Abstract:Based on the simultaneous pressure measurements of the rigid model of Wuhan Tianhe International Airport Phase III (expansion of ATC tower) Project in a wind tunnel test, the characteristics of the wind loads on the oval-shaped high-rise structure were investigated. This paper discussed the distributions of mean and peak wind pressure coefficients on numerous test points under typical wind directions. Based on the time-histories of wind loads and FFT method, the spectra of 3-D wind loads on the oval-shaped structure were obtained for 90° approaching wind direction (corresponding to the maximum windward area). The power spectra were then fitted by using the empirical formula. The mean, background and resonant equivalent static wind loads were determined by the LRC wind load method. The results were compared with those by the inertia wind loading method. It is found that the equivalent static wind loads by these two methods are in good agreement.

Abstract:In order to investigate the wind-induced responses of a tower 838 meters high under the designed wind speed, multi-degree-of freedom aero-elastic model wind tunnel tests were carried out. It was found that the first-order and the second-order frequency inaccuracy of the model, which was measured from the free vibration test, were less than 1% and 28%, respectively, the first-order damping ratio was about 2%, and the translational vibration mode shape was consistent with the actual structure. Wind tunnel test result has shown that the maximum wind-induced dynamic displacement is 0.89m, which is in the standard allowable range. But the wind-induced acceleration of 10 years', 50 years' and 100 years' return period exceeds the specification threshold with the amplitude of 16%, 23%, 29%, respectively. What's more, the lateral response increases remarkably by first order vortex induced vibration，in which the contribution of aerodynamic damping is close to 37%.And in order to ensure acceleration response under one hundred years' wind speed in the allowable range, the structural damping ratio must be larger than 2.9%.

Abstract:The average wind pressure on the internal surface of a super large hyperbolic cooling tower under the operating conditions was simulated in CFD method. Based on computational fluid dynamics software for secondary development, DPM model combined with a UDF function method was used to study the average wind pressure on the internal surface of a super large cooling tower. The Lagrangian method was used to simulate the water phase of the tower and Euler method was adopted to simulate the air phase, the coupling calculation between inner flow field and transformation of heat and mass in cooling tower under the operating conditions was well realized, and the internal pressure distribution law of cooling tower under crosswind direction with running state was analyzed. The results of the tower with no cross wind show that the symmetry of the average pressure on the internal surface goes well, and the water temperature is consistent with the test result, which verifies the effectiveness of the method proposed. The value of the average pressure coefficient of the internal surface of cooling tower under cross wind becomes bigger along the height direction, and the value does not change significantly along the latitudinal direction. The shortcomings of the current code about internal surface pressure coefficient were discussed, and the recommended values were given, which provides methods and basis for the calculation of the internal pressure of super large cooling tower design.

Abstract:Wind tunnel tests were carried out to measure the wind pressure on the internal surface of a 220 m-high super large cooling tower, and then analysis on the three-dimensional effect of internal pressure was conducted, and finally, simplified methods for obtaining the design value were investigated. The analysis results indicate that the wind loads on the internal surface of the cooling tower behave with remarkable three-dimensional effect, and they are not strictly uniformly distributed along both the hoop and the meridional direction. This nonuniformity is particularly serious when the tower is in the construction period. The size and the distribution of the internal pressure have some influence on the wind-induced response, but because the outer pressure plays a dominant role in the wind-induced response of cooling tower, the contribution of the internal pressure to the response is small. So the design value of internal pressure can be simplified as constant -0.50, which is proved to be very safe for the structure. The results can provide reference for both the design of 200 m high super-large cooling tower and our specification revision.

Abstract:To effectively suppress the larger displacement of both the isolation layer and the main structure of base-isolation structures, the top-absorption and base-isolation type seismic reduction structure (SRS) was designed, and a new non-stationary random seismic response analysis method applied to this structure was also presented. This seismic reduction structure was constructed by installing a tuned mass damper on the top of a base-isolation structure, and the hysteretic properties of both the isolation layer and each storey were simulated in Bouc-Wen and Bouc-Wen stiffness degradation model. The CCIM, which was applied to solve the non-stationary random response of SRS, was presented by introducing the composite Cotes integral into precise integral method and combining the pseudo excitation method. The dynamic reliability limits state equation, which took structural inter-storey displacement angle as the evaluation index, was established on the basis of the first excursion failure criterion. Both the high efficiency and the high precision of the CCIM were validated by computing the random seismic response of SRS and comparing CCIM's results with those of Monte Carlo method and time domain explicit Monte Carlo method, respectively. Taking the 30-storey steel frame structure as a numerical example, the random seismic response of SRS, base-isolation and non-isolation structures subjected to 8 and 9 degrees rare earthquake were computed, respectively. The analysis results indicate that the whole reliability of SRS presented is higher than those of base-isolation and non-isolation structures, and this SRS has great value in practical engineering.

