Advanced Materials Research Vols. 639-640

Abstract: The fluctuating wind field is simulated for digital by using the AR method. A three-dimension finite element model of high-pier long-span rigid frame bridge is presented in this paper. Based on this model, the gust-induced static response of the bridge under the longest cantilevered construction stage is computed. By comparing with those of two similar span rigid frame bridges with low piers, the gust-induced response characteristics of the internal force under the bottom of the piers of the high-pier long-span bridges are investigated, which is helpful for the safe design of bridges. The buffeting responses of the bridge under the longest cantilevered construction stage are also calculated in the time domain, taking account of the longitudinal and vertical turbulence action. Through the spectral analysis of the response, the comfort index of Diekemann is obtained. The effects of buffeting response on the workers’ safety under the most unfavorable construction stage are discussed.

Abstract: The finite volume method and multigrid method are presented to solve Navier-Stokes equations. MG method is introduced in this work and applied on solving the discrete systems of the governing equations. For turbulent flow, the standard k-ε model is adopted. The non-orthogonal collocated grid systems are generated. The numerical prediction were done for the flow over sinusoidal hills. The numerical results were obtained from the simulations of flow over three types of sinusoidal hills. Comparisons have been made between experimental data and the computational data and agree with each other.

Abstract: Wind tunnel test of 1:500 rigid model of tall building with atrium was carried out. Based on the experimental results, characteristics of wind pressures on atrium facades and wind loads on the structure were investigated in detail. The results show that the formation of flow separation on the building top plays a critical role in the generation of wind pressures on the atrium facades. Meanwhile, wind pressure coefficient distributions on the atrium facades are found to be relatively uniform. Moreover, the horizontal and vertical correlations of pressure coefficient exhibit high at most locations on atrium facades. With the increasing of the opening ratio, the mean wind pressure coefficients first decreased and then stabilized, and the fluctuating wind pressure coefficients first decreased and then increased. A design guideline for the wind-resistant design of atrium facades was proposed, and the results predicted by the proposed guideline were in good agreement with those from the wind tunnel tests, indicating that the proposed guideline can be used in engineering applications. When the opening ratio is no more than 5.33%, the effect of the facade pressures within the atrium on the wind loads on the structure can be ignored. For such cases, the wind-resistant design for a tall building with atrium can refer to that of a similar shape tall building without atrium.

Abstract: The Shenzhen New Railway Station (SNRS) has roof dimensions of 450 m long and 408 m wide. This paper presents the results of wind loads acting on the large-span roof structure. In the wind tunnel test, wind-induced pressures including mean and fluctuating components were measured from the roof of a 1:200 scale SNRS model under suburban boundary layer wind flow configuration in a boundary layer wind tunnel of HD-2 at Hunan University. Based on the data obtained simultaneously from the wind tunnel tests, the distributions of the mean and fluctuating wind pressure coefficients and the characteristics of probability density functions of wind pressures of typical pressure taps were analyzed in detailed. The outcomes of the experimental study indicate that: (1) The maximum mean negative wind pressure coefficients on the roof occur at the windward leading edge region, where the maximum fluctuating wind pressure coefficients occur also in this region; (2) There are some differences of the maximum mean negative wind pressure coefficients and RMS wind pressure coefficients under conditions with different number of trains inside the station, but such effects on the overall pressure distributions on the whole roof are negligible; (3) There are clearly negative skewed distributions for some pressure taps at the windward leading roof edge and much longer negative tails are observed, which follow Non-Gaussian distributions. The results presented in this paper are expected to be of considerable interest and of use to researchers and professionals involved in designing complex long-span roof structures.

Abstract: For the reasons of prestressing and other factors, the lateral bending would appear on the post-tensioned concrete T-beam during the pre-tensioning. In this paper, a simulation model is established as an example of the edge beam of 40-m T-beam which is widely used. According to the stress and displacement of main girder under different orthogonal force, the effects of lateral bending on the main girder are analyzed. Finally, some guidelines are suggested.

Abstract: The control of subgrade settlement has been the main influencing factor on highroad pavement quality, so estimating settlement amount after construction based on designed embankment height and planning the construction filling height beforehand through the settlement prediction is a very important work. Because of the complex coupling properties and high nonlinear characteristics of the factors influencing foundation settlement, a soft-roadbed settlement prediction model based on RBFNN (Radial Basis Function Neural Network) is proposed, combining the global fitting properties of RBFNN. The analysis shows that the model owns good fitting property and high prediction precise, and certain practical value.

Abstract: Based on unascertained mathematical theory, the unascertained average clustering model (UACM) is established in the ratio design of stone matrix asphalt (SMA). Six parameters including Marshall stability, flow value, volume of air voids (VV), void in the mineral mixture (VMA), VCAmix, and asphalt saturation are selected as the index in the clustering analysis to establish UACM of design indexes including penetration, ductility, softening point, percent passing 9.5 mm sieve, percent passing 4.75 mm sieve, percent passing 0.075 mm sieve, and the asphalt-aggregate ratio respectively. The study shows that UACM has strong applicability; the results meet the engineering requirements, and can be provided a new way of SMA mixture ratio design in practical engineering.

Abstract: Bayes discriminant analysis theory (BDAT) is used to create an evaluation method to determine the condition of urban road traffic safety. The resulting Bayes discriminant model (BDM) is designed to strictly adhere to BDAT. Three indexes including death ratio per ten thousand vehicles, death ratio per hundred thousand bicycles and death ratio per hundred thousand citizens are selected as the factors in the analysis of urban road traffic safety. The grade of condition of urban road traffic safety is divided into three grades that are regarded as three normal populations in Bayes discriminant analysis. Bayes discriminant functions rigorously constructed through training a set of samples are employed to compute the Bayes function values of the evaluating samples, and the maximal function value is used to judge which population the evaluating sample belongs to. The optimality of the proposed model is verified by back-substitution method. The study shows that the prediction accuracy of the proposed model is 100% and could be used in practice.

Abstract: This paper, aiming at rigid-continuous girder bridge with high piers, uses the large mass method (LMM) to analyze the seismic response of such special structure under a series of different phase differences by considering both rigid foundation and elastic foundation models. In addition, this paper discusses the influence rules for extreme response of different parts of structure due to traveling wave effect. The result shows that traveling wave effect greatly affects the rigid-continuous girder bridge with high piers. When considering the traveling wave effect, the internal force of bridge piers presents increasing trend, and the displacement of pier top reduces with increasing phase differences. The internal force and extreme displacement response of bridge structure present cyclical variations with phase differences, and that cycle is consistent with the characteristic period of bridge.

Abstract: Dynamic performance of prestressed concrete bridge of box girder with corrugated steel webs has been researched in this paper. First, the analysis theory and methods were discussed. Then, the finite model on the background of Li- Jia River bridge is built to analyse the dynamic characteristics. On the basis of original model, the geometric parameters are changed to analyse the change rule of dynamic characteristic. Finally, the range of optimum parameters are abtained.