Abstract:OpenSees based substructure pseudo-dynamic test method was investigated. Several key problems, such as real-time inquiry of substructure responses, boundary condition simulation, and data exchange of request displacements and feedback forces between substructures and time history analysis program, were discussed. Using the method, a virtual pseudo-dynamic substructure test was conducted to simulate the seismic response of an eight-story steel frame with buckling restrained braces. The test results were compared with time history analysis results calculated with OpenSees, and the good agreement verifies the feasibility and effectiveness of the method.

Abstract:The requirements of shear-weight ratio in the codes of United States and some other countries were introduced. The regulations and related contents regarding the minimum story shear for the seismic design of buildings issued in Chinese Code for Seismic Design of Buildings (GB 50011-2010) and Technical Specification for Concrete Structures of Tall Buildings (JGJ 3-2010) were briefly described. A comparison between Chinese code and other seismic design codes was made. The basic structural period of tall structures satisfying shear-gravity ratio of the code was introduced. Based on the requirement for seismic shear-gravity ratio, the curves of seismic influence coefficient can be divided into two situations. In either situation, the curves of seismic influence coefficient can be divided into five sections. In each section, the relationship between structural period and the minimum seismic shear gravity ratio was introduced. The calculation results of the basic structural period satisfying the base shear factor issued in the code were obtained. It can be easy to determine the basic structural period satisfying the base shear factor issued in the code by using this table. The analysis result was checked with some engineering examples.

Abstract:This paper put forward a new concrete superimposed slab with connections to solve the problem that the prefabricated layer of two-way slab is difficult to be hoisted and transported if it is too big. In order to study the bearing capacity of the new slab, this study first conducted a uniformly distributed load experiment on the new slab in the range of elasticity, and then conducted a destructive experiment in the condition of the concentrated load compared with the superimposed one-way slab. The major contents include the deflection, reinforcement strain, concrete strain variation with the load and crack development. The uniform loading comparative experiment indicates that the new slab has high loading capacity. The destructive concentrated loading comparative experiment shows that the new slab has good two-way loading capacity. It shows that this new slab has good loading capability and is easily hoisted and transported, so it is worth popularizing this new slab structure.

Abstract:Two constitutive models for steel (Steel01 and Steel02) and two constitutive models for concrete were firstly selected to simulate two pseudo static tests for reinforced concrete columns in OpenSees based on the fiber model. Then, a constitutive model in OpenSees, i.e., Reinforcing Steel, was used to simulate the monotonic loading test, cyclic loading test, fatigue test for steel and the pseudo static test for the reinforced concrete columns. It is found that the constitutive models for concrete fibers are quite applicable for the numerical simulation and the results are not markedly affected by the change of the constitutive model for concrete fibers, while the constitutive models for steel need to be further improved because they can't perfectly meet the precision demand. Different models for steel will lead to different results. The Reinforcing Steel model can effectively improve the precision of the simulations. However, it also has some disadvantages in that it cannot clearly reflect the pinching effect of the hysteresis curves obtained from the cyclic loading tests for steel, the simulation is complex, the calculation results tend to be too conservative and are hard to converge.

Abstract:This study investigated the behavior of double steel plate composite shear walls (SC), which are typical prototypes for nuclear shear walls. The testing program involved three 1/4 scaled SC wall specimens with different stud spacings and stiffening ribs. Cyclic loading tests were applied to those specimens to observe the failure patterns, bearing capacity and ductility performance .The result proves that the wall has strong shear strength and integrity. Setting the stiffening rib can effectively improve the bearing capacity, stiffness and ductility of the walls. Based on the experimental research, the specimens with different thicknesses of steel plate, concrete strength, axial compression and different contents of stiffener were simulated by using FEA to study the influence of these parameters on the shear strength. Finally, a formula of the shear bearing capacity of the SC wall was proposed, and this can be a guideline for nuclear containment design.

