Abstract:In this paper, the differences between static instability and dynamic instability are explored with the aid of a nonlinear spring model. It is pointed out that the dynamic instability of structures can not be identified by the pseudo static stiffness criterion. The concept of intrinsic energy of system is then put forward and it is found that the essence of dynamic instability of structures lies in that the intrinsic energy surpasses the energy imported into the structure, where a novel criterion for the identification of dynamic instability of structures is proposed accordingly. The relevant numerical computations indicate that the proposed criterion can analyze and judge the dynamic instability of structures subjected to arbitrary dynamic loadings effectively.

Abstract:The acceleration response spectrum for predicting floor vibration subjected to single person’s jumping load was investigated. Five hundred and six jumping load records from ninety two test subjects were collected by experiments. Each record was then applied to single degree of freedom system to calculate the corresponding peak, 10 s and 1 s running root mean square (RMS) acceleration responses spectra, on which a design oriented spectrum was developed. Spectrum parameters were determined by statistical analysis on the experimental records. These parameters can be calculated by given structural damping ratios and confidence levels. Furthermore, conversion rules between different vibration quantities, i.e. peak and RMS, were established. Finally, the applicability and reliability of the proposed design spectrum were validated by comparing its perditions with experimental and field measurements. The comparison shows that the suggested design spectrum can be used to predict the maximum acceleration response of floors subjected to one person jumping.

Abstract:An X shaped elastic plastic damper (XSEPD) was used to replace the concrete shear key for girder displacement control and seismic response mitigation of substructures. First, the force displacement relationship of laminated rubber bearing (LRB) and XSEPD was analyzed. Then, the effect of different XSEPD layouts on transverse seismic response of the bridge was investigated through parametric study based on a typical irregular girder bridge. Results indicate that XSEPD can effectively control pier girder relative displacement and reasonably distribute seismic forces among piers if the proper design parameters are selected.

Abstract:In order to avoid the brittle failure of glulam bolted connections, a reinforcing method, which used plain round rod as reinforcement perpendicular to grain, was proposed. Through monotonic and low frequency cyclic loading tests of reinforced and non reinforced glulam beam to column bolted connections, the stiffness, ductility, moment resistance capacity, failure modes and seismic behaviors of the connections were studied. The results show that the cracks of non reinforced bolted connections appear early with rapid development and the main failure mode of non reinforced connections is splitting, while the main failure modes of reinforced connections are wood crushing and blots bending. Besides, the moment resistance capacity, ductility and seismic performance of the connections reinforced with plain round rod are enhanced significantly.

Abstract:Combined with the basic assumption of load transferring method, an iterative algorithm was established for analyzing the deformation and axial force of pile shaft in layered soil. Given the settlement of pile top, the displacement, axial force and strain of pile shaft could be obtained through integrating the strain of pile shaft and the spring force of soil around pile. The procedure for iteration was dominated by the strain increment convergence of pile shaft. Then the pile side friction resistance, pile tip resistance and load on pile top were also obtained. A case study indicates that the proposed method has good adaptability with various load transferring functions and is generally in good agreement with the field observed values and calculated results from other approaches.

Abstract:Theoretical solutions for tunneling induced long term ground settlements in clays are presented by modifying displacement solutions of drained contraction of cavity based on the Sagaseta’s image technique and the Park’s displacement boundary condition. The proposed solutions are compared with quoted centrifuge tests， finite element simulation based on displacement controlled model (DCM) and field studies. The results indicate that for the prediction of long term surface settlements， the theoretical solutions under uncorrected boundary condition 1 deviate significantly from the centrifuge tests， while those under the remaining three boundary conditions are in good agreement with the centrifuge tests and finite element method， and boundary condition 2 is recommended as a conservative approach. Generally agreement of the predicted surface settlements can be seen with field observations.

Abstract:A model test system was introduced for studying the effects of shear history on sand liquefaction characteristics. First, different levels of pre shear strains were applied on the model foundation by using the component force of gravity along the tilt direction through tilting the shear box. Then, the sand was liquefied by using a small shaking table, and simultaneously excess pore water pressure and acceleration within the foundation were collected by measurement system to analyze the sand liquefaction characteristics. Test results show that the buildup of excess pore water pressure within the soil with shear history is smaller than that without shear history. In other words, shear history can enhance the liquefaction resistance of sand.

