Applied Mechanics and Materials Vols. 438-439

Abstract: Effective vibration control technology for stay cables is extremely critical to safe operations of cable-stayed bridges. This paper focuses on a new cable vibration control technology and introduces an electromagnetic damper being tested for its electrical performance. Control performance of a model cable attached with a passive electromagnetic damper was investigated in the laboratory. The test results show that modal damping ratios of the cable in the first four modes can be improved significantly with the electromagnetic damper. As such, advantages and feasibilities of this new cable vibration controlling system are finally demonstrated.

Abstract: The rheological properties of special self-compacting concrete paste played a major role on its performance. The Brookfield R/S SST2000 soft solid tester and TAM AIR 8 channel isothermal calorimeter were used to test the rheological properties and hydration heat effect of special self-compacting concrete paste. The initial cement hydration-rheological model was proposed through the systematical experiments with different water-cement ratio and the chemical admixture, combined with the heat of hydration model of Portland cement. The results showed that the hydration-rheological model of cement paste acted as N, according to the two mutation points on the stress-time curve, which could be divided into three stages, i.e. suspension with no structure, flocculation state structure, condensed state structure. To extend structure mutation values corresponding to the point in time, it can improve the rheological properties of loses with time. With the increasing of water content, heat of hydration effect shows positive effect, but the mechanical effect is weakened. The adding of the superplasticizer delayed the hydration exothermic rate and initial hydration shear stress mutation process.

Abstract: To keep the perfect, artistic and natural characteristics of fair-faced concrete, it is necessary realizing its weather fastness. This paper introduces the simulated environment test for weather fastness of fair-faced concrete considering the environmental actions at all seasons such as washing of acid rain, sand blown by the wind, exposure to blazing sunlight, salt-fog, carbonization and freeze-thaw. Test methods for sand blown by the wind, washing of acid rain, slow freeze-thaw and exposure to blazing sunlight were invented. The mass change of concrete were measured, and the surface quality was evaluated by the glossiness, the pixel difference and the variance of pixel difference. The results showed that the mass had a little change under the comprehensive actions. The factors decreasing the surface quality in sequence from serious to slight were the washing of acid rain, the salt-fog, the freeze-thaw and the carbonization. The erosion degree increased with the increasing pH value in rainwater and the increasing density of sulfate-ion in salt-fog solution. The surface of concrete damaged by the long-term freeze-thaw and carbonization. The sand blown by the wind, and the exposure to blazing sunlight had little influence on the surface of concrete.

Abstract: As the high-performance concrete with remarkable characteristics of artistic presentation and ecological sense, fair-faced concrete is becoming more and more attention by the department of urban construction. As part of the research project, this paper gives the supplement study of the mix proportion and basic properties of C50 fair-faced concrete, and summarizes the experimental results of the apparent quality of C30 and C50 fair-faced concrete affected by the mold releases. Considering the parameters of water to cement ratio, cement dosage, percent of pulverized fly ash, sand ratio, water reducer and mold releases, the workability of fresh concrete and the compressive strength of hardened concrete at 7 days, 28 days and 56 days, as well as the apparent quality and surface brightness were measured, the mix proportions of C30 and C50 fair-faced concretes for construction of urban bridge were determined. Based on the measurements of surface brightness, color uniformity, resistance to water penetration, stain resistance and compressive strength of fair-faced concrete, the formwork lacker can be firstly selected as the mold release, and the mix oil (diesel: machine oil=3:7) can be the alternative selection.

Abstract: In order to perfectly make the bridge function, structural style, architectural art modeling with the surrounding environment, this paper, based on the design of landscape five-span arch footbridge, studies the span arrangement, structural style, building materials, railing shape, ornament style and color, and lamplight illumination of the bridge considering the factors such as hydrology, geology, surrounding environment (e.g. buildings and park), traffic flow and entire urban planning. To reduce the stress of main arch and the horizontal thrust of substructure, the new structure of T-frame with sloped plate was put forward to bear the deck loads with the assistance of main plate arch. The thin concrete walls were cast on the top sides of the main plate arch, which were decorated by fine stone with the modern decoration construction technology. The white marble railings present lively morphology with carved lotus and pomegranate on the column cap, and many kinds of flowers on the panels. The spotlights make dramatic night sense for the bridge. Therefore, the landscape footbridge in the classical arch graceful shape was constructed by the modern building material and the optimized reinforced concrete structure, which presents the unity and coordination of structural design and artistic expression.