Abstract:On the basis of the proposed stress-strain relationships of steel and concrete of concrete-filled circular steel tubes (CFCST) at each stage of fire exposure, fully coupled thermal-stress analysis model in finite element soft ABAQUS was developed to predict the load-deformation relationship curves of axially loaded CFCST stub columns after exposure to ISO-834 standard fire. The predicted results were in good agreement with test results. The finite element analysis model was then used to investigate the behavior of CFCST stub columns by examining the load-deformation relationship, the cross-sectional stress distributions of steel tube and concrete core and their interaction during the entire stage of fire exposure. Parametric analysis was conducted to investigate the influence of heating time, initial axial, steel ratio, steel yield strength, concrete cube strength, spray insulation thickness and sectional size on the residual strength of axially loaded CFCST stub columns. Finally, a set of formulas was proposed to predict the residual strength of axially loaded CFCST stub columns after exposure to fire.

Abstract:In this study, a three-dimensional vehicle-bridge coupled model was developed to study the dynamic impact of vehicle braking on bridges. The dynamic responses and impact factors of simply-supported prestressed concrete girder bridges were obtained under the braking of a typical three-axle vehicle model. A parametric study was performed to investigate the effect of several important parameters, including the vehicle braking position, deceleration rate, initial vehicle speed, road surface condition and bridge span length, on the impact factors. In addition, a comparison was conducted between the calculated dynamic impact factors and those specified in the current Chinese bridge design code. The results show that the impact of vehicle braking on bridges increases with the increase of braking force, and braking within the first half span causes greater impact than braking within the second half span. Furthermore, the dynamic responses and impact factors of bridges due to vehicle braking are notably greater than those due to the vehicles moving at constant speeds, and the impact factors may exceed those specified in the current Chinese bridge design code.

Abstract:In order to confirm that the effective notch stress method is applicable to the fatigue assessment of orthotropic steel bridge deck, the local stress characteristics of two different transition forms in the arc notch details of diaphragm was studied. The effective notch stress in the weld toe and the weld root of the rib-to-diaphragm was computed separately and compared. The result has shown that the crack is easier to generate in the weld toe. The experiment result was assessed by S-N curve, and the result has shown that the effective notch stress method is suitable for assessing orthotropic steel bridge deck. The notch radius was assumed to be zero and it would result in conservative results. Based on the comparison of different rib thickness, it is found that the crack initiation in the rib-to-diaphragm seems to be easier to generate with the increase of rib thickness. This study can provide important information for design of orthotropic steel bridge deck, as well as for the evaluation of the fatigue performance of orthotropic steel bridge deck.

Abstract:To study the vibration characters of the bridge in-service, the impact factor of bridge structures under random traffic loads was presented. The method of influence surface was firstly used to simulate the functions, which was used to obtain the max-value of static displacements by solving the max-value of the function. Secondly, based on each three-dimensional vehicle model and the program of the vehicle-bridge coupled system, the impact forces between each vehicle and the bridge were obtained and then used instead of the whole three-dimensional vehicles in the simulating random traffic loads. And finally, a new method of calculating the impact factor under random traffic loads was obtained and verified. Compared with the impact factor obtained by the Chinese bridge standard and the above method, the results have shown that the proposed method can effectively calculate the impact factor of bridge structures under random traffic.

Abstract:A traditional rail-beam-pier plane model and a rail-beam-pier grillage model were built by adopting the mechanism of ideal elastic-plastic ballast resistance with the background of a (36+112+36) m double-track continuous beam-arch composite bridge on the new Chengdu-Lanzhou Railway line. The aim was to study the difference between grillage models and plane models about the distribution of longitudinal forces in continuous beam-arch composite bridges. The results show that the distribution of longitudinal forces is basically the same in the grillage models and plane models, but the results of the plane models are conservative. Plane models can not accurately reflect the spatial mechanical properties with multi-track under asymmetric loads. Therefore, the grillage model is more effective in the calculation of CWR(continuously welded rail) on the multi-track long span railway bridge.

