Abstract:Based on the high resolution data of the wind speed and direction，as well as the wind pressure data measured from an instrumental gable roof of a low rise building during the tropical storm of Mujigae, the influences of vertical wind angles on the roof pressures of the low-rise gable roof building are investigated when the incident flow is perpendicular to the ridge line during tropical cyclone. The results show a clearly linear relationship between the non-conventional pressure coefficients and incident vertical wind angles. As the distance between pressure taps and leading edge increases, the non-conventional pressure coefficients affected by the incident vertical wind angles decrease. In addition, due to the influence of the ridge, leeward roof area that is close to the ridge is greatly affected by the incident vertical wind angles. The incident vertical wind angle may be one of the main causes for the discrepancy between the experimental pressure coefficients and field measurements near the leading edge and the ridge. Therefore, the influences of the incident vertical wind angles should be considered in the wind tunnel tests.

Abstract:Multiple numerical models were established by Computational Fluid Dynamics (CFD) method, and the reliability of the numerical results was also verified by the comparison with that of a wind tunnel test. The CFD analysis was then systematically carried out to study the influence of three geomorphological factors, the length of the canyon, distance between two peaks, and slope of the mountain, on the mean wind speed-up effect. The analysis results showed that the speed-up effect at the mountaintop was significantly affected by the slope of the mountain. The larger the slope was, the more significant the speed-up effect was in the near surface. Furthermore, the speed-up effect inside the canyon was influenced by the multiple geomorphological factors, and the variation trends were complicated. Therefore, the influence of the side slope boundary layer of the canyon and the three-dimensional effect of airflow should be considered. When the length of the canyon and the distance between two peaks decreased, and the slope of the mountain increased, the speed-up effect at the windward canyon entrance was more obvious in the near surface. Finally, the wind pressure terrain correction coefficient of the typical canyon was calculated and compared with the prescription of Chinese design code for building structures.

Abstract:It is known that a reasonable three-dimensional fluctuating inlet boundary condition plays an important role in the accurate numerical simulation of wind field in the mountainous area. Taking Li Shui Bridge as the engineering background in this paper, the fluctuating wind field satisfying the characteristics of the wind field in the mountainous area was generated based on field measuring data processed by the weighted amplitude wave superposition (WAWS) method. The fluctuating velocity data was used for the inlet boundary of Large Eddy Simulation (LES) by the secondary development of the commercial software FLUENT. The comparison of the computational results from the proposed method and the method without considering fluctuating inlet boundary shows that the method developed in this paper can better reflect the actual flow field in the mountainous area. Finally, the wind field of the bridge in the mountainous area under different wind directions was simulated. It is found that the proposed method provides a reference for the refined simulation of the fluctuation wind field in mountainous area.

Abstract:A prestressed concrete-steel hybrid tower structure was proposed to replace a conventional 2 MW steel tubular wind turbine tower structure. The height and section size of the prestressed concrete-steel hybrid tower were optimized by an updated partial swarm optimization algorithm, where the cost was taken as the optimal objective function, and the constraint conditions including the strength, stability and the stiffness of the prestressed concrete and steel tubular segments, as well as the fatigue, natural frequency, and the maximum top deflection of the hybrid tower structure were considered, but the shape of the tower was kept unchanged. The optimization results show that the total construction cost of the prestressed concrete-steel hybrid wind turbine tower satisfying all of the constraint considerations is about 27 % less than that of the conventional steel tubular wind tower.

Abstract:In order to study the fatigue behavior of the crumb rubber concrete and steel composite beam, six fatigue tests were conducted. This study focused on examining the influence of the rubber particles, shear connection degree, stud diameter and sectional dimension on the fatigue life, accumulated fatigue damage and failure mode. Concrete strain, residual slip, residual deflection and bending stiffness of the composite beams at different loading cycles were measured and analyzed. The test results showed that the plain section assumption cannot be applied to the partial connected composite beams under fatigue loading; the fatigue failure was governed by the shank failure of the studs showing good ductility in the shear span; crumb rubber concrete decreased the crack width and improved the fatigue life effectively; larger residual slip due to the rubber particles improved ductility; larger shear connection degree increased the fatigue life and reduced the shear stiffness degradation; and larger diameter of the studs decreased the fatigue life and ductility. It is shown that this study is helpful for the application of crumb rubber concrete into the composite beams.

