. It is shown that simulation results are in good agreement with experimental data.

Abstract:Finite element analysis models were established to analyze the variable characteristics of key structural parameters of threetower suspension bridge, threetower cablestayed bridge and threetower cablestayed suspension bridge. By using ANSYS parametric design language (APDL), a calculation program was prepared to analyze the maximum deflection of boxgirders, the maximum displacement of tower and the antislide coefficient of main cable and their sensitivity to the stiffness of boxgirders and tower, the appropriate stiffness of longitudinal constrain between boxgirders and tower, risespan ratio and central buckle of main cable in consideration of the effect of geometric nonlinearity. Finally, the reasonable range of the stiffness of boxgirders and tower was determined. It is shown that the stiffness of boxgirders has little effect on suspension bridge. The stiffness of tower is the key factor that affects the structural characteristics of the bridges and the appropriate stiffness of longitudinal constrain is beneficial to the structural characteristics of the bridges. The reduction of risespan ratio or the setting of central buckle of main cable can improve the structural stiffness, but reduce the antislide capability of main cable of cable supported bridge.

Abstract:The impacts of cable clamps on the completed state of a selfanchored suspension bridge were analyzed based on the finite element method (FEMC). The cable clamp could raise the shape of main cable in a middle span. If the unstressed length of each boom was kept unchanged, the pulling force of each boom would increase. In the same way, if each boom was made to reach the designed force on the completed stage of a bridge, the unstressed length of each boom should be increased. Based on FEMC, the impacts of parameters, e.g. length, crosssectional area and moment of inertia on the completed state of a bridge, were studied respectively. Furthermore, the simplified formulas were established, which could calculate the elevation increment of midposition of main cable in the middle span and the average increment of each boom force by the length ratio and area ratio of cable clamp. It is verified that results from FEMC are in good agreement with the measured data.

Abstract:A nonlinear fiber beamcolumn element was used to simulate quasistatic tests of circular concrete bridge piers reinforced with HRB335 and HRB500E longitudinal bars based on CoffinManson lowcycle fatigue damage model for reinforcing steel. The effects of lowcycle fatigue damage on the strength degradation of reinforcing steel and reinforced concrete specimens were studied. In order to further verify the effect of lowcycle fatigue of reinforcing steel on the cumulative damage of reinforced concrete specimens, two quasistatic tests proposed by Takemura and Kunnath with different loading modes were conducted. The results indicate that, the fiber beamcolumn element could simulate the cumulative damage and strength degradation of reinforced concrete columns under different loading modes when considering the lowcycle fatigue of reinforcing steel on material level by using CoffinManson model.

Abstract:A new kind of reinforced concrete shear wall with replaceable corner components was put forward. Then, the design method of the shear wall was introduced. Finally, numerical simulation and comparison analysis were carried out. The results show that the new shear wall has superior antiseismic capability, and the damage mainly concentrates at the replaceable components.

Abstract:Twelve concrete beams reinforced with 500 MPa stirrups were tested and some relevant factors including shear behaviors, crack width and deflections were analyzed. Based on analysis results, some corresponding suggestions to “Code for design of concrete structures”(GB 50010—2010) were put forward. It is shown that the code can precisely predict the shear capacity of highstrength concrete beams. In serviceability limit states, the design value of shear strength cannot exceed 80% of that in the code. Moreover, the effects of shear deformation should be considered when caculating the deflection of the member subjected to shear deformation with the code.

Abstract:Based on computational modelling and energy flow perspective, this paper investigates the failure process and dynamic responses of three types of connections, including web unreinforced flange bolted (WUFB), web cover plated flange (WCPF) and reduced beam section (RBS) under progressive collapse scenario. The results show that the WCPF connection has strong rotational and tensile capacities, and the corresponding beamcolumn assembly has stout flexure mechanism and catenary action. It follows that the beamcolumn assembly with the WCPF connection has high energy absorption capacity and favorable performance under disproportional collapse scenario. The RBS connection has strong rotational capacity, and the corresponding beamcolumn assembly has strong catenary action mechanism and improved energy absorption capacity. However, the RBS connection has reduced flexural stiffness, and thus the external work done by the same gravity load of the corresponding beamcolumn assembly is maximum, which contributes to the slightly lower bearing capacity of the RBS connection under progressive collapse scenario. The study also indicates that the stress states of connections under progressive collapse scenario are quite different from those in seismic tests and that the rotational capacities of connections under progressive collapse scenario are significantly greater than those in earthquakes.

Abstract:A series of soil conditioning laboratory tests with three types of additives were performed to investigate and assess the conditioned effect of hardplastic highviscosity soil in Shanghai ⑥ layer, and analyze the optimal injection rate ranges synthetically. It is shown that the optimum foam injection ratio is 30.0% under 30.0% moisture content (MC). While the optimum injection ratios of polymer and detackifier are 6.0% and 5.5% respectively under the same MC. Moreover, the optimum injection ratios of combination materials with polymer and foam are 3% (polymer) and 20% (foam) respectively, and the optimum injection ratio of combination materials with detackifier and foam are 3% for detackifier and 15% for foam respectively. Succeeding field tests show that the optimum injection ratios of additives significantly improve the performance of earth pressure balanced (EPB) excavation and can be used as guidelines under such soil conditions.