Abstract: The compression index is an important soil property that is essential to many geotechnical designs. As the determination of the compression index from consolidation tests is relatively time-consuming. Support Vector Machine (SVM) is a statistical learning theory based on a structural risk minimization principle that minimizes both error and weight terms. Considering the fact that parameters in SVM model are difficult to be decided, a genetic SVM was presented in which the parameters in SVM method are optimized by Genetic Algorithm (GA). Taking plasticity index, water content, void ration and density of soil as primary influence factors, the prediction model of compression index based on GA-SVM approach was obtained. The results of this study showed that the GA-SVM approach has the potential to be a practical tool for predicting compression index of soil.

Abstract: Dynamic consolidation method has been widely used in improving soft land, but always inefficient to saturated soft clay land, which is hard to improve, and even leads to rubber soil. Dynamic and drain consolidation method will deal with it well, with drainage system, pore-water can be expelled instantly from saturated soft clay as impacting. The pore-water pressure and earth pressure test in construction, the standard penetration test, plate loading test, geotechnical test after construction, which are all effective methods for effect testing. There is a comprehensive detection through different depth of soil layer with different detecting means on construction site. The results show that improving saturated soft clay land with dynamic and drain consolidation method has obtained good effect, and the fruit can be guidance for such construction in the future.

Abstract: The unconsolidated-undrained fast shear tests of saturated-unsaturated remolded soil samples under different moisture content which is 1.1%, 10.1%, 14.9%, 19.9%, 24.2%, 29.9%, 37.7% respectively, and normal stress which is 50kPa, 100kPa, 200kPa, 300kPa, 400kPa respectively, were studied by the modified SDJ-1-type strain direct shear apparatus and U.S. Lab VIEW data acquisition system. The shear strength parameters of unsaturated soil samples, i.e. general cohesion and general internal friction angle were obtained based on Mohr-Coulomb strength theory. The test results showed that the general cohesion firstly increased and then reduced with the moisture content increasing, and the general internal friction angle increased with the moisture content decreasing. The function between the general shear strength parameters and the moisture content was studied. The concept of general shear strength parameters was proposed in the paper, and would provide a simple and practical method to obtain the strength parameters for engineering practice.

Abstract: According to the tested physical and mechanical soil parameters of the Coastal Railway in West Guangdong along the broad coastal plain region, the correlation relations between compression modulus, compression coefficient and void ratio, moisture content, density, standard penetration number are analyzed by the linear regression method. The results show that the compression modulus increases with the increase of water content and void ratio, with correlation coefficients being 0.6985 and 0.8147, respectively; the compression modulus decreases with the increase of density and standard penetration number, with correlation coefficients being 0.7827 and 0.4934, respectively; the compression coefficient decreases with the increase of water content and void ratio, with correlation coefficients being 0.9131 and 0.9412, respectively; the compression coefficient decreases with the increase of density and standard penetration number, with correlation coefficients being 0.8187 and 0.4985, respectively. The parameters which are hardly obtained from the test directly can be easily evaluated by using these formulas.

Abstract: Dynamic constitutive models and liquefaction characteristics of soil are critical in the seismic stability analysis on embankment dams. The P-Z constitutive model, which is a kind of the multi-mechanism plastic model based on generalized plasticity, is mainly introduced in this paper. Considering soil as two-phase media, based on the Biot fluctuation theory and the P-Z model, the dynamic analysis formulation of two-phase media is established, and the criterion of soil liquefaction is proposed through investigations, where the generation and dissipation process of soil pore pressure and the variations of effective stress are taken into account. Furthermore, the interface conditions between two-phase media and the other types of medium are derived and the examples of verification are presented.