Abstract:The general idea of mechanical analysis for deconstruction of structures is established.Safety and reusability are proposed as control attributes of deconstruction, and the aim, objects, conditions, problems, and methods of the mechanical analysis are clarified. Besides, the state dispersion method and the spatial segmentation method are recommended as the methods for simplification. In this way, the whole deconstruction process is divided into multiple states, and the analysis of each state is divided into local analysis, structural analysis, and component analysis, of which the contents are summarized. Furthermore, the available tools in conceptual analysis, analytical analysis, and computational simulation are screened, based on which， deconstruction scenarios of simple concrete and steel frame structures are analyzed, and future research directions and difficulties are pointed out, in order to provide research foundation for the safety of deconstruction, the reuse of components, and the enhancement of efficiency.

Abstract:The salt fog originated from offshore zone and was easy to gather in the semi-closed space formed by beams and slabs of pile-supported wharf called gridiron space. It could induce the premature failure of substructure durabilityof the wharf. Therefore, numerical simulations are conducted to construct the natural ventilation models and the auxiliary ventilation models to simulate the spatial flow field changes in the gridiron space. It is concluded that when the shield ratio (defined as the height ratio of the edge stringer to the air inlet) in the natural ventilation group is 1.15, the airflow inside the gridiron reaches the weakest turbulence. Under this condition, three auxiliary ventilation measures are proposed to enhance the durability of the pile-supported wharf. The numerical simulation results show that the opening radius of the three measures have little effect on the variation of the air circulation characteristics in the gridiron space. A smaller aperture will greatly reduce the wind speed in the gridiron inlet area. Considering construction difficulty and engineering cost, the plan for opening holes on the board is the best.

Abstract:In this paper, the failure characteristics and mechanical behavior of newly-casted reinforced concrete beams and long-term service reinforced concrete beams in fire were compared and analyzed by considering the loads and heating mode. Meanwhile, the data such as pore pressure, displacement and strain development of beam specimens in fire were obtained by using the vapor pressure measuring device and a non-contact optical strain collector. The test results show that the spalling degree of newly-casted reinforced specimens depended on the water content. Due to the environmental action, the water content of long-term serviced beams was low, which made the spalling degree much smaller than that of new specimens. However, natural carbonation lead to the decrease in the strength of reinforced concrete beams in long service, and there are many fine cracks. This phenomenon makes the stressed steel bar fail more easily under the action of high temperature, which makes the concrete beam brittle and cracked. In addition, under the combined action of fire and tensile stress, the spalling time of reinforced concrete beam is advanced, while the peak value of vapor pressure decreases.

Abstract:The strength of wood will gradually decrease at a long-term sustained load. The obvious duration of load (DOL) effect is one of the characteristics that distinguish wood and wood products from other building materials, and such a DOL effect must be properly considered in the design of timber structures. Based on the limit state design and the probabilistic statistical model of wood structure according to the current Chinese timber design code, an exploratory research was conducted in this paper to determine the DOL effect of timber structures at different load combinations including dead load, floor live load, and snow load in five Chinese cities (i.e., Nanjing, Harbin, Beijing, Shanghai, and Jinhua), using the JC method and the Foschi-Yao damage accumulation model. The different ratios of the nominal live load to the nominal dead load ρ, and the different coefficients of variation of wood strength were also considered in the reliability analysis. The value of the DOL coefficient K_DOL in different load combinations was calibrated. The results show that when the load ratio ρ is small, the DOL coefficient K_DOL increases with the increase in ρ.Besides, when the load ratio is large, K_DOL does not change with the value of ρ. Moreover, the coefficient of variation of wood strength has less influence on the DOL coefficient K_DOLwith the increase in load ratio ρ.

Abstract:In order to study the finite element analysis method of charring rate of cross-laminated timber (CLT) floor, three groups of domestic CLT floor fire experiments were conducted under ISO834 standard temperature rising conditions. Tensile and shear tests of the adhesive layer were simulated by using the finite element method, and two kinds of finite element models of charring rate of CLT floor were established: the finite element model without considering the delamination of the laminate and that considering the delamination of the laminate. The temperature-time curve and charring depth (rate) curve obtained from the test data were compared with the simulation results of the finite element model.The results show that the longer the fire time is, the higher the charring rate is.Besides, it is feasible to simulate the adhesive in the CLT plate by using cohesive element.Moreover, the finite element simulation results of the carbonization rate considering the delamination of the laminates agree well with the results of the carbonization rate obtained by the test.

Abstract:Based on the uniaxial tension experiments on 3 bolted ball-cylinder (BBC) joints, the finite element (FE) models of the tension specimens were established by using ABAQUS and were proved by comparing with experimental results. Then 87 FE models were established to analyze the influence parameters of the uniaxial tension bearing capacity of the joint. Meanwhile, the ultimate bearing capacity of the joint under uniaxial tension was defined. The FE results indicate that with the drop of the diameter of the cylinder and the length of the chord member, and the increase of the thickness of the cylinder wall, the height of the cylinder, the spacing and the size of the bolts, the bearing capacity of the joint increases. The joints with rib stiffeners produce a better stiffness and bearing capacity than ordinary ones. The insufficiency of the screw-in length of high strength bolts will cause the evulsion of bolts. Therefore, it is suggested that the screw-in length of bolts should be larger than the bolt diameter. Based on theoretical analysis, practical calculation formulae for the bearing capacity of BBC joints under uniaxial tension were proposed. The relative errors between the fitting formulae calculations and the numerical and experimental results are less than 10%.