Abstract:Based on the buffeting force model and the model for the wind-vehicle-bridge system presented in the paper, an approach to study the coupling vibration of wind-vehicle-bridge system considering the coherence of buffeting forces was developed and the corresponding calculating program was built. The application of the proposed methodology on the Jiangshun Bridge in China was presented as a numerical example. The coherence of the buffeting forces of the bridge and the aerodynamic parameters of the bridge and the vehicle considering the aerodynamic interference between the bridge and the vehicle were measured in wind tunnel. The effect of the coherence of buffeting forces of the bridge on the dynamic performance of both the bridge and the vehicles under cross winds were discussed. It is found that the coherence of the buffeting forces of the bridge has significant effect on the dynamic responses of the bridge, and some impact on the dynamic responses of the vehicle.

Abstract:The stable performance of the orthotropic bridge deck with simply supported, made from steel-polyurethane sandwich plate, was studied by means of experiments and the numerical calculation method. The impact of several parameter changes of the bridge deck on the first four order buckling modes was analyzed through the calculation of elastic stability, and the impact of material nonlinearity and geometric nonlinearity of structure on the critical load was also analyzed. The results have shown that, when sandwich bridge deck is in a state of compression, the influence degree of the wheel effect on the top and bottom steel plate stress will be quite different, and that, among the three parameters, i.e. the core layer thickness, the longitudinal stiffener spacing and steel plate thickness, the first two parameters have a greater influence on the stability of the bridge deck. When designing the orthotropic sandwich bridge deck, it is recommended to set a reasonable thickness of sandwich plate at first, then to choose the longitudinal stiffener spacing by trying to calculation in order to reduce the workload.

Abstract:This paper used Particle Flow Code (PFC3D) to simulate the model experiment of the process of the initiation of debris flow. Based on the previous simulation studies and considering the unsaturated features of sand soil, it simulated water with small granules in the numerical simulation of the initiation phase of sandy debris flow, and set a bond model to simulate the matrix suction between soil particles. Compared with the results of the numerical simulation with laboratory model tests, the result of the study shows that the start of debris flow forms with rear soil pushing the front soil rapid decline. Under the condition of unsaturated, the matrix suction between soil particles provides soil strength. When the penetration and gravity are beyond the bond force between particles, soil turns from unsaturated to saturated and debris flow will start. Compared with the results in the simulated method which does not consider the condition of unsaturated, the method of considering the unsaturated is suitable to simulate the initiation process and failure mode of flow-slip mudslides.

Abstract:To study the unlined elliptical tunnel stability, strength reduction method was introduced into the finite element upper bound method. The relations between safety factor and influence factors such as shear strength parameters, buried depth and span were studied with self-made program. Meanwhile, the failure modes were also explored for limit states derived from strength reduction method. The results show that strength reduction method can be easily embedded into finite element upper bound method. The relation curves have shown a positive correlation between rock safety factors and shear strength parameters, while rock safety factors have negative correlations with buried depth and span. The influence of the tunnel span on the safety factor is obvious, and the reduction in rock safety factors has been found to vary approximately in a range of 27%~46% when the ratio of tunnel span and height (B/D) increases from 0.5 to 2.0. The failure modes with distinct characteristics reveal that the main slip surface starts from the bottom or the side wall of the tunnels and then extends up to the ground surface. The slip lines are mainly focused on the top of the tunnel arch and side wall. Meanwhile, horizontal extents of the damage area are less than 1.5 times of tunnel height.