Abstract:In order to find a seismic strengthening method of brick masonry infill walls with wood frame, three small-scaled wall specimens were tested under low reversed cyclic loadings. Based on the experimental investigation, structural seismic performances including failure modes, hysteresis curves, skeleton curves, load-carrying capacity, ductility, and energy dissipation capacity were evaluated. The test results showed that the non-strengthened specimen failed due to shear cracks and out-of-plane collapse of masonry wall, but the wood frame was not damaged; the use of the embedded steel bars and externally fixed steel plates to strengthen the brick masonry infill wall effectively improved their load-carrying capacity and ductility; and the limited initial cracks had no influence on the nominal yield strength and peak strength, but decreased the ductility and energy dissipation capacity of the brick masonry infill walls with wood frame.

Abstract:A new type of self-centering confined masonry wall equipped with both unbounded tendons and external steel dampers was proposed. Its hysteresis behavior was studied through pseudo-static tests under cyclic loading, which focused on investigating the influence of the initial prestress of the tendon and the yield load of dampers on the energy dissipation capacity of the proposed wall. Based on the test results, a simplified numerical analysis model was established. It is showed that flag shape was a typical hysteresis curve of the wall. During the loading and unloading process, the wall specimen remained intact, and significant degradation of strength and stiffness was not observed. It is also found that the increase of the initial prestress in tendons led to the enhancement of the self-centering ability but the reduction of the energy dissipation capacity of the wall on the other hand, when the yield force of steel dampers increased, the energy dissipation capacity of the wall was improved, but some residual displacement occurred. Moreover, the numerical analysis results matched well with the test results, which indicate that the proposed numerical models can well capture the mechanical behavior of the wall.

Abstract:On the basis of the fundamental damage mechanism of concrete, damage accumulation and residual deformation of concrete under fatigue loading were considered, and the constitutive equation of concrete expressed by Helmholtz free energy was derived. An energy based fatigue damage constitutive model was then proposed by using the variation principle. Meanwhile, based on the development law of the residual deformation of concrete under fatigue load, the influencing coefficient of the residual deformation with definite physical meaning was defined, which was then included into the plastic damage constitutive model of concrete together with the damage factor of deformation modulus in order to provide a more accurate and convenient fatigue constitutive model. To verify the accuracy and applicability of the proposed model, the results of the numerical examples were compared with the experimental data, where no more than 3% of error was observed.

Abstract:In this study, an explicit non-linear analysis program of LS-DYNA was employed to simulate a concrete gravity dam with either normal or empty reservoir under contact explosion. Considering the effect of high strain rate of concrete under the contact explosion, HJC (Holmquist-Johnson-Cook) constitutive model was adopted to simulate the damage characteristic and plastic deformation of the dam. Firstly, “Explosive-Air-Water-Concrete Test Cube” model was constructed and verified. “Explosive-Air-Water Storage-Dam-Foundation” dynamic full coupled model was then developed to evaluate the dynamic response and damage characteristic of the concrete gravity dam under the contact explosion denoted by TNT explosive on both normal water level dam and empty dam. The test shows that the analytical method is reliable to study the contact explosion of the concrete gravity dams, and it also covers the shortage of experimental study. In the case of the normal water level, the dynamic response and the damage of the dam are greatly affected by the explosion points in upstream. Therefore, the study of anti-explosion properties for the concrete gravity dam should focus on the damage measurement when the explosion points are disposed in upstream under the normal water level.

Abstract:An analytical study was conducted to develop an effective method for investigating the gap at the corner of the slab caused by the negative temperature gradients. This method considers the principle of minimum potential energy and the determinate curve using quasi-Newton iterative algorithm to estimate the deformation curve in the process of warping. The proposed method predicts well the measured warping displacements of the CRTSⅡ track slab corner in Beijing-Shanghai High Speed Railway. The analysis results also show that the temperature gradients correlate with the warping of the CRTSⅡ slab, and the increment of the foundation coefficient reduces the warping caused by temperature effectively. In addition, the method reducing the gap of the slab was discussed.