Abstract:Two 2-bay, 1-story RC plane frames were tested to study the static and dynamic behavior of RC frame structure after the column's failure. A static experiment was done to obtain the static behavior data of frame structure, and based on another test frame, hammer experiments were used to obtain the frame beam's dynamic response data of displacement, acceleration and steel strain under no load and uniformly distributed load, respectively. The mechanic behavior of the frame beam under hammer load was studied by comparing the static and dynamic test results. The tests results were as follows: there was a linear relationship between the dynamic displacement amplitude and the input impulse under hammer load; with the increase of the hammer load, the damping of the structure changed little while the frequency decreased; the frame beam with uniformly distributed load formed the arch effect under hammer load, so its stiffness increased slightly; the maximum hammer load exceeded the frame beam's maximum resistance force, but the frame beam did not collapse because of the small impact energy.

Abstract:This study conducted a test to analyze the self-insulation lintel by filling the slit in lintel with the insulation materials to prevent the thermal bridge. Two solid lintels and eight self-insulation lintels were tested to study their flexural properties. The result shows that both the outer wythe and the inner wythe of the self-insulation lintels cooperate well with each other. The measured maximum crack width under the limit state of normal use is smaller when compared with the limit value under short-term load, so it can meet the normal requirement. In addition, the slit and width ratio of the self-insulation lintels has little effect on the initial crack load and failure mode, and because of the slit, the ultimate strength of the self-insulation lintels is slightly less than the solid lintels, while the difference is obvious. Though the heat-transferring coefficient of the self-insulation lintels decreases by 65% compared with the solid lintels, it has much better thermal performance.

Abstract:The bending of a new typical gas holder under gas pressure is crucial to ensure the normal operation of the structure. It can be simplified to elastic bending of ring stiffened cylindrical shell, which is under partial internal pressure and has multiple circular reinforced ribs. Stripe Beam on Elastic Foundation Method (SBEFM) was extendable to the structure system. At the same time, traditional discrete stiffened method (TDSM) was improved. A gas holder of 300 000 m3 was taken as an example for analysis. On this basis, the method judging ring stiffened cylindrical shell smeared or discrete was presented. The new analysis shows that SBEFM has a wider applicability, higher accuracy and better efficiency than other methods and the improved discrete stiffened method is effective when the ring spacing is greater than 3.875 (Rh)1/2.

Abstract:Structural over-strength is an important factor for structural collapse prevention when the structures suffer major earthquakes, however, it isn't included in our current Chinese seismic design code, and the seismic design specifications for structural safety calculations are based on structural members, with no more consideration on global carrying capacity of the whole structure. 17 RC frame buildings with different fortification intensities and storeys were designed according to the current Chinese Codes. These structures were modeled and analyzed in the platform OpenSees. By comparison of the quasi-static test data for RC frame structures with the analytical data correspondingly, the OpenSees models were verified and validated. For these 17 RC frames, structural seismic response was analyzed by nonlinear dynamic procedures (NDP), and the values of the “capacity” of structural overstrength factors and their variation rules with structural storeys and design fortification intensities were analyzed and derived. It is shown that structural ultimate load carrying capacity in collapse prevention performance level can be estimated by structural overstrength factor “capacity”. For RC frames designed in seismic fortification intensity Ⅵ, Ⅶ, Ⅷ, structural global overstrength factors “capacity” are 6, 4, 3 above respectively, and the minimum value agrees with the value 3 given in NEHRP recommended provisions.

Abstract:In order to address the dam concrete covering uplift effect caused by the dynamic load of grouting pressure, in which the dam concrete covering will damage the anti-seepage properties of the dam, a simplified model was developed for the hysteretic nonlinear dynamic response analysis of concrete covering under consolidation grouting pressure fluctuating load. The nonlinearity, hysteresis, accumulated deformation and stiffness degeneration characteristics of concrete covering under grouting pressure fluctuating load were considered. Then, the Bouc-Wen degradation hysteresis model was adopted to analyze the hysteretic effect of nonlinear dynamic response of concrete covering by considering the soil and rock stratum under the concrete covering with different stiffness and damping coefficients. According to the actual grouting parameters, the result shows that the predictions of the model are in very good agreement with values measured from experiments.

