Applied Mechanics and Materials Vols. 488-489

Abstract: The effect of non-zero initial conditions of measured structural responses on the structural parameter identification methods based on dynamic response sensitivity is investigated and an effective method is proposed to eliminate the negative effect. A twelve-story shear building structure is studied for validating the proposed method. Numerical simulation results show that the non-zero initial conditions of measured data bring larger identified errors in the dynamic response sensitivity methods. To overleap some measured data points in the initial period of the time interval is an effective method for eliminating the identified errors caused by non-zero initial conditions. The optimal number of overleaped data can be determined from the attenuation trend of the 1st-order free modal vibration of the structure.

Abstract: In this paper, the effect of carbonization performance of concrete by freeze-thaw action in Ningxia Hui Autonomous Region have been studied. Based on the concrete carbonation depth prediction model modified, the effects of the carbonation depth of concrete by freeze-thaw action with dry weather in Yinchuan and Yanchi County are studied. These influential factor include water-cement ratio, cement dosage, the air relative humidity, carbon dioxide concentration.

Abstract: The matric suctions were measured by the filter paper method, and the parameters of soil-water characteristic curve were obtained. In order to investigate the effect of moisture content on cohesive subgrade soils dynamic resilient modulus, a series of dynamic-triaxial test were carried out. Based on the matric suctions measured by the filter paper method, the relationship between dynamic resilient modulus and matric suctions were analyzed. The study demonstrated that the dynamic resilient modulus values decrease with the increase of circular deviator stress and moisture content, in reverse of matric suctions. Considering that the dynamic resilient modulus is a function of deviator stress and bulk stress, based on the present three parameters compound constitutive model which reflects the effect of bulk stress and deviator stress, the effect of matric suctions which could indirectly reflect the effect of moisture content was introduced. And then the prediction model incorporating the effect of stress and moisture for cohesive subgrade soils was established. The model was utilized for experimental data regression analysis, a high coefficient of determination shows that the model is accurate and credible. The prediction models not only can evaluate the long-term performance of subgrade soil in Southern China's rainy areas, but also can provide parameters for the pavement design based on dynamic method.

Abstract: Hydraulic fracturing process in fractured rockmass which with an existing single natural fracture at its various conditions: its different angles and different lengths was simulated by using RFPA^2D(2.0)-Flow version which adopts the finite element method and considers the heterogeneous characteristics of rock in meso-scale, creates seepage-stress-failure coupling model. The effect tendency of natural fractures angle and length on the seepage characteristics of fractured rockmass was given through the description of tensile fracture initiation and propagation in the rock specimens. The simulation results show that the effect of these two factors on fractures initiation, propagation and rockmass stability under the hydraulic fracturing could be remarkable.

Abstract: The reference basis for channel buoy design in China at present is the inland navigation standard, but about bridge channel buoys design, there are a lot of insufficient places in the standard. The channel buoy reasonable design method is put forward in this paper according to the ship maneuvering characteristics.

Abstract: Taking the draw water tunnel of the Jiulong river across railway in Fujian province as the research object,the influence of the subgrade settlement of Yingtan-Xiamen double railway and Xiamen-Shenzhen high-speed railway as a result of the double draw water tunnel excavation is analyzed by FLAC^3D. Through numerical simulation the condition of whether the subgrade is reinforcement and whether have train load on the subgrade, the result of subgrade settlement in both single tunnel perforation and double tunnel perforation is derived. It shows that: the position of maximum settlement is just above the tunnel centerline, the proportion of subgrade settlement caused by the right line excavation is 67.5% and the one caused by the left line excavation is 32.5% when subgrade is unreinforced and there is no train load; the proportion of subgrade settlement caused by the right line excavation is 60% and the one caused by the left line excavation is 40% when subgrade is reinforced but there is no train load. The proportion of subgrade settlement caused by the right line excavation is 63% and the one caused by the left line excavation is 37% when subgrade is reinforced and there is train load. The results fit well with monitoring data and can be used as a reference for similar engineering projects. Currently, with the rapid development of China's economic, the situation of other engineering projects crossing the existing railway line has been increasing. Most researchers is carried out through the way of on-site monitoring to analyze deformation of ground surface and the railway embankment, and then comes up with the safety assessment and displacement control measures of the tunnel construction^[. The common methods of ground surface deformation analysis and prediction contain empirical formula, model test and numerical simulation^[. There are a lot of numerical simulation achievements for new construction crossing the existing railway^[3-, which mainly focused on the embankment settlement for single or multiple tunnel beneath a single railway line. Based on previous studies, this paper analyzes the railway embankment settlement under the condition whether there is reinforced roadbed or not, and whether the two-lane tunnel crosses many railway line with a combination of train load conditions through the method of three-dimensional model, and compares with the measured data to verify the reliability of numerical simulation. 1 Engineering project and its engineering geological conditions

Abstract: The essay gets started from research of current problems of the Suzhou Old Town and tries to propose development ideas of modern renewing of the Old Town by interpreting the habitat quality, environment, heritage protection and other aspects. At the same time, it provides possible directions and useful lessons for the future renewing and developing of the Old Town with assistant of analysis of domestic and foreign related cases and theoretical technical means.

Abstract: According to the compaction mechanism of oscillatory roller, a simulation model for oscillatory compaction implementation in bridge deck pavement was constructed via ANSYS. Contrast analysis on dynamic responses to bridge structure when vibratory roller or oscillatory roller is in operation shows that dynamic response of oscillatory roller is much smaller than that of vibratory roller under approximate compaction degrees. In this way, disturbance for the bridge structure can be reduced greatly, risk of bridge deck pavement construction can be decreased, and service life of the bridge can be increased effectively.

Abstract: Using the fuzzy evaluation theory,through the establishment of the safety of large cross construction of fuzzy evaluation model, using AHP to evaluate the safety of large cross construction, the comprehensive safety evaluation,and points out its advantages and disadvantages. The fuzzy control is conducive to the management level of large-scale cross constructionsafety improve, to the great guidance for other types ofcity rail traffic.

Abstract: The causes of collapse accident of formwork are analyzed, and the concepts for dynamic computation formula and dynamic coefficient are proposed; the dynamic impact coefficient of two different free falling bodies during safety computation of formwork support without considering or incorporating cross bar, and the countermeasures for safety computation are proposed.