Abstract:This paper studied the shear performance of waterproof cohesive layer of a rubber epoxy asphalt stone (REAS)on steel deck pavement, and examined the relationships between the shear performance and the frequent change of bridge slope and environment temperature. Firstly, the oblique shear tests were conducted under different shear angles and freeze-thaw cycle times. Considering the linear relationship between normal stress and shear strength, the cohesive force and the internal friction angle of REAS waterproof cohesive layer were calculated. According to the energy method, shear dissipated energy was analyzed. The test results showed that new chemical cross linking and physical entanglement occurred in the epoxy asphalt binder with rubber power, which exhibits better bonding performance, anti-deforming capability and cryogenic flexibility. Under different shear angles and freeze-thaw cycle times, the shear strength and shear displacement of REAS waterproof cohesive layer were greater than those of EA waterproof cohesive layer. It is demonstrated that the REAS waterproof cohesive layer has better shear performance. On the other hand, the shear strength of the REAS waterproof cohesive layer decreased as a power function with the increase of the shear angle, while it decreased as a parabolic curve with the increase of freeze-thaw cycle times. After five freeze-thaws cycle times, the shear dissipated energy of REAS waterproof cohesive layer decreased by 46.0%, which indicates that the freeze-thaw cycles significantly influenced the shear performance of REAS waterproof cohesive layer.

Abstract:In order to investigate the crashworthiness of unban bridge piers impacted by heavy vehicles, a refined finite element model of the bridge in conjunction with vehicle was developed. The bridge model has two spans of superstructures and one bent supported by two piers. Beam and shell elements are adopted for the superstructures, while solid elements are used for the substructure. Additionally, a modified heavy vehicle model with various lengths and weights was developed. The proposed bridge model in conjunction with the vehicles was verified against the actual damage modes reported in vehicle-impacting-bridge accidents. The validity of the proposed model was also evaluated by the energy balance curve of the impacting process. Time history impact load due to the heavy vehicle with various weights was then presented. The development trend for the magnitude and location of impact load was also discussed. Numerical results show that at a fixed impact velocity the peak impact force increases with the increase of the vehicle weight. A lagging tendency of the peak crash force occurs in the heavier vehicle, and the collision center is mainly concentrated near the first contact point. A secondary collision at the rear compartment may take place for the shorter and heavier vehicle.

Abstract:This paper chooses a long-span station hall of Beijing South Station as engineering background to evaluate the comfort of “Building-bridge Integration” structures. On the basis of the results of numerical simulation that applies train loads to the structure model at the actual location, dynamic response of the elevated station hall is presented and examined. The result shows that train type and load location significantly influence the structure behavior. Compared with existing standards for structure vibration comfort, the measured vibration intensity is close to or greater than the current specification limits. The actual annoyance rate does not agree with the theoretical value, which indicates that existing comfort evaluation criteria are not suitable to evaluate the comfort of “Building-Bridge integration” structure system.

Abstract:One model test beam is made to study effective distribution width of the deck of girder with corrugated webs. Then static non-destructive testing is conducted to study distribution of transversal force of this structure. And by combination to the current road bridges criterion value and data of finite element analysis, on the basis of comparetion of three kinds of effective distribution width values, the road bridges criterion value was modified and the effective distribution width correction coefficient under different loading conditions was obtained. And the results demonstrated that the road bridges criterion value was smaller than test results and data of finite element analysis, in order to apply to the effective distribution width calculation of box girder with corrugated steel webs, the former should be multiplied by the coefficient of more than 1.0.

Abstract:In this study, wavelet transform was firstly applied to deal with a numerically simulated signal that was unable to obviously identify axle information. The analysis result showed that the wavelet transform was able to magnify the slope discontinuities so as to accurately identify the silhouette of passing vehicles. Subsequently, based on the field-tested FAD signals through which the vehicle configuration was difficult to be directly identified, the most appropriate transform scales and the best suitable wavelet function performing wavelet transform were selected from the minimum Shannon entropy and maximum correlation. The results demonstrated that the wavelet transform in pattern recognition effectively identified the vehicle configuration (including vehicle velocity, axle numbers, and axle spacing), especially for the unidentified FAD signals. Therefore, wavelet domain analysis can effectively improve the efficiency and accuracy for the vehicular axle identification in BWIM system, and it is beneficial for the successful application of BWIM system in controlling and monitoring overweight vehicles.

Abstract:The structural performances including shear-strength, stiffness, and failure mode of structural adhesives with two different curing schedules at room and high temperatures were investigated. The test results showed that the high temperature curing on the structural adhesive after room temperature curing can improve the value of glass transition temperature Tg by about 30 ℃. Moreover, the shear performances of the structural adhesives were deteriorated with the increase of the temperature, and the maximum degradation rate occurred within the temperature range of Tg±20 ℃. It is indicated that the glass transition temperature Tg was critical to the shear behavior of the structural adhesive at the high temperature. In a whole, the high temperature curing can improve the value of glass transition temperature, and it is helpful to delay the degradation of shear performance at the elevated temperature. Based on the test results, the normalized relationship between the shear performances and temperature were eventually proposed, in which glass transition temperature was considered.