Abstract:This paper investigated the pore structure of fly ash with the object of undisturbed fly ash samples prepared by freeze drying. By incorporating microscopic digital imaging technology and professional image processing technology, the porosity density dimension of fly ash was derived on the basis of the fractal theory, and the cause of the multi-fractal property of pore structures of fly ash was analyzed. A function quantifying the relation between the permeability and the porosity density dimension of the fly ash was derived by employing capillary bundle model and Poiseuille equation. Parametric analysis indicates that the permeability of fly ash increases with the increase of the maximum pore radius and the inflection point of pore radius, and decreases with the increase of the fractal dimension of the pore radius distribution in sections I and Ⅱ.

Abstract:In the existing research methods for determining the ultimate bearing capacity of foundation near Slope, the vertical uniform force instead of embedded depth of foundation was adopted，which did not consider the contribution of the soil shear strength in depth enough. In view of the problems, the Meyerhof Theory was introduced. First of all, based on the engineering characteristics of strip footing, the failure mechanism of strip footing near slope was thoroughly analyzed. Meanwhile, the new unilateral sliding failure mode considering the soil shear strength in the strip footing embedded depth of foundation adjacent to slope was established for further in-depth study of the method for determining the bearing capacity of strip footing near slope. Then, on the basis of the failure mode, the ultimate bearing capacity analysis model of strip footing adjacent to slope was derived in the rigid body limit equilibrium analysis method, based on the Meyerhof theory to solve the impact of the soil shear strength in depth. The method reflects not only the soil shear strength in depth, the distance effect from the top of the slope, different embedment depth on both sides of the footing, but also the friction effect between the wall of strip footing and the soil in depth. The simplified calculation formula is simpler and engineering applicative, compared with the existing research results. Finally, the feasibility and rationality of the proposed approach were shown through an engineering example calculation and comparison with current research results.

Abstract:The mechanical properties of unsaturated soil under different normal stresses and water contents were systematically studied with the cyclic simple shear test, where the water content is 5.4%～25.4% and the normal stress ranges from 25 kPa to 300 kPa. It mainly investigated the influence of the normal stress and water content on the mechanical properties of unsaturated sandy soil. Experimental results show that there is an equilibrium water content. When water content is greater than the equilibrium water content, the curve of the shear stress and shear displacement of unsaturated sand soil will change from hyperbolic to Double Broken Line model. The shear stress changes in small range when the water content of the unsaturated sand soil is under the equilibrium point. Whereas the shear stress drops sharply as the water content increases .The water content has important influence on the mechanic performance of unsaturated sandy soil, such as cohesion, internal friction, dilatancy and so on.

Abstract:Based on the Gongzhufen Station of Beijing Subway Line 10 closely-attached intersecting the existing Gongzhufen Station of Line 1, which has applied the technology of “center cross diagram(CRD) method + multiple top bracing”, the finite difference procedure FLAC3D was used to establish a 3D numerical calculation model. The change of soil plastic zones and deformation law of existing subway station in the construction process of the new station were studied. The results have shown that carrying on the closely-attached intersecting construction using “center cross diagram (CRD) method + multiple top bracing techniques” can effectively control the structure deformation and meet the requirements of settlement limiting value. By comparing the simulated deformation curves and the measurements, a good agreement was obtained. Once the construction is completed, the profile of the existing structure presents double-groove shape deformation while the lateral shows “V” glyph settling tank, which is similar to Peck curve, and the sedimentation value of the bottom plate is slightly larger than that of the top plate. Jacks unloading may cause large deformation or even cracking on the structures' local parts, so the axial force should be graded to release. During the process of excavation, the soil mainly experiences a shear failure and the plastic zones tend to extend outward into a butterfly shape in the four corner area. In order to realize the active control of the settlement deformation of existing structures, the construction idea of “synchro jacking-up, servo control” was put forward.

Abstract:Through orthogonal numerical experiments, the significance of the effect of four thermal environmental parameters on PMV was compared, which indicates that the degree of the influence of four thermal environmental parameters on PMV in descending order is air temperature, indoor wind velocity, mean radiant temperature and relative humidity within the usual range. Furthermore, the influencing laws and the significance of the effect of the four environmental parameters on energy consumption under PMV control were analysed. Under the premise that PMV remains unchanged, the energy consumption of different combinations of thermal environment parameters were compared. It is found that there is a huge difference between different combinations on energy consumption, which indicates the presence of an optimal combination consumes the minimum energy while satisfying human thermal comfort. The above analysis provides directions and basis for the further study of PMV optimal control of air-conditioning systems.