Abstract:The movement of debris flow occurred at Gangou in Hongse Village of Dujiangyan City of Sichuan Province was analyzed with field measurements. A two dimension numerical model of the debris flow was set up with DEBRIS 2D software to simulate the debris flow in the region. It is shown that computational results and on site observations are in good agreement. Different scenarios of the debris flow spreading caused by different rainfall intensities were also simulated. The results quantitatively reveal that with abundant debris source, the reduction of rainfall intensity leads to a slower movement and a higher stop position of debris flow. Taking the rainfall intensity of 150 mm·h-1 as a reference, if the rainfall intensity reduces to 100 mm·h-1 and 50 mm·h-1, the increase on final front position will be 25 m and 75 m respectively and the reduction on average deposit thickness will be 0.06 m and 0.14 m respectively.

Abstract:A shaking table model test was carried out to study the mesoscopic mechanism of fluidization for iron ore concentrates in bulk under dynamic loading. By means of micro visualization system, meso evolutions of granular fabric were investigated including orientation of particle long axis, average coordination numbers and porosity. And the interaction between particles and water during the fluidization was analyzed. Then, the connection between meso mechanism and macro phenomenon was discussed. The results show that the water transfer, namely, the rising of water level, is important in the fluidization of iron ore concentrates. The mesoscopic fabric of iron ore concentrates, which is consistent with macro phenomenon, is an important parameter for the control of macroscopic mechanical behavior of iron ore concentrates.

Abstract:An algorithm for the valid path set generation of passenger was proposed under both space and time constraints. It was developed on the basis of train trajectory searching algorithm and space time prism. The train trajectory searching algorithm allowed us to obtain passenger’s travel trajectories. Within the method of space time prism, these trajectories could form an accessible region searching from origin and a passing region searching from destination. A set of valid paths was then generated from the intersection of the two regions. Finally, Shanghai Metro Network was taken as an example to illustrate the correctness and effectiveness of the algorithm. The results show that the proposed algorithm generated new valid paths and delete invalid paths in comparison with conventional methods.

Abstract:Based on the analytical characteristics and evaluation indicator system of rural public transit, a service quality gap model considering passenger demand and a comprehensive evaluation model using set pair analysis (SPA) were applied to the study of rural public transit service. A case study in Cixi city of China was used to validate the models. The results show that SPA is practicable to evaluate the service quality of rural public transit.

Abstract:In order to realize the accurate detection of joint faulting on cement concrete pavement, a kind of three dimension detection method based on line structure light was proposed. The structured light emitted from laser irradiated vertically on the road and the charge coupled device（CCD） camera captured the beam which was formed by the pavement diffuse reflection, so as to realize the data acquisition. Then, the road three dimension information was calculated based on laser triangulation algorithm. According to the three dimension information data characteristics and the shape of cement concrete pavement joint faulting, the dense joint faulting value calculation method was proposed. The average value and maximum value of joint faulting were obtained. Experiment results show that 91% of the absolute error between three dimension method results and measurement results by ruler is within 2 mm.

Abstract:A contacting constitutive model was established and a biaxial numerical test method on graded broken stone(GBS) was proposed based on particle flow code. Influence laws of the numerical test were studied, and the reliability and practicality of the numerical test were verified. The results show that compared with displacement control mode, the results of the numerical test are more stable than that of strain rate control mode. When the value of loading rate is 0.5%·min-1 and the size of specimen is Φ300 mm×h600 mm, the loading rate and size of specimens have little effect on the results of the numerical test. The deviatoric stress increases linearly with confining stress. Poisson’s ratio has a little effect on the numerical test results. The peak point of deviatoric stress increases linearly with the increase of friction coefficient and shear modulus.

Abstract:A classical plate theory is used to derive governing differential equations of axisymmetric buckling of orthotropic annular circular thin plates with in plane variable stiffness. Assume that the stiffness of the annular circular plates vary along radial direction according to any continuous function. Critical buckling values of the annular circular plates with variable stiffness for elastically restrained edges are calculated by the method of weighted residuals. Numerical results obtained are in good agreement with those given in the existing literatures. Finally, the effect of elastically restrained edges, variable stiffness and other parameters on the buckling of the annular circular plates with variable stiffness is also shown. The results can provide a reference on the optimization design for annular circular thin plates with variable stiffness.

Abstract:An automatic integrated multi objective optimization platform was built by using optimal Latin hypercube design method, approximation model, multiple island genetic algorithm and compiled program. Based on the platform, the installation position of spoiler was obtained to meet the optimization objective requirements with attack angle and ground clearance as experimental variables. By simulation results, the validity was confirmed and the internal mechanism was revealed. Finally, the scope of efficient application was clarified.

Abstract:The characteristics of integrated electro hydraulic brake(I EHB) system were analyzed based on experiments and friction chatter compensation was proposed. Then, a mathematical model was built and experiments were conducted. The experimental results show that low speed creeping is eliminated by using the chatter compensation. Meanwhile, the linearity is increased and the dead zone during the conversion between pressure increasing and decreasing is eliminated. In addition, the cut off frequency is increased by 55.6% from 4.5 Hz to 7.0 Hz, and the tracking performance is increased by 30.9%, 59.5% and 47.8% for different aim signals.

