Applied Mechanics and Materials Vols. 105-107

Abstract: The objective of this study is to introduce a dynamic assessment method about simple-supported girder bridge .This paper introduces the dynamic test contents, test methods, test results and the assessment index. The dynamic tests included ambient vibration tests which were used to identify the bridge modal parameters and forced vibration tests based on controlled traffic loads which were used to obtain the and vibratory response. The analytical results showed that the dynamic performance was in good condition and the bridge had great potential of carrying capacity. This method provided effective means for the assessment of the existing simple-supported girder bridge.

Abstract: The surface settlement is affected by many factors due to EPB shield. This paper takes the shield construction of Guangzhou Metro Line 5 as an example, carries out three dimensional numerical experiments on the ground settlement rule. The result indicates that soil warehouse pressure and the efficiency of grouting is important factors of the surface displacement. To increase grouting pressure and shorten the grouting time can reduced the ground settlement in effective. With the increase the soil warehouse pressure, the settlement behind the working face is reduced and the front working face is increased. When the soil warehouse pressure is at the over balance condition, the raising ground is increased and the settlement is reduced. The value of settlement is much larger than the value of raising. So to increase the soil warehouse pressure is another effective method to reduced the ground settlement on the premise that the front soil body of shield does not be destroy.

Abstract: The OD volume of railway luggage and parcel on Beijing-Guangzhou Corridor is forecasted by using the gray model and the gravity model. According to the historical statistical data, firstly the sending and arrival volume of railway luggage and parcel of the major cities on Beijing-Guangzhou Corridor is forecasted by applying the gray model and it takes the Beijing volume of railway luggage and parcel for example to show the calculative process. Secondly, by using the least squares method to calibrate the sample data, obtain the value of each coefficient to be determined, get the calibrated gravity model and then the OD volume of railway luggage and parcel is forecasted by adopting the gravity model. Finally the rationality of the forecasting results is analyzed and the forecasting results which can be used in the railway luggage and parcel organization work have a high accuracy and meet the actual needs.

Abstract: Elastic deformation of wheelset should be considered for wheelset dynamic research. In this article, a new wheel-rail contact point searching algorithm that can be used for flexible wheelset simulation was developed based on wheel-rail contact line method. For given position and deformation of wheelset, normal vectors of a point on each rolling circle and its project on rail were calculated to find out possible contact point, which formed wheel-rail contact line. The final contact point was determined by minimum vertical distance of contact line and rail section profile. Rigid-flexible coupling dynamic equations of single wheelset were established and dynamic simulation was executed. The impact of wheelset deformation on wheel-rail contact position and creepage were discussed. Comparison of rigid and flexible wheelset results show that the new method gets more accurate contact point position.

Abstract: The daily temperature change of a pavement structure has an important impact on its crack production and propagation. First of all, a one-dimensional transient mathematical model of heat conduction and a heat convection boundary condition that can take solar radiation and ground radiation into account were established according to the characters of the pavement structure and heat conduction. Secondly all the computational formulae were deduced for the above model utilizing SAM. Finally, the hourly temperature field of a typical pavement structure was calculated using ANSYS and SAM respectively. Results show that SAM solutions at different depths are in good line with ANSYS solutions. Therefore, SAM is an easy-programmed, fast and high precise method, and is deserve to be popular. In addition, the daily temperature changes at different depths were discussed, and some suggestions were provided for the thermal crack control and prevention of the structure

Abstract: Coal mining can cause the strata distortion and surface subsidence. With infrastructure construction scale in our country enlargement, the case of approaching excavation caused by coal mining is increasing and more complicated. The calculation method of current regulations is too simple and don't conform to the present coal mining technology, so it will cause serious waste of resources. By using numerical simulation, this paper regards the influence of coal mining on the above tunnel as approaching excavation problem and studies the tunnel deformation law with three different coal mining mode. Based on the analysis and calculation, this paper proposes measures to ensure that the coal seam mining and tunnel's safety. The result indicates the more smaller the dip angle of coal block the more larger the displacement and the deformation range of tunnel. The most effective method for decrease deformation is the backfill method. If the conditions are permitted, backfill method is the preferred method and longwall caving method is last.

Abstract: According to the extensive application of shield tunnel, large-diameter shield tunnel in particular, structure stiffness of shield tunnels varies in a large rang. In this paper, shield tunnels with different diameters and thicknesses are analyzed and calculated by time-history method. Stiffness ratio is identified to measure the relationship of structure’s stiffness and soil’s stiffness. The results indicate that dynamic moment and shear forces of shield tunnels have positive correlation with the stiffness ratio. Axial forces have positive correlation with thickness and diameter of lining structure.

Abstract: As for shallow tunnels through the rock layers, the stability of the overburden rock has a decisive role on the tunnel stability; furthermore, analyzing the stability of the overburden rock is very important to the supporting design and the choice of excavation method. Method of elastic foundation beam is used to research the moment of overburden rock, and the formula of overburden rock stable thickness is finished. Seven sections of JIAOZHOU Bay Subsea Tunnel are took for example to analyze the safety factor of different span and overburden rock thickness, then the stability of overburden rock is analyzed. The results show that the overburden rock safety factors of these seven sections of JIAOZHOU Bay Subsea Tunnel are range from 0.65 to 0.85. Compared with the experimental results, theoretical analysis of the results are more consistent The actual example verifies that the overburden rock stability in this paper is feasible.

Abstract: According to the extensive application of shield tunnel, large-diameter shield tunnel in particular, a simplified seismic design method is in urgent need. The equivalent static method is more suitable for the rigid underground structure, rather than flexible structure such as large-diameter shield tunnel. In this paper, shield tunnels with different diameters and thicknesses are analyzed and calculated by time-history method and free field deformation method. The calculation and analysis above help to identify the stiffness ratio to measure the relationship of structure’s stiffness and soil’s stiffness and the derivation of a revised stiffness solution based on the free field deformation method. The results indicate that this method can calculate seismic stress of shield tunnels with different diameters and thicknesses accurately.

Abstract: A specific issue in seismic analysis of large span bridge, study on inconsistent ground motion input is reviewed in this paper. The building of spatial model for ground motion field based on observation of motions on dense arrays and coherence validation of the synthesized ground motion field are deal with respectively. Points are emphasized that spatial correlation between motions with distance of several hundred meters to each other comes from one same source and very similar path, similar/different site condition. A comprehensive procedure taking source, path and site condition all into account to synthesize the motion field is convenient to reveal and express the physical nature of the motion field. Spatial structure of a synthesized motion field is validated by means of the coherency coefficients. The result is consistent with the conclusion from the statistics of the observed data on some dense arrays.