Abstract:The effect of different failure criteria and settlement control requirements on the reliability analysis of foundation piles was studied. The bias factor defined with respect to the s-lgt failure criterion was introduced to each of the seven failure criteria collected. The synthetic reliability analysis method with consideration of different failure criteria, model uncertainties and settlement control requirements was presented by using model factors for ultimate limit state (ULS) and serviceability limit state (SLS). Finally, the impact of the randomness of limiting tolerable settlement of pile head on reliability analysis was studied. The following conclusions are drawn. First, variation of settlement control requirements has a great influence on reliability index while does not create a change of the ranking of reliability levels based on seven failure criteria. Second, reliability index increases with the limiting tolerable settlement although the increase rate gradually diminishes, which is independent of failure criterion. Third, there is a close correlation between the evaluation principles of foundation pile reliability for ULS and SLS. Therefore, this study recommends the combination of failure criteria and settlement control requirements for the comprehensive assessment of foundation pile reliability.

Abstract:A method for the tendency prediction of collapse-landslide caused by earthquake was developed, which meets the precision requirement of railway location principle stage. Based on the theory of the erosion cycle (youth-maturity-old age), this paper discussed the sequence of within-reaching-deviation from the critical slope in one ideal cycle, then put forward the principle that the tendency prediction of collapse-landslide induced by earthquake could be estimated by judging the development stage of the drainage basin. Based on the feedback mechanism of the valley and valley slope, the method of distinguishing different stages of the basin by selecting the profile feature was proposed. This method eliminates the spatial dependency on small drainage basins. At last, the method was validated with the field data of Yushu earthquake, Wenchuan earthquake and Lushan earthquake, which are the three strong earthquakes with M≥7.0 within 21st century in China. The tendency of collapse-landslide caused by earthquake is most serious when the Strahler's Integral is between 0.5~0.6. The gap to the value is bigger and the tendency is minor.

Abstract:A novel thermoelectric heat pump air heater using thermoelectric heat pump for heating was formulated, and a simulation model of the device based on thermodynamics was set up to simulate the performance of the air heater. The influence of the operating voltage and the cold and hot side resistance on the heater was analyzed. The simulation results have shown that the optimum operation voltage is 5.0V. The reduction of cold and hot side resistance can improve the performance of the heater. Exhaust heat recovery helps to decrease the temperature difference between the cold side and the heat side, which can improve the systematic performance. The coefficient of performance can reach as high as 2.9. The device is more energy-efficient compared with traditional electric heater, whose coefficient of performance is only about 0.9.

Abstract:The design temperature difference between chilled water supply and return of district cooling systems is usually considered by using empirical values or only from the view point of energy consumption. In this paper, an optimization model of temperature difference between the chilled water supply and return of a district cooling system (DCS) was established with dynamic annual commuted cost method from the economic aspect. This model was used to optimize the temperature difference of the chilled water of a district cooling system in a community in a zone hot in summer and cold in winter. Besides, the influence of power price, specific frictional resistance, cooling supply distance and air conditioning load on the economic temperature difference was also analyzed. The results have shown that annual cost is the lowest when economic temperature difference is 6.3℃ and the corresponding design chilled water supply temperature is 5.9℃. Compared with the conventional design temperature of 7/12℃, it saves RMB 24,000 a year and the economic benefit is remarkable. Moreover, the economic temperature difference decreases with the growth of power price and increases with the growth of specific frictional resistance, cooling supply distance and air conditioning load.

Abstract:The environmental benefit of New Energy Vehicle’s(NEV’s) application in the logistics industry was studied. Firstly, this study established the carbon emission model of the urban logistics industry and predicted the cargo turnover of the three major cities of Beijing, Shanghai and Tianjin with the modified Gompertz model. Based on this, this paper analyzed the NEV’s ability of carbon emission reduction, calculated the quantity of carbon emission reduction after the application of NEV. Then, we conclude that the NEV has the ability of carbon emission reduction. And more carbon emission will be reduced with the development of the NEV’s technique. Considering external economy of the logistics industry, the government should construct an urban logistics system suitable for the NEV, intensify the support of the NEV in the urban logistics industry and follow the market demand of developing the NEV technology in order to promote the development of urban logistics of the NEV.