Abstract:Based on the dynamic finite element model of electric powertrain, modal analysis was implemented with and without a reducer. After analyzing the mechanism of vibration and noise of the powertrain, dynamic responses of the reducer was calculated by numerical simulation method, which takes the internal dynamic excitation of gears and electromagnetic excitation into consideration. The effects of integrated structure on motor dynamic characteristics were obtained by using frequency domain analysis upon the motor vibration and noise. Finally, an experimental bench was used to test the vibration acceleration and radiation noise of the powertrain in semi anechoic room, verifying conclusions reached by theoretical analysis. The results show that the modes and the performance of noise, vibration and harshness(NVH) have changed after integrating with the reducer.

Abstract:With a combination of genetic algorithm and space filling curve (SFC), an optimal design method for production line layout was proposed to minimize the total cost including work in progress (WIP) holding cost, buffer allocation cost and material handling cost in consideration of buffer allocation. A case study of production line for a diesel engine cylinder block was given to verify the availability and advancement of the design.

Abstract:A mathematical model for steam organic Rankine cycle (S ORC) power generation system at 150～350 ℃ was established. S ORC power generation system consists of steam Rankine cycle（SRC）and organic Rankine cycle（ORC）power generation systems. Thermal efficiency, exergy efficiency, operation pressure and capacity of the systems were compared under the same heat source conditions. The results show that under the condition of 150~210 ℃ heat source, ORC has the highest thermal efficiency, exergy efficiency and power generation. While under the condition of 210~350 ℃ heat source, the performance of S ORC has an advantage over SRC and ORC. Its thermal efficiency and exergy efficiency are higher than those of SRC and ORC power systems.

Abstract:A new similarity measure method based on hybrid attribute distance was introduced. Overall distance between two cases was determined by distances between attributes and synthesis weights. First, a degree of similarity was characterized by overall distance. Based on the distance formula of interval numbers and the theory of fuzzy set, a distance formula of fuzzy numbers and fuzzy interval numbers was given and the distance formula of membership function was improved. Meanwhile, the deviation information of distance values was used to calculate objective weights regarding weights assignment, then objective weights and subjective weights were integrated into synthesis weights to calculate the overall similarity of the cases. Lastly, the method was applied to the conceptual design of valve. The effectiveness and feasibility of the method in case retrieval were demonstrated.

Abstract:Focusing on the routing optimization of data transmission in wireless sensor network (WSN), the network and energy models of WSN were analyzed based on the energy constraint of sensor nodes. In addition, a route optimization algorithm based on the improved quantum genetic algorithm (IQGA) was proposed. The performance and feasibility of the algorithm was verified by means of the optimization trial on the complex continuous functions. The simulation results reveal that when applied to the route optimization of WSN, IQGA is capable of searching minimum energy cost route with higher expeditiousness and stableness, which indicates that the energy cost of WSN sensor nodes is diminished, and the WSN service life is extended.

Abstract:An evaluation framework consisting of 32 evaluation indicators grouped under 7 categories was built. The weights of the indicators were obtained through an expert questionnaire survey and were then computed using fuzzy analytic hierarchy process(FAHP), which generated 30 groups of back propagation neural network(BPNN) training samples and 5 sets of calibration samples. Based on the results, a nonlinear mapping relation model of the financial risk control of international megaprojects was constructed. Finally, an EPC(engineering, procurement, construction) project in Saudi Arabia was used as a case to illustrate the evaluation system.

Abstract:In consideration of limited defense resources, an idea based on zero sum game was proposed to solve the problem of risk assessment for terrorism attacks. With quantitative analysis, a damage probability model was used to make decisions for attack targets under the limited resources. By analyzing the calculation method of key parameters of the model, an optimal resource allocation scheme was achieved. Finally, taking the target for urban subway stations as an example, through risk level qualitative assessment of the stations, loss probabilities of each target were calculated and compared under different defense resources to determine the optimal resource allocation scheme. The results show that the proposed scheme is practical and effective.

Abstract:This paper builds an asymmetrical evolutionary game model of research and development talents between inflow region and outflow region. Through analyzing the phase diagrams, the evolutionary game system’s stability strategies under different conditions are studied. Consequently, the mechanism of the talents’ agglomeration, replacement, dissipation and stagnation is found. The results show that the talents’ decision on mobility is not only based on cost and income, but also based on intangible benefits from the external effect of talent agglomeration. Therefore, the government can choose the evolutionary path by adjusting talent mobility costs, talent subsidies, social benefits and by controlling the convenience of knowledge spillovers.