Abstract:The video-based traffic surveillance is widely studied nowadays. But the existing methods are always challenged by the influence of light changing, weather effects, and a large amount of computation. This paper proposed a novel method of using sequence diagram of vehicle square wave pulse to process and analyze road monitoring videos based on spatial-temporal profileaiming at providing real-time detection of traffic flow parameters and vehicle classification for intelligent transportation system (ITS). First, based on the setting of virtual detection line, this method reduces a large number of traffic monitoring videos into spatial-temporal profiles, which contain time and space information. Next, the foreground of the spatial-temporal profile is extracted to generate a vertical-projected pixel histogram. Finally, vehicle objects are detected and the traffic state parameters are calculated, including traffic flow, time headway, occupancy, vehicle speed, and vehicle classification. The analysis result shows that the proposed method can obtain traffic flow parameters quickly and accurately even with the interference of weather and light. The accuracy rate of the method is as high as 97.32%, which is efficient and practicable to satisfy the real-timeand accuracy requirements of detection of traffic flow parametersin intelligent transportation systems.

Abstract:To improve the processing efficiency of video data used in intersection operation evaluation and to realize real-time diagnosis of intersection problems, a structured video-data based method is proposed, with headway as the primary analysis object. First, an algorithm based on the reproducibility of the flow curve is presented to search for the peak period. Then, the headway curve is used to realize the synchronous comparison of video data and signal control schemes. A comprehensive evaluation method of intersection efficiency is proposed from two aspects of signal control scheme and lane. Finally, the dynamic time warping and the grey clustering method are utilized to identify five types of lane headway curves based on actual data, with the corresponding problems and optimization schemes listed. The method provides a solution for problem diagnosing of inefficient lane and phase.

Abstract:Based on the basic performance test, i.e., the dynamic shear rheological test (DSR test), the thermogravimetric analysis test (TGA test), and the Fourier transform infrared spectrometer (FTIR test), the deterioration characteristics of hydrophobic nano-silica modified asphalt inchlorine salt F-T cycles were systematically studied. The experimental results show that the incorporation of hydrophobic nano-silica can effectively inhibit the deterioration process of asphalt inchlorine salt F-T cycles. The basic performance test and DSR test indicate that the penetration, softening point and viscosity of hydrophobic nano-silica modified asphalt increases by 17.46%, 5.82%, and 7.76%, respectively, and the rut factor increases by 17% to 54%.Besides, the growth rate of hydrophobic nano-silica modified asphalt is much smaller than that of base asphalt, which indicates that the incorporation of hydrophobic nano-silica could effectively reduce the sensitivity of asphalt to the chlorine salt F-T cycle. The TGA test suggests that hydrophobic nano-silica could improve the thermal stability of asphalt, but the thermal properties of hydrophobic nano-silica modified asphaltis significantly affected by chlorine salt F-T cycles, which may be due to the chemical bond formed between the hydrophobic nano-silica and asphalt is more easily destroyed in chlorine salt F-T cycles. The FTIR test indicates that the chemical reaction of asphalt occurs in chlorine salt F-T cycles, but no new functional groups appear. The free hydrocarbon group (3 676 cm^-1) has the mostsignificant change, which could effectively describe the damage process of twoasphalt samplesin chlorine salt F-T cycles. There is no obvious change in the functional groups of hydrophobic nano-silica modified asphalt in chlorine salt F-T cycles, and the distribution is relatively stable, with a high performance stability.

Abstract:This paper reviews the effects of iron on anammox process from the perspectives of electron transfer mechanism, microbial activities, and influencing factors. The results show that the iron with different valence statesas electron acceptor or electron donor canpromoteanammox by generating substrate and producing different reactions, such as Feammox and nitrate-dependent ferrous iron oxidation (NAFO). Meanwhile, iron element can promote the enrichment of functional microorganisms, the increase of heme c, and the granulation process, thus obviously improving the treatment effect of Anammox process. This paper also summarizes the optimal parameters such as iron dosing state, temperature, and pH in the process of iron-enhanced Anammox, which can provide reference for future study of iron-enhanced anammox.