Abstract:To achieve the comprehensive assessment goal of economy and energy conservation in energy-saving design scheme selection, based on the life cycle theory, exergy analysis method and thermo-economics, the exergy consumption and CO2 emissions of different energy-saving design schemes and exergy cost models were evaluated and built. The analysis of the two energy conservation schemes of an office building in Zhuzhou indicates that, to reach the true sense of energy conservation, energy saving and CO2 emission cuts in building operation stage should be greater than the consumption in building production stage. The energy consumption and CO2 emission in the building production stage of Scheme one and Scheme two will need 10, 11 years and 4，5 years respectively to be offset. And the exergy consumption in the production stage is far more than the exergy saving in the operation stage. The analysis result of exergy cost reveals lower exergy cost means less investment, more low-grade energy usage and higher exergy efficiency. It shows the energy saving property and sustainability of buildings.

Abstract:A two-dimensional frequency-domain finite-difference (FDFD) model was developed on the basis of the classical finite-difference principle for a pipe-embedded concrete radiant floor to predict its frequency thermal responses. In the meantime, a CFD for this floor was also developed for this floor by using a reference model. The calculated frequency thermal responses of the floor by using FDFD model at typical frequency points were expressed in the form of amplitude and phase lag in time domain, and were then compared with the results by using CFD model. The results indicate that the FDFD model can predict the thermal characteristics accurately. The FDFD model was used to predict the frequency thermal characteristics of the pipe-embedded concrete radiant floor with insulation of different thicknesses, and the effects of the insulation thickness on the thermal responses of the pipe-embedded concrete radiant floor were analyzed and presented. The results indicate that the effect of the insulation thickness on the heat transfer of the floor is obvious in low frequency range while not obvious in high frequency range. Even if the thickness of the insulation is 40mm, the heat loss from the bottom surface of the floor constitutes about 16% of the heat transfer on the pipe surface and cannot be neglected.

Abstract:This paper investigated the cross-flow wet cooling tower, constructed the evaluating indicator on the basis of the heat and mass transfer performance, and then used classical four-variables model to study the effect of different seasons and ambient parameters (temperature, humidity and so on) on the heat and mass transfer of the cooling tower, and finally, gave the suitable operation condition of annual round operation in Nanjing, Wuhan and Chongqing. The results show that the suitable water-air ratio condition of CT is 0.5~1 in July and August of the three cities, and in June and September, 0.3~1. During transition season, the suitable water-air ratio condition of CT is 0.4~0.6, and the suitable operation time is March and November for Nanjing and Wuhan, but CT in Chongqing is not suitable for operation during the transitional seasons. In winter (from December to February), the suitable water-air ratio condition of CT is 0.5~0.76.

Abstract:Based on the analysis of multi-parameter coupling, which is based on ground source imbalance temperature limit, the building load characteristics and the heat transfer mechanism, this paper put forward an evaluation index, including the energy storage imbalance temperature limit, energy imbalance, and system invalidating indicator, and built the evaluation system on ground energy storage condition. Based on this evaluation system, by using the three-dimensional pipe-group model created by CFD software, a calculation method to accurately analyze the ground energy storage condition of ground source heat pump system was proposed. The result of calculation and analysis show that the evaluation system and calculation method reflect ground energy storage condition objectively and the ground source imbalance temperature limit can be concluded on the basis of the characteristics of practical projects in this method. The failure time of energy saving and efficiency can be predicted in the life cycle.

Abstract:Because the test power of the traditional panel unit root tests is unstable and the choice of the null hypothesis of traditional panel unit root tests is subjective, this paper proposed a Bayesian quantile unit root test for panel data based on asymmetric Laplace distribution. On the basis of quantile autoregression panel data model, the full conditional distributions of parameters were inferred and MCMC algorithm was designed. And then, Bayesian quantile unit root tests were conducted. Numerical results were produced via a combination of Monte Carlo simulation, from which we find that Bayesian quantile unit root tests are noticeably efficient and feasible. As a result, it is shown that Bayesian quantile unit root tests solve unstable power problems and the subjective choice of the null hypothesis. Furthermore, the tests are more robust and can provide more complete information.