Abstract:Uniaxial compressive tests and particle contact tests were conducted to investigate mechanical properties and failure modes of gypsum test specimens using rock rheological testing system. Results show that cylinder specimens under the uniaxial compression tests fail directly in condition of uniform stress, while spherical specimens under the contact tests fail repeatedly with particle breakage in condition of stress concentration. In addition, even for the same kind of material, microscopic calculation parameters vary greatly with discrete element model. The microscopic calculation parameters of the specimens under different kinds of stress situation need to be calibrated separately.

Abstract:Based on the problems of the modification of stiffness matrix and the positioning of added structures in the step by step modelling method, a method which divides each construction stage into beginning phase and end phase and analyzes different phases respectively was proposed. Subsequently, a new method for modifying the stiffness matrix of structures was developed in construction process analysis of steel structures. Meanwhile, to determine the position of the added structures, a correction positioning method of design configuration was advised herein. Consequently, the existing step by step modelling method was improved. Furthermore, to simulate the construction process of a twostory frame, the improved step by step modelling method was programmed in Matlab software. The numerical results of the improved step by step modelling method were compared with those of state variable superposition method, birthdeath element method and one step forming method. It is shown that the modification methods of stiffness matrix and the positioning of design configuration are reasonable, effective and accurate.

Abstract:Approachlevel models were developed to accommodate the diversity of approaches within the same intersection. A random effect term, which indicates the intersectionspecific effect, was incorporated into each crash type model to deal with the spatial correlation between different approaches within the same intersection. The model parameters were estimated under the Bayesian framework. Results show that different crash types are correlated with different groups of factors, and each factor shows diverse effects on different crash types, which indicates the importance of crash type models. Besides, the significance of random effect term confirms the existence of spatial correlations among different approaches within the same intersection.

Abstract:Five evacuation behaviors, including the shortest evacuation behavior, avoidance evacuation behavior, herd evacuation behavior, returning evacuation behavior and equilibrium evacuation behavior, were analyzed and modelled in detail. Then a threelayer evacuation model system of dynamic switching pattern was developed based on emergency information stimulation. After analyzing the advantages and disadvantages of different microscopic pedestrian simulation models, a joint simulation system, which contains emergency evacuation decisionmaking model, Astar algorithm and social force model, was built. Finally, with the actual survey data of emergency evacuation of urban rail transit stations, the parameters of the model were calibrated and the simulation results were verified.

Abstract:Microscopic tests, e.g. fluorescence microscopy, infrared spectroscopy and gel chromatography were used to analyze the changes of micro phase structure, oxygen inhalation level of asphalt phase and molecular size makeup during aging phase of styrenebutadienestyrene block copolymers(SBS) modified asphalt. Test and analysis results show that the aging of the SBS modified asphalt has two distinct aging phases. In the first aging phase, the oxygen inhalation rate of asphalt was low; the proportion of small molecules almost remains the same; the SBS particles gradually decrease in size and eventually agglomerate and segregate. In this phase, the toughness of the SBS modified asphalt gradually reduces until complete loss. In the second aging phase, the oxygen inhalation rate of asphalt significantly increases and the proportion of small molecules reduces. In this phase, as styrene still plays the role of modification after SBS’s degradation, asphalt’s consistency increases while its softening point tends to rise.

Abstract:Asphalt mixtures containing different dosages, different particle sizes of municipal solid waste incineration bottom ash aggregate (BAA) were designed by Marshall test method. The effect of BAA on Marshall test parameters and pavement performance was analyzed. Durability performance of asphalt mixture containing BAA was also investigated by freezethaw cycles splitting test, aging test and fatigue test. The results show that as the dosage of BAA in AC20 and SMA13 increases, the designed asphalt content, Marshall stability and flow value increases, hightemperature stability decreases, meanwhile water stability and anticrack performance at low temperature changes differently. Using BAA instead of 10% (by mass) natural aggregate for AC20, 10%~15% for SMA13 can both improve splitting strength after 3 freezethaw cycles, tensile strength ration and its reduction after aging test. When the dosages of BAA in AC20 and SMA13 are respectively 20% and 5%~10%, the mixtures have better anticrack performance at low temperature after aging and longer fatigue life. Based on the test results, the recommended dosages of BAA in AC20 and SMA13 are both 10%.

Abstract:The effects of redispersible emulsion powder, cellulose ether and starch ether on working performance, sag resistance and mechanical properties of building sealing mortar were studied by using the method designed by the authors. The results show that: after adding the emulsion powder to the sealing mortar, the extrusion time is remarkably reduced, but the sag resistance is reduced. After adding the cellulose ether to the sealing mortar, the sag resistance of the sealing mortar is significantly improved, but the extrusion time increases and the strength decreases obviously. The starch ether, emulsion powder and cellulose ether used in conjunction in the sealing mortar can lead to better extrusion performance and sag resistance of the sealing mortar, but the strength decreases.