Abstract:Sewer network hydraulic and quality simulation with consideration of sediment transport is conducted by coupling with the storm water management model (SWMM)with the sediment transport model (STM). Using this coupling model, the sediment load concentration and hydraulic cross section deformation of conduit caused by sediment transport in the sewer network can be quantitatively calculated. The global time step length of the coupling model is determined by the SWMM, and the STM is modified to adapt to the global time step so that the numerical stability in the simulation process can be achieved, and unsteady cases caused by over deposition and over flushing are avoided. The proposed coupling model was applied to two study cases, whose results show that this coupling model is stable and logical. The sediment flushing and deposition cycle and its impacts on load concentration and hydraulic cross section deformation of conduits can be simulated. Comparisons between simulation results and observed data indicate that the simulation results obtained by the proposed coupling process fit the observed data better than the simulation results without the coupling process.

Abstract:Repair jobs resulting from poor assembly quality of jobs in the aircraft assembly process can disturb assembly scheduling plans and cause economic losses. This paper proposes a prediction-rescheduling closed-loop framework in order to solve this scheduling problem. In the front part of this framework, job quality prediction models are trained using historical data of quality-related components in deteriorations and quality characteristic deviations of jobs. Based on the prediction results of jobs, a rescheduling model is established in the later part of this framework and an improved-immune-algorithm (I-I-A) is designed to generate a new scheduling plan for the assembly line. The effectiveness of the I-I-A is verified from different aspects and the advantages and disadvantages of the performance of the closed-loop framework suggested in this paper is analyzed in comparison with other frameworks.

Abstract:The electro-hydraulic brake-by-wire system is the mainstream solution for next-generation automotive brake systems, whose wheel-cylinder hydraulic pressure control is the basis to achieve active safety functions such as vehicle stability control. In view of the cost and redundancy of the integrated-electronic-hydraulic brake system with a four-valve structure, a wheel-cylinder hydraulic pressure control strategy without pressure sensors is proposed. Through the bench test, the working characteristics of the hydraulic control unit were analyzed. A method for estimating the hydraulic pressure of the wheel cylinder is developed based on the combination of Bernoulli equation and PV characteristics. The solenoid-valve control logic and balance control strategy are designed for wheel-cylinder pressure regulation based on depressurization priority. The experimental results show that the root-mean-square error of the pressure control in this method is within 0.21MPa, which is equivalent to the control accuracy of the scheme with a hydraulic pressure sensor.

Abstract:Aimed at the characteristics of complex vibration environment when estimating the fatigue life of rail vehicle equipment, an inductive method of random vibration environment suitable for rail vehicle equipment is proposed, and a fatigue life estimation process of rail vehicle equipment is solved based on the inductive method. Combining the vibration environment data in the parameter hypothesis test, the upper tolerance limit of the sample is estimated, and the measured spectrum and the normalized spectrum are obtained. Taking the fatigue fracture of the axle box lug of a certain type of subway vehicle as an example, the measured stress is statistically analyzed, and the measured spectrum and the normalized spectrum are used as excitation to simulate the fatigue life of the lug. The results show that compared with the fatigue result at the measured stress, the relative errors of the simulation results of the measured spectrum and the normalized spectrum are 1.8% and 4.1%, respectively, which proves that the proposed vibration environment inductive method and the fatigue life estimation method are highly reliable and can provide references for practical engineering applications.

Abstract:TakingSt16 and 6061 aluminum alloy tubes as objects, the feasibility of using a novel plastic joining method to connect these two thin-walltubes was investigated. A finite element model was built using the Abaqus software, and a special moldfor plastic joining of thin-walled tubes was presented. Experiments of tubes plastic joining were performed to verify the precision of the finite element model. The influence of the relative free length of the tube endgap between the die and the tube, and the gap between the mandrel and the tube on the formability of the joint adopted in the plastic compressionjoiningprocess was emphasized. The results demonstrated that the method of plastic joining by compression was a suitable approach for thin-walled tubesof dissimilar materials. The key technology was that the free length of the tubes and the gap between molds and tubes should be correctly designed.The plastic deformation of the two tubes in the compression instability was compatible.Theamountof deformation and the directionof the movement of the wrinkles should be compatible so that the two wrinkles could contact tightly. For the St16/AA6061 tubesinvestigated,the prerequisite condition for a success joining was that the relative free length should located between 1.250 and 1.625. The gap between the tube and the dieshould be between 0.07 and 0.20 times of the thickness of the tube while that between the tube and the mandrel should be between 0.07 and 0.27 times of the thickness of the tube.

Abstract:Based on a new probability criterion to select the working rows from the coefficient matrix, a greedy-distance randomized Kaczmarz method was proposed to solve large sparse linear systems. The theoretical analysis demonstrates that this method converges to the least-norm solution when the linear system is consistent, and the convergence factor of the greedy-distance randomized Kaczmarz method is smaller than that of the randomized Kaczmarz method. Moreover, the numerical results have verified its effectiveness.

Abstract:Existing methods for European and American option pricing under the VG model are quite complex and time consuming in calculation. Thus, an efficient and accurate Willow tree method is proposed in this paper. Johnson curve is used to construct the asset price nodes in the VG process and the FFT-COS method is used to calculate the transfer probability between asset price nodes. Besides, the theoretical convergence of the Willow tree method for European options is analyzed. Moreover, some numerical experiments are conducted to demonstrate the efficiency and accuracy of the proposed method.