Abstract:Elastic modulus E，Poisson ratio μ，shear modulus G and fracture toughness KIC of the slates with different stratification angles were obtained by the uniaxial compression tests and relaxation method of double torsion constant displacement load using SANS and MTS-insight testing machines. The relationships among the stratification angle, compressive strength, and fracture toughness were examined. The analysis results show that the uniaxial compression and fracture toughness decrease and then increase with the increase of angle β, which shows a U-shaped relationship curve. When the angle β of the slate is 45°, the fracture toughness is minimized. The crack initiation and crack propagation are developed under the axial load, and the slate is destroyed regardless of c and φ values. Moreover, when the angle β is known, the value of the related fracture toughness can be estimated by using the experimentally derived relationship.

Abstract:In order to study the tensile mechanical behaviors of selvages in gabion meshes with different mesh sizes and selvage ways, a selvage stretching device was designed according to European Standard(EN10223-3:1997). Selvage tensile tests were carried out on the gabion meshes of 60 mm×80 mm and 80 mm×100 mm with type-A and type-B selvage ways. The mechanical behaviors of gabion meshes were analyzed, and the typical failure mode of the selvage tension was discussed. The test results showed that the selvage tensile strength of the gabion mesh with type-A selvage way was greater than that of type-B. According to the damage mode of gabion mesh, selvage tensile failure was classified into three failure modes: pull-out failure of the wire wound on the edge wire, tensile failure of mesh wire and tensile failure of mesh wire after pulling out of some enwinding wires. It is also found that selvage quality was dependent on the winding turns and compact degree of the wire wound on the edge wire. Selvage tensile mechanical characteristics of the gabion mesh were significantly affected by the mesh size, wire size, and selvage quality. This study is expected to provide some useful references for the design and construction of reinforced gabion structures.

Abstract:The separated heat pipe can effectively reduce the energy consumption of telecommunication base station, and the micro-channel heat exchangers can be adopted as the evaporator and condenser. In order to investigate the effect of the filling ratio on the heat transfer rate，EER，refrigerant pressure and temperature, and the variation of optimal filling ratio range and heat transfer rate under two air volumes and different outdoor temperatures, experimental test was carried out in the enthalpy difference laboratory, taken R22 as working fluids. The heat transfer rate and EER were 4.0 kW and 11.8, respectively, and the optimal filling ratio was 79.3% to 105.8%. The pressure of the system increased with the increase of the filling ratio. As filling ratio increased，the temperature difference between the inlet and outlet of the evaporator decreased firstly, and then increased slightly. When the air flow rate was reduced from 3 000 m3/h to 1 700 m3/h, the optimum filling ratio was almost remained, but the air temperature of evaporator outlet decreased and the maximum heat transfer rate decreased by 29%. Finally, the system was tested under different outdoor operating conditions. The test results showed that the range of the optimal filling ratio became narrow with the decrease of the outdoor temperature. The results are useful for modeling, design, and operation control of the micro-channel separate heat pipe.

Abstract:This study focuses on the evaluation index system of resilient city based on the framework of "society, economy, urban system and service, and urban management". Through literature statistics, a factor group is obtained, and non-conforming factors in the national condition and statistical system of our country are removed. By means of frequency analysis, the same typed indexes are merged, and expert questionnaire based on Delphi Method is used for index selection. Analytic hierarchy process method is used to build such indexes into a three-layered structure with four criterion layers and multiple filed and factor layers according to their correlation and subordination. Experts will score the relationship between every two indexes to finally work out the ranking weight for indexes at all levels, providing the basis and reference for empirical evaluation research of resilient cities.

Abstract:The clustering analysis method is used to transform the dynamic comprehensive evaluation of multiple experts into the static comprehensive evaluation problems. The scatter degree method is adopted to determine the weight of each index objectively, combined with the subjective weight, and the mathematical programming method is used for the index integration. Finally, Bayesian networks model is used to make a classification evaluation of 24 scientific and technological achievements, and give the probability measurement of each scientific and technological achievements awarded to a certain place and rank within each level. The empirical research suggests that most of Chinese scientific researches have achieved the fruitful results with high research values while lack of creativity and breakthroughs.