Abstract:Thermal tensile tests of 22MnB5 steel sheet were conducted with Gleeble 3500 thermomechanical simulator at temperatures of 900 ℃ to 600 ℃ and strain rates of 0.01 s-1 to 0.40 s-1, then stressstrain behaviors during deformation were analyzed. The microstructure was investigated by optical microscopy, scanning electron microscopy and Xray diffraction analyzer. The results show that, when the specimen is deformed at 800 ℃, the deformation induces ferrite transformation as the strain rate reaches 0.10 s-1; transformation to ferrite is promoted by the deformation at 700 ℃; and bainite, instead of ferrite, is induced accounting for deformation at 600 ℃. During the hot deformation process at the temperature range of 800~600 ℃, the decrease of deformation resistance and the increase of ductility lead to the improvement of formability for 22MnB5 steel, since the strain induces or promotes austenite transformation to other phases. Meanwhile, tensile strengthes are about 900~1 000 MPa.

Abstract:A mathematical model on thermoelastic instability (TEI) of two dimensional disc brake was built. Change rules of critical speed, growth rate of perturbation and its migration velocity in metal disk and frictional pad were respectively resolved by utilizing perturbation method with the assumption that hot spots were antisymmetrically distributed on frictional surfaces. Then, the effects of frictional pad’s thickness, material properties and finite contact length on critical speed were analyzed and compared. The results show that, critical speed will decrease firstly and then grow again with wave number and there is an opposite trend of migration velocity in brake disk and frictional pad. Meanwhile, it is almost zero in metal disk with higher thermal conductivity. The stability of sliding frictional system can be enhanced by increasing the thickness, thermal conductivity and specific heat of the frictional pad.

Abstract:To reduce the possibility of motion interference of manipulators, a pose constraint was proposed according to the mechanism characteristics of manipulators for a hydraulic tunneling rig with two 6DoF (degree of freedom) manipulators. The pose constraint is that the end link of manipulator keeps perpendicular to working cross section during whole motion process. Then, kinematic methods for the realization of the constraint and the minimum distance between spatial links were given. Finally, motion simulation of manipulators was made for a tunneling cross section with 64borehole design pattern. The results show that the pose constraint of end link perpendicular to working section during the motion of manipulators is effective for collision avoidance.

Abstract:Based on basic parameters of vehicle and rotational parameters of real driveline system components, e.g. torsional inertia, stiffness and damping, the coupling model of nonlinear torsional vibration of vehicle powertrain and longitudinal translation was established. With the coupling model, each unloaded gear pair rattling phenomenon was reproduced when the vehicle in gear one was accelerating. Then, gear rattle sensitivity was analyzed for different impact factors. It is shown that appropriate gear backlash and torsional inertia could inhibit the gear rattle phenomenon of manual transmission.

Abstract:Both numerical simulation method and wind tunnel test were used to measure the aerodynamic force of a sedan. Then, experiment results were corrected by the existing correction method. Comparison results show that the aerodynamic force obtained by the numerical calculation method has good consistency with the test results. Moreover, the study on moving belt form and tangential blowing angle indicates that different moving belts have little effect on the measured value of the aerodynamic force, and the difference of drag coefficient is less than 0.002; the tangential blowing angle also has little effect on the aerodynamic force.

Abstract:A standard kε model was used to analyze the effect of transverse tube pitch and longitudinal tube pitch on the flow and heat transfer performance of rectangular finned elliptical tube bundles. It is found that the performance differs significantly in different transverse tube pitches, while the effect of longitudinal tube pitch could be ignored. The comprehensive performance is reduced with the increasing of transverse tube pitch. With the existing of disturbing holes, the impact of transverse tube pitch is enhanced, but the function of longitudinal tube pitch is weakened. The presence of disturbing holes reduces the performance of tube bundles.

Abstract:A new fitting method based on both the position and the velocity of satellite is presented in this paper and a fitting formula is deduced. Then, the fitting and the extrapolating accuracy are compared between conventional position based fitting method and the new positionvelocity based fitting method. Compared with conventional fitting method, the new fitting method shows a significant improvement in velocity accuracy, with a slight improvement in position accuracy. Besides, the new method’s advantage is more obvious when the fitting epoch is few.

Abstract:This paper proposes a method to calibrate the location and gesture of laser scanner in a mobile mapping system. Firstly, vehicle and laser scanner coordinate systems were defined to simplify the calibration of the scanner as the calculation of transformation parameters. Secondly, a total station was taken to observe the coordinates of common points which consist of center of standard target ball and feature point of the scanner. With the help of the observed coordinates in a horizontal coordinate system, the transformation parameters of the vehicle and scanner coordinate systems were figured out. Finally, the method was proven to be good in repeatability through multiple experiments. The reliability is also be proven by the process of data collected on Yixian elevated road with the mobile mapping system.